A High-Efficiency Cultivation Pattern of Strong-Gluten Wheat in Huang-Huai-Hai Plain of China

Abstract

Different cultivation methods significantly affect wheat quality. However, the optimal cultivation pattern for strong-gluten wheat in Shandong province remains unclear. Through field experiments conducted over three consecutive wheat-growing seasons, wheat-quality-related traits under traditional cultivation practices (TC) and different cultivation patterns for Jimai44 (a strong-gluten wheat variety) were investigated. Plowing, delayed sowing date and increasing seeding rate could enhance grain protein content, SDS sedimentation value, wet and dry gluten content, and also had a clear positive effect on thousand-kernel weight and test weight. Employing a protocol of increased basal nitrogen (300 kg/ha) and topdressing water and fertilizer twice significantly increased wheat grain protein and nitrogen content, flour yield, gluten index, SDS sedimentation value, dough stability time, and extensibility. On the basis of the two wheat seasons experiments, we developed an optimized cultivation practice (Opt, that is, combined with plowing, delayed sowing date, seeding rate of 3.15 million or 3.60 million, basal nitrogen fertilizer application of 300 kg/ha, topdressing fertilizer twice, topdressing water twice or three times). Compared with TC treatment, the optimized cultivation demonstrated superior performance in grain protein content, flour yield, SDS sedimentation value, wet and dry gluten content, stability time, formation time, extension area, extension, and maximum retensibility with high grain yield. Meanwhile, we found that the expression of TaGlu1 was significantly increased under the optimized cultivation practice. In summary, the optimized cultivation practice might be a promising approach for improving strong-gluten wheat quality in the Huang-Huai-Hai Plain.

1. Introduction

Winter wheat (Triticum aestivum L.), as the second most important staple crop in China, plays a critical role in safeguarding national food security [1]. After milling, flour can be processed into a wide variety of staple food products, providing essential nutrients for humans. However, due to inadequate cultivation practices, wheat quality potential has not been fully achieved.

Crop quality is determined both by cultivation practices and the environment [2]. Studies indicate that both excessive early sowing (such as ten days earlier than the optimal planting date) and suboptimal seeding rates are detrimental to wheat grain quality, leading to declines in protein content, thousand-kernel weight, and test weight [3]. The grain quality index declined with the increase in sowing rates, and protein and wet gluten content were maximized at the lowest sowing rate [4]. As a pivotal factor in fertilization, nitrogen fundamentally determines wheat quality. Rational nitrogen management enhances population growth dynamics and canopy structure, ultimately boosting both grain yield and quality through an improved grain-filling rate [5]. Previous studies also found that appropriate nitrogen application significantly increased wheat grain protein content, dry and wet gluten content, sedimentation value, dough stability time, and extensibility [1,6]. Additional N application could increase grain hardness as well as gluten and protein content [7,8]. A positive correlation was observed between nitrogen application rates and the concentrations of grain protein and wet gluten [9]. The quality parameters of wheat were significantly superior under the higher nitrogen application rates (N240 and N180) compared to the N120 treatment [10]. Protein and wet gluten content were significantly enhanced by increasing both the total nitrogen (N) rate and the proportion of topdressed N applied after the elongation stage [11]. N fertilizer topdressed at the jointing stage (BBCH 31 (Biologische Bundesanstalt, Bundessortenamt and Chemical industry)) significantly increased sedimentation volume, dough developmental time, and dough stability time [12]. As another critical factor for wheat, irrigation frequently comes at the cost of grain quality, increasing yield while diminishing traits such as protein content [13,14]. Fischer [15] found that managing irrigation to maintain drier conditions from the late dough stage to harvest could improve critical wheat quality traits. Water deficiency could lead to a decrease in gluten index, grain protein content, and sedimentation volume [16].

Glutenin is a critical determinant of wheat quality, which is divided into high-molecular-weight glutenin subunit (HMW-GS) and low-molecular-weight glutenin subunit (LMW) according to their molecular properties [17]. Many previous studies have shown that HMW-GS plays an important role in dough processing quality [18,19]. The absence of specific high-molecular-weight glutenin subunits, such as 1Bx7, has been directly implicated in weaker dough strength [4,10]. Lower N levels could reduce HMW-GS content [20]. The application of nitrogen at the jointing stage (BBCH 31) led to elevated ratios of HMW/LMW-GS, which was critical for improved dough strength [21]. It was also found that nitrogen application at the booting stage (BBCH 41) significantly improved the structural and thermal properties of wheat gluten, notably in the glutenin subunits Dx2 and Dy12 [22]. Zhang et al. (2025) also found that HMW-GS decreased under high irrigation levels [23].

Above all, although numerous studies have investigated optimal tillage practices, sowing dates and rates, drip irrigation, irrigation frequency, and nitrogen application rates, few have focused on the combined effects of different cultivation practices [24,25,26,27,28]. There remains a critical knowledge gap regarding the integrated effects and potential interactions of combining different tillage practices with optimized water–fertilizer coupling strategies. Understanding these interactions is essential for developing synergistic cultivation systems that can simultaneously optimize multiple quality traits, rather than addressing them piecemeal. Therefore, unlike previous studies that often examined factors in isolation, our research specifically investigates the effects of the combined application of different tillage practices with synchronized water and fertilizer management on the development of wheat quality traits. The objectives were to (i) investigate the effects of tillage practices, sowing date/rate, and water–fertilizer coupling on wheat quality; (ii) identify the optimal cultivation practice for strong-gluten wheat in the study area; and (iii) analyze the mechanisms of appropriate cultivation methods influencing wheat quality.

2. Materials and Methods

2.1. Experimental Materials and Site Description

Using the high-quality winter wheat cultivar Jimai 44 as planting material, field experiments were conducted across multiple locations in Shandong province from 2019 to 2022.

The experiment was conducted in three locations within Shandong province: Pingdu (P), Qingdao City (Shandong province, China; 36.58° N, 120.11° E); Jiaozhou (J), Modern Agricultural Science and Technology Demonstration Park (Shandong province, China; 35.53° N, 119.58° E) of Qingdao Agricultural University; and Weifang (W), Changyi (Shandong province, China; 36.91° N, 119.46° E). Monthly rainfall during the 2019–2022 period is shown in Figure 1.

2.2. Experimental Materials and Design

The field experiments were conducted from 2019 to 2022 in three regions: Pingdu District, Jiaozhou District of Qingdao City, and Changyi County of Weifang City, Shandong province. The wheat variety Jimai44, which was released by Yinyou Cao (Crop Research Institute, Shandong Academy of Agricultural Sciences) in 2018, was used as the planting material. Jimai 44 is a semi-winter wheat cultivar with a growth cycle of 233 days. It exhibits a plant height of 89.7 cm and a relatively compact plant architecture, demonstrating good lodging resistance. The panicle number per mu reaches 429,000, with 31.6 grains per panicle and a 1000-grain weight of 44.3 g.

The purpose of this study is to uncover the optimal cultivation practice for strong-gluten wheat. Firstly, we analyzed the effects of tillage practices, sowing date/rate, and water–fertilizer coupling on the quality of strong-gluten wheat cultivar Jimai 44. Based on the results, we identified the optimization measures. The global workflow is shown in Figure 2.

From 2019 to 2021, the small plot experiments were conducted by strip sowing with a row spacing of 25 cm (according to the standard for China). Each site had 54 plots, each plot covering an area of about 13.34 m². Three single-factor experiments were set up, tillage method (

Table 1. Experimental design of tillage treatment.

Treatment	Cultivation	Sowing Date	Broadcasting Volume (P, J)	Broadcast Volume (W)
T1	Plowing	15 October	225 grains per m2	270 grains per m2
T2	Plowing	23 October	270 grains per m2	315 grains per m2
T3	Plowing	30 October	315 grains per m2	360 grains per m2
T4	Rototilling	15 October	225 grains per m2	270 grains per m2
T5	Rototilling	23 October	270 grains per m2	315 grains per m2
T6	Rototilling	30 October	315 grains per m2	360 grains per m2

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site.

), fertilizer (

Table 2. Experimental design of base fertilizer treatment.

	Application Amount of Base Fertilizer
	Nitrogenous Fertilizer (kg/ha)	Organic Fertilizer (kg/ha)	Potassium Dihydrogen Phosphate (kg/ha)	Potassium Chloride (kg/ha)
N0	0	1200	150	29.14
N150	150	1200	150	29.14
N300	300	1200	150	29.14

and

Table 3. Experimental design of topdressing treatment.

Treatment	Topdressing Amount	Total Amount of Topdressing	Top Dressing Method
Z1	225 kg N/ha/time	225 kg N/ha	Furrow Application (BBCH 25)
Z2	112.5 kg N/ha/time	225 kg N/ha	Furrow (BBCH 25) + Furrow (BBCH 31)
Z3	75 kg N/ha/time	225 kg N/ha	Furrow (BBCH 25) + Furrow (BBCH 31) + Broadcast (BBCH 51–54)

), and irrigation (

Table 4. Experimental design of irrigation frequency treatment.

Treatment	Amount of Watering	Total Amount of Watering	Watering Method
WT1	1050 m3/ha/time	1050 m3/ha	Flood Irrigation (BBCH 25)
WT2	525 m3/ha/time	1050 m3/ha	Flood Irrigation (BBCH 25 and at BBCH 31)
WT3	350 m3/ha/time	1050 m3/ha	Flood Irrigation (BBCH 25, BBCH 31 and BBCH 51–54)

and

Table 5. Design of irrigation volume treatment experiment.

Treatment	Amount of Watering	Watering Method
WA1	300 m3/ha/time	Flood Irrigation (BBCH 25 and at BBCH 31)
WA2	450 m3/ha/time	Flood Irrigation (BBCH 25 and at BBCH 31)
WA3	600 m3/ha/time	Flood Irrigation (BBCH 25 and at BBCH 31)

), each with six treatment levels and three repetitions. Other field management measures followed local conventional wheat practices. Urea (pH: 7.0–7.5, total N:46%) was applied as basal fertilizer one or two days before sowing. River water was used for irrigation water. The irrigation frequency was divided into three treatments: WT1, irrigation only at the regreening stage (BBCH 25); WT2, irrigation at both the regreening (BBCH 25) and jointing stages (BBCH 31); and WT3, irrigation at the regreening (BBCH 25), jointing (BBCH 31), and heading stages (BBCH 51–54). Three irrigation levels were established as experimental treatments, WA1, 300 m³/ha per application; WA2, 450 m³/ha per application; and WA3, 600 m³/ha per application, applied during both the regreening (BBCH 25) and jointing stages (BBCH 31).

Based on the results of the 2019–2021 small-plot experiments, optimized control trials were conducted with a 667 m² area in two cities in Shandong during 2020–2021 and with a 6670 m² area during 2021–2022. The optimized cultivation practice (Opt) and traditional cultivation practices (TC) are shown in the table below (

Table 6. Design of regional optimized controlled trials.

Treatment	Cultivation Measures	Water and Fertilizer Coupling
		Base Fertilizer Ratio	Top Dressing Period (Time)	Irrigation Treatment
Opt	Plowing, late sowing, 3.15–3.6 million seedlings/ha	Base fertilizer (nitrogen) 300 kg/ha	Topdressing at wheat regreening (BBCH 25) and jointing stages (BBCH 31)	Irrigation at regreening, jointing, and heading stages, 450 m3/ha each time (J and P); 600 m3/ha each time (W)
TC	Rototilling, appropriate sowing, 2.25–2.7 million seedlings/ha	Base fertilizer (nitrogen) 120 kg/ha	Topdressing at regreening (BBCH 25), jointing (BBCH 31), and heading stages (BBCH 51–54),	Each irrigation 300 m3/ha according to conventional farmer schedules

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site.

).

2.3. Measurement Items and Methods

2.3.1. Wheat Dry Matter Accumulation

Samples of wheat were taken at the flowering stage (BBCH 65), measuring half a meter of double rows. The samples were divided into leaves, stems, and spikes and dried at 105 °C for 30 min and then at 75 °C to constant weight, with each part weighed separately.

2.3.2. Wheat Leaf SPAD Value and Photosynthetic Parameters

Before and after the flowering stage (BBCH 60–69) (0, 7, 14, 21, and 28 days), SPAD values were measured using an SPD 502 chlorophyll analyzer (Konica Minolta, 1-6-1, Marunouchi, Chiyoda-ku, Tokyo, Japan) in sunny weather from 9 to 11 a.m. Photosynthetic parameters were measured using a Li-6400 photosynthesis system (LI-COR, Lincoln, NE, USA).

2.3.3. Wheat Yield and Yield Components

During the maturity stage (BBCH 89), the number of spikes, grains per spike, and thousand-grain weight were investigated using a one-meter double row. Actual yield was measured with a grain moisture content of 13.0%.

2.3.4. Wheat Grain Protein and Total Nitrogen Content

0.5 g of ground flour samples were digested with sulfuric acid and a mixture of potassium sulfate and copper sulfate. Total nitrogen and crude protein contents were measured using a Kjeldahl apparatus (AOAC Official Method 991.20) (each gram of nitrogen is equivalent to 6.25 g of protein, enabling the conversion of nitrogen content to protein content). The Kjeldahl apparatus was manufactured in Haineng, China, K1160 (Haineng Future Technology Group Co., Ltd., High-tech District, Jinan, China).

2.3.5. Wheat Flour Quality and Stretching Parameters

According to GB/T 14615-2019 [29], using a YUCEBAS flour-stretching machine manufactured in Turkey, INTEGRATED FLOUR DOUGH TESTING SET-Y01 (Tenovo International Co., Beijing, Limited, Daxing District, Beijing, China), stretching indices were measure. Dough was divided and stretched, with each treatment repeated three times.

2.3.6. Wheat SDS Sedimentation Value

A total of 5 g of flour was mixed with Bromophenol Blue solution and lactic acid–SDS solution. The sedimentation volume was read after shaking and resting (Sedimentation value (mL) = Measured value × (100 − 14)/(100 − Sample moisture %).

2.3.7. Wheat Flour Yield, Gluten Content, and Gluten Index

Wheat grains were ground, and flour yield was calculated. Gluten content and index were measured using GLUTEN WASHING DEVICE-Y07 (YUCEBAS Co., Izmir, Turkey) and GLUTEN INDEX DEVICE-Y08 (YUCEBAS Co, Izmir, Turkey), which were manufactured by YUCEBAS, Izmir, Turkey.

2.3.8. Near-Infrared Spectroscopy for Wheat Quality

(1)

Establishment of NIR Quality Detection Model

Spectra were collected using a FT-NIR quality analyzer (ThermoFisher Scienticfic Inc., Waltham, MA, USA). A PLS model was established using full spectral data.

(2)

Sample Detection

Samples were scanned using a NIR spectrometer (ThermoFisher Scienticfic Inc., Waltham, MA, USA), with each sample scanned three times for average spectral values.

2.3.9. Bread Making and Scoring Standards

Bread was made and scored according to GB/T 14611-2008 [30]. Volume, appearance, color, texture, and structure were evaluated, with scores summed for a total score (

Table 7. Scoring items and score allocation for bread.

Project	Scoring Criteria
Bread Volume (45 points)	<360 mL: 0 points
	>900 mL: 45 points
	Increase 1 point per 12 mL between 360 and 900 mL
Bread Appearance (5 points)	Normal color, smooth: 5 points
	Intermediate crown: 4 points
	Small crown: 3 points
	Indistinct crown, no neck: 2 points.
	Indistinct crown, no neck, collapsed: 1 point
	Abnormally colored crust, not smooth, or speckled: 0.5 points
Bread Color (5 points)	White with luster: 5 points
	White without luster: 4.5 points
	Dark gray: 1 point
	The coloration decreases from white–yellow–gray–black, with scores decreasing sequentially
Bread Texture (10 points)	Fine and elastic: 10 points;
	Coarse and inelastic: 2 points
	Between 3 and 9 points
Bread Structure (35 points)	Fine pores: 35 points
	Large, uneven pores: 8 points
	Between 9 and 34 points
Total Score (100 points)	Sum of all criteria

).

2.4. Total RNA Extraction and Expression Analysis of High-Molecular-Weight Glutenin Subunit Genes

Total RNA extraction and first-strand cDNA synthesis were carried out according to Zheng et al. [31]. The expression of high-molecular-weight glutenin subunit genes was performed by real-time PCR (qRT-PCR) using QuantStudio3 (Oppliedbiosystems Thermo, Waltham, MA, USA). The SYBR Green system (Roche, Basel, Switzerland) was used for qRT-PCR analysis. The primers used in the qRT-PCR are listed in Table S1, and the β-actin gene was used as internal control.

2.5. Statistical Analysis

The data was collected by Excel, and the SPSS 22.0 was used to perform ANOVA, multi-factor analysis of variance. Duncan’s test (p < 0.05) was used to determine the significance. The significant differences are indicated in the Figure or Table legends.

3. Results

3.1. Effects of Different Cultivation Practices on Wheat Quality Formation in Plot Experiments from 2019 to 2021

3.1.1. Effects of Tillage Practices and Sowing Date/Rate on Milling Quality Formation of Wheat in Plot Experiments from 2019 to 2021

Over two years, the Year*Location*Treatment (interaction among year, location, and treatment) had a significant impact on thousand-kernel weight and bulk density. Furthermore, both location and treatment, as individual factors, influenced all three parameters of wheat milling quality (

Table 8. The effect of tillage practices on the milling quality of wheat.

Growing Season	Treatment	Thousand-Kernel Weight (g)	Bulk Density (kg/hL)	Flour Yield (%)
2019–2020	P-T1	41.88 ± 2.64 b	77.74 ± 6.02 a	79.45 ± 4.77 a
	P-T2	43.68 ± 2.14 a	77.91 ± 4.48 a	78.14 ± 3.32 ab
	P-T3	43.25 ± 2.23 b	77.91 ± 4.64 a	80.04 ± 4.14 a
	P-T4	39.59 ± 2.51 bc	77.67 ± 7.01 a	71.34 ± 3.18 b
	P-T5	41.12 ± 3.52 b	77.76 ± 5.24 a	76.13 ± 5.16 ab
	P-T6	39.28 ± 2.74 c	77.83 ± 7.53 a	72.54 ± 3.16 b
	J-T1	52.31 ± 1.82 ab	77.64 ± 5.52 a	75.14 ± 4.91 bc
	J-T2	50.61 ± 1.78 bc	77.80 ± 5.23 a	77.56 ± 3.42 a
	J-T3	53.94 ± 3.18 a	77.96 ± 5.27 a	79.17 ± 2.67 a
	J-T4	50.58 ± 1.10 abc	77.69 ± 4.27 a	72.36 ± 1.41 c
	J-T5	50.52 ± 2.27 c	77.64 ± 5.56 a	78.01 ± 2.96 ab
	J-T6	49.02 ± 2.96 c	77.89 ± 4.73 a	74.35 ± 2.19 c
	W-T1	44.21 ± 3.69 b	79.43 ± 5.12 a	69.34 ± 5.02 a
	W-T2	46.27 ± 3.27 b	79.48 ± 5.68 a	73.01 ± 3.79 a
	W-T3	49.58 ± 2.21 a	79.76 ± 5.55 a	73.73 ± 2.79 a
	W-T4	39.59 ± 2.09 c	78.93 ± 6.51 a	68.01 ± 4.44 a
	W-T5	45.70 ± 2.40 b	79.81 ± 7.36 a	71.79 ± 3.11 a
	W-T6	44.14 ± 1.81 b	79.60 ± 6.84 a	64.12 ± 1.54 b
2020–2021	P-T1	42.55 ± 3.04 bc	77.58 ± 6.00 ab	75.05 ± 2.02 b
	P-T2	42.71 ± 2.58 b	77.87 ± 8.50 ab	74.82 ± 3.79 ab
	P-T3	45.03 ± 2.36 a	78.05 ± 6.16 a	78.26 ± 2.79 a
	P-T4	41.25 ± 1.45 c	77.35 ± 6.26 b	67.05 ± 2.54 c
	P-T5	40.16 ± 1.03 d	77.56 ± 7.40 a	68.48 ± 3.51 cd
	P-T6	39.17 ± 1.47 d	77.64 ± 5.50 a	66.15 ± 1.37 d
	J-T1	51.27 ± 1.66 a	77.67 ± 5.68 a	68.03 ± 2.88 ab
	J-T2	50.83 ± 1.98 a	77.71 ± 6.65 a	68.85 ± 1.50 ab
	J-T3	52.85 ± 1.04 a	77.87 ± 4.92 a	70.41 ± 4.47 a
	J-T4	50.14 ± 2.06 a	77.46 ± 7.42 a	64.06 ± 3.11 c
	J-T5	50.05 ± 1.96 a	77.42 ± 4.18 a	67.91 ± 2.00 bc
	J-T6	48.32 ± 2.65 a	77.53 ± 5.52 a	68.15 ± 1.72 ab
	W-T1	42.27 ± 1.80 c	78.25 ± 5.00 a	65.91 ± 4.24 b
	W-T2	45.13 ± 2.31 b	78.32 ± 4.97 a	68.07 ± 2.62 ab
	W-T3	47.37 ± 1.74 a	78.37 ± 5.27 a	71.90 ± 2.60 a
	W-T4	38.35 ± 3.23 d	76.82 ± 5.50 a	64.51 ± 2.30 ab
	W-T5	45.37 ± 2.51 a	78.28 ± 6.22 a	67.38 ± 2.58 b
	W-T6	42.28 ± 3.52 c	78.27 ± 4.02 a	65.03 ± 2.60 ab
2019–2021	Year	ns	**	**
	Location	**	*	*
	Treatment	**	**	**
	Year*Location	**	**	ns
	Year*Treatment	**	**	*
	Location*Treatment	**	**	*
	Year*Location*Treatment	**	**	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

). During the 2019–2020 growing season, no significant differences were observed in the thousand-kernel weight (TKW), flour yield, or bulk density of wheat grains under T3 treatment at P (Pingdu). At the J (Jiaozhou) experimental site, the flour yield under the T3 treatment was significantly higher than that under T1, T4, and T6 treatments, reaching 79%, while no significant differences were found in thousand-kernel weight or bulk density. At W, the TKW under T3 treatment was significantly higher than that under other treatments, reaching 49.58 g, but there was no further increase in response to yield or bulk density (Table 8).

In the 2020–2021 growing season, the T3 treatment significantly increased the TKW to 45.03 g, while the flour yield also increased significantly to 78.26%, outperforming T1, T4, T5, and T6 at P. But at J, the T3 treatment resulted in no significant differences across any measured parameters. At W, the flour yield under the T3 and T5 treatments was significantly higher than that under T1, T2, T4, and T6 treatments, though no notable differences were observed in TKW or bulk density (Table 8). All these results demonstrated that the combination of tillage, suitably delayed sowing date, and increased seeding rate could improve wheat milling quality through higher TKW and flour yield.

3.1.2. Effects of Tillage Practices and Sowing Date/Rate on the Formation of Wheat Nutritional Quality in Plot Experiments from 2019 to 2021

Protein content was significantly affected by the main effects of year, location, and treatment, as well as by their Location*Treatment interaction. Similarly, both treatment and the Location*Treatment interaction had a significant effect on nitrogen content (

Table 9. The effect of tillage practices on the nutritional quality of wheat.

Growing Season	Treatment	Protein Content (%)	N Content (%)
2019–2020	P-T1	14.96 ± 0.36 a	2.48 ± 0.12 b
	P-T2	14.48 ± 0.37 ab	2.49 ± 0.15 ab
	P-T4	14.43 ± 0.28 ab	2.17 ± 0.07 c
	P-T5	14.39 ± 0.36 b	2.26 ± 0.09 c
	P-T6	14.07 ± 0.35 b	2.21 ± 0.08 c
	J-T1	16.22 ± 0.20 a	2.02 ± 0.14 bc
	J-T2	16.67 ± 0.26 a	2.11 ± 0.13 bc
	J-T3	16.92 ± 0.30 a	2.26 ± 0.14 a
	J-T4	16.66 ± 0.23 a	1.98 ± 0.1 c
	J-T5	16.25 ± 0.33 a	2.06 ± 0.12 b
	J-T6	16.13 ± 0.37 a	1.97 ± 0.16 c
	W-T1	14.47 ± 0.21 b	2.03 ± 0.1 c
	W-T2	15.37 ± 0.22 a	2.05 ± 0.17 bc
	W-T3	15.54 ± 0.32 a	2.39 ± 0.12 a
	W-T4	15.44 ± 0.24 a	2.06 ± 0.11 c
	W-T5	15.54 ± 0.28 a	2.37 ± 0.12 ab
	W-T6	15.27 ± 0.32 a	2.27 ± 0.07 bc
2020–2021	P-T1	13.56 ± 0.23 ab	2.13 ± 0.12 b
	P-T2	14.24 ± 0.28 a	1.95 ± 0.07 bc
	P-T3	14.34 ± 0.36 a	2.34 ± 0.14 a
	P-T4	13.76 ± 0.35 ab	1.85 ± 0.14 c
	P-T5	13.74 ± 0.20 ab	1.9 ± 0.12 c
	P-T6	13.32 ± 0.26 b	1.88 ± 0.16 c
	J-T1	15.63 ± 0.30 a	2.13 ± 0.09 ab
	J-T2	13.22 ± 0.23 c	2.18 ± 0.12 b
	J-T3	15.81 ± 0.43 a	2.21 ± 0.12 a
	J-T4	15.32 ± 0.35 b	2.03 ± 0.07 c
	J-T5	14.85 ± 0.34 b	2.12 ± 0.15 bc
	J-T6	14.64 ± 0.64 b	2.04 ± 0.16 c
	W-T1	14.14 ± 0.27 a	2.05 ± 0.15 b
	W-T2	14.83 ± 0.50 a	2.02 ± 0.14 b
	W-T3	15.19 ± 0.52 a	2.24 ± 0.13 a
	W-T4	14.74 ± 0.36 a	2.17 ± 0.14 a
	W-T5	15.01 ± 0.50 a	2.2 ± 0.11 a
	W-T6	14.65 ± 0.32 a	2.25 ± 0.15 a
2019–2021	Year	**	ns
	Location	*	ns
	Treatment	**	**
	Year*Location	ns	ns
	Year*Treatment	ns	ns
	Location*Treatment	**	**
	Year*Location*Treatment	ns	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

). During the 2019–2020 growing season, the T3 treatment resulted in significantly higher grain total nitrogen content at P, J, and W, with values of 2.56%, 2.26%, and 2.39%, respectively, compared to the T1, T2, T4, T5, and T6 treatments. This trend continued in 2020–2021, where the T3 treatment at P maintained the highest nitrogen content (2.34%), differing significantly from all other treatments. At the J site, the T3 treatment also exhibited superior protein and total nitrogen content, showing significant advantages over T2, T4, T5, and T6 (Table 9). These findings demonstrated that the integrated T3 management practice effectively enhanced grain protein and total nitrogen accumulation, thereby improving the nutritional quality of wheat.

3.1.3. Effects of Tillage Practices and Sowing Date/Seeding Rate on the Formation of Wheat Processing and Edible Quality in Plot Experiments from 2019 to 2021

The processing quality of wheat was significantly influenced by the main effects of location and treatment, as well as by the Location*Treatment interaction over the two-year period (

Table 10. The effect of cultivation measures on the edible processing quality of wheat.

Growing Season	Treatment	Extensibility (%)	Stabilization Time (min)	Gluten Index (%)	SDS -Sedimentation (mL)
2019–2020	P-T1	155.57 ± 6.11 a	17.95 ± 0.36 c	96.01 a	47.12 ± 1.40 a
	P-T2	152.71 ± 8.07 a	17.78 ± 0.11 bc	96.02 a	47.73 ± 1.44 a
	P-T3	157.08 ± 5.33 a	17.96 ± 0.27 a	94.02 a	49.58 ± 0.75 a
	P-T4	146.33 ± 3.08 a	17.71 ± 0.15 c	90.02 a	47.49 ± 0.75 a
	P-T5	147.61 ± 6.22 a	17.69 ± 0.16 ab	93.01 a	47.03 ± 1.22 a
	P-T6	147.32 ± 6.56 a	17.64 ± 0.28 c	92.02 a	46.68 ± 1.01 a
	J-T1	173.58 ± 5.25 a	17.65 ± 0.17 a	84.04 ab	54.29 ± 1.18 a
	J-T2	173.78 ± 7.58 a	17.81 ± 0.17 a	82.01 b	54.81 ± 1.03 a
	J-T3	175.78 ± 8.55 a	18.2 ± 0.11 a	89.02 a	55.93 ± 0.9 a
	J-T4	175.83 ± 7.26 a	17.89 ± 0.20 a	88.01 b	53.69 ± 0.86 a
	J-T5	175.07 ± 4.48 a	18.18 ± 0.48 a	86.03 ab	53.29 ± 1.10 a
	J-T6	169.83 ± 5.06 a	18.01 ± 0.32 a	84.02 b	52.97 ± 2.25 a
	W-T1	172.18 ± 6.47 c	18.39 ± 0.23 a	93.02 ab	54.6 ± 1.35 d
	W-T2	186.13 ± 6.6 a	18.39 ± 0.47 a	95.01 b	56.87 ± 0.57 c
	W-T3	186.53 ± 5.69 ab	19.07 ± 0.26 a	95.02 ab	58.08 ± 1.03 ab
	W-T4	174.6 ± 8.41 bc	18.59 ± 0.35 a	93.01 b	54.27 ± 0.79 e
	W-T5	188.37 ± 8.44 a	18.75 ± 0.25 a	92.02 ab	58.32 ± 1.21 a
	W-T6	183.57 ± 7.17 abc	18.85 ± 0.38 a	96.02 a	57.78 ± 1.14 b
2020–2021	P-T1	154.65 ± 5.08 a	17.45 ± 0.27 a	92.02 b	46.46 ± 1.44 a
	P-T2	153.24 ± 6.22 a	16.98 ± 0.38 a	94.02 b	48.05 ± 1.26 a
	P-T3	156.72 ± 4.56 a	17.91 ± 0.17 a	94.01 a	48.75 ± 0.75 a
	P-T4	151.54 ± 5.25 a	17.41 ± 0.20 a	90.02 b	47.14 ± 1.04 a
	P-T5	152.19 ± 7.58 a	17.37 ± 0.32 a	89.02 b	45.86 ± 1.38 a
	P-T6	152.37 ± 8.55 a	17.39 ± 0.33 a	91.03 b	45.16 ± 1.23 a
	J-T1	171.35 ± 7.26 a	16.97 ± 0.22 b	78.02 e	53.85 ± 0.80 ab
	J-T2	172.42 ± 6.45 a	17.55 ± 0.33 a	81.04 d	54.2 ± 1.25 ab
	J-T3	173.47 ± 4.45 a	17.96 ± 0.19 ab	88.02 a	54.69 ± 1.35 a
	J-T4	172.45 ± 7.48 a	17.48 ± 0.26 ab	88.01 a	52.46 ± 1.03 a
	J-T5	172.5 ± 6.02 a	17.82 ± 0.35 ab	85.06 b	51.94 ± 0.75 bc
	J-T6	171.28 ± 7.95 a	17.72 ± 0.33 ab	83.02 c	50.56 ± 1.12 c
	W-T1	169.76 ± 8.01 c	17.85 ± 0.35 a	92.01 a	52.15 ± 1.05 e
	W-T2	177.74 ± 5.25 b	17.72 ± 0.25 a	94.02 a	55.26 ± 1.09 b
	W-T3	186.25 ± 6.13 a	18.25 ± 0.35 a	95.05 a	57.05 ± 1.78 a
	W-T4	168.63 ± 7.32 c	17.62 ± 0.23 a	93.04 a	52.61 ± 1.01 d
	W-T5	182.24 ± 8.6 b	17.71 ± 0.20 a	91.01 a	54.85 ± 0.64 b
	W-T6	178.37 ± 8.94 b	17.92 ± 0.29 a	95.03 a	54.28 ± 0.83 c
2019–2021	Year	**	**	ns	**
	Location	**	**	**	**
	Treatment	**	**	**	**
	Year*Location	*	*	ns	ns
	Year*Treatment	ns	ns	ns	ns
	Location*Treatment	**	**	**	**
	Year*Location*Treatment	ns	ns	ns	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

). During the 2019–2020 season, the T3 treatment significantly improved dough stability time to 17.96 min at the P site compared to T1, T2, T4, and T6. However, no significant differences were observed among the treatments for dough extensibility, gluten index, or SDS sedimentation value at this location. In contrast, at the J site, none of these quality parameters exhibited significant differences. At the W site, the T5 treatment resulted in a relatively high SDS sedimentation value (58.32 mL), which was not statistically different from the value under T3 (Table 10).

During the 2020–2021 season, the T3 treatment significantly enhanced key quality parameters, though the effects were region-specific. At P and J, the gluten index under T3 was significantly higher (0.94 and 0.88, respectively) than in other treatments. In W, T3 resulted in significantly greater dough extensibility (186.25%) and SDS sedimentation value (57.05 mL) compared to other treatments (Table 10). These comprehensive results demonstrated that tillage practices, particularly the integrated T3 approach (plowing, delayed sowing, and increased seeding rate), significantly influenced wheat processing and end-use quality. The consistent improvement in stability time, extensibility, gluten index, and SDS sedimentation value confirms that this management strategy was effective for enhancing dough functionality and overall wheat quality.

3.1.4. Effect of Water–Fertilizer Coupling on the Formation of Wheat Milling Quality in Plot Experiments from 2019 to 2021

The quality of wheat milling was significantly influenced by the location, treatment, as well as by the Year*Treatment and Location*Treatment interactions. Furthermore, bulk density was affected not only by the treatment but also by the year, location, and their interactions (

Table 11. The effect of water–fertilizer coupling on the quality of wheat milling.

Growing Season	Treatment	Thousand-Kernel Weight (g)	Bulk Density (kg/hL)	Flour Yield (%)
2019–2020	P-N0	41.59 ± 2.03 a	77.61 ± 7.53 a	70.20 ± 2.77 c
	P-N150	40.42 ± 3.04 a	77.78 ± 5.86 a	76.34 ± 3.33 b
	P-N300	41.61 ± 3.58 a	77.73 ± 4.18 a	82.01 ± 4.41 a
	J-N0	50.04 ± 1.47 b	77.66 ± 8.50 a	75.74 ± 4.34 b
	J-N150	51.52 ± 2.66 a	77.73 ± 6.16 a	76.01 ± 3.29 ab
	J-N300	51.59 ± 2.98 a	77.81 ± 4.73 a	78.31 ± 2.79 a
	W-N0	40.92 ± 1.53 b	79.09 ± 5.65 a	71.06 ± 4.74 a
	W-N150	41.71 ± 3.05 a	79.06 ± 6.42 a	72.73 ± 3.07 a
	W-N300	42.08 ± 1.93 a	79.25 ± 6.04 a	72.31 ± 2.62 a
	P-Z1	38.06 ± 2.36 b	77.72 ± 4.82 a	77.03 ± 4.14 a
	P-Z2	39.04 ± 1.95 ab	77.79 ± 5.00 a	77.75 ± 2.67 a
	P-Z3	39.70 ± 3.03 a	77.80 ± 6.01 a	73.71 ± 2.41 a
	J-Z1	49.47 ± 2.34 a	77.80 ± 5.55 a	76.74 ± 2.37 a
	J-Z2	49.96 ± 3.06 a	77.97 ± 3.5 a	75.34 ± 2.88 a
	J-Z3	50.00 ± 3.36 b	77.73 ± 5.68 a	74.05 ± 2.50 b
	W-Z1	42.45 ± 3.20 a	79.17 ± 6.13 a	63.64 ± 2.30 a
	W-Z2	42.19 ± 1.76 a	79.44 ± 4.63 a	65.13 ± 4.17 a
	W-Z3	39.74 ± 2.18 b	79.39 ± 4.24 a	66.54 ± 2.17 a
	P-WT1	39.41 ± 1.77 c	77.85 ± 5.56 a	77.95 ± 2.62 b
	P-WT2	39.65 ± 3.50 b	77.79 ± 4.73 a	79.01 ± 2.28 a
	P-WT3	40.52 ± 2.67 a	78.04 ± 6.22 a	76.00 ± 4.14 b
	J-WT1	50.84 ± 2.77 ab	77.69 ± 3.42 a	75.32 ± 2.67 a
	J-WT2	49.24 ± 1.18 b	77.77 ± 5.88 a	77.47 ± 2.65 a
	J-WT3	52.16 ± 2.64 a	77.80 ± 4.97 a	76.63 ± 4.34 a
	W-WT1	41.35 ± 1.80 a	79.37 ± 4.24 a	68.94 ± 3.79 b
	W-WT2	42.22 ± 2.31 a	79.38 ± 7.53 a	73.71 ± 3.51 a
	W-WT3	41.46 ± 1.74 a	78.72 ± 5.52 a	74.85 ± 5.37 a
	P-WA1	45.94 ± 2.27 a	78.07 ± 7.40 a	77.01 ± 3.18 a
	P-WA2	45.62 ± 3.39 a	78.11 ± 5.55 a	78.74 ± 2.46 a
	P-WA3	42.07 ± 1.89 b	78.03 ± 5.15 a	71.74 ± 5.42 a
	J-WA1	50.76 ± 2.30 a	78.06 ± 4.61 a	72.91 ± 2.46 b
	J-WA2	52.80 ± 2.73 a	77.74 ± 5.48 a	75.05 ± 3.29 a
	J-WA3	52.35 ± 2.65 a	77.65 ± 4.64 a	75.81 ± 2.02 a
	W-WA1	42.29 ± 2.23 a	79.31 ± 5.27 a	72.17 ± 2.88 a
	W-WA2	41.64 ± 2.14 a	79.62 ± 4.82 a	69.26 ± 3.50 b
	W-WA3	44.50 ± 1.76 a	79.77 ± 4.27 a	70.05 ± 3.11 b
2020–2021	P-N0	40.86 ± 2.66 a	77.54 ± 6.26 a	65.51 ± 2.18 c
	P-N150	39.75 ± 3.19 a	77.61 ± 7.04 a	73.34 ± 3.33 b
	P-N300	41.16 ± 3.27 a	77.74 ± 5.68 a	77.85 ± 2.62 a
	J-N0	49.51 ± 2.36 a	77.53 ± 5.52 a	69.34 ± 3.62 a
	J-N150	50.15 ± 1.45 a	77.62 ± 6.34 a	68.06 ± 3.16 ab
	J-N300	51.25 ± 2.73 a	77.84 ± 7.00 a	71.01 ± 4.91 b
	W-N0	40.15 ± 2.04 a	78.75 ± 9.40 a	66.611 ± 2.41 c
	W-N150	40.85 ± 2.06 a	78.85 ± 6.22 a	69.86 ± 4.34 b
	W-N300	41.36 ± 1.90 a	79.08 ± 7.02 a	71.12 ± 2.96 a
	P-Z1	37.74 ± 2.21 a	77.62 ± 6.10 a	73.02 ± 3.54 a
	P-Z2	39.74 ± 2.09 a	77.74 ± 5.18 a	75.43 ± 2.75 a
	P-Z3	38.63 ± 2.40 a	77.53 ± 4.64 a	72.93 ± 3.74 a
	J-Z1	48.15 ± 1.47 a	77.55 ± 4.90 a	70.75 ± 4.14 a
	J-Z2	48.63 ± 2.66 a	77.85 ± 4.36 a	69.05 ± 4.42 ab
	J-Z3	49.59 ± 2.18 a	77.54 ± 7.99 a	68.71 ± 2.67 b
	W-Z1	41.38 ± 2.67 a	78.94 ± 6.51 ab	65.16 ± 2.19 a
	W-Z2	41.67 ± 2.27 a	79.35 ± 4.24 a	63.16 ± 3.51 a
	W-Z3	38.61 ± 3.39 b	79.14 ± 5.56 a	61.48 ± 3.11 a
	P-WT1	38.15 ± 2.77 a	77.72 ± 4.73 a	73.36 ± 4.17 a
	P-WT2	39.37 ± 3.50 a	77.74 ± 4.12 a	74.72 ± 2.79 a
	P-WT3	38.26 ± 2.67 a	77.94 ± 6.26 a	78.91 ± 3.38 a
	J-WT1	49.75 ± 2.77 b	77.55 ± 6.02 a	69.18 ± 2.79 b
	J-WT2	48.63 ± 1.18 b	77.53 ± 4.53 a	71.73 ± 2.54 ab
	J-WT3	51.36 ± 3.18 a	77.63 ± 4.24 a	73.10 ± 2.46 a
	W-WT1	40.15 ± 3.69 b	79.07 ± 5.98 a	69.53 ± 2.67 a
	W-WT2	41.36 ± 3.27 a	79.14 ± 6.22 a	71.73 ± 4.28 a
	W-WT3	40.83 ± 2.21 ab	78.27 ± 5.50 a	72.03 ± 3.28 a
	P-WA1	44.27 ± 2.27 b	77.83 ± 6.42 a	71.13 ± 2.51 a
	P-WA2	45.04 ± 3.39 a	78.02 ± 7.36 a	77.05 ± 3.02 a
	P-WA3	41.26 ± 1.89 c	77.95 ± 6.51 a	72.34 ± 3.79 a
	J-WA1	50.26 ± 2.10 a	77.52 ± 7.53 a	68.62 ± 2.94 a
	J-WA2	51.3 ± 3.27 a	77.73 ± 5.52 a	72.01 ± 4.14 a
	J-WA3	50.83 ± 2.99 a	77.53 ± 5.86 a	70.63 ± 3.42 a
	W-WA1	41.37 ± 2.20 a	79.05 ± 4.61 a	69.10 ± 2.77 a
	W-WA2	40.13 ± 1.16 a	79.35 ± 7.01 a	67.73 ± 3.62 a
	W-WA3	43.87 ± 1.68 a	79.57 ± 4.27 a	69.61 ± 4.17 a
2019–2021	Year	ns	**	**
	Location	**	*	*
	Treatment	**	**	**
	Year*Location	**	**	ns
	Year*Treatment	**	**	*
	Location*Treatment	**	**	*
	Year*Location*Treatment	**	**	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

). The effects of basal fertilizer and irrigation treatments on wheat quality parameters during the 2019–2020 season are summarized in Table 11. Regarding fertilizer application, the N300 treatment significantly increased the flour yield rate to 82.01% at P compared to N0 and N150, an effect not observed at other sites. For tillage-sowing treatments, WT3 significantly increased the thousand-kernel weight (TKW) at both P (40.52 g) and J (52.16 g) compared to other treatments. At P, WT2 resulted in a higher flour yield (79.01%) than WT1 and WT3. No significant differences in these parameters were found among treatments at W. Concerning irrigation, significant effects were only observed at W, where the WA1 treatment achieved a significantly higher flour yield (72.17%) than the other two treatments.

During the 2020–2021 season, the effects of management practices were region-dependent (Table 11). For basal fertilizer, the N300 treatment universally enhanced the flour yield rate, achieving significantly higher values of 77.85% in P, 71.01% in J, and 71.12% in W compared to other treatments. Regarding tillage-sowing regimes, the WT3 treatment significantly increased the thousand-kernel weight (TKW) to 51.36 g in J, while the WT2 treatment was most effective in W, yielding a TKW of 41.36 g. For irrigation, a significant effect was exclusive to P, where the WA2 treatment resulted in a higher TKW (45.04 g) than other treatments.

Over the 2019–2021 growing seasons across the three regions, different topdressing nitrogen frequencies exhibited no consistent significant effect on wheat milling quality parameters, including thousand-kernel weight (TKW), bulk density, and flour yield. Grain bulk density remained stable across all water–fertilizer coupling treatments. Our comprehensive results demonstrated that wheat milling quality was influenced by the management of basal fertilizer ratio, topdressing timing, and irrigation scheduling. An optimal nitrogen management strategy—involving a higher proportion of nitrogen applied as basal fertilizer, supplemented with a single topdressing at both the green-up and jointing stages (BBCH 31) and coupled with regionally adapted irrigation practices—proved effective for simultaneously enhancing key grain traits such as TKW and flour yield within an appropriate total nitrogen application rate.

3.1.5. Effects of Water–Fertilizer Coupling on the Formation of Wheat Nutritional Quality in Plot Experiments from 2019 to 2021

Throughout the two-year period, both treatment and the Location × Treatment interaction exerted significant effects on protein and nitrogen content (

Table 12. The effect of water–fertilizer coupling on the nutritional quality of wheat.

Growing Season	Treatment	Protein Content (%)	N Content (%)
2019–2020	P-N0	14.09 ± 0.23 c	2.02 ± 0.16 c
	P-N150	15.09 ± 0.69 b	2.11 ± 0.14 b
	P-N300	15.97 ± 0.38 a	2.46 ± 0.11 a
	J-N0	16.09 ± 0.28 b	2.46 ± 0.16 a
	J-N150	16.40 ± 0.10 b	2.57 ± 0.14 a
	J-N300	16.93 ± 0.26 a	2.76 ± 0.12 a
	W-N0	14.09 ± 0.53 c	1.85 ± 0.07 b
	W-N150	14.31 ± 0.45 b	1.89 ± 0.12 b
	W-N300	14.58 ± 0.21 a	2.31 ± 0.15 a
	P-Z1	14.26 ± 0.25 b	2.11 ± 0.14 a
	P-Z2	14.68 ± 0.36 a	2.23 ± 0.13 a
	P-Z3	14.55 ± 0.27 a	2.18 ± 0.12 a
	J-Z1	14.46 ± 0.42 b	2.11 ± 0.12 b
	J-Z2	15.13 ± 0.28 a	2.18 ± 0.08 a
	J-Z3	14.98 ± 0.53 a	2.14 ± 0.12 b
	W-Z1	14.35 ± 0.32 c	1.86 ± 0.15 b
	W-Z2	15.46 ± 0.40 a	2.07 ± 0.13 a
	W-Z3	14.72 ± 0.19 b	1.97 ± 0.12 a
	P-WT1	14.01 ± 0.42 c	2.00 ± 0.10 ab
	P-WT2	14.17 ± 0.51 b	1.98 ± 0.12 b
	P-WT3	14.81 ± 0.30 a	2.06 ± 0.16 a
	J-WT1	16.42 ± 0.54 a	2.46 ± 0.11 a
	J-WT2	15.65 ± 0.64 a	2.57 ± 0.12 a
	J-WT3	16.7 ± 0.67 a	2.76 ± 0.07 a
	W-WT1	14.17 ± 0.7 a	2.01 ± 0.11 a
	W-WT2	14.56 ± 0.37 a	1.99 ± 0.07 a
	W-WT3	14.28 ± 0.42 a	1.95 ± 0.14 a
	P-WA1	14.7 ± 0.36 a	2.14 ± 0.14 a
	P-WA2	15.38 ± 0.43 a	2.15 ± 0.09 a
	P-WA3	15.15 ± 0.3 a	2.13 ± 0.12 a
	J-WA1	15.11 ± 0.5 b	2.21 ± 0.15 a
	J-WA2	16.3 ± 0.82 a	2.18 ± 0.13 a
	J-WA3	16.13 ± 0.36 a	2.14 ± 0.06 a
	W-WA1	13.77 ± 0.21 b	2.07 ± 0.07 a
	W-WA2	13.75 ± 0.12 b	1.83 ± 0.12 b
	W-WA3	15.01 ± 0.47 a	2.13 ± 0.11 a
2020–2021	P-N0	13.84 ± 0.27 b	1.94 ± 0.12 c
	P-N150	14.32 ± 0.38 b	2.07 ± 0.15 b
	P-N300	14.89 ± 0.70 a	2.43 ± 0.08 a
	J-N0	15.32 ± 0.53 c	2.36 ± 0.10 b
	J-N150	15.67 ± 0.53 b	2.14 ± 0.14 b
	J-N300	16.05 ± 0.25 a	2.81 ± 0.11 a
	W-N0	12.57 ± 0.23 a	1.93 ± 0.09 c
	W-N150	13.57 ± 0.70 a	2.04 ± 0.12 b
	W-N300	13.85 ± 0.57 a	2.47 ± 0.12 a
	P-Z1	13.47 ± 0.26 ab	2.04 ± 0.06 c
	P-Z2	13.96 ± 0.42 a	2.19 ± 0.10 a
	P-Z3	13.52 ± 0.38 ab	2.08 ± 0.12 b
	J-Z1	13.36 ± 0.20 a	2.15 ± 0.12 a
	J-Z2	14.53 ± 0.26 a	2.21 ± 0.12 a
	J-Z3	13.78 ± 0.30 a	2.01 ± 0.16 a
	W-Z1	13.46 ± 0.72 b	1.83 ± 0.15 b
	W-Z2	14.54 ± 0.31 a	2.14 ± 0.08 a
	W-Z3	13.73 ± 0.12 ab	1.91 ± 0.16 ab
	P-WT1	13.87 ± 0.37 a	2.13 ± 0.14 a
	P-WT2	13.98 ± 0.72 a	2.05 ± 0.16 a
	P-WT3	14.31 ± 0.31 a	2.22 ± 0.10 a
	J-WT1	14.75 ± 0.36 a	2.03 ± 0.12 c
	J-WT2	14.13 ± 0.27 a	2.42 ± 0.15 b
	J-WT3	15.47 ± 0.48 a	2.89 ± 0.13 a
	W-WT1	13.62 ± 0.28 b	2.08 ± 0.07 c
	W-WT2	15.53 ± 0.36 a	2.31 ± 0.09 a
	W-WT3	13.82 ± 0.35 ab	2.15 ± 0.14 b
	P-WA1	13.76 ± 0.12 b	2.08 ± 0.12 a
	P-WA2	14.85 ± 0.57 a	2.23 ± 0.11 a
	P-WA3	14.63 ± 0.25 a	2.05 ± 0.07 a
	J-WA1	14.61 ± 0.10 b	2.32 ± 0.12 b
	J-WA2	15.85 ± 0.37 a	2.46 ± 0.13 a
	J-WA3	15.47 ± 0.23 a	2.07 ± 0.05 c
	W-WA1	13.05 ± 0.20 b	1.95 ± 0.12 b
	W-WA2	13.04 ± 0.26 b	2.04 ± 0.12 b
	W-WA3	14.37 ± 0.30 a	2.24 ± 0.12 a
2019–2021	Year	**	ns
	Location	*	ns
	Treatment	**	**
	Year*Location	ns	ns
	Year*Treatment	ns	ns
	Location*Treatment	**	**
	Year*Location*Treatment	ns	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

). The effects of agronomic practices on wheat protein and grain total nitrogen content during the 2019–2020 season are summarized in Table 12. Regarding basal fertilizer, the N300 treatment significantly increased protein content across all three regions (P: 15.97%; J: 16.93%; W: 14.58%) compared to N0 and N150. It also significantly enhanced grain total nitrogen content in P (2.46%) and W (2.31%), but not in J. For nitrogen topdressing frequency, the Z2 treatment was most effective, significantly increasing total nitrogen content in J (2.18%) and protein content in W (15.46%) compared to Z1 and Z3.

Regarding irrigation frequency, the WT3 treatment significantly increased protein content to 14.81% exclusively in P. For irrigation amount, a significant effect was only observed in W, where the WA3 treatment resulted in a higher protein content (15.01%).

During the 2020–2021 season, the management practices significantly influenced wheat protein and grain total nitrogen content, with effects varying by region (Table 12). Regarding the basal fertilizer, the N300 treatment significantly increased protein content in P (14.89%) and J (16.05%) and enhanced grain total nitrogen content across all three regions (P: 2.43%; J: 2.81%; W: 2.47%), compared to N0 and N150. Regarding irrigation frequency, the Z2 treatment was the optimal strategy in specific regions, significantly increasing grain total nitrogen content in P (13.96%) and improving both protein (14.54%) and total nitrogen content (2.14%) in W. For irrigation frequency, WT3 boosted total nitrogen in J (2.89%), while WT2 was best in W (2.31%). For irrigation amount, WA2 increased total nitrogen content in both P (14.85%) and J, whereas WA3 was most effective for both parameters in W.

In summary, a synergistic management strategy that applies additional nitrogen as basal fertilizer alongside balanced organic, phosphorus, and potassium amendments, followed by a single nitrogen topdressing at both the green-up and jointing stages (BBCH 31), significantly enhanced wheat grain protein and total nitrogen content. This could be further optimized by employing regionally adapted irrigation during these stages, supplemented by anthesis irrigation at 450–600 m³/ha, collectively improving the nutritional quality of wheat.

3.1.6. Effect of Water–Fertilizer Coupling on the Formation of Wheat Processing and Edible Quality in Plot Experiments from 2019 to 2021

Analysis over the two years revealed a significant main effect of location and treatment, as well as Location*Treatment interaction, on the end-use quality of wheat (

Table 13. The effect of water–fertilizer coupling on the edible processing quality of wheat.

Growing Season	Treatment	Ductility (%)	Stabilization Time (min)	Gluten Index (%)	SDS Sedimentation (mL)
2019–2020	P-N0	144.27 ± 7.13 b	17.49 ± 0.20 a	90.03 b	49.57 ± 0.76 a
	P-N150	157.09 ± 7.32 a	17.70 ± 0.18 a	92.04 ab	48.71 ± 1.93 a
	P-N300	158.37 ± 8.60 a	17.74 ± 0.24 a	98.01 a	49.18 ± 1.65 a
	J-N0	165.98 ± 7.77 a	17.73 ± 0.21 a	88.06 a	54.04 ± 1.81 a
	J-N150	166.06 ± 8.83 a	17.86 ± 0.18 a	88.03 a	54.08 ± 2.01 a
	J-N300	168.36 ± 3.32 a	17.89 ± 0.28 a	92.06 a	55.61 ± 0.70 a
	W-N0	162.84 ± 8.69 a	17.83 ± 0.25 a	92.07 a	51.80 ± 1.73 a
	W-N150	164.07 ± 5.92 a	17.76 ± 0.35 a	94.02 a	51.45 ± 2.04 a
	W-N300	165.48 ± 6.28 a	17.86 ± 0.23 a	95.04 a	52.48 ± 0.87
	P-Z1	146.14 ± 8.90 a	17.70 ± 0.26 a	95.03 a	47.77 ± 2.21 b
	P-Z2	149.83 ± 8.34 a	17.77 ± 0.19 a	96.05 a	50.94 ± 1.34 a
	P-Z3	144.18 ± 6.87 a	17.72 ± 0.25 a	95.01 a	47.61 ± 1.27 b
	J-Z1	151.13 ± 5.91 a	17.29 ± 0.28 a	91.05 a	48.02 ± 1.57 a
	J-Z2	152.78 ± 7.27 a	17.85 ± 0.33 a	93.03 a	52.26 ± 1.44 a
	J-Z3	149.40 ± 5.90 a	17.66 ± 0.35 a	91.05 a	48.9 ± 1.22 a
	W-Z1	165.01 ± 4.72 b	17.92 ± 0.20 a	90.06 b	51.88 ± 0.82 a
	W-Z2	176.03 ± 7.39 a	18.24 ± 0.29 a	96.03 a	56.35 ± 0.29 a
	W-Z3	169.02 ± 3.09 b	17.88 ± 0.22 a	89.05 b	54.09 ± 1.22 a
	P-WT1	149.09 ± 8.05 a	17.59 ± 0.37 a	93.04 a	48.02 ± 0.86 b
	P-WT2	154.15 ± 7.87 a	17.73 ± 0.36 a	95.04 a	48.02 ± 0.95 ab
	P-WT3	159.82 ± 5.35 a	17.83 ± 0.22 a	97.02 a	50.40 ± 1.12 a
	J-WT1	170.90 ± 5.31 a	17.13 ± 0.35 a	87.06 c	52.42 ± 1.09 a
	J-WT2	159.99 ± 4.44 b	17.31 ± 0.52 a	90.02 b	52.08 ± 0.75 a
	J-WT3	172.01 ± 7.97 a	17.40 ± 0.17 a	97.01 a	52.79 ± 1.55 a
	W-WT1	171.01 ± 9.48 a	18.01 ± 0.31 a	93.05 a	51.71 ± 0.64 a
	W-WT2	175.83 ± 5.02 a	18.04 ± 0.45 a	97.05 a	52.86 ± 1.34 a
	W-WT3	175.38 ± 7.95 a	17.99 ± 0.22 a	93.03 a	51.08 ± 0.83 a
	P-WA1	164.84 ± 8.33 a	17.76 ± 0.33 a	93.04 b	49.08 ± 1.05 a
	P-WA2	166.68 ± 6.64 a	17.90 ± 0.19 a	95.02 a	50.45 ± 1.20 a
	P-WA3	166.48 ± 6.25 a	17.83 ± 0.26 a	92.01 b	50.33 ± 1.70 a
	J-WA1	155.67 ± 4.75 b	17.44 ± 0.22 a	88.02 a	49.35 ± 1.08 b
	J-WA2	172.11 ± 6.45 a	17.95 ± 0.43 a	89.01 a	55.27 ± 1.01 a
	J-WA3	169.22 ± 4.45 ab	17.83 ± 0.30 a	87.04 a	54.97 ± 1.18 a
	W-WA1	162.60 ± 8.01 a	17.72 ± 0.29 a	91.03 b	49.53 ± 1.88 a
	W-WA2	162.74 ± 8.25 a	17.82 ± 0.21 a	92.05 b	50.41 ± 0.85 a
	W-WA3	165.43 ± 7.07 a	18.47 ± 0.25 a	94.07 a	51.82 ± 0.96 a
2020–2021	P-N0	138.93 ± 5.83 b	17.23 ± 0.15 a	89.05 b	47.52 ± 1.14 a
	P-N150	144.73 ± 3.32 ab	17.63 ± 0.21 a	91.01 b	47.16 ± 1.12 a
	P-N300	151.62 ± 5.91 a	17.68 ± 0.18 a	93.06 a	48.95 ± 1.70 a
	J-N0	154.28 ± 5.92 b	17.51 ± 0.25 a	91.01 a	53.15 ± 1.24 a
	J-N150	156.37 ± 5.06 a	17.62 ± 0.25 a	92.05 a	55.33 ± 0.70 a
	J-N300	160.38 ± 7.47 ab	17.69 ± 0.31 a	94.04 a	55.48 ± 1.57 a
	W-N0	154.25 ± 8.44 b	17.61 ± 0.21 a	90.02 c	50.52 ± 1.29 b
	W-N150	157.04 ± 5.17 ab	17.52 ± 0.25 a	92.01 b	50.25 ± 0.79 b
	W-N300	159.82 ± 5.31 a	17.66 ± 0.31 a	95.06 a	53.04 ± 0.70 a
	P-Z1	141.46 ± 7.27 a	17.41 ± 0.28 a	94.03 a	46.52 ± 1.55 b
	P-Z2	145.57 ± 3.90 a	17.71 ± 0.38 a	95.06 a	51.26 ± 1.18 a
	P-Z3	144.56 ± 7.69 a	17.42 ± 0.33 a	93.05 a	47.20 ± 1.35 b
	J-Z1	144.47 ± 6.60 a	16.82 ± 0.45 a	88.04 a	48.03 ± 1.73 a
	J-Z2	146.13 ± 5.69 a	17.34 ± 0.22 a	90.02 a	51.25 ± 2.04 a
	J-Z3	137.34 ± 8.41 a	17.27 ± 0.19 a	89.04 a	50.15 ± 1.87 a
	W-Z1	158.33 ± 7.44 a	17.78 ± 0.27 a	89.02 a	50.15 ± 0.75 b
	W-Z2	164.21 ± 7.97 a	18.03 ± 0.25 a	94.01 a	55.26 ± 1.03 a
	W-Z3	150.14 ± 4.75 b	17.62 ± 0.19 a	87.03 a	53.15 ± 1.22 a
	P-WT1	148.14 ± 6.44 b	17.14 ± 0.26 b	91.02 a	47.46 ± 1.88 b
	P-WT2	153.51 ± 7.97 a	17.26 ± 0.25 b	95.03 a	46.37 ± 0.85 b
	P-WT3	156.63 ± 4.75 a	17.66 ± 0.42 a	96.02 a	49.93 ± 1.95 a
	J-WT1	162.57 ± 3.32 b	16.89 ± 0.30 a	89.02 b	51.26 ± 0.70 a
	J-WT2	157.38 ± 5.91 c	17.14 ± 0.31 a	90.04 b	50.84 ± 1.44 a
	J-WT3	164.73 ± 6.27 a	17.46 ± 0.28 a	95.02 a	51.27 ± 1.22 a
	W-WT1	166.38 ± 5.28 a	17.76 ± 0.35 a	92.05 b	50.85 ± 1.22 a
	W-WT2	167.37 ± 4.72 a	17.83 ± 0.23 a	96.07 a	51.26 ± 1.18 a
	W-WT3	156.38 ± 7.39 b	17.67 ± 0.20 a	93.02 b	50.14 ± 1.10 a
	P-WA1	157.53 ± 6.45 a	17.52 ± 0.17 a	92.01 a	48.38 ± 2.21 b
	P-WA2	156.42 ± 4.45 a	17.73 ± 0.22 a	93.03 a	50.15 ± 1.27 a
	P-WA3	156.52 ± 4.80 a	17.67 ± 0.43 a	92.02 a	48.95 ± 0.91 b
	J-WA1	152.52 ± 6.90 a	17.43 ± 0.33 a	91.01 a	48.37 ± 2.04 b
	J-WA2	167.38 ± 8.69 a	17.73 ± 0.35 a	92.06 a	53.16 ± 1.87 a
	J-WA3	162.74 ± 5.92 a	17.61 ± 0.25 a	88.01 b	52.28 ± 1.29 a
	W-WA1	158.47 ± 8.33 ab	17.21 ± 0.29 a	94.04 a	48.37 ± 1.27 a
	W-WA2	159.34 ± 7.08 ab	17.35 ± 0.18 a	93.08 a	49.04 ± 0.79 a
	W-WA3	175.38 ± 6.22 a	17.89 ± 0.22 a	95.03 a	50.85 ± 1.21 a
2019–2021	Year	**	**	ns	**
	Location	**	**	**	**
	Treatment	**	**	**	**
	Year*Location	*	*	ns	ns
	Year*Treatment	ns	ns	ns	ns
	Location*Treatment	**	**	**	**
	Year*Location*Treatment	ns	ns	ns	ns

Note: P represents Pingdu test site, J represents Jiaozhou test site, and W represents Weifang test site. All data represent the average of three data points (mean ± standard deviation). Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents in significant differences at 0.05 level.

). The exploration of optimal water–fertilizer coupling practices is crucial for enhancing wheat dough rheological properties and end-use quality. The effects of these practices during the 2019–2020 season are summarized in Table 13. Regarding topdressing frequency, the Z2 treatment was particularly effective, resulting in a significantly higher SDS sedimentation value (50.94 mL) in P and superior dough extensibility (176.03%) and gluten index (0.96) in W compared to other treatments. In contrast, no significant differences were observed for these parameters in J. For irrigation management, the WT3 treatment significantly increased the gluten index (0.97) in J. Regarding irrigation amount, the optimal cultivation practice was region-specific: WA2 resulted in a higher gluten index (0.95) in P, while WA3 was most effective in W, achieving a gluten index of 0.94.

During the 2020–2021 wheat growing season, the effects of various fertilization and irrigation regimes on wheat quality parameters were evaluated across multiple regions (Table 13). For basal fertilizer treatments, the N300 treatment significantly increased the gluten index (0.93) compared to other treatments in P. A similar trend was also seen in W, where N300 resulted in a higher gluten index (0.95) and SDS sedimentation value (53.04 mL), differing significantly from both N0 and N150. But no significant differences were observed among treatments in J. Regarding nitrogen topdressing frequency, the SDS sedimentation value (51.26 mL) was observed to be significantly increased under the Z2 treatment in P. Concerning irrigation frequency, WT3 led to significantly longer dough stability time (17.66 min) and higher SDS sedimentation (49.93 mL) than WT1 and WT2 in P. Meanwhile, WT3 significantly improved dough extensibility (164.73%) and gluten index (0.95) in J. But in W, a higher gluten index (0.96) was only observed under WT2 treatment. For irrigation treatments, the SDS sedimentation value (50.15 mL) was significantly higher under WA2 treatment in P.

Based on the experimental findings, the processing quality of wheat can be effectively improved by applying a higher rate of nitrogen fertilizer as basal fertilizer, supplemented with split topdressing at both the regreening (BBCH 25) and jointing stages (BBCH 31). Region-specific irrigation strategies were also identified: an additional irrigation event at the heading stage, with each application supplying 450–600 m³/ha during the green-up and jointing periods, significantly enhanced dough extensibility, stability time, gluten index, and SDS sedimentation value. These practices collectively contributed to improved edible and processing quality of wheat.

3.2. Impact of Optimized Cultivation Practices on Wheat Grain Yield and Quality in Multi-Regional Trials from 2020 to 2022

Based on plot experiments from 2019 to 2021, an optimized cultivation practice (Opt) was developed to enhance wheat quality. This package combined plowing and the tillage method with late sowing dates and region-specific seeding rates: 315 grains per m² in J or P and 3.60 million in W. Fertilization involved a basal nitrogen application of 300 kg/ha, supplemented by two topdressings at the regreening (BBCH 25) and jointing stages (BBCH 31). Irrigation was applied three times (at regreening (BBCH 25), jointing (BBCH 31), and heading (BBCH 51–54)) with 450 m³/ha per event in J or P, and twice (at regreening and jointing) with 600 m³/ha in W. The traditional cultivation practices (TC) followed local conventional management practices.

3.2.1. Effects of Optimized Crop Management on Quality in Large-Scale Regional Trials (2020–2022)

Over two years, the optimized cultivation practice (Opt) significantly enhanced wheat grain nutritional quality relative to the TC, although the effects varied by year and location. We also found that the interaction of Year*Treatment had a significant influence on nutritional quality. The grain nitrogen (N) content increased significantly under the optimized cultivation practice in the two regions. However, grain protein content was elevated only in P over the two years (

Table 14. The effects of optimized cultivation measures on grain quality and yield performance of wheat in large-scale regional trials from 2020 to 2021.

		Nutritional Quality		Milling Quality			Edible Processing Quality
Treatment		Protein Content (%)	N Content (%)	Bulk Density (kg/hL)	Hardness (%)	Flour Yield (%)	Moisture (%)	Water Absorption (%)	Wet Gluten (%)	Dry Gluten (%)	SDS Sedimentation Value (mL)	Stability Time (min)	Formation Time (min)	Extensibility Area (cm2)	Extensibility (%)	Maximum Retensibility (BU)
2020–2021	P-TC	13.49 c	2.04 d	79.20 b	45.66 bc	72.53 b	10.04 c	54.37 d	32.34 d	12.54 d	33.50 e	13.45 c	4.04 cd	74.16 b	138.54 de	258.37 c
	P-Opt	15.59 a	2.37 abc	79.86 a	47.97 a	75.51 ab	11.66 a	58.14 b	34.02 bc	15.37 b	36.56 cd	15.29 b	4.37 c	79.64 b	143.27 cd	W.88
	W-TC	15.29 a	2.23 bcd	79.68 a	46.22 b	72.18 b	10.46 b	59.46 b	35.23 b	16.25 b	39.51 b	15.61 ab	5.28 b	109.98 a	152.71 b	333.92 b
	W-Opt	16.35 a	2.56 a	80.10 a	47.77 a	76.37 a	11.14 b	62.18 a	37.65 a	17.43 a	42.77 a	16.03 a	5.64 a	116.21 a	165.02 a	384.53 a
2021–2022	P-TC	14.69 d	2.05 b	80.01 b	46.32 b	52.15 c	11.24 c	51.06 cd	33.76 b	12.06 c	38.76 c	16.99 bc	4.70 d	102.12 d	145.68 b	347.33 c
	P-Opt	15.88 b	2.40 b	80.25 a	44.01 c	67.72 b	14.73 a	52.38 c	35.55 b	13.47 b	39.89 b	17.31 a	5.24 c	121.98 a	150.92 a	376.40 b
	W-TC	16.03 ab	2.50 a	80.15 b	46.07 b	64.50 ab	11.91 c	55.49 b	36.91 a	13.20 b	42.25 a	16.79 bc	6.40 a	111.01 a	147.78 ab	347.43 ab
	W-Opt	16.54 a	2.54 a	80.43 a	46.54 bc	62.05 b	12.86 a	56.45 b	37.12 a	14.14 a	43.68 a	16.85 bc	6.22 a	104.22 b	150.05 a	377.32 a
2020–2022	Year	ns	ns	ns	ns	ns	**	ns	ns	ns	ns	ns	ns	ns	ns	ns
	Location	**	**	*	ns	ns	**	**	**	**	**	**	**	**	**	**
	Treatment	*	*	ns	*	*	**	*	*	*	*	*	*	ns	**	*
	Year* Location	ns	ns	ns	ns	ns	**	ns	ns	ns	ns	ns	ns	ns	ns	ns
	Year* Treatment	*	*	*	*	*	**	*	*	*	ns	*	ns	ns	*	ns
	Location* Treatment	ns	ns	ns	ns	ns	*	ns	ns	ns	*	ns	ns	ns	ns	*
	Year* Location* Treatment	ns	ns	ns	ns	ns	**	ns	ns	ns	ns	ns	ns	ns	ns	ns

Note: P represents Pingdu test site, W represents Weifang test site, and Opt represents the optimized cultivation practice. Values in a column followed by different letters are significantly different at p < 0.05, * represents significant differences at 0.05 level, ** represents extremely significant differences at 0.01 level, and ns represents insignificant differences at 0.05 level.

).

The optimized cultivation practice (Opt) also significantly improved wheat milling quality, though the effects were region- and year-specific. During the first season (2020–2021), significant increases in grain hardness, bulk density, and flour yield were observed under optimized cultivation practice across all locations. Conversely, in the second season (2021–2022), the optimized cultivation practice led to a significant reduction in grain hardness, which we hypothesized was triggered by excessive irrigation at late growth stages. Concurrently, significant decreases in flour yield were recorded in W (Table 14).

In terms of wheat grain processing quality related to end-use, significant improvements were observed under the optimized cultivation practice compared to TC during the 2020–2021 season across P and W (Table 14). Specifically, wet gluten content, dry gluten content, SDS sedimentation value, dough stability time, dough extension, and maximum resistance increased notably. In contrast, no significant differences in extensibility area were detected between the two regions. Grain moisture content increased significantly only in P. The water absorption rate of wheat grains rose significantly by 6.9% in P and 4.5% in W, while dough formation time increased only in W. During the 2021–2022 season, dry gluten content showed significant increases across the two regions under optimized cultivation practice, with rises of 11.7% and 7.0%, respectively (Table 14). SDS sedimentation value, dough stability time, extension and maximum retensibility significantly increased in P. Grain moisture and extensibility area elevated in P and W. Dough formation time increased significantly by 11.5% in P under the optimized cultivation practice. However, no significant differences in water absorption were observed among the two regions.

3.2.2. Effects of Optimized Cultivation Practices on Yield Composition from 2021 to 2022

Spike density, kernels per spike, and thousand-kernel weight are the three primary components of wheat yield. In order to analyze the effect of different treatments on grain yield and composition, these three main factors constituting wheat yield were measured. According to

Table 15. The impact of optimizing cultivation measures on regional yield composition from 2021 to 2022.

	Plant Height (cm)	Spike Number (103/ha)	Kernels Per Spike	Thousand-Kernel Weight (g)	Grain Yield (kg/ha)
P-TC	67.7 b	6035.6 b	42.8 b	41.5 a	10,717.8 b
P-Opt	76.3 a	6491.1 a	46.4 a	43.2 a	13,023.4 a

Note: P represents Pingdu test site; Opt represents the optimized cultivation practice. Values in a column followed by different letters are significantly different at p < 0.05.

, the optimized cultivation practice demonstrated superior yield-related traits compared to the TC treatment at the wheat maturity stage (BBCH89) during the 2021–2022 growing season in P. Significant improvements were observed in spike density, kernels per spike, and thousand-kernel weight and were 7.5%, 8.4%, and 4.1% higher than those under the TC treatment, respectively. Meanwhile, the grain yield increased by 21.5% relative to the TC, and the plant height was also found to have increased by 12.8%.

3.2.3. Effects of Optimized Cultivation Practices on Dry Matter Accumulation and Photosynthetic Characteristics in Regional Trials from 2021 to 2022

In terms of dry matter accumulation, the optimized cultivation practice (Opt) significantly affected the spike, leaf, and stem weight of wheat compared to the control (TC) across 0, 7, 14, 21, and 28 days after pollination (DAP). The dry matter accumulation of wheat spikes increased progressively after anthesis, peaking at 28 DAP. In contrast, leaf dry matter declined continuously from anthesis onward, with the maximum level recorded at 0 DAP. Stem dry matter exhibited a pattern of initial increase followed by a decrease. Under the optimized cultivation practice (Opt), stem dry matter accumulation reached its maximum at 7 DAP, whereas under the control treatment (TC), the peak occurred at 21 DAP (Figure 3A–C).

Photosynthetic parameters exhibited distinct patterns during the post-anthesis period. The SPAD value of the flag leaf exhibited a pattern of initial increase followed by a decline during the post-anthesis period. The optimized cultivation practice maintained significantly higher values than the control (TC) throughout all observed stages, with the most significant difference recorded at 28 days after pollination (Figure 3D). The intercellular CO₂ concentration (C_i) was slightly higher under the optimized cultivation practice at 0 and 7 DAP compared to TC, but no significance was observed at 14 and 21 DAP (Figure 3E). In contrast, the other three parameters, net photosynthetic rate (P_n), stomatal conductance (G_s), and transpiration rate (T_r), exhibited significant increases under the optimized cultivation practice at 0, 7, and 14 DAP. Specifically, G_s decreased by 4.0% under the optimized cultivation practice at 21 DAP; P_n and T_r increased significantly by 30.3% and 4.2% (Figure 3F–H). These results indicated that the optimized cultivation practice could significantly enhance wheat photosynthetic efficiency, thereby further promoting the synergistic improvement of grain quality and yield.

3.2.4. Effects of Optimized Cultivation Practices on Baking Quality of Wheat in Regional Trials from 2021 to 2022

Over the two regions, the optimized cultivation practice increased the baking quality of wheat significantly compared to TC treatment both in P and W (

Table 16. The effect of optimizing cultivation measures on the baking quality of regional wheat from 2021 to 2022.

	Bread Volume V (mL)	Bread Appearance (5 Points)	Bread Core Color (5 Points)	Bread Core Texture (10 Points)	Texture Structure (35 Points)	Bread Rating (100 Points)
P-TC	550	2.0	1.0	3.0	12.0	34
P-Opt	920	5.0	4.0	8.5	32.0	94
W-TC	835	4.0	4.0	8.5	32.0	88
W-Opt	870	4.5	4.0	8.5	32.0	92

Note: P represents Pingdu test site, W represents Weifang test site, and Opt represents the optimized cultivation practice.

). Specifically, the bread rating was 94 points after appropriate treatment in P, while only 34 points under TC.

3.2.5. Optimized Cultivation Practices Improved Wheat Flour End-Use Quality via Modulation of High-Molecular-Weight Glutenin Subunits Expression in Regional Trials from 2021 to 2022

Gluten proteins, one of the important seed storage proteins, can impact dough elasticity and extensibility. They are primarily composed of glutenin, which is categorized into high-molecular-weight (HMW-GS) and low-molecular-weight (LMW-GS) subunits based on their size. To assess the role of high-molecular-weight glutenin subunits (HMW-GS) in the quality improvement under the optimized cultivation practice, we quantified TaGlu1 expression of different days after pollination. Results indicated that the optimized cultivation practice led to a higher expression of TaGlu1 in the endosperm at 14, 21, and 28 DAP (Figure 4).

4. Discussion

4.1. Effects of Tillage and Sowing Date on Wheat Quality

Tillage practices significantly influence wheat quality parameters. Hao et al. reported that conventional tillage significantly increased grain protein content, wet gluten content, and sedimentation value [32]. Similarly, Zhong et al. observed that wide-strip rotary tillage combined with improved dough rheological properties, including stability time, extensibility area, and maximum resistance to extension [14]. Consistent with previous studies, our experiment demonstrated that plowing resulted in superior wheat quality compared to rotary tillage, significantly enhancing flour yield, dry and wet gluten content, grain nitrogen content, and protein content. Meanwhile, the three-way interaction among year, location, and treatment had a significant effect on thousand-kernel weight, bulk density, protein, and N content.

Sowing date and seeding rate are two additional factors that affect the quality of wheat. Bagherikia et al. found that delayed sowing date could increase wet gluten content and dough development time [33]. Similarly, Procházková et al. indicated that later sowing contributed to higher protein and wet gluten content in wheat grains, whereas increased seeding rates led to a decrease in these parameters [34]. In our study, the results showed that appropriately delayed sowing dates, combined with increased seeding rates, significantly improved grain bulk density, hardness, dry gluten content, wet gluten content, sedimentation value, dough stability time, dough development time, water absorption rate, and maximum resistance to extension.

4.2. Effects of Water and Nitrogen on Wheat Quality Formation

Water is one of the critical elements for crop growth and grain quality. Previous studies indicated that excessive irrigation generally reduced protein content, dry and wet gluten content, and sedimentation value of grains [31,35]. She et al. found that irrigation at the booting stage enhanced dough sedimentation value and farinograph parameters but reduced grain hardness and dough extensibility [36]. Hao et al. reported that irrigation at the grain-filling stage enhanced key quality parameters, including extensibility, flour yield, bulk density, protein content, gluten components, sedimentation value, and dough stability, while reducing dough weakening [32]. Delayed irrigation timing could increase wet gluten content, sedimentation value, dough development time, stability time, and dough extensibility area [6,37,38]. According to the report of Li et al., the strategy of implementing a controlled reduction in irrigation can enhance grain protein content in wheat [39]. Irrigation during critical wheat-growth stages, such as jointing, booting, and flowering, has been shown to have a detrimental effect on final grain protein content [2,40,41]. Qiu et al. reported that increased irrigation volume and frequency during the late growth stages of strong-gluten wheat adversely affected its final quality [2]. Research by Chen et al. demonstrated that the imposition of moderate water stress during the grain-filling phase of wheat promotes the accumulation of grain protein [6]. Our findings recommend distinct irrigation protocols for two regions to improve wheat quality: in J or P, three irrigations (regreening stage (BBCH 25), jointing stage (BBCH 31), and heading stage (BBCH 51–54)) at 450 m³/ha each; in W, two irrigations (greening stage and jointing stage) at 600 m³/ha each.

Alongside water management, nitrogen is a primary factor influencing wheat quality parameters. Qiu et al. reported that appropriate basal fertilization increased both grain protein and wet gluten content, as well as the rheological properties of dough [2]. Previous studies have also shown that applying a basal fertilizer with a higher proportion of organic and phosphate fertilizers relative to nitrogen is an effective strategy to improve grain quality [36,42,43]. Studies have shown that nitrogen application during the late growth stages (jointing or booting stage) significantly enhances wheat grain protein content, wet gluten content, and dough stability time [6,44,45]. Li et al. demonstrated that a management practice of applying supplemental nitrogen at the regreening stage under a fixed total nitrogen input served to improve wheat quality while also enhancing soil organic matter [46]. Hao et al. also found that an increase in drip irrigation fertilization frequency could enhance wheat protein content [32]. The optimal strategy for synergistically improving wheat yield and quality involved moderate nitrogen topdressing at the greening stage and jointing stage, combined with P and K supplementation [47,48]. Our results showed that nitrogen topdressing at the regreening (BBCH 25) and jointing stages (BBCH 31) demonstrated a superior effect on wheat yield and grain quality. Significant improvements were observed in a series of quality parameters, such as grain bulk density, hardness, protein content, dry/wet gluten content, and sedimentation value, stabilization time, formation time, water absorption, as well as extension and extensibility area. But these elements were also affected by year, location, treatment, and their interactions. Regional variations in results were observed, potentially influenced by environmental factors.

4.3. Effects of Water–Fertilizer Coupling on the High-Molecular-Weight Glutenin and Wheat Quality

High-molecular-weight glutenin subunits play an important role in dough processing quality but comprise only about 10% of gluten proteins [18]. Li et al. found that overall glutenin content and its subunit composition (HMW-GS and LMW-GS) were positively correlated with enhanced bread sensory evaluation [49]. Among these gluten subunits, the 7 + 8 subunits at the Glu-B1 locus were identified as the dominant subunits enhancing bread sensory scores. Liu et al. [50] reported that both the expression level and the proportion of HMW-GS in total grain protein were significantly correlated with key farinograph parameters, including dough development time and stability time. This finding was consistent with established effects of specific HMW-GS alleles, where subunits *1* (Glu-A1) and *5 + 10* (Glu-D1) are known to confer superior dough strength compared to their null or weaker counterparts (null and *2 + 12*, respectively), while subunits *7 + 8* and *7 + 9* (Glu-B1) generally exhibit comparable quality effects [50]. The expression levels and proportions of HMW-GS were also found to be positively correlated with sedimentation value [51]. The absence of HMW-GS adversely impairs the formation of the glutenin polymer, which is critical for gas retention [52]. Water stress distinctly modulated the synthesis of glutenin by promoting its overall accumulation rate, while the response of specific HMW-GS (1, 5 + 12, 13 + 16, 14 + 15, 5 + 10) varied significantly with water availability [53]. Our results showed that optimized cultivation practice could improve the expression of TaGlu1 in the endosperm and bread rating, which were consistent with the previous studies.

5. Conclusions

In this study, we proposed a novel cultivation practice to enhance the quality of strong-gluten wheat based on a two-year field experiment. The optimized cultivation practice could enhance strong wheat quality by increasing grain protein content, flour yield, SDS sedimentation value, wet and dry gluten content, stability time, formation time, extension area, extension, and maximum retensibility. Moreover, elevated expression levels of TaGlu1 were also detected under optimized cultivation practice. In summary, the optimized cultivation approach represents a promising strategy for improving strong-gluten wheat quality in the Huang-Huai-Hai Plain.