Effects of Different Base Fertilizers on Water Use Efficiency and Growth of Maize During Growth Period

Abstract

This study hypothesized that different base fertilizer application has different effects on improving the efficiency of maize water utilization and promoting maize growth. Utilizing field positioning sloping farmland micro-zone experiments, six distinct types of base fertilizers were designed: a control group without fertilization (CK), chemical fertilizer alone (T1), a mixture of local farmyard manure (40% pine needles and 60% livestock manure, T2), a 50% reduction in chemical fertilizer combined with farmyard manure (T3), the incorporation of crushed straw through deep plowing (T4), and the fermentation of crushed straw mixed with urea before field application (T5). The results indicate that, compared to the CK treatment, the T3 and T5 treatments significantly enhanced soil moisture content, with increases ranging from 4.06% to 18.67% during the normal year (2023) and the drought year (2024), respectively. Additionally, the water utilization efficiency of maize was improved significantly, with values of 35.38% and 41.54%, and the yield increased by 12.30% to 25.92%. The maize yields under T3 and T5 treatments reached 12.19 and 13.31t/ha, respectively. Therefore, we propose that crushing straw and incorporating urea and water for fermentation as a base fertilizer in maize fields can ensure efficient water use in this region, leading to higher yields.

1. Introduction

The southwestern alpine canyon region of China is characterized by its rugged topography, consisting of numerous mountain ranges and deep valleys [1]. This river basin is marked by towering peaks, intersecting ravines, and pronounced canyons, resulting in significant altitude variations and a complex, dynamic landscape. Yunlong County, located in northwestern Yunnan Province, lies within the longitudinal valley of the Lancang River, south of the middle section of the Hengduan Mountains. The region belongs to the lower Xianjiang River Basin, a major tributary of the Lancang River, and is shaped by typical alpine canyon and plateau canyon topography. The fragmented terrain in this area is a defining feature of its unique geographical setting. In this area, rain-fed agriculture on sloping land is the primary means of sustaining agricultural production and farming activities. However, the uneven temporal and spatial distribution of rainfall poses substantial challenges to crop yields, as the soils in this region exhibit poor water and fertilizer retention capacities. The distribution of cultivated land is highly fragmented and sporadic, with over 70% of the farmland located on slopes steeper than 10° [2]. Agricultural constraints become even more severe on slopes exceeding 25°, where farming practices and excessive fertilizer application further degrade soil quality. These conditions have resulted in widespread soil degradation, declining soil fertility, and reduced cultivated land quality. Additionally, severe soil erosion and frequent natural disasters, such as landslides, further hinder agricultural sustainability, ecological restoration, and the region’s socioeconomic development.

In recent years, significant progress has been made in research on the combined application of various base fertilizers, including organic, inorganic, and biological fertilizers. Studies have explored their mechanisms of influence on soil physical and chemical properties, microbial community structures, and crop growth. Soil amendments have been shown to improve soil aggregate composition, enhance water and nutrient retention capacities, increase crop water use efficiency (WUE), and positively impact soil physical and chemical characteristics, among other benefits [3]. These improvements ultimately contribute to enhanced land productivity and increased crop yields [4]. Dong et al. demonstrated that, from a long-term perspective, optimal fertilization strategies for maize fields should integrate organic fertilizers, chemical fertilizers, and straw into the soil [5]. This approach significantly enhances maize water use efficiency and promotes higher yields. Similarly, Zhang et al., through five consecutive years of field experiments, found that applying high concentrations of chemical fertilizers in years with adequate water availability can lead to excessive soil moisture depletion. Conversely, applying a moderate amount of fertilizer maximizes maize water use efficiency and has a particularly pronounced effect on yield, especially in both normal and water-deficient years [6]. Furthermore, Wang et al., based on three years of field experiments, reported that soil moisture levels are lower in unfertilized fields compared to those receiving fertilizer applications [7]. Similarly, Jia et al. found that the long-term application of inorganic fertilizers gradually depletes surface soil moisture, causing it to migrate to deeper soil layers [8]. Additionally, Zhang et al. highlighted that combining organic and inorganic fertilizers reduced soil evaporation, increased soil moisture content, and enhanced crop water use efficiency [9]. As a major grain crop, maize is highly sensitive to water and fertilizer management, which directly affects its growth and yield. Implementing rational fertilization and irrigation strategies can significantly improve both maize yield and water use efficiency. During its growth period, particularly from the jointing stage to grain filling and maturation, maize exhibits a high moisture demand. Soil moisture levels and water use efficiency play a crucial role in maize growth and final yield, making them key determinants of agricultural productivity. Given the challenges of water scarcity in sloping farmland and the pressing need to reduce excessive fertilizer use, exploring efficient and environmentally friendly fertilizer allocation strategies is essential for promoting sustainable agricultural development and ensuring global food security.

However, most existing research focuses on evaluating the effects of single fertilizers or simple combinations, lacking a systematic investigation and comprehensive assessment of the compound application of multiple base fertilizers. A thorough evaluation following the combined application of various base fertilizers is essential to identify the most suitable fertilization strategies. This process not only advances the theoretical framework of water-saving cultivation for maize but also provides a scientific foundation for optimizing fertilizer use in agricultural production and offers essential technical support. Against this backdrop, this study focuses on maize, a crop with a high water demand during its growth period, particularly from the jointing stage to the grain-filling stage and maturity. This study systematically examines the effects of various basal fertilizer application strategies on soil moisture dynamics, maize WUE, and maize yield throughout its growth period on sloping farmland in Yunlong County, northwest Yunnan. The specific objectives of this study are as follows: Through field positioning experiments, provide an accurate measurement of moisture utilization efficiency during the maize growth period and identify the optimal base fertilizer application plan that significantly enhances both water utilization efficiency and yield. Ultimately, a precise balanced fertilization strategy is established to optimize maize moisture utilization, ensuring maximum yield in a controlled environment. The findings of this study will contribute to improving soil quality on sloping farmland in northwestern Yunnan, providing a scientific basis for optimizing fertilization strategies in maize cultivation.

2. Materials and Methods

2.1. Experimental Site Description

The experiment was conducted near the Baolu Reservoir in Yunlong County, Dali Prefecture, Yunnan Province, China (26°05′38.82″ N, 99°29′54.30″ E). An overview of the study area is presented in Figure 1.

The study area experiences a combination of mountain plateau and subtropical climates, with a regional average temperature of 10.9 °C. The annual evaporation rate is 1564.7 mm, while the average annual rainfall is 612.54 mm. The rainy season extends from late May to October, accounting for approximately 60% of the annual rainfall, while the dry season lasts from mid-October to late May of the following year. The soil is primarily brown soil, characterized by low levels of nitrogen, phosphorus, and potassium. It exhibits high bulk density and poor water retention capabilities, resulting in fragmented soil structure, diminished quality of cultivated land, and significant soil erosion. Additionally, irrigation infrastructure is highly limited, further constraining field crop production. The primary economic crops cultivated in the region are maize (Zea mays L.) and flue-cured tobacco (Nicotiana tabacum).

2.2. Experimental Design

This study evaluated the effects of various base fertilizer applications on soil and crop performance. Basal fertilizers were applied following land preparation on 10 May 2023 and 21 May 2024, with maize subsequently planted in two standard runoff plots measuring 5 × 20 m each. The previous field management model for the test field was designed to facilitate the planting of conventional slope arable land for local farmers, effectively serving as a representative example of the local slope arable land for experimental planting. The experimental land is a field with a certain slope, so maize can get more light and grow better than with flat planting. The maize variety used was “Kenfeng 670”, planted at a density of 40,000 plants per hectare. The experimental layout utilized galvanized iron frames to establish six groups of quadrats (0.5 × 1 m each), corresponding to different basal fertilizer treatments. Each treatment group was replicated three times to facilitate statistical comparisons among treatments. A 1 m distance was maintained between each quadrat to ensure separation. To avoid bias, each fertilization treatment and its repetitions were applied in a random layout. Micro-plot experiments were conducted, and the soil background values at the experimental site are provided in

Table 1. Basic indices of soil before seeding in experimental plots.

Index	Unit	Soil Depth/cm
		0–10 cm	10–20 cm	20–40 cm
Organic Matter	g kg−1	47.50	23.16	19.48
Total Nitrogen	g kg−1	0.34	0.23	0.16
Total Phosphorus	g kg−1	0.83	0.78	0.75
Total Potassium	g kg−1	3.78	3.48	2.38
Available Nitrogen	mg kg−1	38.26	27.53	18.73
Available Phosphorus	mg kg−1	36.47	15.50	6.69
Available Potassium	mg kg−1	10.98	10.30	9.32
Bulk Density	g cm−3	1.46	1.52	1.58
Volume Moisture Content	%	17.14	20.55	24.36
Texture (Sand/soil/clay)	%	14.30, 31.41, 54.10	12.37, 35.45, 52.77	13.12, 35.55, 49.25
pH		5.15	4.92	4.81

. After investigating the traditional fertilization practices of local farmers in sloping farmland, it was found that they generally apply both farmhouse fertilizers and chemical fertilizers. Previous research conducted by our team indicated that the application of chemical fertilizers in conjunction with maize stalks significantly enhances soil nutrient levels and helps maintain soil moisture [10]. Maize is a predominant crop in the local area, and fertilizers made from maize stalks and livestock manure are readily available. Given the region’s economic challenges, the selected fertilizers are the most accessible, cost-effective, and efficient options available to the local farmers. The study included six treatment groups: no fertilization control (CK), chemical fertilizer alone (T1), local farmyard manure alone (a mixture of 40% pine needles and 60% livestock manure, T2), optimized application of 50% less chemical fertilizer combined with farmyard manure (T3), straw incorporation through deep plowing (T4), and straw incorporation with urea for fermentation before returning it to the field (T5). Each treatment was replicated three times, ensuring consistency in basal fertilization, top dressing, and field management practices, following local farming techniques.

The fertilizers applied to the experimental groups included a specialized compound fertilizer for maize with a nutrient ratio of N:P₂O₅:K₂O of 27:5:8, supplemented with urea (46% nitrogen content), farmyard manure, and maize straw. The farmyard manure, sourced from local farmers, primarily consisted of pine needles mixed with livestock and poultry manure. The method of straw incorporation involved deep plowing before sowing. Before sowing, phosphate fertilizer, potassium fertilizer, and organic fertilizer were simultaneously applied as base fertilizers. Nitrogen fertilizer was applied in two stages following the maize growth cycle, with 30% applied at the jointing stage (30 d) and 70% at the trumpet stage (70 d), ensuring an optimal nutrient supply throughout the crop’s development. In February 2023 and 2024, maize straw was crushed into varying particle sizes and subjected to retting in March. The retting process involved stacking the straw to a height of 30 cm, followed by sufficient water application to achieve a moisture content of 60–70%. Urea, amounting to approximately 3/5 of the total required dosage, was evenly sprinkled over the straw. Next, an additional 15 cm layer of straw was added, followed by another portion of urea (1/5 of the total amount). This layering process was repeated one final time with an additional 15 cm layer of straw. Once fully layered, the straw was tightly sealed with plastic agricultural film to retain moisture [10]. Prior to planting, the retted straw was incorporated into the top 0–20 cm of soil and thoroughly mixed. The fermentation process occurs at an approximate temperature of 20 degrees Celsius under standard conditions, with a duration of about 60 days. For the use of farm manure, if its humidity is controlled at about 10% to 20%, it will not stick to the hand. The humidity of the straw is controlled at 60~70%. That is, after grabbing the group by hand, the hand will not leave a watermark, the straw ball will not drip the water, and it will not spread the best after putting it down. The amount of base fertilizer applied across each treatment is as follows: CK: 0, T1: 1000 g/m² of farm fertilizer, T2: 500 g of maize-special compound fertilizer, T3: 500 g of farm fertilizer plus 40 g of maize-special compound fertilizer, T4: 1500 g of straw, and T5: 1500 g of straw plus 37.5 g of urea. The total nitrogen application amounts for each treatment were as follows: 0.014835 kg, 0.019545 kg, 0.041835 kg, 0.033045 kg, 0.0194475 kg, and 0.2208 kg. The nitrogen, phosphorus, and potassium contents of the farm fertilizer, straw, and specialized compound fertilizers for maize and urea were measured at 9.42, 1.6, and 6.21 g·kg⁻¹; 6.15, 2.7, and 22.38 g·kg⁻¹, 675, 125, and 200 g·kg⁻¹; and 460, 0, and 0 g·kg⁻¹, respectively. The specific dosages of fertilizers and materials applied for each treatment are presented in

Table 2. Specific fertilizer application rates for each treatment (g/m²).

Group	Fertilizer Type	Base Fertilizer	Jointing Fertilizer	Trumpet Fertilizer
CK	0	0	21.5	43
T1	Organic	1000	21.5	43
T2	Inorganic	80	21.5	43
T3	Organic, Inorganic	500, 40	21.5	43
T4	Straw	1500	21.5	43
T5	Straw, urea	1500, 37.5	21.5	43

.

2.3. Soil and Maize Sample Treatment

(1) During the maize growth periods from May to October in 2023 and 2024, soil temperature and moisture dynamics were monitored using the Shunkeda TR-8D device (Shunkeda, Shenzen, China) to assess soil volumetric moisture content. The instrument’s induction probe was inserted directly into the soil, enabling separate measurements at different depths: 0–10 cm, 10–20 cm, and 20–40 cm. Each depth was measured three times per sampling event to ensure accuracy. Throughout the maize growth stages, measurements were conducted weekly, spanning from the jointing stage to crop maturity. The average soil volumetric moisture content for a given period was determined by calculating the mean value of multiple measurements collected within that timeframe. In addition to soil moisture monitoring, the following parameters were calculated: soil water storage capacity (W) [11], farmland water consumption during the growth period (ET) [12,13], maize WUE [13,14], and rainfall use efficiency (RUE). For the Comprehensive Evaluation Index of Fertilizer Effect, the method of Tang et al. [15] and other methodologies were utilized to calculate the fertilization membership degree for each indicator. Principal component analysis was employed to assess each indicator and compute the comprehensive evaluation index of fertilizer application under varying base fertilizer application levels (D). This index serves as a foundation for evaluating the effects of different base fertilizer applications. The specific calculation formulas are as follows:

$$W=w_i{h}_{i}r$$

(1)

$$ET=P+(W1-W2)$$

(2)

$$WUE={\displaystyle \frac{QY}{ET}}$$

(3)

$$RUE={\displaystyle \frac{QY}{QP}}$$

(4)

$$R\left(X_i\right) ={(X}_i-X_{min})/(X_{max}-X_{min})$$

(5)

$${\omega }_i=P_i/{{\displaystyle \sum }}_{i=1}^n{P}_i$$

(6)

$$D=({{\displaystyle \sum }}_{i=1}^n{\omega }_i\times R(X_i))$$

(7)

In Equation (1), W represents the soil water storage capacity (mm); wi denotes the mass moisture content of each soil layer (%); hi indicates the thickness of each soil layer (mm), and r is the bulk density of each soil layer (g cm⁻³).

In Equation (2), ET refers to farmland water consumption during the growth period (mm), P denotes the total precipitation during the growth period (mm), W1 represents soil water storage at the beginning of the jointing stage (mm), and W2 indicates soil water storage at the maturity stage (mm). Equation (3) defines WUE as the water use efficiency of maize grains (kg/ha·mm), while Equation (4) defines RUE as the rainfall use efficiency (kg/ha·mm), where QY is the maize grain yield (kg/ha), and QP is the precipitation during the growth period (mm).

In Equations (5)–(7), R$\left(X_i\right)$ denotes the membership function value of the i-th indicator, where $X_i$ represents the i-th comprehensive indicator value, $X_{max}$ is the maximum value of the i-th comprehensive indicator, and $X_{min}$ is the minimum value of the i-th comprehensive indicator. Additionally, ${\omega }_i$ signifies the weight of the i-th comprehensive indicator among all indicators, while $P_i$ indicates the contribution rate of each processing i-th comprehensive indicator. The variable n represents the total number of evaluation indicators, and D denotes the comprehensive evaluation value of the fertilization treatment effect.

(2) During the maize growth and maturity stages in the 2023 and 2024 growing seasons, three well-developed maize plants were selected from each micro-plot as representative samples. The following morphological parameters were measured: plant height, ground diameter (measured 2 cm above the soil surface), and leaf area index (LAI). LAI measurements were conducted hourly from 9:00 to 11:00 AM on clear mornings using an LI-3000C leaf area meter (LI-COR Environmental, Lincoln, NE, USA). During each assessment, fully unfolded leaves at the top of the plant were selected for measurement. At the maturity stage, three representative plants were harvested from each micro-plot, and the maize ears were collected and transported to the laboratory for further analysis. The following parameters were recorded: ear weight, number of ear rows, and number of kernels per ear. After threshing and air-drying at a natural temperature of approximately 20 °C, the grain moisture content was determined using a nationally recognized and calibrated grain moisture meter (PM-8188-A (YIMA, Shenzen, China)). The final grain yield was calculated based on the national standard moisture content for maize (14.0%). Following one month of air-drying at 20 °C, the 100-kernel weight was measured. Maize yield was then calculated based on the actual harvested yield and converted to area yield (t/ha).

2.4. Data Processing

The collected data were organized using Microsoft Excel 2019, while IBM SPSS Statistics 25 was used to perform one-way ANOVA and trend analysis to evaluate differences among treatment groups based on different basal fertilizer types. Pairwise differences between treatment groups were assessed using the least significant difference (LSD) test at a significance level of p = 0.05, principal component analysis and membership calculations. To ensure the validity of statistical analyses, data normality was examined using the Shapiro–Wilk test, followed by an assessment of variance homogeneity conducted with Levene’s test. Origin 2022 Pro was utilized to generate histograms and multi-factor box plots for visualizing variations in key indicator parameters. Furthermore, redundancy analysis (RDA) was conducted using Canoco software to investigate the correlation between water parameter indicators and maize growth indicators, as well as to compare the relative contributions of plant growth parameters to water utilization efficiency.

3. Results

3.1. Effects of Different Base Fertilizers on Soil Volumetric Moisture Content

The application of different basal fertilizers had a significant impact on soil volumetric moisture content (p < 0.05). As illustrated in Figure 2, the soil moisture content in all treatment groups exhibited an increasing trend from 2023 to 2024, indicating that prolonged fertilizer application enhanced soil water retention over time. The soil moisture content among the treatments followed the order: urea combined with straw composting (T5) > straw composted and returned to the field (T4) > farmyard manure combined with reduced chemical fertilizer (T3) > chemical fertilizer alone (T2) > farmyard manure alone (T1) > no base fertilizer (CK). In the 0–10 cm soil layer, volumetric water content increased by 4.04%, 9.97%, 8.54%, 5.09%, 12.79%, and 10.84% for the T1, T2, T3, T4, T5, and CK groups, respectively, compared to 2023. Notably, no significant differences were observed between the T3 and T4 treatments. In the 10–20 cm soil layer, volumetric water content increased by 4.97%, 7.77%, 2.89%, 13.00%, 7.72%, and 12.29% for the respective treatment groups, with the T3 and T5 treatments showing the most pronounced increases, both exceeding 10%. In the 20–40 cm soil layer, volumetric water content increased by 5.70%, 18.67%, 7.04%, 5.88%, 4.61%, and 5.22% for the respective treatments. However, these increases were not statistically significant for most treatments, except for T1, which showed a notable increase. Across the 10–20 cm soil layer, differences between the T3, T4, and T5 treatments were minimal, but all were higher than those of other treatments. Overall, in these three soil layers, the T5 treatment demonstrated the best performance, suggesting that the combination of straw incorporation and urea fermentation significantly enhanced soil moisture retention.

3.2. Effects of Different Base Fertilizer Combinations on Soil Water Consumption During Maize Growth Period

As illustrated in Figure 3, significant differences in water consumption were observed between 2023 and 2024, influenced by the application of different base fertilizers. Water consumption in 2023 was notably higher than in 2024, likely due to the substantial rainfall received in 2024. In contrast, 2023 was a relatively dry year, leading to increased soil water uptake by plants to compensate for the limited water availability. Overall, water consumption patterns varied under normal and dry conditions. In years with adequate water supply, soil water absorption by maize decreased across most fertilization treatments. Conversely, under drought conditions, all fertilization treatments enhanced root water absorption, leading to increased water consumption. During the maize growth period, water consumption ranged from 322.31 mm to 337.49 mm across treatments. In 2024, treatments involving chemical fertilizer alone (T2), farmyard manure combined with chemical fertilizer (T3), and urea combined with straw retting (T5) exhibited significantly higher water consumption compared to the control (CK) group, with increases of 5.58% and 6.30%, respectively. Notably, the T3 treatment recorded the highest water consumption, reaching 256.62 mm.

3.3. Effects of Different Base Fertilizers on the WUE of Maize

As shown in Figure 4, the application of different base fertilizers from 2023 to 2024 had a significant impact on both the WUE and RUE of maize. In both years, the urea combined with straw retting treatment (T5) exhibited the highest grain WUE, significantly outperforming the other treatments. Compared to the control group (CK, no fertilizer application), WUE in the T5 treatment increased by 25.81% and 21.27% in 2023 and 2024, respectively. In 2024, WUE for all fertilization treatments increased by 40.87%, 36.32%, 28.30%, 34.17%, 39.34%, and 35.38%, respectively, compared to 2023. However, apart from the significant differences between CK and T5, no statistically significant differences were observed among the other fertilization treatments.

The trend in RUE from 2023 to 2024 followed a pattern similar to that of WUE, with all fertilization treatments demonstrating significantly higher efficiency than the no-fertilization control (CK). Among the treatments, T3 and T5 exhibited the greatest increases in RUE, with improvements of 11.36%, 11.51%, 15.26%, and 19.73% compared to CK. In 2024, RUE for each fertilization treatment increased by 34.59%, 34.59%, 36.58%, 39.29%, 39.42%, and 41.57%, respectively, compared to 2023. The ranking of precipitation utilization efficiency in 2024 followed the order T5 > T3 > T4 > T1 > T2 > CK.

3.4. Effects of Different Base Fertilizers on Growth Traits of Maize

As illustrated in Figure 5, the application of different base fertilizers had a significant impact on the maize plant height, stem diameter, and LAI over two consecutive years. Overall, all fertilization treatments resulted in improved growth indices compared to the no-fertilization control (CK). From 2023 to 2024, maize growth parameters showed a consistent increasing trend across all treatments: In 2023, growth rates ranged from 3.16% to 17.38% for plant height, 1.15% to 14.94% for stem diameter, and 5.22% to 25.54% for the LAI; In 2024, growth rates further increased, ranging from 1.62% to 26.34% for plant height, 9.22% to 18.54% for stem diameter, and 2.37% to 33.18% for the LAI. After two consecutive years of fertilization, maize growth indices in the T3, T4, and T5 treatment groups reached statistically significant levels compared to CK. Among the treatments, T5 exhibited the greatest improvements in growth traits, with significantly higher values than those in the CK group. The most pronounced increases in plant height and the LAI were observed with the combined application of inorganic and organic fertilizers. Specifically, the LAI in the T5 treatment increased by 1.33 times compared to CK. However, no significant difference in plant height was observed between T5 and CK.

3.5. Effects of Different Base Fertilizers on Maize Yield and Its Constituent Factors

The yield characteristics of maize under different base fertilizer treatments are presented in

Table 3. Lower maize yield with different base fertilizers.

Year	Treatment	Panicle Weight (g)	Panicle Length (cm)	Grain Number (No/Ear)	100-Grain Weight (g)	Yield (t/ha)
2023	CK	327.90 d	20.13 b	521.67 c	29.85 d	10.49 c
	T1	347.62 c	20.60 b	557.00 c	34.87 c	11.12 b
	T2	342.34 c	20.28 b	582.00 b	34.13 c	10.96 b
	T3	367.96 b	20.87 b	577.33 b	35.73 b	11.78 a
	T4	349.00 c	21.73 ab	600.33 b	35.31 b	11.17 b
	T5	395.43 a	23.79 a	734.33 a	36.64 a	12.65 a
2024	CK	330.41 c	15.60 c	560.67 c	29.70 b	10.57 d
	T1	355.19 c	20.00 ab	595.33 b	35.21 a	11.37 c
	T2	347.41 c	19.53 ab	600.00 c	36.16 a	11.12 c
	T3	380.83 ab	19.80 ab	607.33 b	38.47 a	12.19 b
	T4	361.53 b	20.13 ab	605.33 b	37.24 a	11.57 c
	T5	415.95 a	21.87 a	677.33 a	38.44 a	13.31 a

Different lowercase letters in the table indicate significant differences between treatments within the same year (p < 0.05). CK: no base fertilizer; T1: chemical fertilizer alone; T2: farmyard manure alone; T3: chemical fertilizer combined with farmyard manure; T4: straw composted and returned to the field; T5: straw mixed with urea, composted, and returned to the field.

. Figure 6 provides a comparison of maize harvested from each treatment. The results indicate that the application of various base fertilizers over two consecutive years significantly enhanced maize yield. Compared to the control group without fertilization (CK), all fertilization treatments resulted in a substantial yield increase. Among the treatments, the combination of farmyard manure with chemical fertilizer (T3) and the incorporation of straw with urea (T5) exhibited the most pronounced yield improvements, reaching 12.65 t/ha and 13.31 t/ha, respectively. In 2023, yields increased by 12.30% (T3) and 20.59% (T5) compared to CK. In 2024, yields further increased by 15.33% (T3) and 25.92% (T5). The year-over-year yield increase from 2023 to 2024 was 3.48% for T3 and 5.22% for T5. The most significant increase in the 100-kernel weight was observed in 2024, with T3 and T5 treatments reaching 38.47 g and 38.44 g, respectively. Differences in the 100-kernel weight among the other treatments were less pronounced, except for the CK group, which had the lowest values. Additionally, ear weight, ear length, and the number of kernels per ear were significantly higher in all fertilization treatments compared to the CK group. The overall ranking for maize yield and yield-related traits was as follows: T5 > T3 > T4 > T1 > T2 > CK.

3.6. Relationship Between Maize Water Use Parameters and Maize Growth Traits Under Different Base Fertilizer Combinations

To further analyze the relationship and correlation between water use parameters and maize growth indicators, RDA was conducted. The response variables included soil volumetric moisture content, water consumption during the growth period, maize grain WUE, and RUE, while the explanatory variables consisted of plant height, stem diameter, LAI, yield, and 100-kernel weight. This high proportion suggests a strong relationship between the response and explanatory variables. Among the explanatory variables, maize yield, LAI, 100-kernel weight, plant height, and stem diameter all contributed to variations in water use characteristics. As shown in

Table 4. Effects of water factors on maize growth characteristics in 2023–2024.

Indicators	Explains/%	Contribution/%	Pseudo-F	p
GY	54.3	82.8	19	0.002 *
LAI	3.8	5.7	1.3	0.024 *
HW	3.3	5.1	1.2	0.034 *
H	3.5	5.3	1.3	0.320
D	0.7	1.1	0.2	0.864

Note: * indicates that p < 0.05 has a significant impact on maize growth traits. HW indicates the weight of 100 grains of maize; GY refers to yield; LAI represents leaf area index; D denotes ground diameter; and H indicates plant height.

, the contributions of each factor were as follows: maize yield contributed the most significantly (82.8%, p < 0.05), indicating its dominant influence. The LAI contributed 5.70% (p < 0.05), suggesting a moderate impact. Plant height contributed 5.3% (p > 0.05), indicating no statistically significant effect. The 100-kernel weight contributed 5.10% (p < 0.05), highlighting a minor but significant influence. Stem diameter contributed 1.1% (p > 0.05), indicating minimal relevance. A significant positive correlation was observed between soil volumetric moisture content, grain WUE, RUE, and water consumption during the growth period (p < 0.05). Additionally, the LAI, 100-kernel weight, and soil volumetric moisture content were positively correlated with both grain WUE and RUE, but showed no significant correlation with water consumption during the growth period (p > 0.05). Plant height and stem diameter had low explanatory contributions to maize water use characteristics (p > 0.05), suggesting that their impact on maize WUE was limited.

To evaluate the role of each fertilization treatment more clearly, all indicators presented in this study were selected as comprehensive evaluation factors, alongside the fertilization quality indicators. Formulas (5)–(7) from Section 2.3 were employed to calculate the comprehensive membership of each fertilization treatment, followed by principal component analysis, which identified two principal components with a cumulative variance contribution rate exceeding 85% (where the characteristic value of each principal component is greater than 1). This cumulative variance contribution rate effectively explains the degree of variance in fertilization. The relevant factors associated with each principal component are displayed in

Table 5. Fertilizer quality evaluation index principal component correlation factor.

Index	PCA 1	PCA 2
Soil volumetric moisture content	0.149	0.029
Soil water consumption	−0.037	0.494
Water use efficiency	0.153	−0.049
Rainfall use efficiency	0.15	0.044
Maize plant height	0.007	0.538
Maize stem diameter	0.155	−0.032
Maize leaf area index.	0.149	−0.169
100-grain Weight	0.136	0.26
Yield	0.15	0.038
Eigenvalue	6.362	1.569
Variance contribution rate	70.685	17.438
Cumulative variance contribution rate	70.685	88.123

, while the comprehensive evaluation values of each fertilization treatment’s effectiveness are illustrated in Figure 7. The soil quality indices for each treatment are 0%, 41.73%, 32.02%, 65.85%, 52.08%, and 81.43%, respectively. These findings indicate that the single application of farm fertilizers and chemical fertilizers is less effective than the combined application of organic and inorganic fertilizers. Notably, straw fertilization demonstrated the most significant effect, effectively promoting maize growth and increasing yield.

4. Discussion

4.1. Effects of Different Base Fertilizer Combinations on Soil Water Content and Soil Water Consumption During the Maize Growth Period

In rain-fed agriculture, water and fertilizer are two of the most significant environmental factors influencing crop growth [16,17,18]. The application of various organic and inorganic base fertilizers significantly improves soil structure, regulates moisture content across different soil layers, reduces water evaporation, and enhances soil water retention and storage capacity. The combined application of farmyard manure and chemical fertilizers, along with urea-treated straw incorporation, promotes downward moisture migration, significantly increasing soil moisture content in deeper layers. This process provides a stable moisture supply throughout the maize growth period. These findings align with those of Panjaitan [19], who reported that the combination of organic fertilizer and rice husk biochar improved soybean growth and soil moisture retention. Although the water supply (rainfall) provided by each fertilizer treatment is consistent, there is a significant difference in soil volumetric moisture content across all treatments. The moisture content in the surface soil is primarily influenced by precipitation, evaporation, root absorption, and the fixation of fertilizer on soil water. Total rainfall during the maize growth periods in 2023 and 2024 was 328.6 mm and 244.2 mm, respectively. In 2023, a year with normal precipitation levels, the increased rainfall may have accelerated fertilizer decomposition while also leading to nutrient leaching and rainwater runoff. The enhanced solubility of soil fertilizers in response to high rainfall can increase soil salinity, loosen soil particles, and compromise soil structure, thereby reducing soil permeability and overall moisture retention. This, in turn, weakens the ability of maize roots to absorb water and nutrients [20]. Although the precipitation in 2023 was higher than in 2024, the volumetric moisture content of the 0–10 cm soil layer remained similar across each treatment. However, the volumetric ratios of the 10–20 cm and 20–40 cm soil layers were significantly higher in 2023 compared to 2024, particularly in the T3, T4, and T5 treatments that included organic fertilizer.

The water consumption of maize during its growth period is influenced by factors such as precipitation, soil water storage, and fertilizer supply. The coupling of water and fertilizer can enhance the utilization and absorption of water by maize. Generally, higher precipitation correlates with increased water consumption. In 2023, the soil water consumption for each treatment group was 60–70 mm greater than that in 2024. This discrepancy is largely attributed to the fact that rainfall during the maize breeding season in 2023 was 84.4 mm higher than in 2024. In the relatively dry year of 2024, water consumption during the maize growth period under fertilization treatments was 4.50% lower than that of the control (CK), suggesting that higher precipitation in 2023 reduced the overall crop water demand. As fertilizer application increased, soil water consumption decreased, which is consistent with the findings of Zhang et al. [21]. In contrast, precipitation in 2024 was lower than in 2023, leading to an overall reduction in crop water consumption. Under drought conditions, however, soil water consumption tends to increase as fertilizer application rates rise [22]. The application of fermented straw and farmyard manure may limit microbial activity and the decomposition rate of organic matter, allowing for a gradual release of moisture and nutrients over an extended period. This process ensures adequate water and nutrient supply for maize growth while minimizing nutrient loss [23,24]. Overall, the application of various base fertilizers improved soil fertility, which subsequently promoted maize growth and root water uptake, leading to a 6.30% increase in water consumption compared to the CK treatment. Different fertilization strategies moderately increased soil water consumption while also contributing to enhanced crop yields [25].

4.2. Effects of Different Base Fertilizers on WUE and Agronomic Traits of Maize

Water plays a crucial role in plant growth and biochemical processes, with crop WUE directly influencing growth conditions and yield potential [26]. While fertilization can improve WUE, traditional applications of single-type base fertilizers often fail to meet the substantial water and nutrient demands of maize, particularly after the jointing stage, when both vegetative growth and reproduction occur simultaneously. The sole application of either organic or inorganic fertilizers is generally less effective in improving maize WUE than their combined application [27,28]. The long-term integration of organic and inorganic fertilizers significantly enhances crop water utilization efficiency by synchronizing the rapid release of inorganic nutrients with the sustained supply of organic nutrients. This synergistic relationship between water and fertilizers improves maize’s ability to absorb and utilize water more efficiently [29,30]. In this study, the combined application of organic and inorganic fertilizers over two consecutive years (2023 and 2024) resulted in an average WUE increase of 11.16% and 23.54%, respectively, compared to single-fertilizer applications. Additionally, annual precipitation levels are closely linked to crop WUE [31]. In this study, 2023 was classified as a normal precipitation year, while 2024 was considered a dry year. The results showed that maize WUE was higher in the dry year (2024) compared to the normal precipitation year (2023). However, maize yield was greater in 2024 than in 2023, which may be attributed to excessive precipitation in 2023. At the onset of the maize breeding period, the precipitation recorded in May 2023 was significantly higher at 291.4 mm compared to only 69.5 mm in May 2024. High rainfall levels throughout the breeding period leads to increased soil infiltration, transpiration, and water loss. In contrast, in 2024, when water availability was lower, the high water retention capacity and sustained nutrient release provided by straw and farmyard manure fertilizers ensured a stable moisture and nutrient supply, supporting maize growth under water-deficient conditions. The study also found that different base fertilizer treatments positively correlated with maize WUE across both years, despite variations in precipitation levels. Among the different treatments, the combined application of organic and inorganic fertilizers had the most significant effect on improving maize WUE.

The basal application of various organic and inorganic fertilizers effectively enhances and regulates soil moisture and nutrient availability, promoting crop growth, increasing the maize LAI, improving water utilization efficiency, and boosting dry matter conversion efficiency, ultimately leading to higher yields. The growth of maize is influenced by water supply and fertilizer availability, with both water stress and fertilizer stress negatively impacting maize plant development. This study indicates that the maize growth indicators (Figure 5) in 2024 surpass those observed in 2023, suggesting that the vegetative growth stage of maize in 2024 is more favorable than in 2023, while the reproductive growth in 2023 was less optimal compared to 2024. This discrepancy may be attributed to heavy rainfall in 2023, particularly 291.4 mm in May, which likely led to fertilizer loss and a reduction in nitrogen supply. Mushore et al. [32] found that rainfall intensity significantly affects fertilizer loss; high-intensity rainfall decreases soil nitrogen content, which is detrimental to maize growth. The thickness of the maize stem and plant height are critical morphological traits that enhance resistance to lodging. In this study, both stem thickness and plant height increased with the duration of fertilization. The initial fertilization in 2023, coupled with the slow decomposition of organic fertilizers, contributed to a residual effect that promoted maize growth in 2024. It is noteworthy that the impact of a single application of chemical fertilizer (T1) on maize plant height growth is the most significant. This may be attributed to the efficiency of chemical fertilizers in supplying nutrients to maize; however, they do not effectively maintain soil moisture. Consequently, moisture stress may have inadvertently promoted greater plant height. While excessive plant height can hinder the maize’s resistance to lodging, an excessively low plant height can adversely affect leaf stretching and overall photosynthetic performance. The T5 treatment resulted in the largest stem thickness, and the leaf area index reached its highest level under T5 treatment in 2024. The combination of inorganic fertilizers and decomposed straw can provide sufficient moisture to maize during periods of drought, thereby enhancing the plant’s stress resistance and lodging resistance. Compared to other treatments, the addition of urea to straw resulted in long-term improvements in soil moisture and structure, similar to the effects of organic fertilizers, while also maintaining the efficient and rapid nutrient release characteristics of inorganic fertilizers. Furthermore, microbial processes involved in the fermentation and decomposition of organic matter from straw degradation facilitated a more effective interaction with inorganic fertilizers, thereby providing maize with a more abundant and balanced nutrient supply. Notably, this process supplies a significant amount of potassium, which plays a critical role in enhancing photosynthetic capacity, improving water use efficiency, ensuring robust crop growth, and ultimately increasing maize yield [33,34]. Overall, field fertilization strategies prove to be the most effective approach for enhancing maize yield. This method not only reduces production costs but also improves agricultural efficiency in the region.

The existing body of research has consistently demonstrated that prolonged fertilizer application induces significant changes in soil physicochemical properties and microbial ecosystems. However, the present study was limited to a two-year experimental period, during which the combined application of inorganic fertilizers with eco-friendly straw amendments exhibited synergistic effects in enhancing soil fertility parameters. These preliminary findings highlight the need for comprehensive long-term studies to (1) optimize fertilization strategies by systematically evaluating nutrient ratios and application rates to maximize soil health and crop productivity; (2) elucidate the temporal dynamics of soil organic matter accumulation and nutrient cycling under different fertilization regimes, providing insights into long-term soil fertility trends; and (3) assess the sustainability of these agricultural practices through continuous monitoring of soil acidification potential, heavy metal accumulation, and microbial community evolution. Future research should focus on identifying more suitable fertilizer ratios and concentrations while investigating their long-term effects on soil health.

5. Conclusions

This study examines the effects of various organic and inorganic fertilizer applications on water utilization efficiency and the growth of maize. The results indicate that the combination of inorganic and organic fertilizers significantly enhances maize’s water utilization efficiency, promotes growth, and increases yield. High-intensity precipitation impacts water usage in maize. In drought conditions, the application of fertilizers (T3) and straw combined with fertilization (T5) can still yield favorable results, improving maize’s resistance to water stress and lodging. The fertilizer quality evaluation index demonstrates that the application of agricultural and chemical fertilizers (T3) and straw treated with urea fermentation and decomposition (T5) have the most positive effect on maize’s moisture utilization and the enhancement of agronomic traits. The application of straw alone ranks second; however, it is not advisable to use any single type of base fertilizer in isolation. This is particularly relevant given the prevalent water shortages in agricultural practices on sloping farmland. Pre-treating organic and inorganic fertilizers through fermentation and decomposition can significantly enhance their effectiveness. Based on this study, and considering the complexity of soil ecosystems, further research and continuous observations are necessary to explore the interactions between organic and inorganic fertilizers and their effects on soil water dynamics, as well as on plant and microbial ecosystems.