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Article

Effects of Alternate Wetting and Drying (AWD) Irrigation on Rice Growth and Soil Available Nutrients on Black Soil in Northeast China

by
Chaoyin Dou
*,
Chen Qian
,
Yuping Lv
and
Yidi Sun
College of Hydraulic Science and Engineering, Yangzhou University, Yangzhou 225009, China
*
Author to whom correspondence should be addressed.
Agronomy 2025, 15(10), 2372; https://doi.org/10.3390/agronomy15102372
Submission received: 13 September 2025 / Revised: 6 October 2025 / Accepted: 9 October 2025 / Published: 10 October 2025
(This article belongs to the Special Issue Influence of Irrigation and Water Use on Agronomic Traits of Crops—2nd Edition)
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Abstract

Extensive practice has demonstrated that the continuous pursuit of high yields in the black soil region of Northeast China resulted in imbalances in soil nutrients and declines in both soil quality and water use efficiency. Alternate wetting and drying (AWD) irrigation offers a promising solution for increasing rice yield and maintaining soil fertility. However, the success of this irrigation method largely depends on its scheduling. This study examined the threshold effects of AWD on rice growth, yield, and soil nutrient availability in the Sanjiang Plain, a representative black soil region in Northeast China. A two-year trial was conducted from 2023 to 2024 at the Qixing National Agricultural Science and Technology Park. “Longjing 31”, a local cultivar, was selected as the experimental material. The lower limit of soil water content under AWD was set as the experimental factor, with three levels: −10 kPa (LA), −20 kPa (MA), and −30 kPa (SA). The local traditional irrigation practice, continuous flooding, served as the control treatment (CK). Indicators of rice growth and soil nutrient content were measured and analyzed at five growth stages: tillering, jointing, heading, milk ripening, and yellow ripening. The results showed that, compared to CK, AWD had minimal impact on rice plant height and tiller number, with no significant differences (p > 0.05). However, AWD affected leaf area index (LAI), shoot dry matter (SDM), yield, and soil nutrient availability. In 2023, control had little effect on rice plant height and tiller number among the different irrigation treatments. The LAI of LA was 11.1% and 22.5% higher than that of MA and SA, respectively, while SDM in LA was 10.5% and 17.2% higher than in MA and SA. Significant differences were found between LA and MA, as well as between LA and SA, whereas no significant differences were observed between MA and SA. The light treatment is beneficial to the growth and development of rice, while the harsh growth environment caused by the moderate and severe treatments is unfavorable to rice growth. The average contents of nitrate nitrogen (NO3−-N), available phosphorus (AP), and available potassium (AK) in LA were 11.4%, 8.4%, and 9.3% higher than in MA, and 16.7%, 11.5%, and 15.0% higher than in SA, respectively. Significant differences were observed between LA and SA. This is because the light treatment facilitates the release of available nutrients in the soil, while the moderate and severe treatments hinder this process. Although panicle number per unit area and grain number per panicle in LA were 7.5% and 2.3% higher than in MA, and 10.8% and 2.2% higher than in SA, these differences were not statistically significant. Seed setting rate and thousand-grain weight showed little variation across irrigation treatments. The yield of LA was 10,233.3 kg hm−2, 9.1% and 14.1% higher than that of MA and SA, respectively, with significant differences observed. Compared with the moderate and severe treatments, the light treatment increases indicators such as the number of panicles per unit area, grains per panicle, thousand-grain weight, and seed setting rate, resulting in significant differences among the treatments. Water use efficiency (WUE) decreased as the control level increased. The WUE of all AWD irrigation treatments was significantly higher than that of the control treatment (CK). Compared with CK, AWD reduces evaporation, percolation, and other water losses, leading to a significant decrease in water consumption. Meanwhile, the yield remains basically unchanged or even slightly increases, thus resulting in a higher WUE than CK. The trends in rice growth, soil nutrient indicators, and WUE in 2024 were generally consistent with those observed in 2023. In 2024, the yield of LA was 9832.7 kg hm−2, 14.9% and 17.3% higher than that of MA and SA, respectively, with significant differences observed. Based on the results, the following conclusions are drawn: (1) AWD irrigation can affect the growth of rice, alter the status of available nutrients in the soil, and thereby cause changes in yield and WUE; (2) LA is the optimal treatment for increasing rice yield, improving the availability of soil available nutrients, and improving WUE; (3) Both MA and SA enhanced WUE; however, these practices negatively impacted rice growth and the concentration of soil available nutrients, leading to a concurrent decline in yield. To increase rice yield and maintain soil fertility, LA, with an irrigation upper limit of 30 mm and a soil water potential threshold of −10 kPa, is recommended for the Sanjiang Plain region.

1. Introduction

Rice, one of China’s three major food crops, plays a crucial role in ensuring food security. It occupies 28% of the total land devoted to food crops nationwide, and accounts for 40% of the country’s total grain production. Stabilizing rice yield is vital for maintaining social stability [1]. Water supply and soil nutrients are key factors in achieving high yields. The Sanjiang Plain, located in Heilongjiang Province in Northeast China, is known as the “granary of China” due to its abundant land and water resources. The region’s black soil, rich in nutrients and organic matter, is highly fertile. However, ongoing industrialization and rising living standards have intensified conflicts among industrial, domestic, and agricultural water use. Between 2000 and 2023, the proportion of water used for irrigation relative to total water consumption decreased from 28.5% to 25.6% [2]. Meanwhile, the region has continued to rely on extensive irrigation practices, with water use reaching up to 552.7 mm [3]. This combination of water resource scarcity and inefficient management has created significant challenges in maintaining stable, high grain yields. Moreover, soil quality has progressively declined due to sustained over-exploitation.
Studies show that, after 100 years of reclamation, the soil organic matter content in the top 0–20 cm layer of black soil has decreased from 150.6 to 50.2 g kg−1. The contents of available nitrogen, phosphorus, and potassium have decreased by 50–70 g m−3, 20–30 g m−3, and 30–60 g m−3, respectively [4]. Between 1980 and 2010, total nitrogen, total phosphorus, and total potassium in black soil decreased by 1.8%, 15.2%, and 8.9%, respectively [5]. Additionally, the black soil region experiences an annual surface soil loss of 0.3 to 1.0 cm [6]. Predictions suggest that, without intervention, some cultivated land could be lost within 40 to 50 years due to continued erosion [6]. Consequently, water and soil management issues in this region have attracted significant attention from researchers committed to finding sustainable solutions. The application of water-saving irrigation techniques, such as controlled irrigation (CI), wet-shallow irrigation (WSI), and alternate wetting and drying irrigation (AWD), has been shown to improve water use efficiency (WUE) significantly. Compared to conventional irrigation, CI, WSI, and AWD can reduce water use by 24–45.9% [7], 25–30.0% [8], and 15.7–35% [3], respectively. Furthermore, the use of soil amendments, such as biochar, can enhance nutrient availability and improve soil fertility [9]. However, existing research has primarily focused on singular objectives—either improving WUE or enhancing soil quality—with limited emphasis on their synergistic effects.
AWD irrigation is a water management practice that involves maintaining a shallow water layer in the field for a specified period, allowing the soil to naturally dry to a specific threshold before re-irrigation. This method alternates cyclically between soil saturation and controlled drying phases, optimizing WUE while maintaining crop productivity [10]. AWD is a widely adopted water-saving technique for rice cultivation in China and has proven successful in practice. For example, in the Erhai Lake Basin, AWD reduced irrigation water use by 50% compared to conventional irrigation, while simultaneously increasing rice yield by 6.9% [11]. In Henan Province, AWD reduced irrigation water consumption by 30% and increased rice yield by 8.6% compared to conventional irrigation [12]. In Vietnam, AWD reduced water use by 33% and increased rice yield by 4.4% [13]. In contrast to WSI, which maintains a continuous water layer, AWD includes dry periods after the water layer evaporates. The duration of this dry phase depends on the lower limit of irrigation control. This drying phase allows AWD to conserve more water than WSI and provides an opportunity to capture and utilize rainfall, further reducing irrigation needs. Additionally, the increased water storage capacity of the field reduces drainage and mitigates soil nutrient loss. However, the drying process in AWD may accelerate soil organic matter mineralization and nutrient decomposition, potentially compromising long-term soil fertility. Although this phenomenon has not been explicitly documented in existing AWD studies, similar effects have been reported in research on controlled irrigation (CI) [14]. CI maintains no water layer throughout the growth period, and the drying phase in AWD is like that in CI. This suggests that while AWD’s yield-enhancing benefits are reliable, its impact on soil nutrients depends on the degree of drying, particularly the determination of the lower irrigation limit.
Therefore, this study implemented AWD in the black soil region, controlling different irrigation lower limits and investigating crop growth, yield, and soil nutrient availability. The objectives of this study were to assess the effects of different AWD irrigation lower limits on rice growth, yield, and WUE in the black soil region; examine the impact of varying irrigation controls on soil nutrient availability; and determine optimal irrigation parameters that simultaneously achieve water conservation, yield enhancement, and improved soil quality.

2. Materials and Methods

2.1. Experimental Site Description and Plant Materials

Field experiments were conducted at the Qixing National Agricultural Science and Technology Park, Beidahuang Group, Heilongjiang Province, China (132°39′42″ E, 47°16′25″ N), during the rice-growing seasons from May to October in 2023 and 2024. The site is situated in plain area with a cold temperate humid monsoon climate. Winters are long and cold, while summers are short but warm. The average annual temperature is approximately 1.8 °C, and the annual total effective accumulated temperature is about 2760 °C. Precipitation and high temperatures coincide during the growing season. Annual precipitation ranges from 500 to 600 mm, with most rainfall occurring from June to August, contributing to about 70% of the total precipitation during the growing period. Annual evaporation ranges from 1200 to 1500 mm. The average annual sunshine duration is approximately 2400 h, and the frost-free period lasts about 137 days. The soil in the experimental field is meadow albic soil, with average concentrations of alkali-hydrolyzable nitrogen (N), Olsen phosphorus (P), and exchangeable potassium (K) of 162 mg kg−1, 40.8 mg kg−1, and 142 mg kg−1, respectively. Precipitation data for the rice-growing seasons in 2023 and 2024 were collected at a nearby weather station, with the details shown in Figure 1.
The local japonica cultivar Longjing 31 was used in both years. Seedlings were raised in seedbeds and transplanted on 18 May 2023 and 18 May 2024 at 12 cm × 30 cm spacing with three seedlings per hill. Individual plots measured 2.4 m × 4 m. Fertilizer sources were urea (46.4% N), potassium sulfate (50% K2O), and calcium superphosphate (13.5% P2O5). Nitrogen (105 kg N ha−1) was split 4:3:3 among basal, tillering, and panicle applications. Phosphorus (60 kg P2O5 ha−1) was applied entirely at basal, while potassium (75 kg K2O ha−1) was split 5:5 between basal and panicle stages. The resulting N:P2O5:K2O ratio was 1.75:1:1.25.

2.2. Experimental Design

The experiment was conducted as a completely randomized trial, with conventional flooding irrigation (CK) as the control. Rice was irrigated using the alternate wetting and drying (AWD) method. In the AWD regime, irrigation was applied under wet conditions and withheld until the soil water potential at a depth of 15 cm reached −10 kPa, −20 kPa, and −10 kPa during the early to mid-tillering, late tillering, and jointing to ripening stages, respectively (LA). For the other two treatments, wet conditions were set at −20 kPa, −30 kPa, −20 kPa (MA) and −30 kPa, −40 kPa, −30 kPa (SA) (Table 1). Each treatment was replicated three times, resulting in 12 experimental plots. Both AWD and CK treatments began 10 days after regreening and continued until rice maturity. Under the CK regime, a water layer of 10–50 mm was maintained throughout the growing season, except for a 10–30 mm water layer during the regreening stage, and the water layer was allowed to naturally dry during the yellow ripening stage. In the AWD regime, a tension meter (Institute of Soil Science, Chinese Academy of Sciences, Nanjing, Jiangsu, China) was installed in each rice plot to record soil moisture readings. Irrigation was initiated when the soil water potential reached the lower threshold and continued until the water depth reached 30 mm, which was set as the upper irrigation limit.

2.3. Statistical Analysis

All experimental data were processed and analyzed using Microsoft Excel 2021 (Microsoft Corp., Redmond, WA, USA). Statistical analyses, including analysis of variance (ANOVA), were performed using IBM SPSS Statistics (version 27.0; IBM Corp., Armonk, NY, USA). Graphs were generated using Origin 2021 (OriginLab Corporation, Northampton, MA, USA).

2.4. Evaluated Variables

2.4.1. Plant Growth and Yield

Rice plant height (cm), tiller number (tillers per plant), leaf area index (LAI), and shoot dry matter (SDM) (g) were measured at the tillering, jointing, heading, milk ripening, and yellow ripening stages. For each plot, five plants were selected, and plant height, leaf length, and leaf width were measured using a ruler. The single leaf area was estimated as the product of leaf length and leaf width, multiplied by 0.75 [15]. LAI was calculated as the ratio of the total leaf area to the land area it covered. SDM dry weight was determined after oven-drying at 70 °C to a constant weight.
At maturity, plants were hand-harvested to assess grain yield and yield components. The number of panicles per square meter, grains per panicle, seed setting rate, and thousand-grain weight were determined from 20 randomly selected plants (excluding border plants) per plot. The seed setting rate was defined as the percentage of filled grains (with a specific gravity ≥ 1.06 g cm−3) relative to the total number of spikelets. Theoretical yield was calculated by multiplying the values of the aforementioned parameters and adjusting for 14% moisture content.
WUE was calculated using the following formula: WUE = grain yield (kg hm−2)/water consumption during the growing season (m3 hm−2).

2.4.2. Soil Sampling

Soil samples for the determination of nitrate nitrogen (NO3−-N) (mg kg−1), available phosphorus (AP) (mg kg−1), and available potassium (AK) (mg kg−1) were randomly collected using a 5 cm-diameter soil auger from the 0–30 cm soil layer at three locations within each plot. Sampling was conducted at each growth stage, though the sampling times were not necessarily synchronized with the plant stages. After collection, the samples were air-dried and sieved through a 2 mm mesh. Nutrient extraction was performed using 0.01 mol L−1 calcium chloride for NO3−-N, and the concentration was measured using an ultraviolet spectrophotometer. Olsen phosphorus (AP) was extracted using 0.5 mol L−1 NaHCO3 at pH 8.5, with phosphorus content determined following the method of Olsen and Sommers (1982) [16]. AK was quantified using a flame photometer, with 1.0 mol L−1 CH3COONH4 at pH 7.0 as the extractant.

3. Results

3.1. Rainfall and Irrigation

In 2023, rainfall occurred 70 times, totaling approximately 475.5 mm. Of these events, 22 had rainfall amounts greater than 5 mm. Precipitation was mainly concentrated from June to August, with a cumulative total of 320.2 mm, accounting for 70% of the total rainfall during the growing season. The highest single precipitation event occurred on 10 July, with 59.7 mm. Due to the distribution and type of rainfall, irrigation was mainly applied during the jointing to milk ripening stages. The three treatments received irrigation 4, 3, and 2 times, respectively, with total amounts of 109 mm, 94 mm, and 33 mm.
In 2024, rainfall occurred 61 times, with a total of approximately 379.9 mm. Of these, 23 events had rainfall amounts greater than 5 mm. Like 2023, most precipitation occurred between June and August, totaling 292.9 mm, or 77.1% of the total rainfall during the growing season. The highest single precipitation event occurred on 21 July, with 91.9 mm. Compared to 2023, rainfall in 2024 was more unevenly distributed. The three treatments received irrigation 3, 2, and 2 times, respectively, with total amounts of 123 mm, 58 mm, and 56 mm.

3.2. Plant Growth and Yield

3.2.1. Plant Height

The changes in rice plant height during the growth period are illustrated in Figure 2. The height of all treatments increased rapidly from the tillering to the heading stage. Specifically, the increase from the tillering to the jointing stage was approximately 88.9%, while the increase from the jointing to the heading stage was about 24.6%. Plant height peaked at the heading stage and remained stable thereafter.
During the tillering stage, the plant height in the CK treatment was greater than that in the AWD treatment. From the jointing to the heading stage, the average height of the AWD treatment increased more rapidly than that of the CK treatment. At the heading stage, the mean plant height in the AWD treatment was 99.0 cm, which was similar to that in the CK treatment. The difference between the CK and AWD treatments was not significant.
In 2023, at the tillering stage, plant heights across all AWD treatments ranged from 43 to 46 cm, with a variation of 2.6%. At the jointing stage, rice height increased by approximately 39.7 cm. The LA treatment exhibited the greatest increase, growing by 40.6 cm to a height of 85.2 cm, which was 1.8 and 2.3 cm higher than the MA and SA treatments, respectively. At the heading stage, plant height continued to increase steadily. Among the treatments, LA exhibited the greatest growth, with a final plant height of 101.1 cm, which was 0.2 cm and 1.3 cm higher than the MA and SA treatments, respectively. During the milk ripening stage, plant height in the LA and MA treatments increased slightly, while in the SA treatment, plant height decreased. The LA treatment had the highest plant height, which was 1.4 and 6.6% higher than the MA and SA treatments, respectively. The differences among the AWD treatments were not significant throughout the entire growth period, except during the milk ripening stage, when the LA treatment was significantly taller than the SA treatment. This phenomenon may be attributed to premature senescence in the SA treatment, which resulted in a decrease in plant height.
In 2024, at the tillering stage, plant heights across all AWD treatments ranged from 38 to 41 cm. The LA treatment exhibited the highest plant height, which was 1.6% and 3.8% greater than the MA and SA treatments, respectively. Differences between LA and MA, also LA and SA, were significant, while no significant difference was found between MA and SA. At the jointing stage, the LA treatment increased by 35.4 cm, a greater increment than those observed in the MA and SA treatments. The difference between LA and SA was significant, but no significant differences were detected between LA and MA, or between MA and SA. At the heading and milk ripening stages, the plant height in the LA treatment was 87.7 cm and 100.7 cm, respectively, slightly higher than that in the MA and SA treatments. However, during both stages, differences among the AWD treatments were not significant.
These results suggest that as the lower irrigation threshold increased, plant height tended to decrease. Traditional flooding irrigation proved more favorable for plant height development compared to water-saving irrigation. Moreover, the effect of water control levels on plant height appeared to be influenced by the rainfall patterns in different years. A comparison between 2023 and 2024 indicated that abundant rainfall early in the growing season (as in 2023) could mitigate premature senescence in rice, while rainfall accumulation in the later stages reduced the differences caused by varying water control treatments.

3.2.2. Tillering

The tiller numbers for the different treatments are shown in Table 2. In 2023, the number of tillers at the end of the tillering stage for AWD treatments ranged from 23.7 to 25.3, with a variation of 6.8%. The LA treatment had 1.6 and 0.6 more tillers than the MA and SA treatments, respectively. The average tiller number for the AWD treatments was 24.6, which was 8.8% lower than that of the CK treatment; however, the differences among these treatments were not statistically significant. In 2024, the number of tillers at the end of the tillering stage for AWD treatments ranged from 23.1 to 24.7. The LA treatment exhibited the highest tiller number, which was 2.5% and 6.9% greater than the MA and SA treatments, respectively. The average tiller number for the AWD treatments was 24.0, which was 8.7% lower than that of the CK treatment. Analysis of variance revealed that the difference between the CK and AWD treatments was significant, while no significant differences were found among the AWD treatments.
Compared with continuous flooding, AWD consistently reduced tiller density, and the magnitude of reduction intensified with stricter soil-drying thresholds. In years when early-season rainfall was abundant, precipitation attenuated these irrigation-induced differences. Between 2023 and 2024, LA (−10 kPa) suppressed ineffective tillers without hampering effective ones, improving nutrient-use efficiency and ultimately increasing yield. In contrast, SA (−30 kPa) inhibited both ineffective and effective tillers, predisposing the crop to yield loss. From a tillering perspective, light or moderate water stress (LA or MA) is therefore recommended.

3.2.3. Leaf Area Index (LAI)

The variations in leaf area index (LAI) for each treatment are presented in Figure 3. LAI for all treatments increased rapidly from the tillering to the heading stage. Specifically, LAI increased by 105.9% from the tillering to the jointing stage, but only by 11.5% from the jointing to the heading stage. LAI peaked at the heading stage, after which leaf senescence led to a decrease in LAI.
In 2023, at the tillering stage, LAI for all AWD treatments ranged from 1.9 to 2.2, with a variation of 15.0%, and no significant differences were observed among them. From the tillering to the jointing stage, LAI for the LA treatment increased by 88.1%, while the increases for the MA and SA treatments were 52.6% and 78.9%, respectively. As a result, at the jointing stage, LAI for the LA treatment was 4.3, significantly higher than for the MA and SA treatments. No significant differences were found between the MA and SA treatments. At the heading stage, although LAI for all AWD treatments increased compared to the previous stage, the variation and significance among the treatments remained unchanged. LAI for the LA treatment increased by 9.6%, reaching 4.7, which was 19.4% and 31.5% higher than for the MA and SA treatments, respectively. At the milk ripening stage, LAI for the LA treatment decreased by 11.1%, but remained 15.1% higher than for the MA treatment and 22.1% higher than for the SA treatment. At the yellow ripening stage, LAI further decreased, ranging from 2.4 to 2.6, with a variation of 8.3%. In both the milk ripening and yellow ripening stages, no significant differences were observed among the AWD treatments. LAI for the CK treatment increased rapidly from the tillering to the jointing stage, remaining higher than for the AWD treatments at both the jointing and heading stages. Differences between CK and the MA and SA treatments were significant, while no significant difference was observed between CK and the LA treatment. However, LAI for the CK treatment decreased dramatically after the heading stage, falling below that of the AWD treatments during the milk and yellow ripening stages. Differences between CK and the AWD treatments were not significant, except during the milk ripening stage, when CK was significantly lower than LA.
In 2024, at the tillering stage, LAI for the LA and MA treatments was 2.2 and 2.1, respectively, which were 11.1% and 5.2% higher than that of the SA treatment. From the tillering to the jointing stage, LAI for the LA treatment increased by 142.6%, reaching 5.1, which was 5.0% and 6.5% higher than for the MA and SA treatments, respectively. At the heading stage, LAI for the LA and MA treatments was 5.7 and 5.6, which were 5.8% and 4.1% higher than that of the SA treatment. From the heading to the milk ripening stage, LAI for the LA treatment decreased by 32.9%, reaching 3.8, while LAI for the MA and SA treatments decreased by 44.3% and 43.2%, respectively, to 3.1 and 3.0. At the yellow ripening stage, LAI for the LA treatment was 3.1, representing a 19.0% decrease from the previous growth stage. The LAI for the MA and SA treatments was 3.0 and 2.8, respectively, which were 3.9% and 9.2% lower than that of the LA treatment. Throughout the growth period, the order of LAI for the AWD irrigation treatments was consistently LA > MA > SA, with significant differences between LA and SA. At the tillering and heading stages, there were no significant differences between MA and LA, but both treatments were significantly higher than SA. At the jointing and milk ripening stages, LAI for the LA treatment was significantly higher than for MA, but no significant difference was observed between MA and SA. The CK treatment exhibited an LAI like that of LA and MA at the tillering and jointing stages, but it was significantly lower than that of LA. From the heading stage onward, the LAI for the CK treatment was between those of LA and MA, significantly higher than SA, but not significantly different from LA, except at the milk ripening stage, when it was significantly lower than LA.
A comparison of data from 2023 and 2024 showed that concentrated rainfall during the early growth stage in 2023 was unfavorable for LAI formation. In contrast, adequate rainfall combined with light to severe alternate wetting and drying irrigation was favorable for LAI formation. In 2024, concentrated and heavy rainfall in the later growth stages led to a significant decline in LAI.
These results suggest that as the lower control threshold increased, LAI tended to decrease, and differences between treatments became less significant as the growth stages progressed. Over two consecutive growing seasons, the overall order of LAI was consistently LA > MA > SA, indicating that the LA treatment promoted LAI more effectively than both the MA and SA treatments.

3.2.4. Shoot Dry Matter (SDM)

Figure 4 and Table 3 illustrate the dynamic changes in shoot dry matter (SDM) throughout the growing season. The SDM of all treatments consistently increased, reaching its peak at the yellow ripening stage. The most rapid increase occurred between the tillering and jointing stages, with an average growth of 197.8%. After the jointing stage, the growth rate slowed, with an average increase of 42.6%.
In 2023, at the tillering, jointing, and heading stages, the SDM of MA reached 9.5 g, 26.4 g, and 40.3 g, respectively. These values were 0.9 g, 1.8 g, and 0.6 g higher than those under light control, and 1.5 g, 2.0 g, and 6.5 g higher than those under severe control. From tillering to heading, the SDM growth rates were 358.7%, 323.9%, and 322.4%, respectively. During the milk ripening and yellow ripening stages, the SDM under the LA treatment reached 59.3 g and 81.5 g, which were 6.9 g and 7.7 g higher than under the MA treatment, and 10.1 g and 11.9 g higher than under the SA treatment. The SDM growth rates from milk ripening to yellow ripening were 37.3%, 40.7%, and 41.1%, respectively. The CK treatment exhibited lower SDM than the AWD treatments during the jointing and heading stages. After the heading stage, SDM increased rapidly, reaching 54.5 g and 76.0 g during the milk ripening and yellow ripening stages, respectively. These amounts represent increases of 73.7% and 39.5% compared to the preceding growth stage. These values were between those of the LA and MA treatments. During the first three growth stages, there were no significant differences among the AWD treatments. However, in the final two growth stages, the LA treatment was significantly higher than the SA treatment, and during the yellow ripening stage, the difference between the MA and SA treatments was also significant. The CK treatment was significantly lower than both LA and SA during the heading stage, but it showed no significant differences from the AWD treatments at other stages. These results suggest that, in the early growth stages, water control enhances dry matter accumulation. As the lower limit of water control increases, dry matter content initially rises and then declines, with similar SDM growth rates across treatments during this period. However, from the milk ripening stage onward, the rate of SDM accumulation decreases as water control limits increase, leading to lower dry matter content. LA was the most beneficial for dry matter accumulation, while MA and SA were less favorable.
In 2024, during the tillering stage, SDM under the AWD treatment ranged from 7.5 to 8.0 g, with a variation of 6.6%. At the jointing and heading stages, dry matter under the LA treatment reached 27.6 g and 40.5 g, respectively, which were 2.1 g and 1.1 g higher than under the MA treatment, and 2.5 g and 2.8 g higher than under the SA treatment. From tillering to heading, the growth rates of SDM for LA, MA, and SA were 408.4%, 402.9%, and 405.0%, respectively. During the milk and yellow ripening stages, SDM under the LA treatment reached 62.4 g and 73.0 g, respectively, which were 1.5 g and 6.4 g higher than under the MA treatment, and 2.5 g and 7.7 g higher than under the SA treatment. The growth rates of dry matter from milk ripening to yellow ripening were 17.1%, 9.4%, and 9.2%, respectively. Except for the tillering stage, where the CK treatment had higher SDM than the AWD treatments, the SDM of the CK treatment fell between those of LA and MA at other stages. From the jointing to the milk ripening stage, significant differences were observed among the AWD treatments. At the yellow ripening stage, the LA treatment was significantly higher than both the MA and SA treatments, while no significant difference was found between the MA and SA treatments. The CK treatment showed no significant difference from the MA treatment but was significantly lower than the LA treatment. Except at the yellow ripening stage, where no significant difference was observed between CK and SA treatments, the CK treatment was significantly higher than the SA treatment at other stages. These results suggest that SDM decreases as the lower limit of water control increases. The LA treatment promoted dry matter accumulation, while the MA and SA treatments were less conducive to SDM accumulation.
Comparing the two years with different rainfall patterns, SDM in 2023 was lower than in 2024 during the first three growth stages. Although SDM in 2023 remained lower than in 2024 at the milk ripening stage, the gap narrowed. From milk ripening to yellow ripening, the growth rate of SDM in 2024 was lower than in 2023, and by the yellow ripening stage, SDM values in both years became similar. These findings suggest that concentrated or excessive rainfall hindered SDM accumulation.

3.2.5. Yield and Its Components

Table 3 presents the rice yield and its components for each treatment across two growing seasons.
In 2023, the LA treatment had panicle numbers and grains per panicle of 603.3 and 78.1, respectively, which were 7.5% and 2.2% higher than those of the MA treatment, and 10.8% and 2.2% higher than those of the SA treatment. The seed setting rate and thousand-grain weight ranged from 88.3% to 88.6% and from 24.4 g to 24.8 g, with variations of 0.3% and 1.6%, respectively. The theoretical yield for LA was 10.2 t ha−1, which was 9.1% and 14.1% higher than that of MA and SA, respectively. Compared to the AWD treatments, CK had the lowest grains per panicle, 5.1% lower than LA. However, CK exhibited the highest seed setting rate and thousand-grain weight, which were 2.5% and 3.3% higher than LA, respectively. The panicle number of CK was 558.8 panicles m−2, which was intermediate between MA and SA. The yield of CK was 9.5 t ha−1, 7.3% lower than that of LA. Among the yield components, no significant differences were found among the AWD treatments, although significant differences in yield were observed between treatments. The yield components of CK showed no significant differences compared to the AWD treatments, except for thousand-grain weight, which was significantly higher than that of LA and SA. The yield of CK was not significantly different from that of MA but was significantly different from that of LA and SA. LA promoted an increase in panicle number and grains per panicle but reduced seed setting rate and thousand-grain weight. As water control intensity increased, panicle number and grains per panicle decreased, while seed setting rate and thousand-grain weight remained relatively unchanged. The impact of water control on panicle number and grains per panicle was greater than its impact on seed setting rate and thousand-grain weight. Ultimately, LA was beneficial for increasing yield, whereas increasing water control intensity led to yield reduction, with MA and SA further decreasing yield.
In 2024, the panicle number and grains per panicle in the LA treatment were 587.0 and 74.6, respectively, which were 1.0% and 5.8% higher than those in the MA treatment, and 3.9% and 7.5% higher than those in the SA treatment. The seed setting rate and thousand-grain weight ranged from 82.1% to 88.1% and from 25.2 g to 25.5 g, with variations of 7.3% and 1.2%, respectively. The theoretical yield for LA was 9.8 t ha−1, which was 14.9% and 17.3% higher than that of MA and SA, respectively. Compared to the AWD treatments, CK had the lowest grains per panicle, 9.5% lower than LA. However, CK exhibited the highest seed setting rate and thousand-grain weight, which were 3.7% and 0.6% higher than those of LA, respectively. The panicle number of CK was 579.6 panicles m−2, which was intermediate between MA and SA. The yield of CK was 9.0 t ha−1, 8.8% lower than that of LA. Among the yield components, no significant differences were found among the AWD treatments. No significant differences were observed between MA and SA, but both were significantly lower than LA. Significant differences in yield were observed between treatments. CK showed no significant differences in yield components compared to the AWD treatments, except for seed setting rate, which was significantly higher than that of MA. The yield of CK was not significantly different from that of MA and SA, but it was significantly different from that of LA.
The yield components and yield in 2024 followed a trend similar to those in 2023. Compared to 2023, the yield components and yield in 2024 declined to varying extents, except for thousand-grain weight. This suggests that high rainfall during the late growth stages may reduce yield, indicating that rainfall patterns directly influence yield. However, this does not diminish the effectiveness of alternate wetting and drying (AWD) irrigation.
Table 3. Rice yield and its components of each treatment.
Table 3. Rice yield and its components of each treatment.
YearTreatmentPanicle per Unit Area (Panicles m−2)Grain Number per PanicleSeed Setting Rate (%)Thousand-Grain Weight (g)Theoretical Production (kg hm−2)
2023LA603.3 ± 19.7 a78.1 ± 0.6 a88.3 ± 1.4 a24.6 ± 0.2 b10,233.3 ± 152.8 a
MA561.3 ± 25.9 a76.4 ± 3.7 a88.5 ± 1.6 a24.8 ± 0.4 ab9383.3 ± 144.3 b
SA544.7 ± 38.2 a76.5 ± 4.7 a88.6 ± 2.6 a24.4 ± 0.5 b8966.7 ± 189.3 c
CK558.8 ± 36.0 a74.3 ± 2.0 a90.6 ± 2.0 a25.4 ± 0.3 a9533.3 ± 125.8 b
2024LA587.0 ± 34.0 a74.6 ± 5.8 a88.1 ± 1.4 ab25.5 ± 0.2 a9832.7 ± 15.7 a
MA581.5 ± 11.6 a70.5 ± 1.9 a82.1 ± 1.1 b25.4 ± 0.2 a8555.4 ± 162.9 b
SA564.8 ± 25.1 a69.4 ± 12.7 a84.7 ± 2.8 ab25.2 ± 0.4 a8384.8 ± 186.6 b
CK579.6 ± 19.5 a68.1 ± 7.4 a91.3 ± 6.3 a25.7 ± 0.3 a8970.2 ± 330.0 ab
Note: Data were analyzed using one-way analysis of variance (ANOVA) and presented as mean values (n = 3). Values followed by different lowercase letters indicate significant differences at the p < 0.05.

3.2.6. Water Consumption and WUE

Table 4 presents the water consumption and WUE of rice across two growing seasons.
In 2023, the water consumption for the LA treatment was 4013.0 m3 hm−2, which was 3.7% higher than that of MA and 11.3% higher than that of SA. CK consumed 4729.0 m3 hm−2, 17.8% more than LA. Significant differences were observed between CK and AWD treatments, but no significant differences were found among the AWD treatments. For WUE, LA achieved 2.6 kg m−3, which was 8.3% higher than MA and 4.0% higher than SA. CK had a value of 2.0, 23.1% lower than LA. No significant differences were found among AWD treatments, while CK was significantly lower than all AWD treatments.
A similar trend was observed in 2024. Water consumption in the AWD treatments ranged from 3989 m3 hm−2 to 3509 m3 hm−2, and WUE varied between 2.0 kg m−3 and 2.5 kg m−3. CK consumed the most irrigation water, approximately 1420.0 m3 hm−2, significantly higher than all AWD treatments. Meanwhile, the WUE of CK was 2.0, significantly lower than that of all AWD treatments.
These results indicate that AWD significantly reduced the application rate of irrigation water. As the intensity of water control increased, water irrigation application decreased. AWD also significantly enhanced WUE. Under experimental conditions, WUE decreased with the increase in water control intensity.

3.3. Nutrient Availability in the Soil

3.3.1. Soil Nitrate Nitrogen (NO3−-N)

Figure 5 illustrates the changes in soil nitrate nitrogen (NO3−-N) content in paddy fields. The NO3−-N content in all treatments exhibited a decrease-increase-decrease pattern. It decreased by 16.9% from the tillering to the jointing stage, increased by approximately 5.5% from the jointing to the heading stage, and remained stable from the heading stage to maturity, with a variation of less than 5.0%.
In 2023, at the tillering stage, NO3−-N content in the LA treatment was 18.1 mg kg−1, which was 8.1% and 15.1% higher than in the MA and SA treatments, respectively. At the jointing stage, NO3−-N content in LA decreased by 18.8%, but remained 15.3% and 19.8% higher than in the MA and SA treatments, respectively. At the heading stage, NO3−-N content in the control treatments ranged from 13.3 to 15.5 mg kg−1. At the milk and yellow ripening stages, NO3−-N content in the LA treatment was 15.5 mg kg−1 and 15.1 mg kg−1, respectively, which were 12.7% and 11.4% higher than in the MA treatment, and 18.2% and 16.7% higher than in the SA treatment. Throughout the growing season, NO3−-N content in the CK treatment fell between that of the LA and MA treatments. The differences between the LA, MA, and CK treatments were not significant, except at the milk ripening stage, where the difference between MA and CK was insignificant, and both were significantly lower than LA. The difference between SA and MA was insignificant, while the difference between SA and LA was significant, except at the heading stage. At the tillering stage, the difference between SA and CK was significant, but no significant difference was observed at other stages.
In 2024, the changes in NO3−-N content across treatments were consistent with those observed in 2023. The treatments, ranked from highest to lowest NO3−-N content, were as follows: LA, CK, MA, and SA. The peak NO3−-N content in 2024 was lower than that in 2023. At the tillering stage, NO3−-N content ranged from 12.7 to 15.2 mg kg−1, and at the heading stage, it ranged from 12.1 to 13.8 mg kg−1. At the yellow ripening stage, NO3−-N content ranged from 12.6 to 14.0 mg kg−1, which was also lower than the content observed at the same stage the previous year. Analysis of variance revealed that at the jointing stage, LA was significantly higher than both MA and SA, while at the milk ripening stage, SA was significantly lower than both LA and CK. No significant differences between were observed among treatments at other stages.
Results from two consecutive years indicate that NO3−-N content tends to decrease as the lower control limit increases.

3.3.2. Soil Available Phosphorus (AP)

Figure 6 illustrates the changes in soil available phosphorus (AP) content during the growing seasons of 2023 and 2024. The maximum AP content was observed at the early stage of the growing season, followed by a gradual decline across all treatments. From the tillering to the milk ripening stage, AP content decreased, with an average reduction of 18.8% across all treatments. From the milk ripening to the yellow ripening stage, AP content increased slightly, with an average increase of 3.6%.
In 2023, at the tillering stage, AP content in the LA, MA, and SA treatments was 12.0, 13.3, and 14.1 mg kg−1, respectively, while in the CK treatment, it was 12.3 mg kg−1. The variation in AP content among all treatments was approximately 17.1%. A similar trend was observed in subsequent stages, with AP content ranked from highest to lowest as LA, MA, CK, and SA. AP content ranged from 11.0 to 13.1 mg kg−1, 10.4 to 12.4 mg kg−1, 9.7 to 11.6 mg kg−1, and 10.1 to 11.9 mg kg−1 at the jointing, heading, milk ripening, and yellow ripening stages, respectively. The variations were 19.0%, 19.5%, 20.6%, and 18.5%, respectively. Differences among treatments were not significant, except at the jointing and yellow ripening stages, where AP content in the LA treatment was significantly higher than in SA and CK. The results indicate that AP content decreased as the lower threshold of water control increased, particularly in the SA treatment, where AP content was lower than in CK throughout the growing season. The variation in AP content between LA and SA increased over time. By the end of the growing season, AP content had decreased in all treatments.
In 2024, as shown in Figure 6b, the effect of water control on AP content mirrored that observed in 2023. The highest AP content was recorded in the LA treatment, with values of 14.4, 13.3, 12.4, 11.9, and 12.2 mg kg−1 at the tillering, jointing, heading, milk ripening, and yellow ripening stages, respectively. In contrast, the lowest AP content was found in the SA treatment, with values of 11.9, 11.1, 10.6, 10.0, and 10.5 mg kg−1 at the same stages. AP content in the CK treatment was intermediate, positioned between the MA and SA treatments throughout the growing season. Analysis of variance showed no significant differences among treatments, except at the heading and yellow ripening stages, where AP content in the LA treatment was significantly higher than in both SA and CK. Thus, the results were consistent with those from the previous year.

3.3.3. Soil Available Potassium (AK)

Changes in soil available potassium (AK) content under different water control treatments during the rice growing periods of 2023 and 2024 are presented in Figure 7. Across both years, AK content in all treatments initially increased, reaching a peak at the jointing stage with an average increase of 15.8%. Subsequently, AK content steadily declined from the jointing to the yellow ripening stage, with an average reduction of 19.4% across all treatments.
As shown in Figure 7a, in 2023, the AK content ranked from highest to lowest across treatments as follows: LA, MA, CK, and SA. This same ranking was observed in 2024 (Figure 7b). In 2023, the LA treatment exhibited the highest AK content among all treatments, with values of 176.1, 206.0, 178.7, 171.2, and 165.0 mg kg−1 at the tillering, jointing, heading, milk ripening, and yellow ripening stages, respectively. In contrast, the SA treatment showed the lowest values, with 159.7, 180.1, 155.5, 146.7, and 139.0 mg kg−1 at the corresponding stages. The difference between the maximum and minimum values increased throughout the growing season, from 16.4 mg kg−1 at tillering to 26.0 mg kg−1 at yellow ripening. In 2024, the maximum and minimum AK contents at the respective stages were 174.1, 208.3, 194.5, 187.2, and 179.3 mg kg−1, and 160.5, 186.9, 167.0, 162.6, and 145.0 mg kg−1, respectively. The difference between them increased from 13.7 mg kg−1 at tillering to 34.3 mg kg−1 at yellow ripening. Analysis of variance indicated that in 2023, LA was significantly higher than both SA and CK at the jointing, milk ripening, and yellow ripening stages, and significantly higher than SA at the heading stage. However, no significant differences were observed among treatments at other stages. In 2024, no significant difference was found between LA and MA throughout the growing season. A significant difference between LA and SA was found, except at the tillering stage, and a significant difference between LA and CK was observed after the jointing stage. No significant differences were found among MA, SA, and CK.
These findings suggest that topdressing was the primary factor influencing changes in AK content. Water control also affected AK content, which decreased as the lower limit of water control increased. In the SA treatment, AK content remained consistently lower than in the CK treatment throughout the growing season. The difference in AK content between the LA and SA treatments increased over time. Overall, AK content declined by the end of the growing season.

4. Discussion

4.1. Effects of AWD on Rice Growth and Development

Plant height, tillering dynamics, and shoot dry matter (SDM) are key indicators of crop population quality and growth status, significantly influencing final yield formation.
Rice, as a hygrophyte, suffers from continuous hypoxia stress in its rhizosphere under long-term flooding conditions, which leads to the formation of a reducing environment in the root zone. This leads to the accumulation of toxic reductive substances such as CH3CH2OH, Fe2+, and S2− in the soil. Additionally, flooding reduces root activity and respiratory intensity, severely hindering nutrient absorption and limiting the growth of above-ground plant parts [17]. In contrast, alternate wetting and drying (AWD) irrigation improves soil aeration by inducing water stress, promoting oxygen diffusion into the rhizosphere, and increasing dissolved oxygen content. This enhances the activity of aerobic microorganisms, increases soluble sugar and protein content in the roots, and boosts root respiration intensity, providing energy for root physiological processes. Furthermore, AWD accelerates the decomposition of soil organic matter and the mineralization of organic nitrogen, enhancing nutrient uptake by the roots. As a result, rice plants exhibit improved production and transport capacity, which accelerates growth, development, and yield formation [18,19]. Moderate water stress can also inhibit weak tiller growth, reducing nutrient competition in later stages and allowing nutrients to be concentrated and transported to effective tillers. Xu et al. [20] found that light water stress increases NO3− content in paddy fields, which in turn promotes root growth, including root length, surface area, and volume, thereby enhancing nutrient absorption capacity.
Xiao et al. [21] found that light water stress increased grain yield and water use efficiency by 12.1% and 12.3%, respectively. Hossain et al. found that compared with CK, alternate wetting and light drying irrigation throughout the growing season significantly increased rice yield by 3.0% [22]. Regarding the impact of irrigation methods on rice plant height, no consensus has been reached. Some studies suggest that AWD irrigation significantly reduces plant height compared to continuous flooding [23,24], while others report no significant difference between the two methods [25,26]. This study found that AWD irrigation reduced rice plant height, possibly because during the soil drying phase of alternate wetting and drying irrigation, the soil is in a water-deficient state. This limits the root system’s absorption of water and nutrients, leading to shortened internodes and, consequently, inhibited rice plant height growth. Moreover, AWD irrigation reduced the number of ineffective tillers and increased the accumulation of shoot dry matter. The development of leaf and stem tissues improved photosynthetic efficiency and nutrient transport capacity, promoting the synthesis and transport of shoot dry matter. This resulted in a significant increase in shoot dry matter during key growth stages, laying a foundation for higher yields, consistent with previous research findings.

4.2. Effects of AWD Irrigation on Paddy Soil Nutrients

The lower the irrigation control threshold, the greater the irrigation amount and the longer the soil remains moist, which promotes the release of NO3−-N [27]. Topdressing significantly increases soil NO3−-N content, and different irrigation control treatments also influence the conversion of urea to NO3−-N [28,29,30], with consistent trends observed across treatments after topdressing. In this study, the variation in NO3−-N content across different water control levels and irrigation treatments aligned with previous findings. NO3−-N is highly mobile and can be leached from the root zone by rainfall, which accounts for the inter-annual differences observed in this experiment [31,32]. In 2023, rainfall concentrated after the jointing stage, leading to NO3−-N levels at the tillering stage being significantly higher than in subsequent stages, with only minor differences observed among the later stages. In 2024, rainfall was more abundant and evenly distributed, resulting in minimal differences among stages. Overall, rainfall mitigated the effects of irrigation control, suggesting that the type of year has a greater impact on NO3−-N levels than irrigation management.
The content of available phosphorus (AP) in soil is related to the release, absorption, leaching and migration of phosphorus [33,34]. Increased irrigation volumes promote phosphorus release [27,35]. In this study, AP continuously declined from tillering to the milk ripening stage, then increased at the yellow ripening stage. This pattern reflects the balance between phosphorus release and rice absorption and leaching: during early growth, phosphorus release was outweighed by absorption and leaching, while in later stages, phosphorus release exceeded absorption and leaching. Over the entire growth period, soil available phosphorus decreased, consistent with prior studies [36]. As a result, supplemental fertilization is necessary each spring. Phosphorus is relatively immobile in soil, and rainfall has a limited impact on its availability [37,38,39]. Therefore, despite significant differences in rainfall patterns between the two experimental years, both the content and temporal trend of available phosphorus during crop growth were similar. This indicates that soil available phosphorus is more influenced by irrigation than by rainfall patterns. From the perspective of crop growth, mild AWD control promotes phosphorus release; however, from a soil fertility standpoint, increasing the water control lower limit would be beneficial.
The high solubility and mobility of available potassium make its content strongly dependent on soil moisture availability [40,41,42]. Background analyses revealed that the experimental soil was rich in potassium. Consequently, soil moisture levels under various irrigation treatments became the primary factor influencing potassium content. The results of this study indicated that, as water control increased, the available potassium content in the soil decreased, aligning with findings from previous research [35,43]. Furthermore, the available potassium content in all treatments exceeded 150 mg kg−1, which is adequate to meet crop nutrient requirements. As potassium fertilizer is applied annually, AWD irrigation does not pose a risk to potassium availability.

4.3. Effects of AWD Irrigation on Rice Yield and WUE

AWD irrigation significantly reduces water use, thereby enhancing WUE [44]. However, its effect on rice yield remains controversial. Some studies suggest that AWD can maintain or even increase yield, while others report yield reductions [45,46,47]. For example, Xu et al. found that AWD shortened the grain-filling period and decreased above-ground shoot dry matter accumulation, leading to rice yield reduction [45]. In contrast, this study demonstrates that mild AWD irrigation reduces water consumption while increasing rice yield. This effect results from optimal soil moisture regulation under AWD, which increases the availability of nitrate nitrogen, available phosphorus, and potassium in the soil. Furthermore, increased rhizosphere oxygen content stimulates root physiological activity, enhancing water and nutrient absorption as well as nutrient transport to above-ground parts. These changes result in a higher percentage of effective tillers, improved grain filling, increased dry matter accumulation, and an overall enhancement of rice population quality.
In contrast, moderate and severe AWD significantly reduced irrigation water input and substantially enhanced WUE compared to CK. However, excessive water stress decreased panicle number per unit area, grains per panicle, and dry matter accumulation, thereby degrading population quality. Additionally, water stress inhibited root growth, development, and activity, limiting nutrient and water absorption by the roots, which ultimately led to a reduction in yield [48]. Liu et al. [49] reported that when the soil water potential in the root zone dropped to −10 kPa and supplementary irrigation was applied, grain yield and water use efficiency increased by 12.4–14.5% and 22.8–26.7%, respectively.
Alternate wetting and light drying irrigation reduces non-effective field percolation and evaporation, thereby ensuring water availability during the critical growth stages of rice. Concurrently, light water stress stimulates root growth in rice plants, enhances nutrient uptake and utilization, and ultimately contributes to increased grain yield. Under the combined influence of these two mechanisms, a significant improvement in WUE is achieved. In contrast, moderate and severe alternate wetting and drying irrigation involves excessive water control, which maintains soil water in a state of deficit. Although water consumption by rice is substantially reduced, the root water absorption capacity is inhibited, and the physiological processes governing rice growth are disrupted—both of which lead to a decline in rice yield. However, because the magnitude of the reduction in water consumption exceeds that of the reduction in yield, WUE remains higher relative to the CK treatment. This finding is consistent with the results reported by Xu et al. [45] and Gao et al. [50].

5. Conclusions

(1)
Alternate wetting and drying irrigation reduced plant height and tiller number, with the reduction was increased as water control intensity intensified. Light water regulation was beneficial for leaf area index and shoot dry matter, while moderate and severe water regulation had adverse effects.
(2)
Light and moderate water regulation facilitated the release of soil nutrients, including nitrate nitrogen, available phosphorus, and available potassium. The advantages may weaken as the intensity of water control is enhanced. Thus, alternate wetting and drying irrigation with severe water control decreased those soil available nutrients.
(3)
Alternate wetting and drying irrigation accelerated the rice grain-filling in the Sanjiang Plain, increased effective panicles per unit area and grains per panicle, but reduced the seed setting rate and thousand-grain weight. Yield decreased as water control enhanced. Compared to check treatment, light water control increased yield while moderate and severe water control reduced it. The water use efficiency of alternate wetting and drying irrigation was significantly higher than that of the check treatment, though it decreased as the control level increased.
In conclusion, alternate wetting and light drying irrigation benefits paddy soil fertility and stable rice yields, making it a sustainable agronomic practice for rice production in the Sanjiang Plain. It is important to notice that, since in the experimental area the irrigation amount is much less than the precipitation, i.e., the precipitation plays the biggest role in this area, these conclusions cannot be generalized for all similar cultural situations, but opinion for reference.

Author Contributions

Methodology, C.D.; investigation, C.D. and C.Q.; writing—original draft, C.D. and C.Q.; writing—review and editing, C.D., Y.L., Y.S. and C.Q.; project administration, C.D. All authors have read and agreed to the published version of the manuscript.

Funding

This study was supported financially by the National Key Research & Development Program of China (2022YFD1500402), and by the Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD).

Data Availability Statement

The original contributions presented in the study are included in the article, and further inquiries can be directed to the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

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Agronomy 15 02372 g001
Figure 1. Precipitation during the rice growth period.
Figure 1. Precipitation during the rice growth period.
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Figure 2. Dynamic changes of rice plant height in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 2. Dynamic changes of rice plant height in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Figure 3. Dynamic changes of LAI in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 3. Dynamic changes of LAI in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Figure 4. Dynamic changes of SDM in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 4. Dynamic changes of SDM in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Figure 5. Dynamic changes of NO3−-N in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 5. Dynamic changes of NO3−-N in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Figure 6. Dynamic changes of AP in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 6. Dynamic changes of AP in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Figure 7. Dynamic changes of AK in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Figure 7. Dynamic changes of AK in 2023 and 2024. Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Table 1. Water management under different irrigation patterns.
Table 1. Water management under different irrigation patterns.
TreatmentIrrigation ThresholdRe-Growth StageEarly to Mid-Tillering StageLate Tillering StageJointing-Booting to
Heading-Flowering Stage		Milk-Ripening Stage
CKUpper limit30 mm50 mm50 mm50 mm50 mm
Lower limit10 mm10 mm10 mm10 mm10 mm
LAUpper limit30 mm30 mm30 mm30 mm30 mm
Lower limit10 mm−10 kPa−20 kPa−10 kPa−10 kPa
MAUpper limit30 mm30 mm30 mm30 mm30 mm
Lower limit10 mm−20 kPa−30 kPa−20 kPa−20 kPa
SAUpper limit30 mm30 mm30 mm30 mm30 mm
Lower limit10 mm−30 kPa−40 kPa−30 kPa−30 kPa
Table 2. Tiller number of each treatment in 2023 and 2024.
Table 2. Tiller number of each treatment in 2023 and 2024.
Treatment20232024
LA25.3 a24.7 b
MA23.7 a24.1 b
SA24.7 a23.1 b
CK26.7 a26.3 a
Note: Data were analyzed using one-way analysis of variance (ANOVA) and presented as mean values (n = 3). Values followed by different lowercase letters indicate significant differences at the p < 0.05.
Table 4. Irrigation water and WUE of each treatment.
Table 4. Irrigation water and WUE of each treatment.
YearTreatmentIrrigation Water (mm)Precipitation (mm)Field Drainage (mm)WUE (kg m−3)
2023LA109.0 ab457.5165.22.6 a
MA94.0 b457.5164.42.4 a
SA33.0 c457.51302.5 a
CK111.0 a457.595.62.0 b
2024LA122.0 b379.9103.02.5 a
MA58.0 c379.978.52.4 a
SA56.0 c379.985.02.4 a
CK142.0 a379.980.02.0 b
Note: Data were analyzed using one-way analysis of variance (ANOVA) and presented as mean values (n = 3). Values followed by different lowercase letters indicate significant differences at the p < 0.05.
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Dou, C.; Qian, C.; Lv, Y.; Sun, Y. Effects of Alternate Wetting and Drying (AWD) Irrigation on Rice Growth and Soil Available Nutrients on Black Soil in Northeast China. Agronomy 2025, 15, 2372. https://doi.org/10.3390/agronomy15102372

AMA Style

Dou C, Qian C, Lv Y, Sun Y. Effects of Alternate Wetting and Drying (AWD) Irrigation on Rice Growth and Soil Available Nutrients on Black Soil in Northeast China. Agronomy. 2025; 15(10):2372. https://doi.org/10.3390/agronomy15102372

Chicago/Turabian Style

Dou, Chaoyin, Chen Qian, Yuping Lv, and Yidi Sun. 2025. "Effects of Alternate Wetting and Drying (AWD) Irrigation on Rice Growth and Soil Available Nutrients on Black Soil in Northeast China" Agronomy 15, no. 10: 2372. https://doi.org/10.3390/agronomy15102372

APA Style

Dou, C., Qian, C., Lv, Y., & Sun, Y. (2025). Effects of Alternate Wetting and Drying (AWD) Irrigation on Rice Growth and Soil Available Nutrients on Black Soil in Northeast China. Agronomy, 15(10), 2372. https://doi.org/10.3390/agronomy15102372

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