Front. Plant Sci. Frontiers in Plant Science Front. Plant Sci. 1664-462X Frontiers Media S.A. 10.3389/fpls.2025.1626882 Plant Science Original Research Optimize the farming system to improve the physical and chemical properties of soil in Northeast China, thereby increasing maize yield Qi Xiangkun † Huang Weidong † Li Yicong Xie Jiachuang Huang Fenglin Wang Yufeng Fu Jian * Yang Kejun * College of Agronomy, Heilongjiang Bayi Agricultural University, Key Laboratory of Modern Agricultural Cultivation and Crop Germplasm Improvement of Heilongjiang Province, Daqing, China

Edited by: Kailou Liu, Jiangxi Institute of Red Soil, China

Reviewed by: Vesna Vasić, Educons University, Serbia

Tianfu Han, Zhengzhou University, China

*Correspondence: Kejun Yang, byndykj@163.com; Jian Fu, fujian_hl@163.com

†These authors have contributed equally to this work and share first authorship

 11 08 2025 2025 16 1626882 12 05 2025 17 07 2025 Copyright © 2025 Qi, Huang, Li, Xie, Huang, Wang, Fu and Yang. 2025 Qi, Huang, Li, Xie, Huang, Wang, Fu and Yang

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Northeast China’s black soil region faces soil fertility decline, inadequate straw usage, and low maize yields. To address these issues, we conducted a two-year field experiment. The seven treatments comprised rotary ridge tillage (Con), no-tillage (T1), straw return + no-tillage (T2), deep-plowing straw return + ridge tillage (T3), deep-plowing straw return + flat tillage (T4), straw crushing and return + ridge tillage (T5), and straw crushing and return + flat tillage (T6). We examined the impact of various tillage methods on the structure of soil water-stable aggregates, soil nutrients, enzyme activity, and maize yield. The findings indicated that from 2021 to 2022, the soil macroaggregate content in the T4 considerably increased by 23.52% compared to the Con. Compared to Con, T4 significantly increased the mean weight diameter (MWD) and geometric mean diameter (GMD), enhancing soil fertility. Additionally, T4 reduced bald tip length while boosting the 100-Kernels weight by 24.01%, ultimately increasing maize yield by 13.62%. Consequently, deep-plowing straw return + flat tillage significantly enhanced soil structure, augmented soil fertility, and elevated maize production, rendering it the most appropriate tillage strategy for this region.

 maize tillage methods soil nutrients aggregate production section-in-acceptance Plant Nutrition Introduction

Maize is among the most essential food crops globally. As the world’s second largest producer of maize. China constitutes 22.4% of global maize production while employing under 20% of the total worldwide maize growing area (FAOSTAT, 2021). The semi-arid area in western Heilongjiang Province is a principal maize production zone in China, where ridge tillage is the primary spring cultivation method. Prolonged agricultural automation and constant tillage have resulted in soil structure deterioration and a loss in fertility (Afshar et al., 2022). The region faces arid springs and wet summers, leading to severe soil moisture depletion under conventional ridge tillage in spring and waterlogging risks in summer. These conditions significantly reduce maize production in the area. Consequently, examining suitable agricultural practices in this region is essential for guaranteeing food security and safeguarding the agro-ecological ecosystem. Different tillage systems can significantly alter soil properties, including physical, chemical, and biological characteristics. Conventional tillage methods often caused substantial soil erosion and water depletion, ultimately resulting in decreased soil fertility and degradation of the agro-ecological environment (Huang et al., 2018). In contrast to conventional tillage methods, no-tillage increased soil bulk density, which could inhibit crop root growth and development (Ji et al., 2013). Flat tillage methods could markedly decrease soil water evapotranspiration and improve soil moisture retention capability (Liang et al., 2021). Straw incorporation was widely acknowledged as an essential agricultural method for improving soil fertility (Zhao et al., 2019). Straw mulching has been shown to increase soil organic matter content (Akhtar et al., 2018), significantly reduce soil moisture evaporation, mitigate soil compaction, and diminish soil nutrient loss (Lv et al., 2023). Deep plowing straw returning could significantly mitigate soil compaction and adhesion, reduce insect and disease prevalence, facilitate straw decomposition, and improve soil fertility (Al-Kaisi et al., 2014; Liu et al., 2022). Therefore, when analyzing the impact of tillage systems on soil physicochemical characteristics, it is essential to consider the incorporation of diverse straw return schemes with tillage practices.

China’s semi-arid western regions face three critical challenges: deteriorating soil fertility, underutilized straw resources, and suboptimal maize productivity. Implementing conservation tillage with straw return methods presents an effective solution to these problems (Chen et al., 2022; Zhao et al., 2023). The efficacy of conservation tillage and straw return strategies for soil enhancement varies considerably across diverse regions and environmental situations. We conducted a two-year field experiment to evaluate different tillage and straw returning methods on soil aggregate stability, nutrient dynamics, enzyme activity, and maize yield. We hypothesized that deep-plowing straw return + flat tillage improved soil aggregate stability, enhanced fertility, and increased yield, making it the optimal tillage method for this region. This research establishes a theoretical basis for optimizing tillage methods, improving straw resource management, and attaining elevated maize yields in the semi-arid areas of western Heilongjiang Province.

 Materials and methods Experimental site

The research location is situated in Zhao Zhou County, Heilongjiang Province (N 46°00′28″, E 125°3 2′81″). The area is level, characterized by an average frost-free duration of 130–135 days. Supplementary Figure S1 illustrates the air temperature and precipitation distributions for the maize growing seasons of 2021 and 2022. The soil is classified as chernozem. The fundamental fertility parameters of the topsoil at a depth of 0–20 cm are as follows: organic carbon, 14.83 g kg-1; pH, 7.9; total nitrogen, 1.19 g kg-1; available phosphorus, 17.2 mg kg-1; and available potassium, 240.4 mg kg-1.

 Experimental design

This experiment included a positioning assessment, with data collected annually from 2021 to 2022. In this paper, positioning research denotes the process of ongoing investigation, observation, and analysis conducted at a designated site, maintaining both the testing location and agricultural practices throughout the study. Seven treatments were employed for comparison in the experiment: rotary ridge tillage (Con), no-tillage (T1), straw return + no-tillage (T2), deep-plowing straw return + ridge tillage (T3), deep-plowing straw return + flat tillage (T4), straw crushing and return + ridge tillage (T5), and straw crushing and return + flat tillage (T6) ( Table 1 ). Rotary ridge tillage was used as a Con. The tested variety is ‘Dongxu 20’. Each treatment was repeated three times with a random block arrangement, and the experimental plot was designed to be 0.33 hm2 (100 m×32.5 m). The planting density of the maize was 75000 plants hm-2, and the compound fertilizer was applied at 650 kg hm-2 (N:P2O5:K2O = 27:10:12). All the farming practices including herbicide and insecticides were performed in each plot and consistent with local agronomic practices during the entire experimental seasons. Maize was planted on 2 May 2021 and 28 April 2022 and harvested on 1 October 2021 and 2 October 2022.

Experimental design.

Treatment Measure
Rotary ridge tillage (Con) After mechanical harvesting in autumn, all straw was removed from the field. In spring, rotary tillage and ridging were conducted at a depth of 15–20 cm, followed by sowing and a one-time application of base fertilizer into the 15–20 cm soil layer.
No-tillage (T1) After mechanical harvesting in autumn, all straw was removed from the field. In spring, no-tillage practices were implemented, followed by flat sowing of maize and a one-time application of base fertilizer into the 15–20 cm soil layer.
Straw returning + no-tillage (T2) After autumn harvest, all straw was crushed to sh0 cm lengths and evenly distributed as surface mulch. In spring, no-tillage practices were implemented, followed by flat sowing of maize and a one-time application of base fertilizer into the 15–20 cm soil layer.
Deep plowing straw returning + ridge tillage (T3) After mechanical harvesting in autumn, all straw was crushed to sh0 cm lengths and the straw was deep plowed into the field to a depth of 25–30 cm. In spring, rotary tillage and ridging were conducted, followed by sowing and a one-time application of base fertilizer into the 15–20 cm soil layer.
Deep plowing straw returning + flat tillage (T4) After mechanical harvesting in autumn, all straw was crushed to sh0 cm lengths and the straw was deep plowed into the field to a depth of 25–30 cm. Without ridging, sowing was conducted in spring, accompanied by a one-time application of base fertilizer into the 15–20 cm soil layer.
Straw crushing and returning + ridge tillage (T5) After mechanical harvesting in autumn, all straw was crushed to sh0 cm lengths and evenly distributed on the soil surface. The straw was then incorporated into the 0–20 cm soil layer using a combined soil preparation machine. In spring, rotary tillage and ridging were conducted, followed by sowing and a one-time application of base fertilizer into the 15–20 cm soil layer.
Straw crushing and returning + flat tillage (T6) After mechanical harvesting in autumn, all straw was crushed to sh0 cm lengths and evenly distributed on the soil surface. The straw was then incorporated into the 0–20 cm soil layer using a combined soil preparation machine. Without ridging, sowing was conducted in spring, accompanied by a one-time application of base fertilizer into the 15–20 cm soil layer.
Sample collection

Soil samples were taken at depths of 0–10 cm, 10–20 cm, and 20–30 cm using a soil auger during the maize jointing, tasseling, and maturity phases throughout the 2021–2022 growth seasons for each treatment. Residual roots, straw pieces, and other contaminants were manually extracted from the soil samples, which were subsequently brought to the laboratory in sealed containers for drying, grinding, and sifting prior to analysis. Soil water-stable aggregates were categorized by the wet sieving technique (Elliott, 1986), yielding six specific size classifications: >5 mm, 2–5 mm, 1–2 mm, 0.5–1 mm, 0.25 - 0.5 mm, and<0.25 mm.

 Measurement and methods Measurement of the soil nutrient content

The soil organic matter content was determined via the potassium dichromate volumetric method (Nelson, 1982). The soil total nitrogen content was determined via digestion with H2SO4 and an automatic Kjeldahl apparatus (Nelson and Sommers, 1980). The soil-available nitrogen was determined via the sodium hydroxide-boric acid-available nitrogen diffusion method (Mulvaney and Khan, 2001). Soil-available phosphorus was extracted via the 0.5 mol L-1 NaHCO3 colorimetric method (Truog, 1930). Soil-available potassium was measured via atomic absorption spectrophotometry with 0.5 mol L-1 NH4OAc (Mehlich, 2008).

 Measurement of soil enzyme activity

The catalase activity was determined based on the method described by (Ren et al., 2016). Two grams of each air-dried soil sample was weighed and placed in a 100 ml conical bottle, 5 mL of 3% H2O2 solution and 40 mL of deionized water were added, and the mixture was shaken for 20 min and then filtered. Five milliliters of H2SO4 solution containing 1.5 mol L-1 H2SO4was added to the clear liquid, and then 25 ml of H2SO4 solution was removed after filtration. The volume of KMnO4 solution consumed was recorded by titrating with 0.02 mol L-1 KMnO4 solution until the liquid was slightly red and did not change color for 30 s.

The urease activity was determined based on the method described by Ren et al. (2016). Fresh soil samples (5 g) were transferred to a 100-ml conical flask and were incubated by adding citrate solution (20 ml, pH 6.7) and urea solution (10 ml, 10%, w/v) for 24 h at 37°C. The mixed solution was shaken at 180 rpm for 20 min and then filtered. Then, the filtrate (1 ml), sodium hypochlorite solution (3 ml), and so­dium phenol solution (4 ml) were mixed in a 50-ml volumetric flask. Deionized water was added to the volumetric flask to a constant volume of 50 ml. The absorbance of the solution was measured at 578 nm using a spectrophotometer (UV2550, Shimadzu, Japan).

The alkaline phosphatase activity was determined based on the method described by Ren et al. (2016). Five grams of air-dried soil was placed in a 200-triangle bottle with 2.5 ml of toluene. After 15 min, 20 ml of 0.5% sodium phenyldisodium phosphate was added, the reaction mixture was incubated at 37°C, the mixture was cultured for 24 h, 100 ml of 0.3% aluminum sulfate solution was added to the culture medium, and the mixture was filtered with dense filter paper. Three milliliters of filtrate was placed into a 50 ml volumetric bottle, 5 ml of buffer and 4 drops of chloroform-p-benzoquinone imide reagent were added to each bottle, the mixture was diluted to scale after color development, and the color at a wavelength of 660 nm was compared via a spectrophotometer.

 Evaluation of soil aggregate stability indices

(1) The mass percentage of aggregates at a given particle size level was calculated according to the method described by (Choudhury et al., 2014)

W i = M i M × 100 %

where Mi is the mass of the i-level soil water-stable aggregate after sieving (g), and M was applied to determine the total mass of the aggregates (g).

(2) Soil aggregate stability was determined using the MWD and GMD. The calculation formulas of MWD and GMD (Haynes and Swift, 1990) are as follows:

MWD = [ ∑ i = 1 n ( W i X i ) ∑ i = 1 n W i ] GMD = exp [ ∑ i = 1 n ( W i ln X i ) ∑ i = 1 n W i ]

where Wi is the weight percentage of each aggregate (%), and Xi is the average diameter (mm) of each particle size.

(3) The fractal dimension of the soil water-stable aggregates was calculated following (Rasiah et al., 1993)

D = 3 − lg [ M ( r < X i ) M T ] / lg [ X i X max ]

where M (r< Xi) is the aggregate weight (g) with a particle size smaller than Xi, MT is the total weight of the aggregates, Xi is the average diameter of a certain level of the aggregate, and X max is the maximum particle size of the aggregates.

 Measurement of maize yield

At the maize maturity stage, four rows (5 m long with 0.65 m row spacing) were selected from the central area of each plot. All maize ears were harvested, and the grain moisture content was measured using a PM8818 moisture analyzer. The final yield was adjusted to a standard moisture content of 14%.

 Statistical analysis

Excel 2010 was used to organize the data. Different treatments were compared via Duncan’s test at the 0.05 probability level (P ≤ 0.05). Analysis of variance was performed for grain yield, soil aggregates, organic carbon, soil nitrogen, and soil enzyme activity via SPSS22.0 (SPSS Inc., Chicago, USA). Origin 2021 software (Origin Lab, USA) was used for figure preparation.

 Results Soil water - stable aggregates

Y and T had significant effects on soil aggregate content(P<0.01; Figure 1 ). In 2021 and 2022, the content of soil water-stable aggregates gradually increased as the aggregate particle size decreased. Compared to the Con treatment, all other treatments increased the content of large aggregates. In the 0–10 cm soil layer, all other treatments significantly increased the content of large aggregates compared to the Con treatment. In the 10–20 cm soil layer, the T4 treatment showed the highest contents of water-stable aggregates in the size fractions of > 5 mm, 2–5 mm, 1–2 mm, and 0.5–1 mm, with increases of 54.88%, 45.04%, 42.16%, and 27.01%, respectively, compared to the Con treatment. In the 20–30 cm soil layer, the T4 treatment exhibited the highest content of R > 0.25mm.

Effects of tillage methods on the particle size composition of soil water-stable aggregates. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Bar charts compare the proportion of different water-stable aggregate sizes across three soil depths (0-10 cm, 10-20 cm, 20-30 cm) for treatments from 2021 to 2022. Aggregate size categories are color-coded, ranging from less than 0.25 mm to greater than 5 mm. Each bar represents a treatment with corresponding error bars, and letters denote statistical significance. Soil water - stable aggregate stability

Y and T significantly influenced MWD (P< 0.01), while T significantly affected GMD (P< 0.01), and T also had a notable impact on GMD (P< 0.05; Figures 2a, b ). In the 0–10 cm soil layer, the T2 treatment showed the highest MWD and GMD, with significant increases of 25.42% and 23.91%, respectively, compared to the Con treatment. In the 10–20 cm soil layer, all treatments except T1 significantly increased the MWD and GMD of aggregates compared to the Con treatment. In the 20–30 cm soil layer, the T4 treatment exhibited the highest MWD and GMD values, with significant increases of 15.72% and 15.89%, respectively, compared to the Con treatment.

Effects of tillage methods on soil water-stable aggregate stability. Mean weight diameter (MWD) (a) and geometric mean diameter (GMD) (b). Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). MWD, mean weight diameter; GMD, geometric mean diameter. Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). *, Significant at p < 0.05. **, Significant at p < 0.01.

Bar chart showing mean weight diameter (MWD) and geometric mean diameter (GMD) of soil at different depths (0-10 cm, 10-20 cm, 20-30 cm) for 2021 and 2022 across treatments Con, T1, T2, T3, T4, T5, and T6. MWD results are presented at the top and GMD results at the bottom for each year. Treatments are color-coded. Error bars indicate variability, and letters denote statistical differences. Organic carbon in soil water - stable aggregate

T significantly influences the organic carbon content of aggregates (P< 0.01; Figure 3 ). In the 0–10 cm soil layer, all treatments significantly increased the water-stable organic carbon content in soil aggregates compared to the Con treatment. In the 10–20 cm soil layer, the organic carbon content of aggregates larger than 5 mm, between 2–5 mm, and between 1–2 mm in the T4 treatment was considerably elevated compared to the Con treatment, with increases of 12.96%, 10.43%, and 12.83%, respectively. Within the 20–30 cm soil layer, the T4 treatment had the greatest organic carbon concentration across all aggregate size fractions.

Effects of tillage methods on the soil soil water-stable aggregate organic carbon content. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Stacked bar charts showing soil aggregate organic carbon content in grams per kilogram across different treatments in 2021 and 2022. Each chart represents a soil depth category: 0-10 cm, 10-20 cm, and 20-30 cm. Bars are color-coded by aggregate size classes: less than 0.25 mm, 0.25-0.5 mm, 0.5-1 mm, 1-2 mm, 2-5 mm, and greater than 5 mm. Each treatment includes labeled significance letters to indicate statistical differences. Soil organic carbon content

The influence of Y and T on the soil organic carbon content was highly significant (P<0.01; Figure 4 ). In 2021 and 2022, the SOC content across all treatments shown a progressive decline with increasing soil depth. In the 0–10 cm soil layer, T2 treatment demonstrated a substantial increase of 16.77% relative to the Con treatment. In the 10–20 cm soil layer, the SOC content of the treatments ranked as follows: T4 > T3 > T2 > T5 > T6 > T1 > Con. The T4 treatment exhibited a notable increase of 18.45% in the 20–30 cm soil layer compared to the Con treatment.

Effects of tillage methods on the soil total organic carbon content. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). SOC, soil organic carbon. Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Bar charts show organic carbon content in grams per kilogram across three soil depths (0-10cm, 10-20cm, 20-30cm) for various treatments (Con, T1-T6) over 2021 and 2022. Statistical significance is indicated, with different letters denoting significant differences among treatments. Error bars represent standard deviation. Soil nitrogen content

In the 0–10 cm soil layer, the T2 treatment exhibited the greatest TN content during the growth phases from jointing to tasseling ( Table 2 ). In the 10–20 cm soil layer, the T4 treatment demonstrated the most significant improvement in TN content, with increases of 15.58%, 16.36%, and 15.26%, respectively, compared to the Con treatment. In the 20–30 cm soil layer, the T3 and T4 treatments shown elevated TN content relative to the Con treatment.

Effects of tillage methods on the soil total nitrogen content.

Soil depth (cm) Treatments Soil total nitrogen content (g kg-1)
2021 2022
Jointing Tasseling Maturity Jointing Tasseling Maturity
0~10 Con 1.20c 1.11c 1.20a 1.22c 1.13c 1.22b
T1 1.32ab 1.13c 1.32a 1.39ab 1.17bc 1.33ab
T2 1.39a 1.35a 1.37a 1.43a 1.35a 1.39ab
T3 1.33ab 1.28abc 1.30a 1.37ab 1.30ab 1.41a
T4 1.37a 1.32ab 1.35a 1.41a 1.34a 1.43a
T5 1.28bc 1.22bc 1.28a 1.32abc 1.24abc 1.32ab
T6 1.26bc 1.15c 1.24a 1.28bc 1.19bc 1.26ab
10~20 Con 1.13b 1.09c 1.17b 1.19c 1.11d 1.19c
T1 1.20ab 1.11c 1.20ab 1.22bc 1.15cd 1.22bc
T2 1.30a 1.24a 1.30ab 1.32ab 1.24abc 1.33ab
T3 1.28a 1.24a 1.28ab 1.33ab 1.26ab 1.35ab
T4 1.33a 1.26a 1.32a 1.35a 1.30a 1.37a
T5 1.26ab 1.20ab 1.24ab 1.28ab 1.24abc 1.30abc
T6 1.24ab 1.13bc 1.22ab 1.26abc 1.19bcd 1.28abc
20~30 Con 0.70c 0.68d 0.66c 0.77c 0.72b 0.79c
T1 0.72bc 0.70cd 0.74abc 0.79c 0.72b 0.83bc
T2 0.77abc 0.73bcd 0.76abc 0.81c 0.76b 0.92abc
T3 0.87a 0.83ab 0.96a 0.96ab 0.91a 0.98ab
T4 0.91a 0.89a 0.92ab 0.98a 0.92a 1.04a
T5 0.85ab 0.79abc 0.79abc 0.87bc 0.81b 0.96ab
T6 0.81abc 0.77bcd 0.72bc 0.83c 0.79b 0.94abc
ANOVA
Y: NS
T: NS
Y×T: NS

Con, rotary ridge tillage; T1, no-tillage; T2, straw return + no-tillage; T3, deep plow straw return + ridge tillage; T4, deep plow straw return + flat tillage; T5, straw crushing and return + ridge tillage; T6, straw crushing and return + flat tillage. TN, total nitrogen; AN, available nitrogen; Different alphabets indicate the significance within the same year at 5% level by Duncan’ tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). *Significant at p< 0.05. **Significant at p< 0.01.

 Soil available phosphorus content

T and Y exerted substantial impacts on AP (P<0.01; Table 3 ). The AP content of the T2 treatment in the 0–10 cm soil layer was superior to that of the T1 treatment. In the 10–20 cm soil layer, the T4 treatment had a markedly higher AP content than the T6 treatment, with increases of 10.81%, 13.92%, and 27.27% from the jointing stage to the maturity stage. In the 20–30 cm soil layer, the T4 treatment exhibited a notable increase in AP content relative to the Con treatment during all growth stages, with increments of 23.54%, 29.88%, and 36.24%, respectively.

Effects of tillage methods on the soil available phosphorus content.

Soil depth (cm) Treatments Soil available phosphorus content (mg kg-1)
2021 2022
Jointing Tasseling Maturity Jointing Tasseling Maturity
0~10 Con 32.73c 24.00d 12.74c 33.33d 25.02d 14.24c
T1 35.07bc 27.25c 18.28a 35.19c 30.08b 18.46ab
T2 38.20a 31.58a 18.94a 39.77a 33.87a 19.36a
T3 36.94ab 28.99bc 17.25ab 37.60b 29.66b 17.80ab
T4 37.60a 30.80ab 18.76a 38.81ab 32.36a 19.06a
T5 35.01bc 24.78d 14.60bc 35.80c 27.43c 17.01ab
T6 34.71bc 24.48d 14.00c 35.43c 26.34cd 16.05bc
10~20 Con 27.61d 22.37b 12.62b 28.57d 24.24c 14.12c
T1 28.51d 22.97b 12.74b 28.75d 24.84bc 14.72bc
T2 35.25ab 26.04a 17.13a 35.56b 26.16b 17.31a
T3 36.28a 26.83a 16.65a 37.00a 28.21a 17.37a
T4 36.40a 27.55a 17.97a 37.60a 28.09a 18.04a
T5 33.63bc 23.87b 14.42b 33.99c 27.97a 15.51bc
T6 33.27c 23.21b 13.94b 33.51c 25.74bc 14.36bc
20~30 Con 26.65c 20.26c 11.72d 27.25c 21.77d 12.08d
T1 27.67c 20.44c 12.20cd 28.03c 21.83d 12.56cd
T2 31.58ab 22.07b 15.33a 31.82ab 23.94c 15.39ab
T3 33.03a 25.74a 16.05a 33.51a 27.43ab 16.35a
T4 32.84a 26.89a 15.75a 33.75a 27.73a 16.65a
T5 32.61a 23.27b 13.88b 32.85ab 26.52b 14.79b
T6 30.14b 22.37b 13.34bc 30.98b 24.48c 13.88bc
ANOVA
Y: **
T: **
Y×T: NS

Con, rotary ridge tillage; T1, no-tillage; T2, straw return + no-tillage; T3, deep plow straw return + ridge tillage; T4, deep plow straw return + flat tillage; T5, straw crushing and return + ridge tillage; T6, straw crushing and return + flat tillage. AP, available phosphorus. Different alphabets indicate the significance within the same year at 5% level by Duncan’ tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **Significant at p< 0.01.

 Soil available potassium content

T and Y exerted substantial impacts on AK (P<0.01; Table 4 ). In the 0–10 cm soil layer, T2 treatments enhanced the AK content at every growth stage, achieving a statistically significant difference at maturity, with a 14.76% increase relative to the Con treatment. The T4 treatment demonstrated significantly elevated AK content in the 10–20 cm soil layer across all growth stages, with increases of 11.21%, 15.83%, and 12.09%, respectively, compared to the Con treatment. In the 20–30 cm soil layer, the average AK content across treatments exhibited the following descending order: T4 > T3 > T5 > T6 > T2 > T1 > Con.

Effects of tillage methods on the soil available potassium content.

Soil depth (cm) Treatments Soil available potassium content (mg kg-1)
2021 2022
Jointing Tasseling Maturity Jointing Tasseling Maturity
0~10 Con 283.25a 237.98a 269.42c 294.37a 236.56b 275.34b
T1 292.94a 257.09a 272.41bc 300.86a 263.72ab 276.26b
T2 312.62a 277.33a 307.41a 323.74a 286.60a 317.39a
T3 299.29a 265.21a 299.57ab 312.48a 272.91ab 312.76a
T4 307.27a 269.13a 305.99a 319.53a 282.25ab 313.62a
T5 293.01a 253.95a 296.51abc 309.20a 266.92ab 300.14ab
T6 298.65a 248.25a 276.40bc 306.70a 264.29ab 282.53b
10~20 Con 270.35c 230.92b 265.14b 280.47a 234.84b 270.63b
T1 272.9bc 237.62ab 268.42b 281.39a 247.60ab 273.20ab
T2 290.66ab 248.10ab 282.75ab 307.13a 257.66ab 296.65ab
T3 293.16a 255.87a 295.87a 309.12a 270.27ab 298.43ab
T4 298.72a 259.44a 297.65a 313.90a 280.18a 302.85a
T5 286.53abc 242.04ab 287.03ab 308.20a 262.65ab 291.02ab
T6 283.75abc 240.98ab 269.28b 305.28a 255.80ab 276.48ab
20~30 Con 254.02b 223.72a 255.87a 261.29a 229.43b 258.58c
T1 257.37ab 230.00a 261.43a 262.00a 241.19ab 262.15bc
T2 254.80ab 234.70a 257.37a 259.63a 247.89ab 264.57bc
T3 275.76a 246.25a 271.27a 280.97a 268.99a 277.69ab
T4 274.34ab 245.75a 275.91a 282.82a 270.42a 288.81a
T5 268.78ab 224.44a 265.43a 274.34a 261.72ab 270.77bc
T6 267.21ab 238.91a 262.08a 271.13a 249.10ab 266.64bc
ANOVA
Y: **
T: **
Y×T: NS

Con, rotary ridge tillage; T1, no-tillage; T2, straw return + no-tillage; T3, deep plow straw return + ridge tillage; T4, deep plow straw return + flat tillage; T5, straw crushing and return + ridge tillage; T6, straw crushing and return + flat tillage. AK, available potassium; Different alphabets indicate the significance within the same year at 5% level by Duncan’ tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **Significant at p< 0.01.

 Soil alkaline phosphatase activity

T had a significant impact on soil alkaline phosphatase activity (P<0.01; Figure 5 ). In both 2021 and 2022, the enzyme activity in the 0–30 cm soil layer for all treatments initially diminished and subsequently grew progressively during the growth period. The alkaline phosphatase activity in the 0–10 cm soil layer was lowest in the Con treatment at every growth stage. In the 10–20 cm soil layer, the T4 treatment exhibited the highest soil alkaline phosphatase activity at each development stage.

Effects of tillage methods on soil alkaline phosphatase activity. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Bar charts showing alkaline phosphatase activity at different soil depths (0-10cm, 10-20cm, 20-30cm) for two years, 2021 and 2022. Each chart compares treatments (Con, T1, T2, T3, T4, T5, T6) during jointing, tasseling, and maturity stages. Data is presented in milligrams per gram of dry soil. Statistical differences are marked by letters above the bars. Soil urease activity

T had a considerable impact on soil urease activity (P<0.01; Figure 6 ). Compared to the T1 treatment, the T2 treatment markedly enhanced soil urease activity in the 0–10 cm soil layer during several growth stages of maize, with increases of 36.29%, 28.40%, and 26.68%, respectively. In the 10–20 cm soil layer, all treatments enhanced soil urease activity relative to the control treatment. In the 20–30 cm soil layer, the soil urease activity in the T3 and T4 treatments was significantly elevated compared to the Con treatment at each maize development stage.

Effects of tillage methods on soil urease activity. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage).Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Bar charts depict urease activity in soil across three depths (0-10 cm, 10-20 cm, 20-30 cm) during jointing, tasseling, and maturity phases in 2021 and 2022. Various treatments (Con, T1-T6) are represented with different colors. Error bars and statistical annotations indicate variability and significance. Soil catalase activity

T had a significant impact on soil catalase activity (P<0.01; Figure 7 ). In the 0–10 cm soil layer, the T2 treatment exhibited significantly higher catalase activity than the Con treatment from jointing to maturity stages, showing increases of 17.76%, 29.13%, and 26.47%, respectively ( Figure 7 ). In the 10–20 cm soil layer, the catalase activity in the T4 treatment was the greatest at each development stage. In the 20–30 cm soil layer, the T4 treatment significantly enhanced soil catalase activity throughout the maize growth period compared to the Con treatment.

Effects of tillage methods on soil catalase activity. Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). Different alphabets indicate the significance within the same year at 5% level by Duncan' tests. In ANOVA, Y, T represent the variable year, treatment. NS, not significant, (p > 0.05). **, Significant at p < 0.01.

Bar charts compare catalase activity levels measured in milligrams per gram deciliter across different soil depths (0-10 cm, 10-20 cm, 20-30 cm) during jointing, teaseling, and maturity phases in 2021 and 2022. Charts are categorized by treatments labeled Con, T1, T2, T3, T4, T5, and T6, using different colors and patterns. Each bar is annotated with statistical groupings using letters. Maize yield

The impact of various Y and T on 100-Kernels weight and maize yield was highly significant (P< 0.01), and their interaction significantly influenced maize yield (P<0.05) ( Table 5 ). In 2021, relative to the Con treatment, the T3 and T4 treatments markedly augmented maize ear length by 10.58% and 9.88%, respectively, diminished bald tip length, and greatly improved 100-Kernels weight by 20.96% and 24.51%, respectively. Furthermore, they markedly enhanced the final yield by 6.00% and 10.44%, respectively. In 2022, the T4 treatment attained the greatest yield of 11130.33 kg·ha-1, reflecting substantial increases of 16.81% and 15.69% relative to the Con and T6 treatments, respectively. The enhancement in yield was ascribed to substantial improvements in maize ear length and 100-Kernels weight.

Effects of tillage methods on yield components of maize.

Year Treatment Ear length (cm) Ear crude (cm) Bald tip length (cm) Ear rows Number per row 100-Kernels weight (g) Yield (kg hm-2)
2021 Con 17.11b 4.94a 2.01ab 16.4ab 36.30a 29.01c 9368.09cd
T1 18.13ab 4.98a 1.51abc 15.80ab 35.60a 32.08b 9133.25d
T2 18.39ab 4.98a 0.67cd 16.0ab 35.40a 31.85b 9572.52c
T3 18.92a 5.04a 1.34bcd 17.20a 39.30a 35.09a 9930.33b
T4 18.80a 5.06a 0.46d 16.60ab 38.10a 36.12a 10345.77a
T5 17.81ab 4.97a 0.97cd 16.40ab 35.20a 30.59bc 9420.50cd
T6 18.87a 5.09a 2.39a 15.6b 37.3a 30.70bc 9376.96cd
2022 Con 17.42b 4.81a 1.96ab 15.40c 35.40a 29.99c 9528.86b
T1 18.25ab 4.80a 1.29abc 16.20abc 37.0a 32.22b 9536.85b
T2 19.35a 4.86a 1.04bc 15.80bc 36.10a 33.69b 9745.17b
T3 19.89a 4.97a 1.09bc 17.6a 38.40a 36.09a 10951.12a
T4 20.02a 5.18a 0.62c 17.00a 37.40a 37.04a 11130.33a
T5 17.44b 4.92a 1.32abc 16.00bc 35.60a 31.79bc 9689.00b
T6 18.65ab 4.98a 2.22a 16.00bc 36.40a 32.08b 9620.51b
Two-way ANOVA Y NS NS NS NS NS ** **
T ** NS ** * NS ** **
Y×T NS NS NS NS NS NS *

Con, rotary ridge tillage; T1, no-tillage; T2, straw return + no-tillage; T3, deep plow straw return + ridge tillage; T4, deep plow straw return + flat tillage; T5, straw crushing and return + ridge tillage; T6, straw crushing and return + flat tillage. Different alphabets indicate the significance within the same year at 5% level by Duncan’ tests. In ANOVA, Y and T were variables of year and treatments. ns, not significant, (p > 0.05); *Significant at p< 0.05; **Significant at p< 0.01.

 Relationships between the soil indices and maize yield

The correlation analysis revealed that maize yield was significantly positively correlated with soil SOC, N, P, and K (P<0.05) ( Figure 8A ). Maize yield was significantly positively correlated with 100-Kernels weight and panicle length (P<0.01). The MWD, GMD, and R>0.25 mm were significantly positively correlated with the soil nutrient content, 100-grain weight, and ear length (P<0.01). These findings indicate that improved soil structural stability could increase the soil nutrient content, thus promoting the transport of nutrients from underground to aboveground parts.

Correlation heatmap (A), principal component analysis (B), and regression analysis (C). Con (rotary ridge tillage), T1 (no-tillage), T2 (raw return + no-tillage), T3 (deep plow straw return + ridge tillage), T4 (deep plow straw return + flat tillage), T5 (raw crushing and return + ridge tillage), and T6 (raw crushing and return + flat tillage). MWD, mean weight diameter; GMD, geometric mean diameter; D, fractal dimension; R>0.25mm, macroaggregate content; TN, total nitrogen; AN, available nitrogen; AP, available phosphorus; AK, available potassium; SOC, soil organic carbon.

A composite image with three panels: A) A correlation matrix showing relationships between variables like MWD, GMD, and yield, with color-coding for significance. B) A PCA biplot with arrows indicating variable directions and group differentiation by color. C) Three scatter plots displaying yield versus enzyme activities (alkaline phosphatase, urease, catalase) with fitted regression lines and confidence intervals.

The contribution rates of the first principal component PC1 and the second principal component PC2 were 84.6% and 5.4%, respectively ( Figure 8B ). PC1 was negatively correlated with D and positively correlated with the other indicators. There were significant differences in the T2, T3, T4, and Con treatments along PC1.

There was a significant linear correlation between maize yield and soil alkaline phosphatase activity, urease activity and catalase activity under the different tillage methods ( Figure 8C ) (R2 = 0.56, P< 0.05). R2 = 0.57, P< 0.05; R2 = 0.54, P< 0.05).

 Discussion Effects of tillage methods on soil water-stable aggregates

The distribution and content of soil aggregates not only influence crop growth and development but also serve as key indicators of soil’s sustainable utilization and erosion resistance capacity (Madari et al., 2004). The conversion between macroaggregates and microaggregates is profoundly affected by tillage methods (Puget et al., 2010). The results demonstrated that all experimental treatments significantly increased the content of water-stable macroaggregates in the 0–10 cm soil layer compared to the Con ( Figure 1 ). In the 20–30 cm soil layer, the T4 treatment exhibited the most pronounced increase in macroaggregate content compared to the Con, with significant enhancements in the mean weight diameter MWD and GMD of aggregates by 12.17%-19.27% and 13.40%-18.37%, respectively ( Figure 2 ). The study results indicated that straw returning greatly increased the content of water-stable macroaggregates and boosted soil structural characteristics (Li and Zhang, 2019). Furthermore, the two-year results demonstrated that the T4 treatment significantly enhanced the content of water-stable aggregates in both 10–20 cm and 20–30 cm soil layers compared to T2 and T6 treatments. This improvement was accompanied by increased MWD and GMD, reduced fractal dimension ( Supplementary Figure S2 ), and elevated organic carbon content in water-stable aggregates ( Figure 2 ). This may be attributed to flat planting, which minimizes soil disturbance, hence mitigating structural damage and enhancing soil permeability (West and Post, 2002). After deep plowing with straw returned to the field, the decomposition of crop stubble in deep soil layers increased SOC content and provided essential cementing materials for deep soil particle accumulation (Eynard et al., 2006). This process promotes the formation of large aggregates (Song et al., 2019) and supplies essential energy for crop growth (Yu et al., 2020). The integration of crop residue with conservation tillage has been shown to regulate soil structure, augment soil carbon and nitrogen sequestration, and improve production and soil nutrient levels (Yang et al., 2019; Yuan et al., 2021).

 Effects of tillage methods on soil nutrients and enzyme activity

Our study confirmed that straw returning increases soil nutrient content and enzyme activity, consistent with findings reported in previous studies (Liu et al., 2025; Peng et al., 2016; Su et al., 2020). The two-year results demonstrated that compared with Con, the T4 treatment increased SOC content by an average of 15.21% ( Figure 4 ), TN content by 26.22% ( Table 2 ), AN content by 16.43% ( Table 3 ), AP by 26.92% ( Table 4 ), and AK by 13.14% ( Table 5 ). The 15.21% increase in SOC content under the T4 treatment was statistically significant and ecologically vital. This increment enhanced the soil’s capacity to sequester carbon, thereby mitigating climate change effects through atmospheric CO2 reduction (Rattan, 2004; West and Post, 2002). Additionally, higher SOC improved soil structure (Bronick and Lal, 2005), increasing water-holding capacity (Hudson, 1994) - critical for sustaining crop growth during dry periods (Lal, 2020) - and reducing erosion risks. As shown in the correlation analysis, soil aggregate content, MWD, and GMD were significantly positively correlated with soil nutrient content ( Figures 8A, B ). This is attributed to the deep tillage with straw returning to the field improving soil structure. The greater incorporation depth increases the contact area between straw and deep soil, enhancing microbial decomposition. During decomposition, straw significantly increases microbial populations and soil enzyme activity ( Figures 5 - 7 ), while activating AP, and AK, thereby improving soil fertility (Piazza et al., 2020). Previous studies have indicated that straw returning can improve soil structure and enhance organic matter input in deeper soil layers (Liu et al., 2021; Zhang et al., 2014). The enhanced soil structure, along with ample organic matter, establishes advantageous nutritional conditions for microbial activity, hence facilitating elevated soil enzyme activity (Ji et al., 2014; Jin et al., 2009).

 Correlation analysis of maize yield with soil nutrient levels and enzyme activities

Our findings indicated that between 2021 and 2022, the T4 treatment yielded the maximum maize production ( Table 5 ), exhibiting a substantial increase of 10.44% - 16.81% relative to Con. This superior yield performance was primarily attributed to significant increases in both ear length (9.88% - 14.93%) and 100-Kernels weight (23.51% - 24.51%). Correlation and principal component analyses demonstrated strong positive associations between maize yield and both soil aggregate structure and nutrient content ( Figures 8A, B ). Regression analysis revealed a substantial linear correlation between maize yield and soil enzyme activity ( Figure 8C ). Consequently, we ascertain that the integration of tillage systems with straw incorporation enhances the structure of soil water-stable aggregates (Kabiri et al., 2015). Enhanced soil structural stability increases the accumulation of nitrogen, phosphate, and potassium nutrients (Guo et al., 2022), enhances microbial activity (Zheng et al., 2022), and rises enzyme activity (Costa et al., 2024). These enhancements promote nutrient transfer from leaves to grains (Tang et al., 2018), augmenting both grain nutrient content and 100-Kernels weight, celevating maize output. These results demonstrated that deep plowing straw returning + flat tillage enhanced soil health and increased maize yield, supporting sustainable agriculture in the black soil region. This approach provided a viable strategy to balance productivity with long-term soil fertility - a key principle for preserving this vulnerable ecosystem. For farmers, deep plowing straw returning+ flat tillage boosted yields and income while maintaining soil quality. For policymakers, promoting this practice through technical training and incentives facilitated sustainable black soil management, safeguarding future agricultural productivity.

 Limitations and future research

This study was conducted over a two-year period. To further validate these findings, the research team plans to continue long-term monitoring in the region. The present investigation was confined to a singular agroecological zone. Our team did not investigate ecological areas with differing climatic conditions. To thoroughly assess the impact of farming practices in various environments on maize production, soil structure, and fertility. Our team plans to examine the response effects of diverse tillage techniques across various ecological zones in the future, thereby offering significant theoretical insights for the progression of sustainable agriculture and field management in this area.

 Conclusion

This two-year study illustrates that deep plowing straw returning + flat tillage markedly enhances soil structure in the semi-arid districts of western Heilongjiang Province, thereby establishing it as an efficacious tillage management strategy. The results indicated that, in comparison to conventional tillage, this tillage method enhanced soil aggregate structure, elevated soil organic carbon, total nitrogen, available nutrients, and enzyme activities, increased the 100-Kernels weight of maize, and ultimately augmented maize yield by 10.44% to 16.81%. These findings provide valuable practical guidance for local policymakers and farmers in the study region.

 Data availability statement

The original contributions presented in the study are included in the article/ Supplementary Material . Further inquiries can be directed to the corresponding authors.

 Author contributions

XQ: Writing – original draft, Conceptualization, Data curation. WH: Writing – original draft. YL: Formal Analysis, Writing – review & editing. JX: Formal Analysis, Writing – review & editing. FH: Methodology, Writing – review & editing. YW: Writing – review & editing. JF: Funding acquisition, Investigation, Writing – review & editing. KY: Funding acquisition, Resources, Supervision, Writing – review & editing.

 Funding

The author(s) declare financial support was received for the research and/or publication of this article. This research was financially supported by grants from by a project funded by Nature Scientific Foundation of Heilongjiang Province (YQ2024C043) and the Strategic Priority Research Program of the Chinese Academy of Science (XDA28130103).

 Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

 Generative AI statement

The author(s) declare that no Generative AI was used in the creation of this manuscript.

 Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

 Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fpls.2025.1626882/full#supplementary-material

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