Northeast China is a vital grain production region of China. By means of Meta analysis, we studied the synergistic effects of agricultural management practices and climatic factors on rice yield in cold regions, to provide a theoretical basis for high and stable rice production in this area.

Literature published from 2003 to 2024 was searched on Web of Science, PubMed, CNKI, WanFang, and VIP databases using the keywords “cold region” or “Northeast China” and “rice yield” or “straw return” or “nitrogen application” or “nitrogen cycle”. The studies were then screened based on the following criteria: 1) Field experiments conducted in the three northeastern provinces of China; 2) Included straw return or nitrogen fertilization treatments, with corresponding controls (no straw return or no nitrogen application); 3) Reported complete data with means, standard deviations (SD) or standard errors (SE), and had at least three replicates (n≥3); 4) Provided rice yield data and at least one indicator of soil properties and/or the abundance of a nitrogen - cycling gene. A total of 175 pieces of literature were acquired from 61 observation sites across the three northeastern provinces. Among these, 570 datasets were extracted from 154 publications, and the effects of straw return duration, nitrogen application rate, tillage, and irrigation methods on rice yield and soil physicochemical properties were quantified using a Random Forest model. Additionally, 73 datasets were obtained from the remaining 21 pieces of literature to examine the correlation between nitrogen-cycling functional genes and soil factors to elucidate the underlying microbially-mediated mechanisms.

The random forest model identified soil organic carbon (SOC) and nitrogen application rate as the dominant factors influencing rice yield, with contribution rates of 27.05% and 24.14%, respectively. Subgroup analysis revealed that the combination of deep tillage with film mulching and controlled irrigation (PFM-CI) increased SOC content and rice yield by 20.46% and 36.24%, respectively. Under conditions of nitrogen application at 90−180 kg/hm², straw return rates of 6000−9000 kg/hm², and a return duration of 5−10 years, medium -maturing rice varieties exhibited higher yield increases compared with early- and late-maturing varieties. The interaction between nitrification and denitrification processes regulated soil nitrogen forms and availability, thereby significantly affecting rice yield in cold regions. Correlation analysis showed that SOC was positively correlated with the abundance of the denitrification gene nosZ (r=0.84), and the abundance of nosZ was significantly positively correlated with total nitrogen (TN) content in the anaerobic paddy soils (r=0.85, P<0.001). SOC also showed a positive correlation with the abundance of the ammonia-oxidizing archaeal gene AOA-amoA (r=0.22).

Rice yield in cold regions is jointly regulated by soil carbon and nitrogen contents as well as microbial transformation processes. Adopting the deep tillage combined with film mulching and controlled irrigation (PFM-CI) mode, optimizing the nitrogen fertilizer-to-straw return ratio, and selecting medium-maturing varieties are key strategies for enhancing rice yield and nitrogen use efficiency in the cold regions of Northeast China.

As the fourth-largest grain-producing province in China, Jilin Province possesses abundant straw resources. Estimating the nutrient resource quantities of major crop straws and their utilization potential under straw return in Jilin Province can provide reference data for the efficient utilization of straw nutrient resources, chemical fertilizer reduction, and green and low-carbon agriculture.

Based on statistical data and literature, using the straw-to-grain ratio method, the straw biomass, nutrient resource quantities, potential for straw incorporation to substitute nutrient inputs, and economic benefits of four major crops were estimated across different cities of Jilin Province in this study.

The average annual resources of maize, rice, soybean and peanut straw in 2019−2023 were 3225.68×10⁴ t, 585.08×10⁴ t, 70.36×10⁴ t, and 103.89×10⁴ t, respectively. Straw resources were mainly distributed in Changchun City, Songyuan City, Siping City, Jilin City and Baicheng City, accounting for 32.15%, 19.30%, 14.98%, 10.69%, and 10.07% of the total crop straw, respectively. The nitrogen (N), phosphorus (P₂O₅) and potassium (K₂O) resources from the main crop straw resources in the province were 35.79×10⁴ t, 12.21×10⁴ t, and 57.41×10⁴ t. The nutrient resources of maize, rice, soybean and peanut (N+P₂O₅+K₂O) accounted for 77.12%, 17.54%, 2.20%, and 3.14%, respectively. The seasonally available nitrogen (N), phosphorus (P₂O₅) and potassium (K₂O) from the main crop straw resources in the province were 18.76×10⁴ t, 8.78×10⁴ t, and 48.66×10⁴ t. The seasonally available resources from maize, rice, soybean and peanut (N+P₂O₅+K₂O) accounted for 77.37%, 17.82%, 1.97%, and 2.84%, respectively. In the main planting areas of the province, the substitution potential of chemical fertilizers by rice straw incorporation per unit sown area was N 27.32 kg/hm², P₂O₅ 12.56 kg/hm², and K₂O 122.06 kg/hm², respectively. The substitution potential of chemical fertilizers by maize straw incorporation per unit sown area were N 33.47 kg/hm², P₂O₅ 16.12 kg/hm², and K₂O 80.55 kg/hm², respectively. The substitution potential of chemical fertilizers by soybean straw incorporation per unit sown area were N 20.58 kg/hm², P₂O₅ 5.15 kg/hm², and K₂O 25.97 kg/hm², respectively. The substitution potential of chemical fertilizers by peanut straw incorporation per unit sown area was N 22.01 kg/hm², P₂O₅ 8.69 kg/hm², and K₂O 36.56 kg/hm², respectively. The average substitution percentage of chemical fertilizers by rice straw incorporation based on the optimal fertilization rate was 15.16%, 18.50%, and 11.06%, respectively. The average substitution percentage of chemical fertilizers by maize straw incorporation based on the optimal fertilization rate was 15.66%, 19.42%, and 78.13%, respectively. The average substitution percent of chemical fertilizers by soybean straw incorporation based on the optimal fertilization rate was 27.26%, 6.96%, and 43.35%, respectively. The average substitution percent of chemical fertilizers by peanut straw incorporation based on the optimal fertilization rate was 17.66%, 9.17%, and 30.85%, respectively. Complete straw return to the field could save about 7.91×10⁸ yuan, 6.22×10⁸ yuan, and 33.09×10⁸ yuan based on the prices of urea, superphosphate, and potassium sulfate, respectively, equivalent to a total of 47.22×10⁸ yuan in chemical fertilizer costs.

Jilin Province is abundant in straw resources, with the straw from major crops amounting to 3985.01×10⁴t, among which corn and rice account for 80.95% and 14.68%, respectively. Complete straw return from major crops to the fields can release available resources of N, P₂O₅, and K₂O of 18.76×10⁴ t, 8.78×10⁴ t, and 48.66×10⁴ t, respectively. Complete straw return can replace approximately 65% of chemical potassium fertilizer input and about 13%−15% of chemical nitrogen and phosphorus fertilizer inputs, saving 4.722 billion yuan in chemical fertilizer costs. Regional and crop-type differences should be taken into account when coordinating straw incorporation practices to achieve efficient utilization of straw resources, reduce chemical fertilizer application, improve efficiency, and achieve considerable economic benefits.

This study aimed to investigate the effects of localized application of controlled-release urea on the three-dimensional spatial distribution of maize root systems and nitrogen uptake and utilization. Specifically, it sought to clarify the advantages of slow-release urea over traditional uniform fertilization and localized quick-release fertilization in maintaining a sustained nutrient supply and matching with root growth, thereby providing a theoretical basis for the efficient utilization of slow-release nitrogen fertilizers.

A soil column experiment was conducted using maize and nitrogen fertilizer as the experimental subjects. Four treatments were established: no nitrogen application (CK), uniform urea application (UU), localized urea application (LU), and localized slow-release urea application (SU). X-ray computed tomography (X-ray CT) was employed for in situ scanning and three-dimensional reconstruction of root systems. Measurements of plant biomass, nitrogen uptake, and soil nitrogen content were integrated to analyze the relationships among root morphological traits, spatial distribution pattern, and nutrient uptake under different fertilization regimes.

Compared with UU and LU, SU increased above-ground nitrogen uptake by 43.8% and 36.9%, respectively, thereby significantly enhancing total maize nitrogen uptake. The SU treatment also substantially increased soil nitrate nitrogen content. Within the localized fertilization zone (2−6 cm soil layer), nitrate nitrogen concentrations in SU treatment were significantly higher than those in the CK, UU, and LU treatments by 200%, 80%, and 103%, respectively. The three-dimensional reconstruction based on X-ray CT revealed that the SU treatment significantly promoted root growth. Particularly in the localized fertilization zone (2−6 cm soil layer), root length density reached 7.3 cm/cm³, representing increases of 182% and 101% relative to the UU and LU treatments, respectively. Moreover, within the fertilization microzone (a 50 cm³ volume surrounding the fertilizer granules), root length under the SU treatment was 3.3 times of that under the LU treatment. Furthermore, correlation analysis indicated that root morphological parameters (root length, root surface area, and root length density) were significantly and positively correlated with soil nitrate nitrogen content and above-ground nitrogen uptake, whereas mean distance exhibited a significant negative correlation with nitrogen uptake.

Localized application of slow-release urea promotes sustained root proliferation in fertilized zones by providing a continuous supply of nitrogen, enhances the spatial coupling between roots and nutrients, and significantly improves maize nitrogen nutrition. X-ray CT technology effectively reveals the spatial characteristics of root-fertilizer interactions and provides crucial technical support for studying root-fertilizer interactions.

This study investigated the effects of one-time basal application of controlled-release urea (CRU) at different blending ratios on grain yield, dry matter accumulation, and nitrogen use efficiency (NUE) in spring maize under rainfed conditions in the Longzhong semi-arid region. The aim was to provide theoretical support for high-yielding and green and efficient fertilization practices in dryland spring maize.

Field experiments were conducted in Baiyin of Gansu Province consecutively in 2023 and 2024, using the high-yielding spring maize cultivar ‘Xianyu 335’. The designed N application amounts included a no-nitrogen control (CK), and three dosages of 180, 225, and 300 kg/hm². Conventional urea treatments included the three N dosages and were applied in two splits, denoted as N180-U1, N225-U1, and N300-U1, respectively; one-time basal application treatments included two N rates (180 and 225 kg/hm²), with the blended ratios of CRU to conventional urea set at 1∶2 (N180-C1, N225-C1), 1∶1 (N180-C2, N225-C2), and 2∶1 (N180-C3, N225-C3). Plant samples were collected at the six-leaf (V6), ten-leaf (V10), silking (R1), milky (R3), and physiological maturity (R6) stages. The biomass and nitrogen content in various parts were measured to calculate nitrogen use efficiency parameters.

Under the three conventional urea treatments, the maximum grain yield was obtained at N 225 kg/hm². At the same N input, the two 1∶1 blending ratio treatments (N180-C2, N225-C2) recorded higher kernel numbers per ear and 100-kernel weight, thereby enhancing both yield and economic returns. Over the two years, the average yields under the N180-C2 and N225-C2 treatments were 7.92 and 8.44 t/hm², which were 4.76% and 8.34% higher than those under N180-U1 and N225-U1, respectively. Compared with N180-C2, the N225-C2 treatment increased yield by 6.57%, and boosted net income and the output/input ratio by 35.71% and 7.09%, respectively. The nitrogen input and blending ratios also significantly affected N content in stems, leaves, grains, bracts, and cobs at harvest, as well as N translocation from stems and leaves. The N225-C2 treatment recorded the highest values. At the 1∶1 blending ratio, the N180-C2 treatment recorded significantly higher nitrogen agronomic efficiency (NAE) and partial factor productivity (NPFP) than did N225-C2, with two-year average increases of 11.36% and 17.32%, respectively. Compared with the conventional fertilization treatment N225-U1, the N225-C2 treatment increased NAE, NPFP, apparent recovery efficiency, and N uptake efficiency by 14.72%, 7.36%, 34.25%, and 29.49% in 2023, and by 16.37%, 8.94%, 39.89%, and 19.78% in 2024.

In the rainfed agricultural region of central Gansu, applying a blend of conventional urea and controlled-release urea as a single basal dressing at the optimal nitrogen rate (225 kg/hm²) enhanced nitrogen uptake and utilization in spring maize and promoted pre- and post-anthesis dry matter accumulation more effectively than split applications of conventional urea. The 1∶1 blending ratio outperformed the other ratios by improving pre-anthesis nitrogen and dry matter translocation, leading to higher grain yield and nitrogen accumulation, along with a significant increase in apparent nitrogen recovery efficiency. Thus, this fertilization strategy can serve as an effective nitrogen management approach for achieving high yield and high efficiency in spring maize production in the rainfed agricultural area of central Gansu.

Oilseed rape-maize (OM) and wheat-maize (WM) are typical rotation patterns in the Yangtze River Basin in China. This study investigated the effects of combined application of chemical fertilizers and organic materials on maize yield and nutrient use under OM and WM rotation systems, aiming to provide a scientific basis for nutrient management in high-yielding maize production.

Field experiments were conducted in Shayang County, Hubei Province in 2020 and 2021. Four fertilization treatments were set up under the OM and WM rotations: no fertilization (CK), chemical fertilizers (NPK), chemical fertilizers+straw return (NPK+S), chemical fertilizers+straw return+manure (NPK+S+M). Maize yield, aboveground biomass, nutrient utilization efficiency and nutrient apparent balance were analyzed.

The average results of the two-year experiment showed that there was a significant difference in maize yield among four treatments under two rotation patterns, and the order from high to low was NPK+S+M>NPK+S>NPK>CK (P<0.05). The maize yield of OM was significantly higher than that of WM under CK and NPK treatments, but not significantly different from that of WM under NPK+S and NPK+S+M treatments. The N, P and K nutrient accumulation of maize shoots were significantly different among the four treatments in both the rotation patterns, showing an order of NPK+S+M>NPK+S>NPK>CK (P<0.05), and the N, P, and K nutrient accumulation of OM maize were 9.6%−52.7%, 9.9%−28.7% and 9.2%−36.2% higher than those of WM, respectively. The input of organic materials reduced the nutrient use efficiency of maize in the four treatments. Compared with NPK treatment, the physiological utilization rates of N, P and K in NPK+S and NPK+S+M treatments decreased by 12.7%−25.4% and 9.1%−28.3%, respectively. Under CK and NPK treatments, the nutrient harvest index and nutrient physiological utilization rate of OM were higher than those of WM, but lower than those of WM under NPK+S and NPK+S+M treatments. Under the two rotation patterns, the apparent surplus of nutrients among the four treatments was significantly different. The apparent surplus of N and P from high to low was NPK+S+M>NPK>NPK+S>CK, and the apparent surplus of K was in order of NPK+S+M>NPK+S>NPK>CK. Under the four treatments, the apparent surplus of N, P and K was WM>OM.

Applying chemical fertilizer alone resulted in significantly higher maize yield and nutrient accumulation under the oilseed rape-maize rotation pattern than under the wheat-maize rotation. However, the combined application of chemical fertilizer with straw return or organic fertilizer significantly increased maize yield and nutrient accumulation. In the wheat–maize rotation system, maize yield and nutrient accumulation could be raised to levels comparable to those in the oilseed rape–maize rotation, and the apparent nutrient surplus was also improved. In the wheat–maize rotation system, it is recommended to apply both chemical and organic fertilizers combined with straw return to fully meet the nutrient demands for high maize yields. In contrast, in the oilseed rape–maize rotation system, considering the organic fertilizer effect of oilseed rape itself, the combined application of chemical fertilizer with straw return is recommended to ensure maize yield and nutrient use efficiency, thereby achieving high and stable yields of both grain and oil crops.

To clarify the characteristics of nitrogen flux balance, nitrogen fertilizer use efficiency, and nitrogen loss thresholds (maximum environmentally permissible emissions) in maize fields of the Qingtongxia Irrigation District, Ningxia, and to establish a corresponding management system.

From 2018 to 2023, total nitrogen input in maize fields across the irrigation district increased from 47800 t in 2018 to 65000 t in 2023, an increase of 35.83%, primarily due to a cropland expansion of 17100 hectares. Concurrently, environmental nitrogen emissions rose from 8900 t (18.70% of input) to 12100 t (18.55% of input), a 34.69% growth, with ammonia volatilization as the dominant pathway (accounting for 56.98% of total environmental emissions), followed by leaching (accounting for 26.54% of total environmental emissions) and runoff/erosion (accounting for 9.99% of total environmental emissions). The nitrogen fertilizer use efficiency in the irrigation district reached 42.92% in 2023, an increase of 5.72 percentage points compared with 2018. Notably, in Jinfeng District, ammonia volatilization risk decreased from 208% above the threshold (high risk in 2018) to low risk in 2023 through fertilizer reduction, while leaching risk was effectively controlled−by 2023, only Xixia District remained at low risk, and all other counties achieved risk-free status. Balanced fertilization combined with enhanced-efficiency fertilizers (S2) was identified as the optimal strategy. Compared with nitrogen reduction alone (S1), S2 increased nitrogen fertilizer reduction potential by 5.19−8.42 percentage points, improved use efficiency by 4.80−5.14 percentage points, reduced total environmental emissions by 44.13% (with all loss pathways below thresholds), and decreased environmental emissions by 52.50% while increasing nitrogen fertilizer use efficiency by 12.45 percentage points, compared with the 2023 baseline (S0).

Integrating balanced fertilization with enhanced efficiency fertilizers, together with water saving engineering measures, can reduce all forms of nitrogen emissions below environmental thresholds in the Qingtongxia Irrigation District, representing a key technological pathway for achieving regional agricultural green development and nitrogen emission mitigation.

In Yunnan’s Erhai Lake Basin, maize growing season coincides with the rainy season, conventional fertilization leads to heavy nitrogen leaching and causes serious non-point source pollution. By means of the existing drip irrigation infrastructure, we tried daily fertigation scheme characterized by low-dose water and fertilizer amount during the heavy rainfall period.

Field experiments were conducted over three consecutive seasons in the Erhai Lake Basin from 2023 to 2024, using sweet maize as the test material. In the first and second seasons, the controls were set at the traditional nitrogen (N) application rate of 400 kg/hm². The treatments involved reduced nitrogen fertilizer rates under 17 and 30 fertilization practices, respectively, and the optimal nitrogen application rate range was proposed. In the third season, the optimal nitrogen application rate range was further refined according to the daily N absorption of maize, and fertigation was automatically triggered when the light intensity was greater than 10000 lux. The fertilization frequency was recorded, and investigations were carried out on sweet maize yield, nitrogen uptake dynamics, nitrogen use efficiency, and residual mineral nitrogen in the 0−60 cm soil layer.

In the first season, there were no significant differences in maize yield under nitrogen application rates ranging from 200 to 400 kg/hm². The nitrogen uptake process of sweet maize conformed to the Logistic model, with a peak nitrogen uptake occurring 35−53 days after emergence, a daily uptake rate of 3.38−4.03 kg/(hm²·d), and a total nitrogen removal of 142−152 kg/hm² over the entire growth period. In the second season, the N application rate was reduced to 180 kg/hm², and the fertilization frequency was increased to 30 times, resulting in a comparable maize yield to the controls, but a 60% reduction in N losses and a 1.2-fold increase in the apparent nitrogen use efficiency. In the third season, the 180 kg/hm² of N rate was evenly divided into the daily requirement and applied with a minimum water volume of 4.5 m³/hm² every day, except on rainy days, and a total of 35 fertigation events were recorded. The scheme significantly enhanced maize dry matter accumulation, yield, and N use efficiency while reducing nitrogen losses. Comprehensive effect analysis revealed that the highest comprehensive score was achieved at a nitrogen application rate of 120 kg/hm² under a scenario where the weights of yield and environment were at 1∶1.

The optimal nitrogen application rate for sweet maize in the Erhai Lake rainy season is 120−180 kg/hm². Sweet maize exhibits a distinct Logistic cumulative pattern of nitrogen absorption, with the peak absorption period concentrated between 35 and 53 days after emergence, reaching a rate of 3.38−4.03 kg/(hm²·d), accounting for over 70% of the total nitrogen uptake during the entire growth period. By reducing the nitrogen application rate from the traditional 400 kg/hm² to 120−180 kg/hm² and utilizing automatic, small-dose, high-frequency drip irrigation triggered by light radiation intensity, the inorganic nitrogen content in the 0−20 cm surface soil can be significantly increased while maintaining yield. This approach notably improves nitrogen use efficiency, reduces apparent nitrogen loss, and represents the optimal nitrogen management technique for sweet maize in Yunnan, balancing both yield and environmental benefits.

This study investigated the effects of long-term straw return on changes in exchangeable potassium (K) content within different fractions of soil macro-aggregates and its coupling mechanism with organic carbon content.

This study was based on an 18-year long-term experiment of rice-wheat rotation in Qianjiang City, Hubei Province. Four treatments were selected: CK (no chemical fertilizer, no straw return), −S (no straw return), +0.5S (50% straw return), and +S (100% straw return). Soil samples collected in September 2023 were analyzed through aggregate density fractionation, exchangeable potassium content, and organic carbon content analyses. Combined with solid-state ¹³C nuclear magnetic resonance (NMR) spectroscopy, the research revealed the effects of straw return on the distribution characteristics of soil macroaggregates and exchangeable potassium allocation.

1) Compared to CK and −S, long-term straw return significantly increased the proportion of >0.25 mm aggregate fractions. Within macroaggregate fractions, the proportion of M(c)POM under +S treatment increased by 21.9%, while that of M-MOM decreased significantly by 55.4% relative to −S. 2) Under long-term straw incorporation, exchangeable potassium content in >0.25 mm aggregates significantly increased, primarily attributable to elevated levels in the M(c)POM and M-MOM fractions. The exchangeable potassium pool in >0.25 mm aggregates was significantly enhanced. Compared with the −S treatment, the exchangeable potassium pool in >2 mm aggregates increased by 111.1% and 242.4% under +0.5S and +S treatments, respectively, with the augmentation primarily originating from the M(c)POM fraction. 3) Under long-term straw return conditions, compared to the −S treatment, the organic carbon content in the >2 mm aggregate fraction increased by 17.6% and 46.5% under the +0.5S and +S treatments, respectively, while the organic carbon pool increased by 55.4% and 87.8%, respectively. This improvement was primarily attributed to the enhancement of the M(c)POM fraction. Compared to the −S treatment, the +0.5S and +S treatments increased the alkyl carbon content in the M(c)POM fraction of macroaggregates by 38.1% and 34.7%, respectively, while the aromatic carbon content decreased by 22.7% and 18.2%, respectively. The increase in alkyl carbon, a type of active organic carbon, can adsorb more exchangeable potassium, thereby improving soil potassium availability. 4) Correlation analysis demonstrated a highly significant positive relationship between organic carbon and exchangeable potassium content in M(c)POM, indicating that straw return synergistically enhanced soil carbon sequestration and potassium supply by promoting M(c)POM accumulation.

Long-term straw incorporation significantly increases the proportion of soil macroaggregates (>0.25 mm), as well as their potassium and carbon reserves. The M(c)POM (macro-organic matter within macroaggregates or coarse particulate organic matter) component emerged as a key factor influencing soil potassium availability. Straw incorporation promoted the accumulation of organic carbon in the M(c)POM fraction, regulating potassium retention and release through processes such as “adsorption–complexation−aggregate stabilization”, thereby effectively enhancing the soil’s potassium supply capacity. As the amount of straw incorporated increased, the improvement in soil potassium supply capacity became more pronounced, indicating that the input of organic carbon directly influences the effectiveness of straw incorporation in regulating potassium. Therefore, the amount of straw incorporated can facilitate the formation of soil macroaggregates and coordinate the retention and release of exchangeable potassium in soil.

To investigate the effects of green manure combined with synergistic materials on soil quality and rice growth in the hilly regions of Sichuan, aiming to provide technical and theoretical support for the rational utilization of green manure and the application of synergistic materials in paddy fields within this region.

The long-term field experiment included two planting systems: winter fallow (WF) and winter planting milk vetch (GM), as well as four combinations of synergistic materials involving without synergistic materials application (CK), Sesbania biochar (Z1), bentonite (Z2), and urease inhibitor (Z3). The effects of different synergistic materials on rice yield and nutrient uptake under two cropping systems were analyzed. Additionally, physical properties (bulk density, porosity, aggregates), chemical properties (pH and nutrients), and biological properties (microbial biomass carbon and nitrogen, enzyme activity) were analyzed. The soil quality was fully evaluated by calculating the soil quality index (SQI).

Compared with GM-CK, the yield of rice under the GM-Z2 treatment was significantly increased by 7.8% in 2023, while that under the GM-Z3 treatment was significantly increased by 9.7% and 13.0% in 2023 and 2024, respectively. Compared with WF-Z2, the yield of rice under the GM-Z2 treatment was significantly increased by 18.3% and 17.6% in 2023 and 2024, respectively. Compared with WF-Z3, the yield of rice under the GM-Z3 treatment was significantly increased by 14.6% and 17.7% in 2023 and 2024, respectively. The GM-Z3 treatment had the best effect on improving grain yield. Compared with GM-CK and WF-Z3 treatments, GM-Z3 significantly increased the nitrogen, phosphorus, and potassium uptake in the above-ground parts of rice plants. Compared with GM-CK and WF-Z1 treatments, the GM-Z1 treatment significantly reduced soil bulk density while increasing soil organic carbon content, total nitrogen content, microbial biomass carbon content, porosity, and sucrase activity. Compared with GM-CK and WF-Z2 treatments, the GM-Z2 treatment significantly increased soil available phosphorus content. Under both cropping systems, the Z1 treatment significantly reduced soil bulk density and significantly increased soil aggregate size distribution, soil porosity, available phosphorus content, and available potassium content. In contrast, the Z3 treatment significantly increased soil aggregate size distribution, soil total nitrogen content, and available potassium content. A comprehensive evaluation of soil quality using the minimum data set method indicated that compared with GM-CK and WF-Z1, the soil quality index under the GM-Z1 treatment was significantly increased by 14.5% and 28.9%, respectively. Compared with GM-CK and WF-Z3, the soil quality index under the GM-Z3 treatment was significantly increased by 5.9% and 11.8%, respectively. The GM-Z1 treatment had the best effect on improving soil quality, and the soil quality index was 0.581.

In the purple soil paddy rice cropping system of the hilly region of Sichuan, winter cultivation of Astragalus sinicus (Chinese milk vetch) significantly enhances integrated soil fertility. The co-application of synergistic amendments further optimizes its effects on yield improvement and soil amelioration. Specifically, the combined use of A. sinicus with a urease inhibitor primarily elevates soil total nitrogen content by mitigating ammonia volatilization and nitrogen loss. The integration of milk vetch with Sesbania biochar stimulates microbial activity, thereby facilitating organic carbon transformation and nutrient cycling. Concurrently, it reinforces soil aggregate stability and improves water and nutrient retention capacity, effectively minimizing nitrogen leaching losses during the decomposition of milk vetch.

The dry-farming soil of the Loess Plateau is characterized by poor structure and weak water and nutrient retention capacity. The application of exogenous organic and inorganic substances is a key technology for improving soil quality and increasing crop yield in this area. This study explored the synergistic effects of the combined application of bentonite and straw on enhancing soil structure, water and nutrient retention capacity, and crop yield in oat fields within this region.

A long-term field experiment was established in 2019 in the dryland farming region of the Loess Plateau in Inner Mongolia. It comprised four treatments: no bentonite or straw application (CK), bentonite application alone (OB), straw application alone (OS), and combined application of bentonite and straw (H). Soil samples were collected from the soil profile after oat harvest in 2023 to determine soil aggregate composition, bulk density, porosity, available nutrient content, soil water storage, and crop yield and its components. Correlation and principal component analyses were conducted to identify the factors influencing yield.

Compared with CK, the other three treatments significantly improved soil structure, water and nutrient retention capacity, and oat yield, with the following order of effectiveness H>OS>OB (P<0.05). The H treatment significantly increased the content of >2 mm and 0.25−2 mm macroaggregates by 33.06% and 37.54%, respectively, reduced bulk density by 6.43%, and increased porosity by 7.86%. These improvement effect extended to the 20−40 cm soil layer. In addition, the contents of alkali-hydrolyzable nitrogen, available potassium, and available phosphorus were significantly increased by 6.89%, 17.28%, and 30.82%, respectively. The H treatment exhibited the highest water-use efficiency and rainfall-use efficiency, increasing them by 36.84% and 35.25%, respectively, compared with CK, both at a significant level. Panicle number per unit area, grains per panicle, 1000-grain weight, biological yield, and grain yield were all significantly higher than those of the control. The increase in biological yield reached 34.42%. Correlation and principal component analysis showed that yield was significantly positively correlated with >2 mm and 0.25−2 mm aggregate content, aggregate stability, and nutrient content, with alkali-hydrolyzable nitrogen and 0.25−2 mm aggregate as the main positive influencing factors.

In dryland oat fields on the Loess Plateau, a one-time basal application of bentonite (18000 kg/hm²) combined with annual straw incorporation (6000 kg/hm²) can synergistically enhance the content of macroaggregates in the 0−40 cm soil layer, improve soil structural stability, reduce bulk density in deeper soil layers, increase porosity, and significantly elevate soil available nutrient content and soil water storage. This ultimately increases oat yield and water-use efficiency, achieving a synergistic effect of soil structure improvement, enhanced water and nutrient retention capacity, and increased oat yield. This approach can serve as an effective technical pathway for enhancing regional farmland productivity and resource-use efficiency.

Application of nitrogen (N) fertilizer or a combination of nitrogen and zinc (Zn) can significantly increase the availability of soil Zn, improve the Zn nutrition and grain yield of winter wheat. Root exudates have been widely recognized for their critical role in mobilizing and activating nutrients within the rhizosphere, thereby facilitating their uptake by plants. In this study, we investigated the combined effects of nitrogen-zinc (N-Zn) fertilizer application and exogenous winter wheat root exudates on the transformation of different Zn forms in calcareous soils.

A hydroponic culture trial was carried out, using winter wheat cultivar Bainong 207 as the test material. Two Zn application levels (0, 10 µmol/L) and two N application levels (0.5, 7.5 mmol/L) were set up to compose 4 treatments. The root exudates were collected, and the composition and concentration of organic acids in the root exudates were analyzed. Subsequently, a rhizobox experiment was carried out using the same wheat cultivar. Each treatment was then divided into two parts: one was added with 50 mL distilled water, and the other with 50 mL root exudates collected in the hydroponic trial. The biomass, N and Zn concentration of various parts of the wheat plant, and the pH, available Zn content, and the contents of Zn fractions in rhizosphere and non-rhizosphere soil were determined.

Compared with the low-nitrogen, zinc-free treatment (N_0.5Zn₀), co-application of N-Zn fertilizers (N_7.5Zn₁₀) markedly elevated the concentrations of aconitic acid, fumaric acid, and malic acid in root exudates, whereas it significantly depressed the levels of pyruvic acid, α-ketoglutaric acid, and succinic acid. Irrespective of root exudate addition, N-Zn application notably boosted grain yield, Zn concentrations in roots, stems, leaves, and grains, as well as N concentrations in glumes and grains. In both rhizosphere and non-rhizosphere soils, this combined application significantly increased available Zn concentrations, along with the contents and proportions of exchangeable Zn, carbonate-bound Zn, and Fe-Mn oxide-bound Zn, while dramatically reducing the concentration and proportion of residual Zn. Under the regime of combined N-Zn application, the supplementation of root exudates further increased grain yield and Zn content, as well as N content in roots, stems, leaves, and glumes. It significantly elevated available Zn and exchangeable Zn concentrations in non-rhizosphere soil, raised the content and proportion of carbonate-bound Zn in rhizosphere soil, but significantly lowered the pH and decreased the content and proportion of residual Zn in rhizosphere soil.

Under conditions of combined N and Zn application, exogenous root exudates from winter wheat facilitate the conversion of residual Zn to carbonate-bound Zn in rhizosphere soils, increase the contents of carbonate-bound Zn and Fe-Mn oxide-bound Zn in both rhizosphere and non-rhizosphere soils, thereby effectively improving soil Zn bioavailability and enhancing Zn uptake by winter wheat.

This study aimed to evaluate the soil acidification characteristics of sugarcane fields in Guangxi under different fertilization treatments and to provide a theoretical basis for mitigating soil acidification in this region.

Based on a long-term field experiment initiated in 2008, four treatments were established: no-fertilizer control (CK), recommended fertilization (OPT), increased N application (OPTN, 50% higher nitrogen (N) application rate than OPT) and recommended fertilization combined with sugarcane leaf mulching and returning (OPTS). Soil pH, exchangeable acidity, acidification rate, exchangeable base cations, cation exchange capacity (CEC), soil acid-base buffering capacity (pHBC) and soil nutrients indicators were determined after 16 years under different fertilization treatments.

After 16 years of long-term experiments, compared with the initial soil, soil pH under the CK, OPT, OPTN, and OPTS treatments decreased by 0.04, 1.74, 2.00, and 1.72 units, respectively. The corresponding soil acidification rates were 0.16, 9.62, 10.41, and 9.81 kmol/(hm²·a), respectively. The soil pHBC of the CK treatment was 24.00 mmol/(kg·pH). Compared with CK, the pH buffering capacity under the other fertilization treatments increased by 20.32%−26.77%, with the greatest increase observed in the OPTS treatment. Compared with the OPT treatment, the OPTN treatment increased exchangeable acidity, exchangeable aluminum (Al³⁺), and exchangeable hydrogen (H⁺) by 19.31%, 15.25%, and 54.75% respectively. The total exchangeable base cations of the OPTN decreased by 14.03%, and base saturation decreased by 15.10%. Soil pH decreased by 0.26 units, and the acidification rate increased by 8.22% under OPTN relative to OPT. Compared with the OPT treatment, the OPTS treatment increased exchangeable acidity and exchangeable H⁺ content by 17.82% and 69.27%, respectively. The total exchangeable base cations increased by 13.45%, mainly due to a 26.22% increase in exchangeable calcium content. CEC increased by 12.67%. However, there were no significant difference in soil pH and acidification rate. Under increased N fertilization, soil total phosphorus, available phosphorus, and readily available potassium contents decreased by 6.99%, 11.06%, and 27.11%, respectively. Under sugarcane leaf mulching and returning, soil organic matter, total N, and available N contents increased by 9.96%, 12.32%, and 26.40%, respectively, while available phosphorus and readily available potassium contents decreased by 17.15% and 34.65%, respectively. In terms of the 5-year average sugarcane yield, compared with the OPT treatment, the OPTN treatment resulted in a 6.23% reduction, while the OPTS treatment resulted in a 2.68% increase.

Long-term excessive N fertilization increased exchangeable H⁺ and Al³⁺ contents while reducing total exchangeable base cations. The increased fertilizer N was not efficiently utilized by sugarcane, further accelerating soil acidification. In contrast, long-term sugarcane leaf mulching and returning effectively increased total exchangeable base cations, CEC, and organic matter content, and improved soil nutrient supply and acid-base regulation capacity. Therefore, rational chemical fertilizer application combined with sugarcane residue mulching and returning can serve as an important strategy for managing soil acidification in lateritic red soil sugarcane fields in Guangxi.

Critical nitrogen dilution curves (CNDCs) have been constructed for nitrogen nutrition diagnosis in many crops. However, the acquisition of the main variable factor, biomass, requires destructive sampling, which significantly reduces the practical feasibility of these curves. We attempted to construct a critical nitrogen dilution curve for flue-cured tobacco using accumulated growing degree days (AGDD, referred to as the “AGDD curve”) and compared the parameter values with those of the curve using shoot dry matter accumulation (referred to as the “dry matter curve”).

The field experiment was conducted in Linqu County, Shandong Province, in 2023, using the flue-cured tobacco cultivar Zhongchuan 208. The experiment employed a two-factor (planting date and nitrogen application rate) complete block design. The two transplanting dates were April 30 and May 10. The nitrogen application rates included five levels: N1 (0 kg/hm²), N2 (45 kg/hm²), N3 (90 kg/hm²), N4 (135 kg/hm²), and N5 (180 kg/hm²). Aboveground dry matter accumulation in tobacco plants was measured at key growth stages, including the rosette, vigorous growth, bud emergence, topping, and maturity stages. Using a hierarchical Bayesian framework model and the Markov Chain Monte Carlo (MCMC) algorithm, two critical nitrogen dilution curves for the aboveground dry matter accumulation of flue-cured tobacco were constructed. One curve was driven by accumulated temperature (T-curve), and the other by aboveground dry matter accumulation (M-curve). The ability of the two curves to differentiate between nitrogen-limited and non-nitrogen-limited conditions was compared. The critical nitrogen concentration and nitrogen nutrition index were calculated using measured data and fitted using the two curves to test the accuracy of the two curves.

Both planting date and N application rate significantly affected the aboveground dry matter accumulation of flue-cured tobacco. The critical nitrogen dilution curves constructed with aboveground dry matter accumulation (PDM) and accumulated growing degree days (AGDD) as driving variables, were Nc = 3.00 PDM^−0.18 and Nc = 2.32 AGDD^−0.33, respectively. For the M-curve, the 95% posterior distribution ranges for parameters A1 and A2 were 2.71−3.40 and 0.10−0.29, with mean values of 3.00 and 0.18, respectively. The curve’s uncertainty level ranged from 0.14% to 1.76%, with relative uncertainties for A1 and A2 being 0.23% and 1.12%, respectively. The discrimination ability between the nitrogen surplus group and the nitrogen deficit group was 75%. The normalized root mean square error (n-RMSE) of the nitrogen nutrition index was 23%. For the T-curve: the 95% posterior distribution ranges for parameters A1 and A2 were 2.23−2.41 and 0.23−0.44, with mean values of 2.32 and 0.33, respectively. The curve’s uncertainty level ranged from 0.12% to 1.12%, with relative uncertainties for A1 and A2 being 0.08% and 0.62%, respectively. The discrimination ability between the nitrogen surplus group and the nitrogen deficit group was 82%. The normalized root mean square error (n-RMSE) of the nitrogen nutrition index was 13%.

Compared to the dry matter-based curve, the accumulated temperature-based curve offers clearer differentiation between nitrogen deficit and nitrogen surplus conditions. The fitted nitrogen nutrition index demonstrates a stronger linear correlation with the actual nitrogen nutrition index, evidenced by a lower normalized root mean square error (n-RMSE) of 13%, indicating higher simulation accuracy. Given the practicality and accessibility of accumulated temperature data, the critical nitrogen dilution curve developed using accumulated temperature as the driving variable is well-suited for non-destructive diagnosis of nitrogen status in flue-cured tobacco.

Soil magnesium (Mg) deficiency was one of the main limiting factors for pepper production. The effect of different Mg fertilizer application amounts on pepper yield and soil exchangeable Mg content was studied, and the mechanisms was also explored.

A field experiment was conducted in east of Guizhou Province during 2018 and 2019, using chilli pepper (Capsicum annuum var. conoides) as test material. Five Mg application levels were set up, including: 0, 22.5, 45, 67.5, and 90 kg/hm², denoted as Mg0, Mg22.5, Mg45, Mg67.5, andMg90, respectively. Chilli pepper yield, yield components, leaf net photosynthetic rate (Pn), leaves chlorophyll content, shoot Mg concentration and soil exchangeable Mg content were measured.

Soil Mg application significantly increased the yield of pepper, with the Mg67.5 and Mg90 treatments showing the best results. In 2018 and 2019, the yields of chilli pepper significantly increased by 20.7%−40.6% and 14.8%−18.0%, respectively, compared to the Mg0 treatment. The yield increase was mainly attributed to improvements in the number of fruits per plant and single fruit weight. Soil Mg fertilization enhanced the Pn, chlorophyll content, and Mg content of the plants during the flowering and fruit-setting stage (a critical growth period). In 2018 and 2019, the Pn were increased by 41.8%−72.8% and 27.3%−71.3%, respectively, total chlorophyll content increased by 23.1%−37.2% and 9.3%−14.8%, respectively, compared to the Mg0 treatment. During the flowering and fruit-setting stage, plant magnesium concentration increased by 57.3%−74.7% and 29.8%−69.8%, respectively. At harvest, plant magnesium concentration increased by 24.7%−78.0% and 17.6%−42.1%, respectively. The 0−20 cm soil layer exchangeable Mg content under Mg-treated plots in 2018 and 2019 was 58.1−79.4 mg/kg and 62.1−101.7 mg/kg, respectively, representing significant increases of 26.8%−52.9% and 34.9%−121.0%, compared to the Mg0 treatment. In 2018, there were no significant differences in exchangeable Mg content among treatments in the 20−40 cm and 40−60 cm soil layers. In 2019, the exchangeable Mg content in the 20−40 cm and 40−60 cm soil layers under Mg treatments was 64.0−92.6 mg/kg and 70.9−97.0 mg/kg, respectively, showing significant increases of 18.3%−71.3% and 11.9%−53.0%, compared to Mg0 treatment. Regression analysis revealed that the Pn during the flowering and fruit-setting stage, as well as the yield of chilli pepper, exhibited a highly significant linear positive correlation with the exchangeable Mg concentration in the 0−20 cm soil layer at harvest. The Mg content in the fruit of chilli pepper reached a plateau value of 1.95 g/kg when the soil exchangeable Mg concentration reached 74.2 mg/kg.

Mg fertilization can effectively improve the exchangeable Mg concentration in 0−20 cm soil layer, providing sufficient Mg nutrition for chilli pepper during the whole growing period. As a result, Mg fertilization can enhance the net photosynthetic rate and chlorophyll content of leaves, and maintain leaf greenness during flowering and fruit-setting stage, and therefore increase the chilli pepper yield and fruit Mg content. Applying Mg 67.5 kg/hm² is recommended for high chilli pepper yield and maximum fruit Mg content, as well as the high soil exchangeable Mg content in the tested area.

Conventional fertilizers often face difficulties in controlling nutrient release rates and exhibit relatively low utilization efficiency. Thus, environment-responsive fertilizers that modulate nutrient release in response to environmental changes are progressively emerging as pivotal technological approaches for advancing sustainable agriculture.

Lignin (L) was hydrolyzed using urea/NaOH (UR/SH) at low temperatures to obtain hydrolyzed lignin (HL). The hydrolyzed lignin was then cross-linked with polyethylene glycol diglycidyl ether (PEGDGE) to prepare a hydrolyzed lignin hydrogel (HLHG). The HLHG was subsequently employed as a carrier for diammonium phosphate (DAP) fertilizer to create a pH-responsive hydrogel fertilizer.

The optimal hydrolysis conditions were determined to be 18 h and −10℃. Under these conditions, the contents of hydroxyl (—OH) and carboxyl (—COOH) groups reached their maximum levels, increasing by approximately 68% and 99%, respectively, compared to untreated L. The obtained pH-responsive lignin hydrogel [HLHG-(−10℃)-18 h] showed an equilibrium swelling ratio of 1216%, with a water retention swelling ratio of 163% after 11 hours. These values were approximately 3 and 12 times of the unhydrolyzed lignin hydrogel (LHG), respectively. pH responsiveness analysis indicated that the hydrogel demonstrated significant pH sensitivity, with equilibrium swelling ratio of 364%, 518%, and 634% at pH 6, 7, and 8, respectively. Between the adjacent gradients of pH 6−7 and pH 7−8, the equilibrium swelling ratios increased significantly by 41% and 70%, respectively, compared to LHG. SEM analysis demonstrated pH-dependent microstructural evolution of the lignin hydrogel. As the pH increased from 5 to 8, the honeycomb network exhibited a progressive pore channel expansion with concomitant wall thinning. When the pH increased to 9, the network structure contracted, resulting in a reduction in pore channels and thickening of the pore wall. This pH-responsive behavior was mechanistically attributed to the ionization/protonation equilibria of abundant —OH and —COOH groups in lignin, as validated through integrated functional group quantification and pH responsiveness assays. Furthermore, the pH-responsive hydrogel was employed as a carrier for DAP to control the release of phosphate fertilizer nutrients. The nutrient release results showed that the cumulative release rate of P₂O₅ from the lignin hydrogel fertilizer in the period of 60 h was 61%, 76%, and 85% at pH 6, 7, and 8, respectively, exhibiting a prominent pH-responsive tendency.

UR/SH hydrolysis of lignin effectively modifies the content of active functional groups and the internal spatial network structure of lignin, it is possible to create pH-responsive lignin hydrogels with enhanced water absorption and retention capacities. Utilizing this pH-responsive lignin-based hydrogel as a carrier for fertilizers offers a valuable reference for the effective utilization of lignin resources and the design of bio-based green fertilizer for nutrient control release.