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.

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.

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.

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.

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.

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.