Optimizing irrigation strategies for sustainable crop productivity and reduced groundwater consumption in a winter wheat-maize rotation system.

Inefficient irrigation practices have hindered crop yields, wasted irrigation water resources, and posed threats to groundwater levels and agricultural sustainability. This study evaluated different irrigation strategies for a winter wheat-summer maize rotation system to identify sustainable practices for maintaining yields while reducing groundwater depletion. A two-year field experiment was conducted, implementing three optimized irrigation strategies during the winter wheat season: I-4 (irrigated until the soil water content (SWC) of the 40 cm soil layer reaches 60% of field capacity (FC), I-6 (irrigated until the SWC of the 60 cm soil layer reaches 80% FC), and a rainfed (R) as control. Irrigation was repeated when the SWC dropped to the specified level. No irrigation level was used during the summer maize season, except for irrigation after sowing that ensuring the normal emergence of maize. WHCNS (Water Heat Carbon Nitrogen Simulator) model was developed to simulate soil water dynamics, field water consumption, and yield of both crops. The result indicated WHCNS model accurately simulated water dynamics, consumption, and grain yield. Compared to R treatment, the I-4 treatment significantly increased annual crop yield by 19.83%-28.65% (p < 0.05), while maintaining similar crop water productivity. Furthermore, the I-4 treatment achieved comparable yields to the I-6 treatment, but with a 33.91% reduction in irrigation water use, resulting in a 33.46% increase in crop water productivity and a 90.53% increase in irrigation water productivity. From a sustainable perspective, the I-4 treatment effectively reduced field water losses and maintained relatively high soil water storage, particularly in the topsoil, which was beneficial for the early growth of subsequent crops. The R treatment greatly contributed to groundwater recharge when precipitation was sufficient, while it led to severe yield losses. Overall, under the condition of annual rotation planting systems, the I-4 treatment sustainably maintained yields with less irrigation, decreasing groundwater consumption. This approach could conserve regional water resources and groundwater table while upholding agricultural productivity and achieving system sustainable water use.

The potential for soil C sequestration and N fixation under different planting patterns depends on the carbon and nitrogen content and stability of soil aggregates.

The winter wheat-summer maize rotation system is common in the Huang-Huai-Hai Plain due to its consistent yield, however, it may cause soil quality degradation and increased risk of greenhouse gas emissions. To evaluate the effects of different planting patterns on soil organic carbon (SOC) and total nitrogen (TN) sequestration, as well as aggregate and C-N distribution, a three-year field experiment that included three annual double-cropping rotation patterns: winter wheat-maize (W-M), winter wheat-soybean (W-S), and winter wheat-sweet potato (W-SP) was conducted from 2020 to 2022, with W-M as the control. Our research revealed significant differences in soil carbon sequestration rates among the various planting systems. Specifically, the SOC stock in the W-S system was 12.21 % to 24.51 % higher than that of the W-M system and 10.28 % to 35.73 % higher than that of the W-SP system. While TN stock demonstrated an increase of 9.85 % to 37.39 % compared to the W-M system and 8.14 % to 67.43 % compared to the W-SP system. Moreover, SOC and TN sequestration were largely related to soil aggregates, with macroaggregates being the primary component in both W-S and W-M planting patterns, while microaggregates were more common in W-SP patterns. The accumulation of SOC and TN occurred mainly in macroaggregates, leading to a significant increase in C and N content in soil macroaggregates under the W-S planting pattern. The structural equation model suggested that the TN stock had both direct and indirect effects on SOC sequestration, with a total impact coefficient of 0.872. Our three-year field results indicate that the W-S model is advantageous in enhancing soil C and N sequestration capacity and had great potential in reducing greenhouse gas emissions in farmland.

Does continuous straw returning keep China farmland soil organic carbon continued increase? A meta-analysis.

The straw returning technique is one of the important measures for soil carbon sequestration and soil organic carbon (SOC) promotion in the world. However, the patterns of straw utilization in China with various methods among regions, the effect and variability of straw returning on SOC in different areas of China remain uncertain. We conducted a meta-analysis of 446 sets of data from 95 studies in China field to explore how the environmental factors and field management affect SOC after straw returning. The results showed that straw returning to the field significantly increase SOC content by an average of 13.97% (n = 446). The SOC increased effects are more obvious under areas with mean annual precipitation (MAP) > 500 mm, temperature (MAT) > 10 °C, loam or sandy soil, or the initial SOC content <10 g kg-1. The effect of straw returning on SOC also depends on planting systems, ranging from 5.43% of rice continuous cropping to 17.05% of the maize-wheat ration. In the rotation system, the SOC increasing effect under paddy-wheat rotation (15.79% in rice and 14.87% in wheat season) was more significant than under wheat-maize rotation (17.05% in wheat and 11.81% in maize season). The proper duration of straw returning is 6-9 years, while it will decrease SOC by 17.06%-20.05% more than 10 years. Moreover, the effects of straw returning under the conditions with deep tillage, the amount of straw more than 9000 kg ha-1, or combined pure N with 180-240 kg N ha-1 were better than other methods.

[Effects of straw returning combined with nitrogen fertilizer on spring maize yield and soil physicochemical properties under drip irrigation condition in Yellow River pumping irrigation area, Ningxia, China]. / æ»´çŒæ¡ä»¶ä¸‹ç§¸ç§†è¿˜ç”°é æ–½æ°®è‚¥å¯¹å®å¤æ‰¬é»„çŒåŒºæ˜¥çŽ‰ç±³äº§é‡å’ŒåœŸå£¤ç†åŒ–æ€§è´¨çš„å½±å“.

Soil compaction and nutrient deficiency are common problems in Ningxia Yellow River pumping irrigation area, which adversely affect crop yield. A two-year (2017-2018) field experiment of straw returning combined with nitrogen fertilizer were designed. Four nitrogen application levels (pure N with 0, 150, 300 and 450 kg·hm-2) were set under the condition of full smashing of maize straw (12000 kg·hm-2) returning, with the conventional nitrogen application (pure N with 225 kg·hm-2) without straw returning as the control (CK) to investigate the effects of straw returning combined with different amounts of nitrogen fertilizer on soil physical and chemical properties and maize yield under drip irrigation condition. The results showed that, compared with no-straw returning treatment, the treatments of straw returning combined nitrogen fertilizer with 300 and 450 kg·hm-2 reduced soil bulk density (0-20 cm) by 3.3% and 5.4%, but increased soil porosity by 3.7% and 7.1%, respectively. Straw returning combined with nitrogen with 300 kg·hm-2 and 450 kg·hm-2 was the best treatment which increased soil organic matter content, available K, P, alkaline N and total N in 0-40 cm soil layer. Compared with the non-returning treatment, straw returning combined with nitrogen fertilizer 300 kg·hm-2 significantly increased soil water storage by 13.6% and 22.1%, increased maize yield by 31.1% and 46.0 % in 2017 and 2018, respectively. The analysis of yield components showed that the high maize yield was achieved mainly by increasing grain number and the100-grain weight. Curve fitting showed that the optimum amount of nitrogen fertilizer was 260 kg·hm-2. Our results provide important basis for soil fertility improvement and sustainable production.