草地农业科技学院知识库

保护性耕作是提高旱作农业系统水分利用效率、培肥地力、改善土壤质量的重要措施，但其效应因地区与气候条件不同而异。围绕黄土高原地区保护性耕作体系中作物产量效应、水分利用状况以及土壤碳库变化等关键内容，本研究首先采用文献调研结合Meta定量分析的方法明确了“面”尺度上黄土高原保护性耕作措施下主要作物的产量效应、水分利用特征以及有机碳库的变化；其次，通过11a长期定位观测试验，在“点”尺度上系统研究了传统耕作处理（T）、传统耕作配合秸秆覆盖处理（TS）、免耕处理（NT）和免耕配合秸秆覆盖处理（NTS）对玉米（Zea mays L.）-冬小麦（Triticum aestivum L.）-大豆（Glycine max L.）轮作系统作物产量、水分利用效率和综合经济效益等影响，并采用支持向量机模型（Support Vector Machine, SVM）对轮作系统的作物产量和水分利用效率等进行了模拟。揭示了保护性耕作措施提质增效的机理和过程，对于该措施的大面积推广应用具有理论和实践指导意义。研究获得如下主要结果:1.   通过Meta分析对黄土高原地区保护性耕作效应的试验结果研究可知，与T处理相比，TS和NTS处理下小麦产量分别增加了9.7%和14.3%（P <0.05），NTS处理下豌豆（Pisum sativum L.）产量增加了29.5%（P <0.05），NT处理下大豆产量有减少趋势（P >0.05）；与T处理相比，TS处理下玉米水分利用效率提高了12%，TS和NTS处理下小麦水分利用效率分别增加了8.3%和11.6%（P <0.05），豌豆水分利用效率分别增加了10.8%和20.7%（P <0.05），而NT处理下大豆水分利用效率有降低趋势（P >0.05）。对于土壤有机碳含量而言，与T处理相比，TS和NTS处理下表层（0-10 cm）土壤有机碳含量显著提高了11.7%和20.2%（P <0.05），而NT处理下土壤有机碳含量的增长趋势不显著（P >0.05）。2. 长期定位研究结果表明：TS处理玉米籽粒产量、地上生物量分别比T、NT和NTS处理提高5.5%、13.1%和7.8%，冬小麦籽粒、秸秆产量和地上生物量在T、TS和NTS处理间无显著差异，但TS处理分别显著高于NT处理11.4%、12.7%和12.2%。秸秆覆盖显著提高了大豆的籽粒产量和地上生物量，耕作处理下作物的水分利用效率显著高于免耕处理。通过支持向量机模型（Support Vector Machine, SVM）验证结果表明：冬小麦、玉米以及大豆籽粒产量拟合R²值分别是0.83、0.76和0.56；水分利用效率拟合R²值分别是0.84、0.71和0.68，模型预测值和实测结果基本吻合，进一步明晰了影响作物产量和水分利用效率的主要驱动因子，为揭示保护性耕作的保水增产机理和评价其在不同自然条件下的适应性提供了依据。3.长期定位试验表明，0-30 cm四个层次土壤有机碳含量的变化趋势均表现为NTS、TS、NT较T处理有显著提高（P <0.05），在表层尤为明显。0-200 cm土层碳库活度、碳库指数和碳库管理指数在NTS处理下最高。长期固碳效益表明，NTS处理在耕作层（0-30 cm）年固碳能力为二氧化碳（CO₂）29.55 t/hm²，按照2016年北京碳交易市场年均成交价计算，NTS处理的农田年均固碳收益为1483元/hm²。4. 能量分析结果表明，在玉米-冬小麦-大豆轮作系统中，TS处理的总能量投入、总能量产出和净能值均为最高，分别为194.9 GJ/hm²、377.42 GJ/hm²和329.07 GJ/hm²，其净能值分别高于T、NT和NTS处理6.4%、9.1%和1.0%；经济效益分析结果表明，TS处理的年均投入和产出最高，分别为11019元/hm²和21563元/hm²，NTS处理年均净收益为5952元/hm²，分别比T、TS和NT处理高出26.3%，12.9%和15.7%。

综上，在黄土高原地区开展保护性耕作可以显著增加作物产量、提高水分利用效率以及提升土壤固碳潜力，具有重要的经济和农业生态价值，在该地区具有广阔的应用前景。

Conservation tillage is an important measure for increasing the efficiency of water use of dryland farming systems, enhancing land fertility, and improving soil health and economic profitability. With the focus on key agronomic production/resilience aspects such as crop yield, water use efficiency, and changes in soil carbon pool; this project integrated traditional field-based studies with meta-analysis, simulation modeling, and economic analysis to reveal how conservation tillage practices improved the quality and efficiency of conservation tillage systems in the Loess Plateau region of China. The research of relevant processes and mechanisms associated with conservation tillage is of important theoretical and practical significance for the wide application of this measure. Thus, the study first used extensive literature review and meta-quantitative analysis to synthesize the yield effects, water use characteristics, and changes in organic carbon pools of major crops under conservation tillage implemented in the Loess Plateau. Secondly, through 11a long-term position observation, this manuscript systematically investigated the influences of traditional tillage (T), traditional tillage combined followed by straw mulching (TS), no-tillage (NT) and no-till followed by straw mulching (NTS) on the crop yield, water use efficiency, and comprehensive economic efficiency of many predominant cropping systems that involve maize (Zea mays L.), winter wheat (Triticum aestivum L.) and soybean (Glycine max L.) in rotation. Additionally, support vector machine (SVM) modeling was used to simulate the crop yield and water use efficiency affected by different ecophysiological and managerial factors a cropping system level. The main findings were as follows:1. The meta-analysis on the experimental results of conservation tillage practices revealed that treatment T increased wheat yield by 9.7 and 14.3% compared with TS and NTS, respectively (P <0.05). Pea (Pisum sativum L.) yield was increased by 29.5% under treatment TS than T or NTS (P <0.05), while soybean yield was decreased by 7% under NT treatment (P <0.05) compared with T. Water use efficiency of maize under TS treatment increased by 12%, water use efficiency of wheat under TS and NTS treatments increased by 8.3 and 11.6% than T, respectively (P<0.05). Likewise, water use efficiency of pea increased by 10.8 and 20.7%, respectively (P <0.05).  Interestingly, water use efficiency of soybean was decreased (P >0.05) under NT treatment than T. In terms of soil organic carbon content, the surface (0-10 cm) soil under TS and NTS treatments had 11.7 and 20.2% greater organic carbon than T, respectively (P <0.05), no increase in organic carbon content under NT treatment was found (P >0.05).2. The results of long-term position study showed that crop yield and above-ground biomass of TS-treated corn were 5.5, 13.1, and 7.8% greater than those under T, NT, and NTS treatments, respectively (P <0.05). There were no significant differences in grain yield, straw yield, and above-ground biomass of winter wheat under T, TS, and NTS treatments. However, these indicators under TS treatment were significantly greater than those under NT treatment by 11.4, 12.7, and 12.2%, respectively. Straw mulching significantly increased crop yield and above-ground biomass of soybean. Crop water use efficiency of under tillage treatments was significantly greater than that under no-tillage treatment. The SVM-based simulation modeling indicated great accuracy in estimating crop yield, with R² values of 0.83, 0.76 and 0.56 for winter wheat, corn and soybean, respectively; and in predicting water use efficiency, with R² values of 0.84, 0.71 and 0.68, respectively. The measured results were consistent with the prediction of the model. This model identified the main driving factors that could affect crop yield and water use efficiency and provided a basis for analyzing the mechanism of water conservation and yield increase of conservation tillage and evaluating the adaptability of the conservation tillage system under different environmental conditions in the future.3. The long-term position experiment showed that total organic carbon content in all layers of soil under NTS, TS and NT treatments increased significantly compared with T and this trend was particularly evident in the surface layer (P <0.05). Carbon pool index and carbon pool management index of 0-200 cm soil layer were the highest under NTS treatment. The benefits of long-term carbon sequestration showed that the annual carbon sequestration capacity in the tillage layer (0-30 cm) under NTS treatment was (CO2) 29.55 t/hm2. According to the average transaction price of the carbon trading market in Beijing in 2016, the annual average benefits of carbon sequestration of farmland under NTS treatment was 1483 yuan/hm².4. Energy analysis results showed that in the corn-wheat wheat-soybean rotation system, the total energy input, total energy output and net energy value under TS treatment were the highest, which were 194.9 GJ/hm², 377.42 GJ/hm² and 329.07 GJ/hm2, respectively. Net energy value of TS was greater than those under T, NT, and NTS treatments by 6.4%, 9.1%, and 1.0%, respectively. The economic benefit analysis results showed that the annual average input and output under TS processing were the greatest, which were 11,019 yuan/hm² and 21,563 yuan/hm² respectively.  The annual average net revenue under NTS treatment was 5,952 yuan/hm², which was greater than the 4,711 yuan/hm² under T treatment, 5,272 yuan/hm² under TS treatment and 5,144 yuan/hm² under NT treatment.

In summary, the implementation of conservation tillage in the Loess Plateau region can significantly increase crop yield, improve water use efficiency and enhance soil carbon sequestration capacity; and it also has great economic and agroecological, thus, should be promoted in this region.