麦玉两熟体系作物秸秆钾转化特征与钾素补偿机制

During the use of potassium in agriculture, maintaining the balance of soil potassium should be pay attention to in the long run. Potassium input is obviously inadequate due to the high degree of intensification of agricultural production in the current. Mineral K resource is poor in our country, and it’s important to utilize straw K high efficiently for sustainable agriculture. Wheat and maize two crops a year is an important and typical planting system in Huang-huai-hai region, and the consumption of soil potassium in rotation system is significantly higher than that of monoculture system. Due to the inherent characteristics of potassium for its poor mobility and low loss rate，theoretically, the application of K fertilizer only need to supplement 15% potassium taken away by the grain under the condition of straw of two crops return. Straw of two crops return to soil is the powerful supplement of soil potassium, but There was a vast distance in compensating soil potassium between straw K and mineral K for that the characteristics of straw K to soil and the influence degree of each factor are not clear, and straw K translation is low efficient during the process of straw return to soil, and so on. Additionally, study on the evaluation of straw K reutilization and soil potassium supplying potential is lack. Aiming at the situation, the characteristic of straw K to soil and regulation technology will be studied to prove up the mechanism of improving the utilization efficiency of straw K and compensation of soil K, and then replace K fertilizer to the greatest degree, which is not only for saving the mineral K resource, but also the important supplement to action plan for zero growth of fertilizer use in China.

农业钾素利用从长远看应注重维持土壤钾素平衡。当前农业生产高度集约化，钾素投入明显不足，针对我国矿质钾肥资源缺乏现状，高效利用秸秆钾对可持续农业意义重大。小麦玉米一年两熟轮作制是黄淮海地区主要的种植制度，轮作模式下的土壤钾素消耗显著高于单作制。由于钾素移动性差、低损失率的固有特点，秸秆全还田条件下理论上只需补充籽粒带走的15%钾素即可。两季作物秸秆全部还田可对土壤钾素进行有力补充，但秸秆还田的实际补钾效果却与施用矿物钾肥以及理论值相差甚远，研究上存在着秸秆钾归田特征不清、各因素影响程度不明、秸秆钾转化利用低效等问题，缺乏还田秸秆钾养分再利用和土壤供钾潜力的研究与评估。本项目拟从作物秸秆钾还田特征及利用调控方面展开研究，探明麦玉轮作农田秸秆钾高效利用与土壤钾素补偿机制，使秸秆钾最大程度替代矿质钾肥使用。这不仅是节约矿质钾肥资源的需要，更是对我国化肥使用量零增长行动方案的重要补充。

我国矿质钾肥资源缺乏，秸秆钾素的高效利用可对矿质钾肥有较大程度的补充，而小麦玉米轮作制下秸秆还田的实际补钾效果低于预期，为此探明还田秸秆钾素的迁移和转换规律、明确秸秆钾素高效利用和土壤钾素补偿机制，这对于土壤可持续利用具有重要意义。.本项目在山东济南、泰安、德州等地通过土柱、盆栽及大田试验，与室内模拟试验相结合，围绕还田秸秆钾素行为特征、土壤含钾矿物演变与供钾潜力差异、秸秆钾高效利用机制等3个方面展开了研究工作，主要结果如下：.一是明确了影响小麦玉米秸秆还田钾高效转化利用的主要因素有降水、温度、土壤质地、腐熟剂添加等。结果发现：模拟降水在前8天作用下能够淋出绝对比例的秸秆钾素，秸秆越细溶出速率越高；在土壤含水量15%，湿度65%~70%条件秸秆即可释放出大部分钾素，小麦秸秆钾素在土壤中当季释放比例在80%~90%，玉米秸秆释放比例为65%~70%，高温更有利于秸秆钾素释放后向缓效钾形态转换；不同秸秆与土作用方式下的速效钾含量增幅在31~67mg/kg，不同质地土壤增钾效果为粘土＞壤土＞砂土；添加腐解剂使秸秆钾素养分时间释放提前。.二是探明了秸秆覆盖、秸秆浅旋、深耕等典型还田模式下秸秆钾素在土壤中运移及利用特点，明确了土壤钾素时空变异特征。秸秆浅旋方式下土壤速效含量增幅高于秸秆覆盖方式，不同有机无机协同模式均可提升土壤速效钾和有机质的含量，而配合腐熟剂施用起到了较好促进效果。.三是探明了连续十年秸秆还田条件下的土壤含钾矿物演变与供钾潜力特征，不同钾素投入模式导致土壤粘土矿物组成发生明显变化，长期钾素缺失与不足导致水云母、蛭石矿物类型向蒙脱石转化，只投入有机物料、无化学钾离子加入不利于高岭石形成。.四是研究得出了麦玉轮作制度不同秸秆还田模式下秸秆钾替代矿质钾肥的产量效应，等量钾素投入下的化学钾肥产量效应略高于秸秆还田处理，其中小麦增产2.65%，玉米增产1.73%，麦玉两季秸秆全还田基础上适量补充钾肥是生产上理想的钾肥运筹模式。