免耕秸秆覆盖下黑土磷素形态转化的微生物调控机制及潜在环境效应

Soil microbial, is considered as an important driver of phosphorus (P) transformation, have major effect on soil P cycle. No-tillage with straw mulching is not only the main way for soil fertility, but is also the essential mean by which soil regulates P availability through microbial. Black soil fertility has been showing a decreasing trend with low efficiency of P utilization in north China, which is the focus in the research of how to improve P effectiveness using no-tillage with straw mulching, based on the conditions of guaranteeing ecological and environmental safety. With typical black soil farmland in northeast as material, P chemical composition, microbial activity and community structure, P converting process and its environmental effect with different mulching will study by P nuclear magnetic resonance (31P-NMR) and phosphate oxygen isotope (δ18OP) technology. The study will demonstrate the effect of no-tillage with different straw mulching on P in the soils, in order to reveal the influence and mechanism of P covering under regulation of microbial with different no-tillage covers on P maintenance, transformation and loss. The results will provide suitable mulching tillage, give the basis for reasonable P fertilization, soil fertility and control non-point pollution after covering straw mulching and no-tillage in the black soil area.

微生物作为土壤磷形态转化的重要驱动者，对土壤磷循环过程和功能产生重要影响。免耕秸秆覆盖是培肥地力的主要方式，也是通过影响微生物磷水平来调节土壤中磷有效性的重要手段。中国北方黑土区目前土壤肥力下降、磷素利用率低，如何利用免耕秸秆覆盖技术既提高磷素有效性又能保障农业环境安全是研究关注的热点。本研究拟以东北典型农田黑土为研究对象，采取液体磷（31P）核磁共振与磷酸盐氧（δ18OP）同位素等关键技术，研究不同秸秆覆盖量下土壤中磷素的化学组成、微生物活性及群落结构、微生物转化磷过程及其环境效应，探明免耕秸秆不同覆盖量对土壤磷形态的调控效果；以期揭示免耕秸秆覆盖下微生物调控的土壤磷周转过程对土壤磷保持、转化及流失的影响及机制，提出适宜的秸秆覆盖量，为黑土区秸秆覆盖免耕后合理施用磷肥、培肥地力和控制面源污染提供依据。

土壤磷素的迁移转化对农业生产和环境安全具有重要意义，但对此方面的研究尚未得到充分探讨。因此本项目开展了免耕秸秆覆盖下土壤磷素形态迁移转化特征的研究。本试验设置5个处理分别为：常规垄作无秸秆覆盖（CT），免耕无秸秆覆盖（NT-0），免耕 33%玉米秸秆覆盖（NT-33%），免耕 67%玉米秸秆覆盖（NT-67%）和免耕100%玉米秸秆覆盖（NT-100%），各处理采样深度为0-5 cm, 5-10 cm, 10-20 cm和20-40 cm。研究结果表明，与常规垄作相比（CT），免耕秸秆覆盖显著增加了土壤磷含量和磷酸酶活性。土壤含水量和pH与土壤有效磷呈显著正相关。免耕秸秆覆盖后，磷进入土壤后抑制了有机酸的释放。与其它处理相比，NT-67%在0-5 cm土层中具有较高的有机磷含量，但具有较低的无机磷含量。结构方程模型研究发现，NT-33%处理中有效磷的来源为无机磷，而在NT-67%处理下有效磷的主要来源为有机磷。此外，phoD功能基因群落多样性与31P NMR也证实了NT-67%对磷素有效性的提升效果最好。本研究表明，土壤磷素的迁移转化机制主要依赖于秸秆的覆盖量，NT-67%可能在土壤有机磷的维持和转化中发挥重要作用。