绿肥提升旱地石灰性土壤磷有效性和冬小麦磷吸收的作用机理

The low availability of soil phosphorus (P) has gradually became the key limiting factor in crop production on the Loess Plateau of China. Therefore, it is of great importance to explore soil P pools and improve P use efficiency of the main crop for the sustainable development of the farmland ecosystem and green production in China. Results of our previous studies showed that growing green manure (GM) legumes during summer fallow period for 6-yrs significantly increased the soil available P and wheat seed P contents, but its mechanism was still not clear. The indoor rhizon-box experiment, field GM decomposition trial, and a long-term experiment will be combined together in our project to investigate the effects of growing leguminous and cruciferous GM crops on the changes in the calcareous soil P fractions and contents at the GM growth and decomposition stages under dryland conditions, respectively. The solution 31P nuclear magnetic resonance (31P NMR) spectroscopy and high performance liquid chromatography-mass spectroscopy (HPLC-MS) methods will be used in this project. Besides, the P release patterns in above- and below-ground tissues of the different GM crops will be studied to figure out the reasonable P fertilizer application during the period of winter wheat growth. This project will also investigate the effects of different GM crops and P fertilization on the subsequent winter wheat growth, yield, and the amount of P uptake, aiming at revealing the mechanisms for GM crops to increase the calcareous soil P availability and the P uptake of winter wheat in the semiarid regions. The results of our project will be used to provide the theoretical basis and technical support for further developing and optimizing the summer green manure-winter wheat cropping system, and improving the utilization efficiency of nutrient resources on the Loess Plateau of China.

黄土高原半干旱区农田土壤磷素较低的有效性，逐渐成为限制农作物增产的重要因素。因此，探索如何充分挖掘土壤磷库、提高作物磷素吸收利用效率，对于我国农田生态系统的可持续发展和绿色生产意义重大。本课题组前期研究发现，连续6年绿肥轮作显著提高土壤有效磷和冬小麦籽粒磷含量，但对其作用机制尚不清楚。本项目拟通过室内根箱模拟、田间腐解和长期定位试验，利用31P液相核磁共振和高效液相色谱-质谱联用技术，重点研究豆科和十字花科绿肥在其营养生长和还田腐解阶段对旱地石灰性土壤不同磷组分、含磷化合物形态和含量变化的影响，阐明不同种类绿肥在冬小麦生长季磷素释放规律，量化绿肥-冬小麦轮作体系中合理的磷肥用量，查明后茬冬小麦生长、产量以及磷吸收对绿肥和磷肥响应的内在机理，揭示绿肥作物提升土壤磷有效性、促进冬小麦磷素吸收的作用机制，为提高旱地养分资源利用率、发展并完善黄土高原地区绿肥作物综合利用技术提供理论依据和技术支撑。

黄土高原半干旱区农田土壤磷素较低的有效性，逐渐成为限制农作物增产的重要因素。因此，探索如何充分挖掘土壤磷库、提高作物磷素吸收利用效率，对于我国农田生态系统的可持续发展和绿色生产意义重大。本项目研究内容包括三大部分：①不同种类绿肥生长阶段根系分泌物对石灰性土壤磷组成和形态的影响；②不同种类绿肥腐解阶段磷素释放规律及其对土壤磷组成和形态的影响；③不同种类绿肥对冬小麦植株生长、产量形成和磷素吸收的影响。通过本项目的实施，取得了一系列创新性的成果：.①结合根箱栽培试验，采用Tissen法查明了石灰性土壤有机和无机态磷组分对于种植不同种类绿肥和供磷水平的响应，发现在旱地种植并翻压不同种类绿肥能在低磷环境中通过活化小麦根际土壤缓效态的有机磷，提高冬小麦根际土壤速效态和缓效态的无机磷含量；同时，施用磷肥有助于提升土壤活性有机态磷和无机态磷、缓效态的无机磷以及残留态磷含量。.②利用31P NMR技术研究豆科和十字花科绿肥生长阶段对土壤具体含磷化合物形态和含量变化特征，发现绿肥作物根际土土壤的正磷酸盐、磷酸单酯、磷酸二酯和膦酸酯较休闲均有显著提升，初步揭示了绿肥作物活化黄土高原旱地农田土壤磷库的作用机制。.③基于课题组已经开展的长期定位试验，明确了不同种类绿肥对旱地冬小麦植株生长、产量形成和磷素吸收的影响，发现绿肥作物有助于提升后茬作物磷素营养和吸收状况，同时系统评价了旱地冬小麦-夏绿肥种植模式下农田生态系统磷盈余状况，建议该模式下磷肥合理施用量调整为100-120 kg P2O5/hm2，更有利于提高磷肥的当季利用效率，减少过量施用磷肥带来的环境问题。这些研究成果，为推动以绿肥为依托的旱地绿色农业可持续发展提供了一定的理论依据和技术支撑。