供磷强度对玉米根系生长空间的补偿机制及其对土壤磷的利用

Maintaining appropriate soil P supply in the root-zone and root growth space is vital for maize to fully exploit the biological potential of roots and improve phosphorus use efficiency, as maize mainly relying on the expansion of root morphology to obtain soil P. However, how soil P supply affect the change of soil P concentration in the rhizosphere and the root morphological characteristics to compensate the limiting root growth space induced by high planting density population was not fully understood. The present study lays emphasis on the compensation effect of soil P supply intensity to limiting root growth space in terms of efficient P acquisition and use for intensive cropping system through field trials and pot experiments in greenhouses. Some key methods and techniques for monitoring dynamic processes and related parameters in the roots and rhizosphere are adopted, including a rhizobox with micro-rhizons, in situ research method for root growth and so on. The main objectives of the present study are to systematically investigate the effect of soil P supply intensity on the change of root morphology (root length, lateral root density, root angle, and AM colonization) and P uptake of maize under different root growth spaces, evaluate the temporal and spatial variation of soil P in the rhizosphere under different root growth spaces, clarify the compensation mechanisms of soil P supply intensity on maize root morphology and P uptake under high planting density population. This study will provide important scientific bases to better understand the compensation mechanisms of soil P supply intensity on maize root morphology and P uptake under high planting density population, and thus improve phosphorus use efficiency for sustainable crop production aiming to high-yield and high-efficiency.

玉米主要依赖根系形态的拓展获取土壤磷，适宜的供磷强度和根系生长空间是玉米充分发挥根系生物学潜力，提高磷利用效率的关键。然而，在高密度群体中，供磷强度对玉米根系生长空间的补偿机制及其对土壤磷的利用，尚不清楚。本项目通过大田试验和室内盆栽模拟试验，以高投入玉米种植体系为研究对象，综合采用根系原位动态采样、土壤溶液微抽提技术等方法，揭示供磷强度调控的玉米根系形态特征（根长、侧根密度、根系夹角和菌丝侵染等）对根系生长空间有效性的补偿机制；探讨不同根系生长空间下，供磷强度驱动的玉米根际磷时空变化特征；阐明高密种植玉米体系中，通过优化供磷强度诱导的玉米根系形态特征对根系生长空间的补偿效应，及其对土壤磷利用的影响。为提高磷利用效率，实现玉米可持续生产提供科学依据。

玉米主要依赖根系形态的拓展获取土壤磷，合适的供磷强度和根系生长空间是玉米充分发挥根系生物学潜力，提高磷利用效率的关键。然而，在高密度群体中，供磷强度对玉米根系生长空间的补偿机制尚不清楚。本研究通过设置不同供磷强度和根系生长空间的玉米盆栽试验辅以大田试验，以高投入玉米种植体系为研究对象，在不同生育时期监测玉米根系生长和地上部磷吸收动态，明确了不同供磷强度和根系空间对玉米地上部生长、磷吸收的影响：根系生长空间对玉米磷吸收的限制作用开始于V6期，并且随生育期的推移，这种限制作用愈发强烈。在V6期，生长空间为D=20的条件下，增施磷肥到75 kg P2O5 ha-1玉米生物量和磷吸收与不施磷处理的根系生长空间D=40相同，而在V13期，增施磷肥到300 kg P2O5 ha-1玉米生物量和地上部磷吸收才与不施磷处理的根系生产空间D=40相同。表明根层供磷强度对根系生长空间的具有一定的补偿效应，且这种补偿效应显著受玉米生育期的影响。提高根层供磷强度主要通过两个途径补偿根系生长空间的不足：（1）本身根层磷供应强度的增加；（2）根层磷供应诱导了根系伸长和根系直径的降低，导致比根长显著提高。这在一定程度上极大的提高了玉米根系与土壤的接触面积，促进玉米对土壤磷的利用。同时本研究定量了根系生长与玉米磷吸收的关系，玉米根系干重每增加1g，地上部磷吸收提高13.3 mg。这些结果为提高集约化条件下高密种植玉米磷利用效率，实现玉米可持续生产提供了参数支撑。相关研究结果已投稿SCI文章2篇。