新疆滴灌苜蓿细根周转和生产性能对磷素水平的响应

Fine root turnover has an important influence on alfalfa aboveground biomass and soil carbon accumulation process, and fine root turnover of alfalfa change occurred again because of its unique way of drip irrigation. Phosphorus is a lot of nutrients necessary for the growth of alfalfa, and fine root turnover and production capacity by a huge adjusting the level of phosphorus. In this project, the drip irrigation in Xinjiang alfalfa as the research object, the minirhizotron dynamic in situ observation and isotopic tracer technique combined method was used. Analysis of drip irrigation of alfalfa production capacity, fine root development, fine root biomass, root absorption area and fine root turnover process under different levels of phosphorus, and to clarify the response mechanism of fine root turnover and production performance of alfalfa to the levels of phosphorus under drip irrigation. And to clear correlation between soil respiration and fine root biomass combined with soil respiration, root respiration and soil organic carbon content. Clarify the effect mechanism of fine root turnover on soil organic carbon storage, and then clarify the relationship between with phosphorus and fine root turnover and production performance of alfalfa, and eventually clarify the mechanism the effect of phosphorus on fine root turnover and then effect the production performance of alfalfa. This project will provide a theoretical basis for drip irrigation of alfalfa fine root turnover and sustainable utilization of soil in theory, and will provide practical guidance for quality and efficient production of alfalfa under drip irrigation in practice.

细根周转对苜蓿地上部生物量及土壤碳积累过程具有重要的影响，滴灌苜蓿因其独特的灌溉方式使细根周转发生再变化，而磷是苜蓿生长发育必需的大量营养元素，细根周转和生产性能受磷素水平的调节作用巨大。本项目以新疆滴灌苜蓿为研究对象，采用微根管动态原位观测及同位素示踪技术相结合的方法，分析不同磷素水平下滴灌苜蓿生产性能、细根发育、细根生物量、根吸收面积以及细根周转过程，阐明滴灌苜蓿细根周转和生产性能对磷素水平的响应机制；并结合土壤呼吸、根系呼吸作用及土壤有机碳含量，明确土壤呼吸速率与细根生物量的相关性，并阐明细根周转对土壤有机碳积累的影响机制，进而明确磷素—苜蓿细根周转—生产性能三者之间的关系，并最终阐明磷素影响苜蓿细根周转进而影响苜蓿生产性能的作用机制。该项目在理论上可为滴灌苜蓿细根周转及土壤可持续利用提供理论依据，在实践上可为滴灌苜蓿优质高效生产提供实际指导。

紫花苜蓿是一种多年生豆科牧草，因其具有产草量高、草质优良、适口性好、适应性强等特点，被称为“牧草之王”。磷是苜蓿生长发育必需的大量营养元素，在提高苜蓿产量的同时，能够对整个苜蓿根系尤其是细根部分的生长、衰老、死亡、脱落和再生长的周转过程产生重要影响，而磷素如何通过对根系的影响进而影响苜蓿生产性能的作用机制尚不清楚。因此，本项目开展了施磷对滴灌苜蓿细根周转、空间分布特征的影响研究，以及不同施磷水平下土壤可溶性有机碳、颗粒有机碳、易氧化有机碳、土壤总有机碳含量的分布特征，研究成果对提高滴灌苜蓿优质高效生产力水平、促进减肥增效、提高土壤肥力具有重要的意义。取得的主要研究结果：（1）随着施磷量的增加，苜蓿细根现存量、细根生产量、细根死亡量、细根周转率和干物质产量呈现先增加后降低的趋势，均在施P2O5 为100 kg/hm2时达到最大值，施磷显著增加苜蓿的细根现存量、细根生产量、细根死亡量、细根周转率和干物质产量。（2）苜蓿细根现存量主要集中在0～20 cm，随着土层深度的增加，苜蓿细根现存量逐渐降低。不同施磷处理下紫花苜蓿总干草产量与年细根现存量、年细根生产量呈极显著正相关。（3）在新疆绿洲区，适宜的施磷量（施P2O5 为100 kg/hm2）具有较高的磷素利用效率，有利于进一步提高滴灌苜蓿的生产性能。（4）适宜的施磷量（施P2O5 为50-100 kg/hm2）增加土壤可溶性有机碳、颗粒有机碳、易氧化有机碳、土壤总有机碳含量；且随土壤深度的增加，土壤可溶性有机碳、颗粒有机碳、易氧化有机碳、土壤总有机碳含量呈逐渐降低的趋势。

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