氮素供应影响茶树镁营养的作用机制及调控

Magnesium (Mg) deficiency is increasingly becoming an important limiting factor in intensive agricultural-production systems. However, Mg nutrition of plants is frequently overlooked in both scientific research and agricultural production. Thus, increasing the availability of soil Mg and improving crop Mg nutrition is a key issue that should be solved in the production of intensive agriculture. Currently, Mg deficiency in tea (Camellia sinensis) plantation has become a fairly widespread phenomenon. Nitrogen (N)-Mg interaction in crop plants plays an important role in affecting the availability of soil Mg. Excess N application decreased the availability of Mg in soil and adversely affected the Mg nutrition status of tea plants. In this innovative project, the combination of field experiments and laboratory simulations will be used to study the mechanisms of Mg nutrition of tea plants affected by N supply and its management. The main contents of this study includes: (1) on the acidic soil of tea plantation, to study N transform processes in soil of different sources and rates of N and its impacts on the availability of soil Mg, Mg distribution in the plants; (2) to study the effect of different sources and rates of N on the Mg absorption and re-translocation in tea plants and its mechanisms; (3) to study the yield, quality and physiological response of tea to varied N sources and rates with different modes of Mg application. This study will give new insights in the mechanisms of Mg nutrition affected by N supply, and offer the technical support for improving Mg nutrition status for achieving high-quality and high-yield tea production.

作物镁营养缺乏的问题日益突出，已成为集约化农业生产中的一个重要限制因素。然而，不管是在科学研究还是在农业生产实践上，作物镁营养却常常被忽视。因此，提高土壤镁的有效性、改善作物镁营养状况是集约化农业生产中亟待解决的关键问题。茶园土壤缺镁的现象极其普遍。氮-镁交互作用是影响土壤镁有效性的重要方面。茶园生产中过量施用氮肥导致土壤镁有效性降低并对茶树镁营养产生很大影响。本项目拟采用田间试验和室内模拟相结合的方法，研究氮素供应影响茶树镁营养的作用机制和调控途径。主要内容包括：研究不同氮素形态和用量供应（1）在茶园酸性土壤中氮素的土壤转化过程及其对土壤镁有效性和茶树镁营养的影响；（2）对茶树镁吸收和再转移的影响及其生理机制；（3）与镁肥施用相结合的调控措施对茶树镁营养、产量和品质的影响。为改善茶树镁营养和保障茶叶优质高产提供坚实的理论基础和技术支撑。

本项目揭示了氮-镁互作机制和镁肥施用对调控茶树镁营养的作用。在低pH茶园土壤下，氮素硝化过程明显受到抑制，培养到28天土壤铵态氮仍然保持很高的浓度。在田间条件下也发现，随着氮肥用量增加土壤中Nmin的含量明显增加，其中铵态氮含量占主体。此外，氮素过量供应导致土壤镁淋洗加剧，尤其是在种植茶树的情况下。氮素供应明显使茶叶镁含量降低，茶叶氮、镁含量间存在明显的负相关关系。过高的氮素供应导致铵浓度过高可能是抑制茶树镁的吸收主要原因。通过镁肥的补充明显提高了镁营养和茶叶产量，再配合适宜的氮肥用量，可以达到改善茶叶镁营养的目的。综上所述，本项目的研究结果表明，在酸性的茶园土壤中氮肥过量施用造成土壤中铵浓度过高而导致与镁产生拮抗作用，同时进一步加剧镁的淋洗损失，这是导致茶树缺镁的双重因素，通过控制氮肥用量并补充镁肥可达到改善茶叶镁营养的目的。在项目的资助下，我们发表了2篇会议论文，申请了3个专利，培养了3个在读研究生。本项目按照预定的计划执行，完成拟定的研究内容和研究目标。