增铵营养缓解石灰性土壤膜下滴灌水稻缺铁的研究

Abstract: rice cultivated by drip irrigation with plastic film mulch is a new-type water-saving technology, which synchronize high-yield and water-saving in rice cultivation, and shows magnitude perspective in rice cultivation, especially in arid and semi-arid area. Despite showed lots of advantages, drip-irrigated rice is easily suffer from Fe deficiency induced chlorosis. Chlorotic hamper rice growth and result in poor yield. So, to study drip-irrigated rice chlorosis mechanism, and to buildup measurement to release Fe chlorosis is essential to guarantee this cultivation system be adopted in theory and in practice. This project study if enhanced ammonia nutrition can release drip irrigated rice chlorosis under high pH and high soil redox in calcareous soil and N-form for rice plant is mainly NO3- due to nitrification, and to explore how enhanced ammonia nutrition promote rice Fe uptake and transportation in drip irrigated rice. The main scientific concerns focus on (1) if the mechanism of drip irrigated rice Fe uptake obstacle is due to the reduce of root Fe uptake or the reduce of transportation from root to shoot, or both? And (2) to prove it is an important mechanism that enhanced ammonia nutrition can reduce root aerenchyma tissue formation, promote root water conductivity, reduce root apoplast pH value, and hence improve Fe2+ uptake and transportation by drip - irrigated rice.

摘要：水稻膜下滴灌是一种兼顾高产和节水的栽培新技术，对我国干旱、半干旱地区发展节水农业具有重要意义。但在石灰性土壤上，缺铁黄化是水稻膜下栽培的常见症状。研究石灰性土壤上水稻缺铁黄化机理，对揭示水稻旱作生理变化以及该技术在更大范围应用都具有重要意义。本研究在石灰性土壤pH值高、氧化还原电位高和膜下滴灌条件下由于通气性改变导致土壤氮素养分通过硝化作用转化为硝态氮的背景下，研究铵态氮结合硝化抑制剂形成增铵营养环境，提高土壤铁养分有效性、抑制根系通气组织形成、提高根系活力、提高水稻铁吸收和运输等方面阐明增铵营养改善滴灌水稻铁营养的机理。解决的主要科学问题是：（1）石灰性土壤膜下滴灌水稻铁吸收障碍的机理是抑制根系铁吸收还是限制铁从根系向地上部运输？还是两者共同起作用。（2）增铵营养抑制水稻通气组织形成、提高根系导水率、降低质外体pH值是其改善膜下滴灌水稻铁吸收和运输的重要机理。

水稻是世界上最多人的主食，也是耗水量最大的作物，世界范围内水资源短缺对水稻生产提出了严峻的挑战。新疆地区采用滴灌种植水稻，可节约灌溉水40%以上，而产量显著高于旱稻，良好种植管理下，产量与水作相当。但是滴灌水稻苗期缺铁十分严重。通过比较系统的研究，项目取得了一些重要的科学发现：滴灌水稻虽然维持相对于陆生植物较高的含水量，但对水稻而言依然是一种轻度的干旱环境，滴灌水稻容易缺铁与其不利的水环境有关。虽然水稻是一种起源于热带-亚热带的作物，但灌溉水中的碱性物质（HCO3-)对水稻的Fe吸收影响不大，对于滴灌水稻而言同样如此。对于干旱的新疆地区而言，地下水灌溉很普遍，但是低温的地下水灌溉对滴灌水稻的危害很大，不仅导致Fe吸收显著下降，而且使水稻产量也下降30%以上。水稻是喜铵作物，滴灌导致的土壤中的硝化作用加强从而使土壤中的氮素以硝态氮为主，这种变化对水稻而言，至少导致根系通气组织增生，且细胞液碱性增强，从而对水稻的Fe吸收产生严重不利影响。基于上述成果，在滴灌水稻中，提升地下水灌溉的温度，以及抑制土壤强烈的硝化作用，是滴灌水稻获得高产的重要措施。在花后维持充足的灌溉，是滴灌水稻获得高产的重要保证。上述科学发现不仅有利于理解滴灌水稻缺Fe机理的理解，也对滴灌水稻生产实践具有明确的指导意义。