干湿交替灌溉水稻根系形态生理和土壤生物学性状的变化及其互作机制

Alternate wetting and soil drying irrigation (AWD) is an important method for increasing grain yield and saving water in rice production. However, the changes of morphological and physiological traits in rice root and biological traits in paddy soil under AWD and their interaction mechanisms have not been very clearly understood. Four rice cultivars (two indica and two japonica cultivars) with different responses to soil moisture will be used as materials, three types of irrigation regimes, including wetting and moderate soil drying irrigation, wetting and severe soil drying irrigation, and conventional irrigation (CK) are designed to investigate:.(1) The changes of morphological (root number, root length, root density, root diameter, root weight, root surface area and ultrastructure of root tip cells) and physiological (the root oxidation activity, total and active absorption area, hormones contents in root and the contents of hormones, organic acids, amino acids in root bleedings and the concentrations of ions and organic acids exuded from roots) traits in rice root at main growth stages (mid-tillering stage, panicle initiation, heading stage and maturity) and before and after rewetting stage..(2) The dynamic changes of biological traits (microbial biomass and main enzymes activities) in paddy soil at main growth stages and before and after rewetting stage..(3) The regulating effects of nutrient management (including wheat straw returning to the paddy field) and soil types (sandy soil, loam soil and clay soil) on morphological and physiological traits in rice roots and biological traits in paddy soil..This study is expected to elucidate the effect of AWD on morphological and physiological traits in rice root and biological traits in paddy soil and their interaction mechanisms, and put forward the cultivating approaches to regulating root growth and yield formation through the regulation of morphological and physiological traits in rice roots and biological traits in paddy soil.

干湿交替灌溉是水稻高产节水栽培的重要措施之一，但干湿交替灌溉条件下水稻根系形态生理和土壤生物学性状的变化及其相互作用机制尚不清楚。本项目拟以对水分反应敏感性有明显差异的水稻品种(籼稻和粳稻各两个)为材料，设置轻度干湿交替灌溉和重度干湿交替灌溉，并以常规高产灌溉方式为对照，研究 ：(1) 主要生育期(分蘖盛期、穗分化期、抽穗期和成熟期)和稻田复水前后水稻根系形态和生理的变化特点。(2) 主要生育期和稻田复水前后土壤生物学性状（微生物量和土壤主要酶类活性等）的变化特征。(3) 养分管理(含麦秸秆还田)和土壤类型(沙土、壤土和粘土)对水稻根系形态生理和土壤生物学性状的调控。以期明确干湿交替灌溉对水稻根系形态生理和土壤生物学性状的影响，阐明根系生长与土壤生物学性状的互作机制，提出调控水稻根系生长和土壤生物学性状提高水稻产量的栽培技术途径，为水稻高产节水栽培提供理论和实践依据。

本项目以不同类型水稻品种为材料，以常规水层灌溉为对照，研究了水分胁迫、全生育期以及关键生育期干湿交替灌溉对水稻根系形态生理、土壤性状和产量的影响，并观察了不同来源土壤、氮肥管理和麦秸秆还田对其的调控效应。主要结果如下：.(1) 根系活性强、叶片细胞分裂素含量和光合速率高、籽粒中蔗糖-淀粉代谢途径关键酶活性强是抗旱性较强水稻品种的基本生理特征。.(2) 全生育期轻度干湿交替灌溉（WMD）对不同来源土壤和不同水稻品种均有一定的增产效应。关键生育期（分蘖期、穗分化期和结实期）轻度干湿交替灌溉不同程度提高了水稻产量（南粳9108分蘖期轻度干湿交替灌溉除外），重干湿交替灌溉（WSD）使产量降低。穗肥减半结合WMD可达与正常穗肥用量相似的产量水平。秸秆还田配合WMD有利于进一步提高水稻产量。.(3) 关键生育期WMD显著改善水稻根系主要形态指标和活力，WSD则相反。穗肥减半配合WMD后与正常穗肥下根系形态生理无明显差异。秸秆还田可改善穗分化期水稻根系形态生理，与WMD结合后进一步促进根系生长。.(4) WMD显著改善土壤理化性质，提高部分土壤酶活性，使氨氧化细菌物种多样性增加，反硝化细菌物种多样性降低，WSD则相反。穗肥减半使土壤养分含量和酶活性均降低。秸秆还田处理下土壤养分、有机质含量和土壤主要酶（脲酶除外）活性提高。相同水分、穗肥和秸秆处理下水稻根际土壤中养分含量以及脲酶活性低于非根际土壤，土壤有机质含量以及其余酶活性均高于非根际土壤。.(5) 分蘖期根系氧化力与土壤蔗糖酶活性显著正相关；根表面积和根体积与土壤蔗糖酶活性显著负相关；根系通气组织与土壤硝态氮含量显著正相关，与土壤蔗糖酶活性显著负相关。穗分化和结实期根系主要形态指标与根际和非根际土壤硝态氮含量、有机质含量和酶活性呈不同程度正相关，与土壤铵态氮含量呈不同程度负相关。.上述研究结果表明，WMD可改善土壤环境和水稻根系形态生理，有利于在提高水稻产量的同时降低灌溉水量。研究结果对水稻高产节水栽培和抗旱品种筛选有重要的参考价值。