免耕水稻养分吸收的根际过程研究

No-tillage rice production has attracted great attentions because of its social, economical and environmental benefits. To date, the researches on no-tillage rice production have been mostly focused on the soil properties of no-tillage rice fields and the yield formation characteristics of no-tillage rice crops, and the results show that the yield formation characteristics of no-tillage rice are different from those of conventional-tillage rice due to its delayed nitrogen uptake. However, it is difficult to identify the factors that are responsible for the delayed nitrogen uptake in no-tillage rice based on the results of previous studies. Moreover, there is limited information available on the effects of no-tillage on phosphorus and potassium uptake in no-tillage rice. Therefore, we plan to carry out field experiments in several seasons to analyze the rhizosphere soil chemical and microbial propeties as well as the root morphological and physiological traits in no-tillage rice. The findings from this study will help to understand the effects of no-tillage on rhizosphere soil nutrient availability and root nutrient uptake capacity in rice, and the relationships between rhizosphere soil properties and root growth in no-tillage rice, and to further clarify the approaches and mechanisms of the effects of no-tillage on rice nutrient uptake, and thus provide theoretical guidance for high efficiency nutrient management for no-tillage rice.

水稻免耕栽培因其良好的社会、经济和环境效益而受到了广泛关注。迄今为止，水稻免耕栽培的研究主要是围绕免耕稻田土壤特性和免耕水稻产量形成特点两个方面开展的，且已明确免耕水稻因氮素吸收延迟而促使其产量形成特点有别于翻耕水稻，但运用现有的相关研究结果难以解释免耕水稻氮素吸收延迟的原因。此外，免耕对水稻磷钾吸收又会产生什么影响目前也还不清楚。因此，本课题拟通过多季大田试验，对免耕水稻根际土壤化学和微生物特性及根系形态生理特性进行研究，以期明确免耕对水稻根际养分有效性和根系养分截获能力的影响及免耕水稻根际土壤特性与根系生长关系，进而揭示免耕影响水稻养分吸收的途径及机制，为免耕水稻养分高效管理提供理论依据。

水稻免耕栽培因其良好的社会、经济和环境效益而受到了广泛关注。目前，有关水稻免耕栽培的研究主要是围绕免耕稻田土壤特性和免耕水稻产量形成特点两个方面开展的，且已明确免耕水稻因氮素吸收延迟而促使其产量形成特点有别于翻耕水稻，但运用已有的相关研究结果难以解释免耕水稻氮素吸收延迟的原因。此外，免耕对水稻磷钾吸收又会产生什么影响目前也还不清楚。据此，本课题在广西南宁和湖南长沙进行大田试验，对免耕水稻根际土壤化学和生物特性及根系形态生理特性进行研究，以期明确免耕对水稻根际养分有效性和根系养分截获能力的影响及免耕水稻根际土壤特性与根系生长关系，进而揭示免耕影响水稻养分吸收的途径及机制。研究结果表明，免耕水稻分蘖中期的根际有效氮磷钾含量比翻耕水稻高9%-18%，但其根干重、根长和根表面积比翻耕水稻少7%-48%，进而使得其氮磷钾吸收量比翻耕水稻低17%-43%。进一步研究表明，免耕水稻分蘖中期根际假单胞菌属细菌比翻耕高26%-37%，且水培条件下添加从免耕水稻根际分离的假单胞菌属细菌可导致水稻根干重、根长和根表面积减少43%-59%，氮磷钾吸收量减少39%-52%。另一方面，免耕水稻抽穗期0-5cm土层土壤有效氮磷钾含量和根系分布比例分别比翻耕水稻高10%-18%和5%-9%，进而使得其根际有效氮磷钾含量比翻耕水稻高11%-16%。此外，免耕水稻抽穗期根系活力比翻耕水稻高37%-49%，因而促使免耕水稻抽穗后氮磷钾吸收量比翻耕水稻高28%-49%。由此可见，与翻耕水稻相比，免耕水稻对氮磷钾的吸收均表现为延迟吸收。根际假单胞菌属细菌富集导致根系生长受阻是免耕水稻前期养分吸收减少的重要原因,根际养分供应和根系生理特性改善是免耕水稻后期养分吸收多的重要原因。上述研究结果可为免耕水稻养分高效管理提供理论依据。