低盐根区施肥缓解棉花盐害的机理研究

Furrow-bed seeding induces non-uniform salinity distribution in saline field, with much more salts in the ridge and less in the furrow. The seedling establishment rate is thus increased owing to part of the root system exposed to low salinity environment under non-uniform salinity. Our previous studies have indicated that fertilization in the low salinity root zone significantly alleviates salt injury, and enhances seedling growth and seed cotton yield. However, the underlying mechanism is still not clear. In order to further explore the rational fertilization methods and understand the mechanism, three experiments will be conducted in a saline field, under potted and solution-culture conditions, respectively. In the first experiment, different fertilization treatments under furrow-bed seeding system will be arranged to study the mitigative mechanism of fertilization in the furrow side on salt injury in a saline field (0.3-0.4% salt content). In the second experiment, non-uniform salinity distribution can be accurately realized with a split-root system in greenhouse. Both root sides can be supplied with different levels of nutrition solution, the mitigative mechanisms of fertilizer in low salinity root zone on salt injury will be studied from the perspective of root activity, Na+ influx and efflux, nutrient uptake character and related genes expression. In the third experiment, the rational proportion of nitrogen sources (NO3--N and NH4+-N) in low salinity side and the mitigative mechanism of reasonable proportion of nitrogen sources on salt stress will be further revealed from the perspective of nitrogen uptake and nitrogen transport. The study is believed to have an important academic value and practical significance for further improving fertilization in saline field of cotton.

盐碱地沟畦植棉（播种时先起垄，垄下为沟畦，棉花播于沟畦内）可诱导盐分向垄背聚集、淡化沟内盐分，从而形成根区盐分差异分布，保证部分根系处在低盐环境中，提高成苗率；我们前期的研究发现集中向低盐根区施肥，能减轻盐害，促进棉苗生长并增产。但迄今关于盐分差异分布下集中向低盐根区施肥减害增产的机理尚不清楚。为此，本项目首先在盐碱地大田采用沟畦植棉模式栽培棉花，设置沟内施肥、垄下施肥等不同的处理，研究盐分差异分布下向低盐根区施肥缓解盐害的机理；其次，在温室盆栽条件下利用嫁接分根模拟根区盐分差异分布，给予两侧根系不同浓度养分供应，从根系活力、Na+吸收与外排、养分吸收特征、养分吸收相关基因表达角度揭示低盐侧施肥减轻盐害的机理；最后，在水培模拟条件下给予低盐侧不同配比氮素形态营养，从N素吸收和N素转运角度揭示低盐侧合理氮素形态配比增强棉花耐盐性的机理。本研究对盐碱地棉花合理施肥具有重要的学术价值和实践意义。

根区盐分差异分布能够明显减轻盐害，但该模式下合理施肥缓解棉花盐害的机理研究较少。本研究在大田条件下研究了沟畦种植模式下的盐分变化规律。在水培条件下利用嫁接分根模拟根区盐分差异分布，通过给予两侧根系不同浓度养分供应，从Na+吸收与外排、养分吸收特征角度揭示了集中向低盐侧施肥减轻盐害的机理，并探究了盐分差异分布下不同氮素形态的效应。结果表明，在水培条件下，在平均盐度相等的情况下，盐分差异分布较均匀分布促进了棉花生长。盐分差异分布且总养分供给量相等的前提下，低盐高养/高盐低养（低盐一侧施高浓度养分，高盐一侧施低浓度养分）处理较低盐低养/高盐高养（低盐一侧施低浓度养分，高盐一侧施高浓度养分）提高了棉花组织内的主要矿质养分积累量，而降低了Na+含量，有效缓解了盐胁迫造成的养分失衡，促进了棉花生长。根区盐分差异分布且施氮量相等的条件下，低盐侧施硝态氮（高盐侧施铵态氮）较高盐侧施硝态氮（低盐侧施铵态氮）能提高棉花叶片光合作用强度，增强对氮素的吸收，并能调控地上部养分向高盐侧转运，为高盐侧根系生长补充养分。由此得出，盐分差异分布条件下应注重在低盐区施肥，通过增加营养元素的吸收提高棉花的耐盐能力。在氮肥形态选择时，硝态氮肥优于铵态氮肥。