外源微生物对水稻根际土壤氮素转化及根系吸收的调控研究

It is of critical importance for the study of effective utilization of nitrogen resource in paddy field to improve nitrogen supply in soil and increase nitrogen uptake capacity in rice as well as decrease nitrogen application rate. Inoculating microbes on rhizosphere is a measure which can direct regulate the nitrogen interaction between soil and rice, and it can be used to regulate the nitrogen transformation in rhizosphere and root uptake in rice. This measure has been not comprehensive studied in the field of nitrogen regulations. This subject studies the effects of inoculating microbes on rhizosphere of rice by field experiment and pot culture experiment. Three kinds of inoculating microbes coupled with six nitrogen rates will be used as the treatments in the experiment. The regulatory effects of inoculating microbes on nitrogen transformation in rhizosphere for paddy field and nitrogen uptake for rice root will be analyzed, and repeatability and stability of regulatory effects of inoculating microbes will be also studied. Finally, suitable combination mode of microbial population and suitable nitrogen rate for improving nitrogen supply potential in soil and nitrogen uptake capacity for rice will be proposed. This study can resolve the problems of low nitrogen use efficiency in rice and high nitrogen losses in paddy field, and can also supply scientific support for the study of effective utilization of nitrogen resource in soil and ecological environment protection in farmland.

提升稻田土壤供氮潜力，提高水稻吸氮能力，并降低化学氮肥施用量对稻田氮素资源高效利用研究至关重要。水稻根际接种外源微生物调控稻田土壤氮素转化及根系吸收是一种直接调控根际土壤氮与水稻氮交互作用的方法。目前，该方法在稻田氮素调控方面的研究并未全面展开。本课题以水稻大田与盆栽根际土壤为研究对象，以3种外源微生物组配方式耦合6个施氮水平为研究手段，解析外源微生物接种对水稻根际土壤氮素转化的调控作用，定量分析外源微生物调控下水稻对根际土壤氮素的利用强度，评价外源微生物接种调控水稻根际土壤氮素转化及根系氮素吸收的重演性和稳定性，明确提高根际土壤供氮潜力并提高水稻吸氮能力的适宜微生物功能种群组配方式及适宜施氮量。此项研究，解决水稻氮肥利用率低、稻田氮素损失大的难题，为土壤氮素资源高效利用、农田生态环境保护提供科学支撑。

以盆栽试验与田间试验相结合为研究方法，以2种外源微生物（巴西固氮螺菌（Mb）与荧光假单胞菌（Mp））组配模式耦合4个氮肥施用水平（田间试验，4个氮肥处理分别为0（N0）、90 kg hm-2（N90）、180 kg hm-2（N180）、270 kg hm-2（N270））为研究手段，研究外源微生物对水稻根际土壤氮素转化及根系吸收的影响。结果表明不同微生物组配模式对水稻根际土壤氮素转化及水稻根系特征等的影响不同，其中起重要作用的是巴西固氮螺菌与荧光假单胞菌共同接种水稻根际环境。外源微生物介入水稻根际环境后，土壤氨化作用强度比对照提高7.4-124.4%，固氮作用强度比对照提高40.2-209.2%，微生物量氮比对照提高101.0-159.4%，水稻根系活力比对照提高10.6-137.5%。土壤矿化氮含量与速效氮含量总体表现为巴西固氮螺菌与荧光假单胞菌共同接种水稻根际环境（Mbp处理）提供更多水稻易吸收氮，其次为单独接种巴西固氮螺菌（Mb处理）与单独接种荧光假单胞菌（Mp处理）。说明巴西固氮螺菌与荧光假单胞菌在水稻根际有很强的定殖能力，二者共同接种可显著增加土壤有效氮供应水平。大田试验条件下不同外源微生物组配模式耦合施氮水平对水稻生长发育及土壤有效氮供应能力的影响不同，但总体趋势与盆栽试验相似，均为Mbp处理显著改善水稻吸氮特征。总体表现为低施氮水平下（低于180 kg.hm-2）外源微生物介入对水稻增产效果显著，超过一定施氮水平后（180 kg.hm-2）外源微生物对产量影响较小。盆栽试验与田间试验结果表明巴西固氮螺菌与荧光假单胞菌共同接种水稻根际，可起到增加土壤有效氮供应水平，提高水稻根系活力及吸氮能力的目标。