氮肥处理对氮素高效吸收水稻根系性状及氮肥利用率的影响

2011—2012年在土培条件下,以氮素吸收效率差异较大的15个常规籼稻为供试材料,研究氮肥运筹对不同氮效率品种根系性状、成熟期吸氮量及氮肥利用率的影响,分析影响氮高效水稻氮素吸收的主要根系性状。结果表明:(1)各氮肥处理下,成熟期吸氮量均表现为氮高效品种氮中效品种氮低效品种。适量增施氮肥及基肥+促花肥处理有利于氮高效品种吸氮量的增加,氮素吸收受品种、氮肥处理的显著影响。(2)在施氮量处理下,氮高效品种单株不定根数、单株根干重、单株不定根总长大或较大,单株根活力在常氮(N2)、高氮(N3)处理下有一定的优势;在施氮时期处理下,氮高效品种单株不定根数、单株不定根总长、单株根干重、单株根系总吸收面积、单株根系活跃吸收面积、抽穗期冠根比多数处理有优势;增施氮肥有利于促进氮高效品种单株不定根总长和单株根活力的提高,适量施氮有利于单株不定根数、单株根干重增加,前期施氮可促进不定根的发生和伸长,后期施氮有利于不定根的充实和根系生理性状的提高。此外,增施氮肥可提高各类品种冠根比;(3)在常氮、高氮处理下,氮高效品种氮肥利用率大于氮中效、氮低效品种。(4)提高单株不定根数、单株不定根总长、单株根活力及抽穗期冠根比有利于各类品种吸氮量的提高,增加根干重对氮高效品种吸氮量的提高也有显著的促进作用。结合相关分析与通径分析结果,抽穗期冠根比及单株不定根数、单株根活力、单株不定根总长、单株根干重是影响氮高效品种吸氮能力的主要根系性状。

The effect of nitrogen fertilizer treatments on root traits and nitrogen use efficiency in Indica rice varieties with high nitrogen absorption efficiency

To investigate the effect of nitrogen management practices on root traits, the amount of nitrogen absorption at grain maturity, nitrogen fertilizer use efficiency, and to analysis the main root traits of rice responsible for high nitrogen absorption efficiency, a total of 15 conventional Indica rice varieties with marked differences in nitrogen absorption efficiency were pot-cultured in 2011 and 2012. (1) The amount of nitrogen absorption (ANA) at grain maturity was differed significantly among rice varieties and nitrogen fertilizer treatments. Among varieties, nitrogen absorption efficiency was positively correlated with ANA at grain maturity in all nitrogen treatments. In rice varieties with high nitrogen absorption efficiency ANA was greater than that in rice varieties with intermediate and low nitrogen absorption efficiency. In rice varieties with high nitrogen efficiency ANA was increased by increasing nitrogen fertilizer application rates or by using the base+ promoting-spikelet fertilizer treatment. (2) Rice varieties with high nitrogen absorption efficiency showed higher adventitious root numbers, root dry weight, total adventitious root length, and also had relative higher root activity at conventional and high rates of nitrogen supply. Rice varieties with high nitrogen absorption efficiency had higher adventitious root numbers, total adventitious root length, root dry weight, root total absorption area and active absorption, as well as crown:root ratio. Increasing the nitrogen application rate increased total adventitious root length and root activity. The appropriate rate of nitrogen application increased adventitious root number and root dry weight. Nitrogen application at the early growth stage promoted the occurrence and extension of adventitious roots, while at the late growth stage nitrogen addition enriched adventitious roots and improved root physiological activity. In addition, increased nitrogen supply improved the crown:root ratio of rice varieties with different nitrogen absorption efficiencies. (3) Rice varieties with high nitrogen absorption efficiencies had higher nitrogen absorption and use efficiencies than those with middle and low nitrogen absorption efficiencies at the conventional and high rates of nitrogen supply. (4) Increasing adventitious root number, total adventitious root length, root activity and crown:root ratio at heading stage improved ANA in all rice varieties. Increasing root dry weight also had a significant and positive effect on ANA in all rice. Correlation analysis and path analysis indicated that crown:root ratio at heading stage, adventitious roots number, root activity, total adventitious root length and adventitious root dry weight were the main root traits that affected nitrogen absorption in the rice varieties with high nitrogen absorption efficiencies.