Physiological indices of irrigated rice affected by flooding and nitrogen fertilization

ABSTRACT The management of water and nitrogen are among the necessary actions to achieve high yield potential in irrigated agricultural systems. The objective of this study was to determine the influence of time of the beginning of flood and N topdressing, in the development stages from V3 - V4 until V12 - V13, on physiological characteristics positively related to grain yield of irrigated rice cultivar BRS Jaçanã in a tropical wetland. A field experiment was conducted at Palmital farm of Embrapa Rice and Beans, Goianira, GO, Brazil, in a Dystrophic Haplic Gleysol, for two consecutive years. The experimental design was completely randomized with six replications arranged in a split-plot scheme. The main plots were comprised by the times of the beginning of flood and subplots by the times of N topdressing of 90 kg ha-1. For both factors, the times were set as 15, 30, 45, and 60 days after emergence, which corresponded to the vegetative development stages V3 - V4, V6 - V7, V9 (VF-4) - V10 (VF-3), and V12 (VF-1) - V13 (VF). As flood delays, tillering, leaf area ratio, and specific leaf area increase and shoot biomass, leaf area index, and leaf area duration decrease. Late N fertilization timing also provides decrease in these physiological indices. Delay in flooding and N fertilization reduced more leaf area than rice grain yield, resulting in higher leaf area efficiency. Nitrogen topdressing performed at the beginning of tillering and continuous flooding at the middle tillering stage result in increased physiological indices, such as leaf area ratio, leaf area index, and leaf area duration, which provide increase in irrigated rice grain yield.

摘要：水氮管理是实现灌溉农业系统高产潜力的必要举措之一。本研究旨在明确从V3-V4至V12-V13的生育阶段内，淹水起始时间与氮肥追施时机对巴西热带湿地种植的灌溉水稻品种BRS Jaçanã（BRS Jaçanã）籽粒产量正相关生理特性的影响。本田间试验于巴西戈亚斯州戈亚尼拉市巴西农牧业研究公司（Embrapa）水稻与豆类研究所下属的帕尔米塔尔农场开展，试验土壤为贫养型普通潜育土（Dystrophic Haplic Gleysol），试验连续进行两年。试验采用裂区完全随机设计，设置6次重复；主区处理为淹水起始时间，副区处理为施用量90 kg·ha⁻¹的氮肥追施时机。两个因素的处理时机均设为出苗后15、30、45、60天，分别对应水稻营养生长阶段V3-V4、V6-V7、V9（VF-4）-V10（VF-3）及V12（VF-1）-V13（VF）。随着淹水时间推迟，水稻分蘖数、叶面积比率及比叶面积（specific leaf area）升高，而地上部生物量、叶面积指数（leaf area index）及叶面积持续期（leaf area duration）降低；氮肥追施延迟同样会导致上述生理指标下降。与水稻籽粒产量的降幅相比，淹水与氮肥追施延迟对叶面积的抑制作用更为显著，最终提升了叶面积利用效率。在分蘖始期追施氮肥，并于分蘖中期实施持续淹水，可提升叶面积比率、叶面积指数及叶面积持续期等生理指标，进而提高灌溉水稻的籽粒产量。