水稻抽穗期叶色诊断指标与叶面积指数及结实期光强的关系

叶色是氮素营养诊断最常用的指标,获得准确的叶色诊断指标是水稻精确定量施氮的基础。叶色诊断指标实际上就是稻谷产量最高时的最适叶色。已有报告指出,叶色诊断指标受到群体大小和结实期光照条件的影响。研究的目的是,找出叶色诊断指标随群体大小和光照条件而变化的规律,为精确定量施氮提供理论和技术依据。2004—2005年早季和晚季,在广州以两系杂交稻粤杂122为试材,设置8种不同氮肥处理,进行2年4季田间试验,抽穗期测定叶色(SPAD)和叶面积指数(LAI),成熟期测产。结果表明:(1)不同季节的最适叶色存在明显差异,4季变动于39～45之间。根据产量与叶色的定量关系,可以准确、快速地确定特定条件下的叶色诊断指标。(2)稻谷产量与抽穗期群体指数(SPAD与LAI的乘积)呈开口向下的抛物线关系。抽穗期SPAD、LAI和结实期日照时数,可以解释不同年度、季节和不同氮肥处理的稻谷产量变异的86%。最适群体指数随着结实期日照时数的增加而提高。(3)最适叶色随着日照时数的增加而提高,随着LAI的增加而降低,3者之间存在显著的定量关系。应用这一关系,可根据结实期光照条件,估计出异地异季的叶色诊断指标。

The Relationship between Leaf Color Threshold and Leaf Area Index at Heading and Light Intensity During Grain-filling

Leaf color is usually used in the diagnosis of crop N status and leaf color threshold (LCT) is the basis for precise fertilizer-N application. The LCT is the optimum leaf color at which maximum grain yield is achieved. It has been reported that LCT is affected by the population size and the light intensity during grain-filling stage. The objective of this study was to determine the quantitative relationship between LCT and population size and light intensity during grain-filling. Four field experiments were conducted at Guangzhou during 2004-2005 early and late seasons. Yueza 122, a two-line hybrid rice, was arranged in eight fertilizer-N treatments. Leaf color (SPAD value), leaf area index (LAI) at heading and grain yield were measured. The results showed: (1) The LCT was different among the 4 seasons, varying between 39~45. The LCT can be derived conveniently and precisely from the quadratic curve with leaf color and grain yield being the independent and dependent variable, respectively. (2) The relationship between grain yield and population index (the product of SPAD and LAI) at heading was a quadratic curve. About 86% of variation in grain yield could be explained by leaf color, LAI at heading and sunshine hours during grain-filling. The optimum population index increased as sunshine hours increased. (3) There existed a quantitative relationship between LCT and sunshine hours and LAI. The LCT increased as sunshine hours increased, and decreased as LAI increased. The LCT for different locations and seasons might be estimated if sunshine hours and LAI were available.