基于上部叶片SPAD值估算小麦氮营养指数

Estimation of nitrogen nutrient index on SPAD value of top leaves in wheat

快速、准确的监测诊断小麦氮营养状态对于评价小麦长势、指导氮肥运筹并预测籽粒产量均具有重要的意义。基于2009—2011年的大田试验,系统分析了小麦上部4张单叶不同叶位的SPAD值和归一化SPAD指数(NDSPADij)与氮营养指数的定量关系,通过简单分组线性回归筛选出在不同年际和不同品种间表现稳定的氮营养指数(NNI)定量方程。结果表明,小麦上部不同叶位SPAD值和NNI随施氮量提高而提高,而NDSPADij随施氮量的提高而降低。小麦单叶SPAD值与NNI的关系呈显著正相关,但这种关系在品种或年份之间不稳定,对小麦氮素诊断存在风险;除NDSPAD12外,NDSPADij与NNI之间呈显著负相关,经简单分组线性分析发现NDSPAD14与NNI之间在年份和品种之间表现最稳定,能够较好的定量估算氮营养指数,从而快速诊断小麦氮素是否亏缺。

Rapid, accurate, and dynamic diagnosis of nitrogen nutrition status is essential for evaluating vigor, for predicting production rates, and for agricultural management of cultivated wheat. To determine the critical nitrogen concentration dilution curve for wheat, two field experiments with different levels of N application （0, 75, 150,225, 300 and 375 kg/hm2） were conducted in Yizheng, China. According to the procedure in Justes＇s curve, the dry matter and nitrogen concentrations under different nitrogen treatments could be compared by analysis of variance at the 5% probability level. Based on this curve, we developed a nitrogen nutrition index （NNI）. In this index, when NNI = 1, nitrogen nutrition was considered to be optimum, NNI〉 1 indicated excess nitrogen, and NNI〈 1 indicated nitrogen deficiency. We further investigated relationships between NNI and soil and plant analyzer development （SPAD） chlorophyll meter values and normalized differential SPADiy（ NDSPADij） values obtained at the top four leaf positions in wheat. We conducted a linear parallel curve analysis with grouped data to determine if the linear quantitative equation relating NNI to SPAD value or NDSPADij showed differences between varieties and/or years. The results showed that the curve had specific biological significance. The relationship between the critical nitrogen concentration and wheat dry matter could be described by the following negative power equations Y16： N nc = 4.65DM-0.44 and N13 ： Ncnc = 4.33DM-0.45. The critical nitrogen curves of the two cultivars of wheat had the same coefficient ＂ b＂ but different coefficients ＂ a＂. Y16 had a higher nitrogenaccumulation capacity than N13. The NNI values ranged from 0.37 to 1.28, and increased with higher nitrogen application rates under the different nitrogen levels. The optimum nitrogen level was 150 kg/hm2 in 2009 - 2010, but was 225 kg/hm2 in 2010-2011. The SPAD values increased with increasing N application rates, and ranged from 34.3 to 52. 8. In contrast, the NDSPAD0 value decreased with increasing nitrogen application rates, which showed that increasing amounts of nitrogen could decrease the differences in SPAD value among the top four single leaves of wheat. The NDSPADij values ranged from 0.01 to 0. 143. The SPAD value at the top four single leaf positions were significantly positively related to NNI. The correlation coefficients ranged from 0. 666 to 0. 823. The strongest correlation was between the SPAD value at the top leaf （ T1 ） and NNI, while the weakest correlation was between the SPAD value at the second leaf （T2） and NNI. A linear parallel curve analysis with grouped data approximated the relationship between SPAD and NNI and its differences between varieties and years. This will be useful for diagnoses of wheat nitrogen nutrition. In contrast, NDSPAD0 was significantly negatively related to NNI, except for NDSPAD12. The correlation coefficients ranged from 0.01 to -0. 849. The strongest correlation was between NDSPAD14 and NNI, while the weakest correlation was between NDSPAD12 and NNI. A linear parallel curve analysis with grouped data demonstrated the relationship between NDSPAD14 and NNI （NNI = -2. 019NDSPAD14＋1. 18, R=-0. 838 ＊＊ ） stably across variety and year differences. This analysis could be used to assess NNI quantitatively and to diagnose wheat nitrogen deficiency quickly.