麦后移栽棉氮素营养诊断与追肥模型

【目的】基于江汉平原麦后移栽棉花适宜氮素诊断指标建立追肥模型,为棉花氮素精准管理提供依据。【方法】于2019年采用田间小区试验,设置6个施氮量处理(0、90、180、270、360、450 kg N/hm²),分析蕾期、花铃期倒4叶叶绿素含量(SPAD值)、叶柄硝酸盐含量(NIT)及24个高光谱参数与前期施氮量的关系,研究麦后移栽棉适宜氮素营养诊断关键指标,结合氮肥效应函数建立氮素追肥模型。【结果】随施氮量的增加,棉花倒4叶SPAD值、叶柄NIT含量显著增大,棉花冠层光谱绿光波段形成的反射峰变缓,但当氮肥增加到360 kg/hm²时不再显著增加(蕾期NIT除外)。蕾期、花铃期倒4叶SPAD值、叶柄NIT含量、冠层高光谱参数(RSI和mND705)与前期施氮量均呈极显著一元二次方程关系(R²＞0.8,RMSE＜1),可作为江汉平原麦后移栽棉氮素营养诊断指标,以产量潜力的95%为临界值,蕾期麦后移栽棉SPAD值、叶柄NIT含量、冠层RSI和mND705临界值分别为34.802、2.307、1.526和0.549,花铃期相应为34.841、4.174、1.589和0.619。【结论】4个指标为江汉平原麦后移栽棉氮素营养诊断指标。麦后移栽棉最适宜施氮量为310.64 kg/hm²,产量潜力为4 662.53 kg/hm²。

Diagnosis of Nitrogen Nutrition and Recommended Model of Topdressing for Transplanting Cotton after Wheat Harvest in Jianghan Plain

【Objective】 To establish topdressing models based on the appropriate nitrogen diagnostic indices for transplanted cotton following wheat harvest in Jianghan Plain with the view of providing the basis for cotton nitrogen accurate management.【Methods】 A field plot experiment was carried out with different nitrogen application rates (0, 90, 180, 270, 360, 450 kg/hm²) in 2019, the relationships between SPAD value (SPAD) in the fourth leaf from the top, the nitrate content (NIT) of petiole, 24 hyperspectral parameters and nitrogen application rate at early stage were analyzed in budding, flowering and boll-forming stages, and the appropriate nitrogen diagnostic indices of transplanted cotton following wheat harvest in high yield field of Jianghan Plain were determined, and the recommended models of topdressing were established combined with nitrogen effect function.【Results】 The results showed that the SPAD and NIT increased significantly with the increase of nitrogen application, but no significant increase was observed when the nitrogen application increased to 360kg/hm² (excluding the NIT in bud stage), and the reflection peak formed in the green light band of the canopy spectrum slowed down with the increase of nitrogen application. The SPAD, NIT, and the 2 hyperspectral parameters (RSI and mND705) were all significantly related to nitrogen application rate at early stage (R² was higher than 0.8, RMSE was lower than 1), which could be used as the appropriate nitrogen diagnostic indices of transplanted cotton following wheat harvest in high yield field of Jianghan Plain. With the 95% of the potential yield as the critical yield, the critical values of nitrogen diagnostic indices of SPAD, NIT, RSI and mND705 were 34.802, 2.307, 1.526 and 0.549 in budding stage respectively, and the critical values were 34.841, 4.174, 1.589 and 0.619 in flowering and boll-forming stage respectively.【Conclusion】 According to the unary quadratic relationship between the appropriate nitrogen diagnostic indices and nitrogen application rate at early stage, the total nitrogen application rate during the whole growth stage, a topdressing recommendation model based on the sui Table nitrogen diagnostic indices is established in the bud stage or the flowering and boll-forming stage.