Feng Weina, Li Xiaofei, Dong Helin, Qin Yukun, Sun Miao, Shao Jingjing, Zheng Cangsong, Li Pengcheng
State Key Laboratory of Cotton Biology, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang, China.
Cotton Research Institute of Jiangxi Province, Jiujiang, China.
Front Plant Sci. 2022 Jan 28;13:801968. doi: 10.3389/fpls.2022.801968. eCollection 2022.
Estimating the precise nutritional status of crop nitrogen (N) after flowering period is not only important to predict deficiency but the excess that could be revised by fertilization in future crops. Critical N dilution curves describing the critical N concentration ([N]) in plant tissues during crop growth have been used to estimate the N status of whole plants in cotton. Little is known, however, about the critical N dilution curve for specific plant organs such as cotton fruits. The objective of this study was to verify the feasibility of fruits-based critical N dilution curve as a useful diagnostic tool for diagnosing the N status of cotton crops. A 3-year field experiment was conducted with seven N application rates (0-360 kg N ha) using the high-yielding cultivars Jimian 228 and Lumian 28, which differ in maturity. The relationship between fruits dry mass (DM) and N concentration ([N]) was analyzed, and a model of [N] for cotton fruits was constructed and validated. The results showed that fruits [N] decreased with increasing fruits DM. The critical N dilution curve based on cotton fruits was described by the equation [N] = 2.49 × DM ( = 0.649, < 0.0001) across cultivar-years. The N nutrition index (NNI) of the fruits (NNI) with the N dilution curve was significantly related to the NNI of shoot DM, relative yield (RY), and boll density at most sampling dates. For an NNI of approximately 1, the RY was nearly 95%, while it decreased with a decreasing NNI below 1. The petiole nitrate-N (NO-N) concentration was also linearly related to the NNI, suggesting that the NO-N concentration in the petiole was a good predictor of the NNI. Therefore, fruits-based critical N dilution curve and the derived NNI values will serve as a useful diagnostic tool for diagnosing N status in cotton crops.
花期后精确估算作物氮（N）营养状况不仅对预测氮素缺乏很重要，而且对预测过量氮素也很重要，过量的氮素可在未来作物施肥时进行调整。描述作物生长期间植物组织中临界氮浓度（[N]）的临界氮稀释曲线已被用于估算棉花整株的氮素状况。然而，对于棉花果实等特定植物器官的临界氮稀释曲线却知之甚少。本研究的目的是验证基于果实的临界氮稀释曲线作为诊断棉花作物氮素状况的有用诊断工具的可行性。使用成熟度不同的高产棉花品种冀棉228和鲁棉28，设置了7个施氮量（0 - 360 kg N ha）的3年田间试验。分析了棉铃干质量（DM）与氮浓度（[N]）之间的关系，并构建并验证了棉花果实的[N]模型。结果表明，棉铃[ N]随着棉铃DM的增加而降低。跨品种年份，基于棉铃的临界氮稀释曲线由方程[ N] = 2.49 × DM（ = 0.649， < 0.0001）描述。在大多数采样日期，基于氮稀释曲线的棉铃氮营养指数（NNI）与地上部干质量的NNI、相对产量（RY）和棉铃密度显著相关。对于约为1的NNI，RY接近95%，而当NNI低于1时，RY随着NNI的降低而下降。叶柄硝态氮（NO - N）浓度也与NNI呈线性相关，表明叶柄中的NO - N浓度是NNI的良好预测指标。因此，基于棉铃的临界氮稀释曲线及其导出的NNI值将作为诊断棉花作物氮素状况的有用诊断工具。
