摘要：The application of nitrogen (N) fertilizer not only increases crop yield but also improves the N utilization efficiency. The critical N concentration (Nc) can be used to diagnose crops’ N nutritional status. The Nc dilution curve model of maize was calibrated with leaf dry matter (LDM) as the indicator, and the performance of the model for diagnosing maize N nutritional status was further evaluated. Three field experiments were carried out in two sites between 2018 and 2020 in Ningxia Hui Autonomous Region with a series of N levels (application of N from 0 to 450 kg N ha−1). Two spring maize cultivars, i.e., Tianci19 (TC19) and Ningdan19 (ND19), were utilized in the field experiment. The results showed that a negative power function relationship existed between LDM and leaf N concentration (LNC) for spring maize under drip irrigation. The Nc dilution curve equation was divided into two parts: when the LDM < 1.11 t ha−1, the constant leaf Nc value was 3.25%; and when LDM > 1.11 t ha−1, the Nc curve was 3.33LDM−0.24. The LDM-based Nc curve can well distinguish data on the N-limiting and non-N-limiting N status of maize, which was independent of maize varieties, growing seasons, and stages. Additionally, the N nutrition index (NNI) had a significant linear correlation with the relative leaf dry matter (RLDM). This study revealed that the LDM-based Nc dilution curve could accurately identify spring maize N status under drip irrigation. NNI can thus, be used as a robust and reliable tool to diagnose the N nutritional status of maize.
关键词：maize; leaf dry matter (LDM); critical N concentration (Nc); leaf N concentration (LNC); nitrogen nutrition index (NNI)
