Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System
Based on a 2-year in situ nitrogen fertilization experiment, this study aims to establish a critical nitrogen concentration (CNC) dilution curve model for cotton under straw incorporation, analyze the effects of the nitrogen application rate on the cotton yield and nitrogen use efficiency (NUE), and...
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2025-05-01
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| author | Yukun Qin Weina Feng Junying Chen Cangsong Zheng Lijuan Zhang Taili Nie |
| author_facet | Yukun Qin Weina Feng Junying Chen Cangsong Zheng Lijuan Zhang Taili Nie |
| author_sort | Yukun Qin |
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| description | Based on a 2-year in situ nitrogen fertilization experiment, this study aims to establish a critical nitrogen concentration (CNC) dilution curve model for cotton under straw incorporation, analyze the effects of the nitrogen application rate on the cotton yield and nitrogen use efficiency (NUE), and determine the optimal nitrogen application rate by integrating the nitrogen nutrition index (NNI). The experiment setup was a randomized block design with five nitrogen application levels under a straw incorporation: 0, 60, 120, 180, and 240 kg N ha<sup>−1</sup> (denoted as N0, N60, N120, N180, and N240, respectively). The cotton dry matter accumulation and nitrogen concentration were measured at the flowering and boll stage, peak boll stage, and boll opening stage. The CNC dilution curve was developed using the data from 2021 and validated with those of 2022. Results showed that the cotton biomass and seed cotton yield at the boll opening stage increased with nitrogen application rates up to 180 kg N ha<sup>−1</sup>. However, no further increase was found in the yield with an N rate higher than 180 kg N ha<sup>−1</sup>. The CNC dilution curve was formulated as <b>y = 3.4921x<sup>−0.416</sup></b> (R<sup>2</sup> = 0.8741). The validation using 2022 data yielded a root mean square error (RMSE) of 0.21% and a normalized RMSE (nRMSE) of 13.40%, confirming the model’s robustness. The NNI, calculated based on the CNC, indicated that an application rate of <b>120 kg N ha<sup>−1</sup></b> maintained NNI values close to one across all growth stages, reflecting an optimal nitrogen status. Significant positive correlations were observed between the NNI and both the seed cotton yield and harvest index (<i>p</i> < 0.05). Nitrogen use efficiency parameters, including the agronomic NUE (NUEa), nitrogen partial factor productivity (NPFP), and internal NUE (NUEi), exhibited quadratic declines with the increasing nitrogen input. Within the range of 120–240 kg N ha<sup>−1</sup>, the highest NPFP was achieved at <b>120 kg N ha<sup>−1</sup></b>. In conclusion, the critical nitrogen dilution curve model combined with the NNI effectively diagnoses the nitrogen status in cotton under straw incorporations. Considering the NNI, yield, and nitrogen utilization efficiency, the recommended nitrogen application rate for cotton in a cotton–rape rotation system with a straw incorporation is <b>120 kg N ha<sup>−1</sup></b>. |
| format | Article |
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| spelling | doaj-art-36ce712ba6694a3ea5122e4a60bf30a02025-08-20T03:30:28ZengMDPI AGAgronomy2073-43952025-05-01156132510.3390/agronomy15061325Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation SystemYukun Qin0Weina Feng1Junying Chen2Cangsong Zheng3Lijuan Zhang4Taili Nie5Jiangxi Provincial Key Laboratory of Plantation and High Valued Utilization of Specialty Fruit Tree and Tea, Jiangxi Economic Crops Research Institute, Jiujiang 332105, ChinaState Key Laboratory of Cotton Bio-Breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, ChinaJiangxi Provincial Key Laboratory of Plantation and High Valued Utilization of Specialty Fruit Tree and Tea, Jiangxi Economic Crops Research Institute, Jiujiang 332105, ChinaState Key Laboratory of Cotton Bio-Breeding and Integrated Utilization, Institute of Cotton Research, Chinese Academy of Agricultural Sciences, Anyang 455000, ChinaJiangxi Provincial Key Laboratory of Plantation and High Valued Utilization of Specialty Fruit Tree and Tea, Jiangxi Economic Crops Research Institute, Jiujiang 332105, ChinaJiangxi Provincial Key Laboratory of Plantation and High Valued Utilization of Specialty Fruit Tree and Tea, Jiangxi Economic Crops Research Institute, Jiujiang 332105, ChinaBased on a 2-year in situ nitrogen fertilization experiment, this study aims to establish a critical nitrogen concentration (CNC) dilution curve model for cotton under straw incorporation, analyze the effects of the nitrogen application rate on the cotton yield and nitrogen use efficiency (NUE), and determine the optimal nitrogen application rate by integrating the nitrogen nutrition index (NNI). The experiment setup was a randomized block design with five nitrogen application levels under a straw incorporation: 0, 60, 120, 180, and 240 kg N ha<sup>−1</sup> (denoted as N0, N60, N120, N180, and N240, respectively). The cotton dry matter accumulation and nitrogen concentration were measured at the flowering and boll stage, peak boll stage, and boll opening stage. The CNC dilution curve was developed using the data from 2021 and validated with those of 2022. Results showed that the cotton biomass and seed cotton yield at the boll opening stage increased with nitrogen application rates up to 180 kg N ha<sup>−1</sup>. However, no further increase was found in the yield with an N rate higher than 180 kg N ha<sup>−1</sup>. The CNC dilution curve was formulated as <b>y = 3.4921x<sup>−0.416</sup></b> (R<sup>2</sup> = 0.8741). The validation using 2022 data yielded a root mean square error (RMSE) of 0.21% and a normalized RMSE (nRMSE) of 13.40%, confirming the model’s robustness. The NNI, calculated based on the CNC, indicated that an application rate of <b>120 kg N ha<sup>−1</sup></b> maintained NNI values close to one across all growth stages, reflecting an optimal nitrogen status. Significant positive correlations were observed between the NNI and both the seed cotton yield and harvest index (<i>p</i> < 0.05). Nitrogen use efficiency parameters, including the agronomic NUE (NUEa), nitrogen partial factor productivity (NPFP), and internal NUE (NUEi), exhibited quadratic declines with the increasing nitrogen input. Within the range of 120–240 kg N ha<sup>−1</sup>, the highest NPFP was achieved at <b>120 kg N ha<sup>−1</sup></b>. In conclusion, the critical nitrogen dilution curve model combined with the NNI effectively diagnoses the nitrogen status in cotton under straw incorporations. Considering the NNI, yield, and nitrogen utilization efficiency, the recommended nitrogen application rate for cotton in a cotton–rape rotation system with a straw incorporation is <b>120 kg N ha<sup>−1</sup></b>.https://www.mdpi.com/2073-4395/15/6/1325<i>Gossypium hirsutum</i> L.nitrogen applicationcritical nitrogen concentrationnitrogen uptakenitrogen use efficiency |
| spellingShingle | Yukun Qin Weina Feng Junying Chen Cangsong Zheng Lijuan Zhang Taili Nie Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System Agronomy <i>Gossypium hirsutum</i> L. nitrogen application critical nitrogen concentration nitrogen uptake nitrogen use efficiency |
| title | Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System |
| title_full | Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System |
| title_fullStr | Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System |
| title_full_unstemmed | Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System |
| title_short | Critical Nitrogen Dilution Curve for Diagnosing Nitrogen Status of Cotton and Its Implications for Nitrogen Management in Cotton–Rape Rotation System |
| title_sort | critical nitrogen dilution curve for diagnosing nitrogen status of cotton and its implications for nitrogen management in cotton rape rotation system |
| topic | <i>Gossypium hirsutum</i> L. nitrogen application critical nitrogen concentration nitrogen uptake nitrogen use efficiency |
| url | https://www.mdpi.com/2073-4395/15/6/1325 |
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