<i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China

The degradation of black soil cropland has occurred to varying degrees in the northern agropastoral ecotone. Crop–forage rotation is an effective way to improve soil quality, with <i>Medicago</i> being the preferred perennial legume. The C, N, and P stoichiometric ratios are key indicato...

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Main Authors: Bo Yuan, Lijun Xu, Jiaqiang Wei, Meji Cuo, Hongzhi Zhang, Yingying Nie, Mingying Guo, Jinxia Li, Xinwei Liu
Format: Article
Language:English
Published: MDPI AG 2025-03-01
Series:Agronomy
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Online Access:https://www.mdpi.com/2073-4395/15/3/724
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author Bo Yuan
Lijun Xu
Jiaqiang Wei
Meji Cuo
Hongzhi Zhang
Yingying Nie
Mingying Guo
Jinxia Li
Xinwei Liu
author_facet Bo Yuan
Lijun Xu
Jiaqiang Wei
Meji Cuo
Hongzhi Zhang
Yingying Nie
Mingying Guo
Jinxia Li
Xinwei Liu
author_sort Bo Yuan
collection DOAJ
description The degradation of black soil cropland has occurred to varying degrees in the northern agropastoral ecotone. Crop–forage rotation is an effective way to improve soil quality, with <i>Medicago</i> being the preferred perennial legume. The C, N, and P stoichiometric ratios are key indicators of soil quality and organic matter composition, reflecting the status of the internal C, N, and P cycles in soil. This study aims to investigate the ecological stoichiometric ratios of <i>Medicago</i> grassland soils with different planting durations, explore the regulatory effects of nitrogen fertilizer on soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) content, and assess the impacts of these changes on the <i>Medicago</i> grassland ecosystem. This study was conducted on the long-term cultivated grassland core experimental platform of the Hulunber National Field Station. Based on forage yield and soil nutrient measurements, field-based observations and laboratory analyses were carried out. <i>Medicago</i> × <i>varia</i> was the study subject, with different nitrogen fertilizer treatments: CK (0 kg N ha<sup>−1</sup>), N<sub>75</sub> (75 kg N ha<sup>−1</sup>), and N<sub>150</sub> (150 kg N ha<sup>−1</sup>). A randomized block design was adopted. Variance analysis, boxplot statistics, and scatterplot fitting methods were used to examine soil properties and assess the effects of nitrogen application on the C, N, and P stoichiometry of soils in established perennial <i>Medicago</i> grasslands. The results indicate that, based on the growth characteristics of alfalfa, soil nutrient dynamics, and its effectiveness in improving soil quality, the optimal rotation period for alfalfa in the northern agropastoral ecotone is 4–5 years, but it can also be shortened to 3 years. Soil carbon, nitrogen, and phosphorus contents are significantly influenced by the planting duration. As the planting years increase, soil carbon and nitrogen contents first increase and then decrease, while soil phosphorus content initially decreases followed by a slight increase. Soil pH gradually rises with both planting years and soil depth. Both low and high levels of nitrogen fertilizer application reduce soil organic carbon concentration (by 0.40% and 10.14%, respectively). Low nitrogen fertilizer application increases soil nitrogen concentration (by 1.50%), whereas high nitrogen fertilizer application decreases it (by 7.6%). Both nitrogen levels increase soil phosphorus concentration (by 36.67% and 35.26%, respectively). For soil from an alfalfa grassland planted for 8 years, the carbon-to-nitrogen ratio ranges from 9.08 to 9.76, the carbon-to-phosphorus ratio from 13.00 to 151.32, and the nitrogen-to-phosphorus ratio from 1.65 to 17.14. In summary, alfalfa yield is primarily influenced by the nitrogen fertilizer application rate, planting duration, stoichiometric ratios, and pH. Nitrogen fertilizer application has a positive regulatory effect on soil stoichiometric ratios. The annual yield can reach 8.94 to 10.07 tons per hectare., but phosphorus remains a limiting factor. These findings provide crucial data for understanding the impact of ecological stoichiometry on crop–forage rotation cycles, as well as optimal land use and quality improvement.
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spelling doaj-art-78778c12bb3a43dbb791406b4d72b71b2025-08-20T02:41:54ZengMDPI AGAgronomy2073-43952025-03-0115372410.3390/agronomy15030724<i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern ChinaBo Yuan0Lijun Xu1Jiaqiang Wei2Meji Cuo3Hongzhi Zhang4Yingying Nie5Mingying Guo6Jinxia Li7Xinwei Liu8State Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaState Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaForeign Studies College, Northeastern University, Shenyang 110057, ChinaState Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaState Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaState Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaHulunber Research Institute of Forestry and Grassland Science, Hulunber 021000, ChinaHulunber Agricultural Reclamation Group Co., Ltd., Hulunber 021000, ChinaState Key Laboratory of Efficient Utilization of Arable Land in China, The Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, ChinaThe degradation of black soil cropland has occurred to varying degrees in the northern agropastoral ecotone. Crop–forage rotation is an effective way to improve soil quality, with <i>Medicago</i> being the preferred perennial legume. The C, N, and P stoichiometric ratios are key indicators of soil quality and organic matter composition, reflecting the status of the internal C, N, and P cycles in soil. This study aims to investigate the ecological stoichiometric ratios of <i>Medicago</i> grassland soils with different planting durations, explore the regulatory effects of nitrogen fertilizer on soil organic carbon (SOC), total nitrogen (TN), and total phosphorus (TP) content, and assess the impacts of these changes on the <i>Medicago</i> grassland ecosystem. This study was conducted on the long-term cultivated grassland core experimental platform of the Hulunber National Field Station. Based on forage yield and soil nutrient measurements, field-based observations and laboratory analyses were carried out. <i>Medicago</i> × <i>varia</i> was the study subject, with different nitrogen fertilizer treatments: CK (0 kg N ha<sup>−1</sup>), N<sub>75</sub> (75 kg N ha<sup>−1</sup>), and N<sub>150</sub> (150 kg N ha<sup>−1</sup>). A randomized block design was adopted. Variance analysis, boxplot statistics, and scatterplot fitting methods were used to examine soil properties and assess the effects of nitrogen application on the C, N, and P stoichiometry of soils in established perennial <i>Medicago</i> grasslands. The results indicate that, based on the growth characteristics of alfalfa, soil nutrient dynamics, and its effectiveness in improving soil quality, the optimal rotation period for alfalfa in the northern agropastoral ecotone is 4–5 years, but it can also be shortened to 3 years. Soil carbon, nitrogen, and phosphorus contents are significantly influenced by the planting duration. As the planting years increase, soil carbon and nitrogen contents first increase and then decrease, while soil phosphorus content initially decreases followed by a slight increase. Soil pH gradually rises with both planting years and soil depth. Both low and high levels of nitrogen fertilizer application reduce soil organic carbon concentration (by 0.40% and 10.14%, respectively). Low nitrogen fertilizer application increases soil nitrogen concentration (by 1.50%), whereas high nitrogen fertilizer application decreases it (by 7.6%). Both nitrogen levels increase soil phosphorus concentration (by 36.67% and 35.26%, respectively). For soil from an alfalfa grassland planted for 8 years, the carbon-to-nitrogen ratio ranges from 9.08 to 9.76, the carbon-to-phosphorus ratio from 13.00 to 151.32, and the nitrogen-to-phosphorus ratio from 1.65 to 17.14. In summary, alfalfa yield is primarily influenced by the nitrogen fertilizer application rate, planting duration, stoichiometric ratios, and pH. Nitrogen fertilizer application has a positive regulatory effect on soil stoichiometric ratios. The annual yield can reach 8.94 to 10.07 tons per hectare., but phosphorus remains a limiting factor. These findings provide crucial data for understanding the impact of ecological stoichiometry on crop–forage rotation cycles, as well as optimal land use and quality improvement.https://www.mdpi.com/2073-4395/15/3/724agropastoral ecotoneartificial grassland<i>Medicago</i>stoichiometric ratioN fertilization
spellingShingle Bo Yuan
Lijun Xu
Jiaqiang Wei
Meji Cuo
Hongzhi Zhang
Yingying Nie
Mingying Guo
Jinxia Li
Xinwei Liu
<i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
Agronomy
agropastoral ecotone
artificial grassland
<i>Medicago</i>
stoichiometric ratio
N fertilization
title <i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
title_full <i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
title_fullStr <i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
title_full_unstemmed <i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
title_short <i>Medicago</i> Pasture Soil C:N:P Stoichiometry Mediated by N Fertilization in Northern China
title_sort i medicago i pasture soil c n p stoichiometry mediated by n fertilization in northern china
topic agropastoral ecotone
artificial grassland
<i>Medicago</i>
stoichiometric ratio
N fertilization
url https://www.mdpi.com/2073-4395/15/3/724
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