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| Effects of soil fertility and N application rates on soil organic N components and N mineralization |
| Received:March 18, 2025 Revised:June 04, 2025 |
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| KeyWord:wheat;yield;N supply;N use efficiency;acid-soluble amino N |
| Author Name | Affiliation | E-mail | | LIU Lin | South Subtropical Crop Research Institute, China Academy of Tropical Agricultural Sciences/Key Laboratory of Tropical Crops Nutrition of Hainan Province, Zhanjiang 524091, China
Institute of Eco-Environment and Industrial Technology, Shanxi Agricultural University/Shanxi Province Key Laboratory of Soil Environment and Nutrient Resources, Taiyuan 030800, China
College of Life Science, Changzhi University, Changzhi 046000, China | | | LI Puwang | South Subtropical Crop Research Institute, China Academy of Tropical Agricultural Sciences/Key Laboratory of Tropical Crops Nutrition of Hainan Province, Zhanjiang 524091, China | puwangli@163.com | | XU Minggang | Institute of Eco-Environment and Industrial Technology, Shanxi Agricultural University/Shanxi Province Key Laboratory of Soil Environment and Nutrient Resources, Taiyuan 030800, China | xuminggang@caas.cn | | MA Haiyang | South Subtropical Crop Research Institute, China Academy of Tropical Agricultural Sciences/Key Laboratory of Tropical Crops Nutrition of Hainan Province, Zhanjiang 524091, China | | | YANG Xueyun | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | | | ZHANG Shulan | College of Natural Resources and Environment, Northwest A&F University, Yangling 712100, China | |
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| Abstract: |
| To investigate the effects of soil fertility and fertilizer N application rates on organic N components and soil N supply capacity, optimize fertilizer N application and improve N use efficiency. Based on a N gradient micro-plot experiment established on plots subjected to various fertilization treatments for 26 years at a Loess soil, we systematically explored the wheat yield, above-ground N uptake, soil mineral N and organic N fractions under five soil fertility levels and at five N application rates, and aimed at established the correlation between organic N components and N mineralization. The result showed that the grain yield of winter wheat and N uptake of above-ground biomass significantly increased with increasing N application rate on low fertility soil, but showed no response to N rate on high fertility soil. Acid-soluble N（TNex）is the major form of soil organic N. The improvement of soil fertility level increased TNex content（691.07- 901.81 mg·kg-1）, but decreased its proportion to total N（TN, 61.24%-78.57%）, and increased the acid non-soluble N content（NHH, 221.46-587.38 mg·kg-1）and its proportion to TN（21.43%-38.76%）. With the increase of soil fertility level, the content of acid-soluble hydrolysable unidentified N（HUN）was significantly decreased, and other organic N contents were significantly increased, especially so for the acid -soluble amino N（AAN）. The proportions of ANN and HUN to TNex decreased with increasing soil fertility, whereas the proportion of AAN to TNex showed a concurrent increase with soil fertility levels. HUN was the main organic N fraction in low fertility soil （F1, F2）, varying from 33.92% to 40.39%, while the major organic N fraction of high fertility soils（F3, F4 and F5）was AAN, ranging from 25.72% to 35.54%. The results of the Random Forest model showed that AAN had the highest relative importance for the apparent N mineralization, followed by the TNex, and that apparent N mineralization increased significantly with increasing AAN. N application rate had no significant effect on organic N components, but soil fertility level changed the distribution characteristics of organic N components in soil, and soil N supply capacity was mainly related to AAN. When soil AAN content arrived 494 mg·kg-1 and 439 mg·kg-1, wheat grain yield and above-ground N uptake maximum. |
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