草地轮作年限和季节对土壤不同组分有机氮含量的影响

Effects of pasture rotational year and season on content of soil organic nitrogen fractions

摘要:

为揭示轮作草地不同粒级土壤有机质及其氮含量在时间序列上的动态特征,以有机农牧场低投入蔬菜生产后的5年草地轮作土壤为研究对象,测定不同组分有机质,颗粒有机氮(PON)和非颗粒有机氮(n-PON)含量变化。结果表明:草地轮作5年土壤有机质含量增加18%,土壤总有机氮含量增加20.6%,第5年显著高于第1、3年但低于永久性草地。随着草地轮作年限的增加,土壤总有机氮中PON比例逐渐增加,n-PON比例逐渐降低,冬季n-PON占比小于春、夏、秋季。草地轮作5年土壤PON增加60%,n-PON增加16.5%,且均接近永久性草地含量,春季草地土壤n-PON含量显著高于冬季,季节对轮作草地土壤总有机氮和PON含量无显著影响。PON敏感指示土壤有机氮变化动态,草地轮作提高了土壤有机氮循环强度和有效性。土壤总有机氮、PON、n-PON含量与土壤容重呈极显著负相关,与有效P、K、Ca、Mg含量和阳离子交换量呈极显著正相关。草地轮作5年土壤不同组分有机氮含量发生显著变化,有效改善了土壤养分状况。

Abstract:

In order to reveal the dynamic characteristics of different size fractions of soil organic matter and nitrogen under rotational pasture.This study quantified temporal changes in different soil organic matter fractions,particulate organic nitrogen (PON) and non-particulate organic nitrogen (n-PON) concentrations during a five-year pasture rotation following vegetable production.The results showed that soil organic matter and total organic nitrogen increased 18% and 20.6%,respectively.The content of total organic nitrogen in fifth rotation year significantly higher than in first and third rotation year,but lower than in permanent pasture.Proportion of PON increased and n-PON reduced in soil total organic nitrogen with increasing pasture rotational year.The proportion of n-PON in winter lower than in spring,summer and fall.Over 5 years pasture rotation,soil PON and n-PON increased 60% and 16.5%,respectively,and became similar to the content of permanent pasture.The content of soil n-PON in spring significantly higher than in winter,but season did not significantly affect total organic nitrogen and PON.The PON sensitively indicate the change of soil organic nitrogen content.Pasture rotation promoted soil organic nitrogen cycling and availability.Soil total organic nitrogen,PON and n-PON showed significantly negative correlation with soil bulk density,but significantly positive correlation with available P,K,Ca,Mg and cation exchange capacity.Overall,different soil organic nitrogen fractions significantly changed and soil nutrient status was improved after 5 years pasture rotation.