Assessment of technical compliance of nitrogen fertilization in organic tea plantation based on nitrogen supply
In organic production and certification,identifying the application of chemically nitrogen(N)fertilizers is a priority issue as it is impossible to differentiate organic and chemical N during the final agricultural product analysis.This study chose five organic tea gardens(ZX,HLS,LS,YS,and YCT)in Pu'er City,Yunnan Province,to explore and assess the risk of chemical fertilizer application in organic tea production of 2022.Based on the principle of N balance of the soil-crop system,and in combination with the supply of N from non-fertilizer sources,such as green manure,straw incorporation,and soils,and with consideration of the N uptake from tea harvest yield,the study estimated the N fertilization quantity to meet with the tea production,and calculated the N satisfaction rate to assess the risk of chemical N fertilization risk in organic tea plantation.The results showed that the annual tea yields of ZX,LS and YCT tea gardens were low,and the N requirement was 53.6,43.1 kg·hm-2,and 27.4 kg·hm-2,respectively,the non-fertilizer N supplies ranged from 93.8 kg·hm-2 to 128.2 kg·hm-2,which were able to satisfy the tea production.The two tea gardens,i.e.,HLS and YS,had high tea yields,and their non-fertilizer N supplies could not satisfy the tea production.The YS tea garden applied an additional 63.0 kg·hm-2(calculated in N)from organic fertilizer complying with organic standards,which supplied more than 50%of the theoretical required fertilizer N input.HLS tea garden had high risk of chemical fertilizer N application,which was not in accordance with Chinese organic agriculture standard.The study shows that the actual fertilization of the 5 tea gardens studied is in high consistency with the assessment results,and the N satisfaction rate proposed in this study is based on the principle of N balance,which can well assess the technical compliance of fertilizer N use.In organic tea plantation production,the improvement of soil fertility through the continuous implementation of green manure,straw return to the field and other measures is an important guarantee to ensure the sustainability of tea plantation production and compliance with organic certification,and should be further verified and promoted for application in organic agriculture.
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