Objective A new approach to analyze and optimize nitrogen management for sustainable tea cultivation in the world was investigated.
Method To accurately quantify greenhouse gas footprint, a global meta-analysis was conducted based on 38 independent field observations with 212 valid data points collected at tea plantations. A weighted assessment method was applied to correct the systematic errors arising from the sampling that was restricted solely to canopy or inter-row microenvironments. Effects of N2O flux, fertilizer type, and soil properties on regulating nitrogen emission and conversion, as well as context-dependent efficacy of biochar in acidic soils, were analyzed using random-effects models to construct a diagnostic decision support framework for sustainable management.
Result By adjusting the spatially biased global direct emission coefficient EFd to 1.93%, the default IPCC standard of 1% was significantly surpassed. A revealed mechanistic decoupling indicated the total emissions to be driven linearly by nitrogen input rates and the emission efficiency modulated by soil nitrate accumulation and pH. Nitrification inhibitors could provide the highest 45.03% reduction on average in mitigating N2O emission. Contrary to the original understanding, a trade-off of biochar application on highly acidic soil was unveiled that it could potentially be ineffective or even bring about adverse results.
Conclusion This study revealed a need of updating the existing global greenhouse gas inventories on tea plantation ecosystem. The previously accepted designation of high nitrogen emission from tea farming might need to be revised. The proposed tiered management framework is anchored by an eco-economic inflection point of 500 kg N·hm−2·a−1 and pH-dependent intervention strategy. It appeared to offer an applicable tool for quantifiable analysis and diagnostic decision framework to support sustainable development of the agriculture in the world.
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