Comprehensive Evaluation Of Carbon Emission And Optimum Fertilization In Guanxi Pomelo Production

Pinghe County?Zhangzhou City,Fujian Province?is known as“the world's pomelo township and Chinese pomelo capital”.In order to obtain more economic benefits,the excessive fertilization is common in pomelo production which increased the cost of cultivation and environmental risks.Based on the questionnaire survey of farmers and the carbon footprint model,we calculated the greenhouse gas emissions of the main polemo producing areas in Pinghe County.Considering the recommended fertilizer dosage of citrus crops,according to“bottom up”technical theory,field experiments were conducted to determine the optimal fertilization input in honey pomelo production.The quality,fertilizer utilization efficiency,and greenhouse gas mitigation were also evaluated in this study.The aim of this study is to provide theory and technic supporting to reduce fertilizer application and improve pomelo quality.Experimental treatments included farmers'habit treatment?FFP?,optimize fertilization treatment?OPT?and optimize fertilization with calcium/magnesium treatment?OPT+CaMg?.The main results are as follows:?1?Based on the Life Cycle Assessment?LCA?and 638 farmers'survey,the carbon emission per unit area of the Guanxi honey pomelo orchard in Pinghe County is 27.8 t CO₂ eq/ha,and the carbon emission per unit of output is0.44 t CO₂ eq/t.Nitrogen?N?fertilizer input has make a largest contribution to carbon emissions,while followed by pesticides.It is necessary to achieve high yield and low emission by optimal N fertilizer input.Block analysis showed that high yield and low output farmers are still have a potential in emission reduction.?2?The dry matters accumulation and the nutrient demand characteristics of fallen flowers,fruit,pruning branches showed that N,P and K nutrients were mainly taken away by fruits under different treatments?taken proportions were65%,86%,78%,respectively?.Mg was mainly taken away by fruits and pruning branches?taken ratios are 49%and 48%,respectively?,Ca was mainly taken by pruning branches?taken away by 85%?,and nutrients taken by falling flowers were less?N,P,K,Mg,Ca take away less than 5%?.The nutrients content required to produce 1000 kg fresh pomelo fruit were 3.44-3.87 kg N,0.48-0.68 kg P,3.11-3.55 kg K,0.26 kg Mg,0.45-0.50 kg Ca.Compared to FFP treatment,OPT treatment can significantly reduce the loss of N,P,K and Ca,mainly due to reduced pruning biomass.The results of nutrient balance analysis showed that N,P,and K nutrients had large surpluses during all treatments.Meanwhile,the OPT treatment could significantly reduce nutrient surplus.In future,it is still necessary to further optimize the nutrient management measures of Guanxi honey pomelo according to the nutrient demand law of fruit trees and soil nutrient supply characteristics.?3?The results of 7-point field trials in 2017-2018 showed that the yields were increased to 3.11 t/ha and 4.27 t/ha at OPT treatment and OPT+Mg treatments which compared with FFP treatment,respectively?The growth rate is 8%and 11%respectively?.The titratable acid content was reduced by 0.02%and 0.05%?decreased by 3%and 7%,respectively?and the solid-acid ratio distribution was increased by 0.54 and 1.44?3%and 9%respectively?,while the fruit appearance quality,edible rate,solubility and solids were no significant difference.Compared with FFP treatment,the input of N,P₂O₅ and K₂O fertilizers in OPT treatment decreased by 478 kg/ha,348 kg/ha and 496kg/ha?43%,45%and 47%respectively?,while the input of N,P₂O₅ and K₂O fertilizers in OPT+CaMg treatment decreased by 478 kg/ha,348 kg/ha and370 kg/ha?43%,45%,35%respectively?.Compared with FFP treatment,OPT treatment and OPT+CaMg treatment fertilizer input decreased by 8300 yuan/ha and 4000 yuan/ha?reduced by 22%and 18%respectively?,and the average profit increased by 22,700 yuan/ha and 22,300 yuan/ha respectively.?increased by 28%and 27%respectively?.Carbon emissions per unit area decreased by7.65 and 7.51 t CO₂/t?reduced by 36%and 36%,respectively?.Carbon emissions per unit of production decreased by 0.29 and 0.28 t CO₂/ha,respectively?decreased by 45%and 44%,respectively?.In summary,this study quantified the composition of carbon footprint of Guanxi pomelo orchard in Pinghe County and the difference in carbon emissions from different groups of farmers.Nitrogen fertilizer is the main source of carbon emissions.Reasonable reduction of nitrogen fertilizer input can achieve high yield and low emissions.Field experiments were conducted to investigate the effects of annual nutrient loss and Optimum Fertilization on yield,quality,economic benefits and environment of Guanxi honey pomelo.Field experiment results showed that OPT treatment and OPT+CaMg treatment could not only reduce fertilizer input,but also increase yield and income,reduce titratable acid,improve solid-acid ratio,improve fruit quality and reduce carbon emissions in orchard production.In the production of Guanxi honey pomelo orchard in Pinghe County,according to the growth and development law of Guanxi honey pomelo,combined with the management experience of high-yield and low-row farmers,it has important significance for improving the quality and efficiency of Guanxi honey pomelo orchard in Pinghe County,increasing farmers'income and environmental friendliness.