Carbon Footprint Of Main Grain Crops And Forage Production In The Longdong Loess Plateau

Agriculture is one of the main sources of greenhouse gas emissions,and its carbon mitigation is of great significance to eliminate global climate change.With the advancement of industrial poverty alleviation represented by pastoral and livestock industry,the adjustment of planting structure has increased the households’income,the harmony of production and ecology and the impact of planting on the environment have been concerned gradually.In order to explore the carbon footprint of two grain crops（wheat,potato）and two forage crops（forage maize,forage sorghum）after the implementation of industrial poverty alleviation in the Loess Plateau,this study used life cycle assessment method to investigate 197 households in Wujiao Town,Huachi County,Qingyang City.The carbon footprint of four crops production processes was quantitatively calculated,the main sources of carbon emissions were determined and the factors influenced carbon emissions was analyzed in this study.It is helpful to understand the carbon mitigation of grain crops and forage production.The main results are as follows:（1）The industrial poverty alleviation policy effectively promoted the forage planting in Wujiao Town.About 98.98%of the surveyed households planted forage maize while 28.43%of the surveyed households planted wheat.The forage planting area（10.76 mu per household for forage maize and 8.65 mu per household for forage sorghum）was larger than that of grain crops（7.29 mu per household for wheat and0.85 mu per household for potato）.With only 35.96%of forage maize and 1.7%of forage sorghum sold,produced grain crops and forage crops were mainly consumed by local household.（2）The carbon footprints of wheat,potato,forage maize and forage sorghum in descending order according to the carbon footprint per unit area were as follows:forage maize 4816.34 kg CO₂-eq/hm²,potato 2893.44 kg CO₂-eq/hm²,wheat 2188.33kg CO₂-eq/hm²,forage sorghum 1888.00 kg CO₂-eq/hm².The descending order of carbon footprint per unit yield was as follows:wheat 1.03 kg CO₂-eq/kg,forage maize0.77 kg CO₂-eq/kg,potato 0.34 kg CO₂-eq/kg,forage sorghum 0.22 kg CO₂-eq/kg.Forage sorghum has the lowest carbon footprint per unit area and per unit yield because of no plastic film engaged during production,and its ecological benefit is the best.（3）Nitrogen,fossil fuel and planting area were significantly positively correlated with carbon emissions in the crop production process（p<0.01）.In the same condition of other inputs,nitrogen application amount had greater influence on carbon footprint per unit area of forage production（forage maize and forage sorghum）.The carbon emissions caused by machine tillage accounted for the highest proportion of the fossil fuel carbon footprint,68.83%for wheat and 59.40%for forage sorghum.Compared with wheat,forage maize and forage sorghum had better ecological benefits under large planting area.While planting area was over 8.65 mu,Forage sorghum had the best ecological benefit and its carbon footprints were 1764.68 kg CO₂-eq/hm² and 0.21 kg CO₂-eq/kg.In view of the adjustment of agricultural planting structure and low-carbon development in the study area,it is suggested to promote forage planting for optimizing agricultural planting structure,to reduce fossil fertilize application amount and develop suitable machinery for low-carbon agriculture development,to strengthen technical training for public ecological awareness.