A Preliminary Evaluation Of The Carbon Footprint And The Effect Of Straw Returning To The Production Of Several Vegetables

In recent years, the reduction of greenhouse gas emissions, the development of low-carbon industries and the building of a "resource-saving and environment-friendly" society have become the common concern of the community. In order to clarify the basic trend of economic and carbon benefits in the vegetable production process, to achieve a scientific development of abatement technology and to explore the road of sustainable and low-carbon vegetable development in China, this study carries out an investigation on pollution-free and organic vegetable production in Liuyang family vegetable farm and aims to develop key technology of reducing the actual carbon cost and economic cost in terms of economic efficiency and carbon efficiency. Combined with the findings, the author studies the overall effect of the straw decomposing solution fertilizer, and the findings are as follows:(1)Carbon footprints of 8 kinds of pollution-free vegetables are between 539.7?4810.4 kg· hm-2, the production cost between 45 921?145 976,45 921?145 976 yuan·hm-2, and the input-output ratio between 0.226?1.22; while carbon footprints of 8 kinds of organic vegetables are between 464.9?3678.03 kg·hm-2, the production cost between 82 806?260 981 Yuan·hm-2, and the input-output ratio between 0.11?0.202. The comparison between the two indicates that the organic vegetable production model is a low-carbon but high economic-efficiency model of vegetable production.(2)For the pollution-free and organic production model, labor cost is the main part, accounting for 74.33% and 94.02% of the total production costs respectively. Regarding the organic model, there is a secondary curve relationship between the crop yields and the used organic fertilizer volume, and when the used organic fertilizer reaches 122,352 kg·hm-2, the crop yields will be the maximum; while for the pollution-free model, there is a secondary curve relationship between the leafy vegetable yields and input of agricultural chemicals, and when the agricultural chemical input reaches 20,103 Yuan · hm-2, the yields of leafy vegetables will be the maximum.(3)For the pollution-free model, carbon emissions of the agricultural chemicals account for 61.83%?71.5% of total carbon emissions, wherein the average greenhouse gas emission from the soil caused by fertilizer N reaches 52.06%, becoming the main carbon emission source, followed by carbon emissions caused by electricity consumption, accounting for 9.68%-16.27% of total carbon emissions. For the organic production model, the carbon emission is mainly caused by the use of organic fertilizer, accounting for 33.72% of the total carbon emissions, less than that caused by fertilizer used in pollution-free production, followed by carbon emission caused by use of irrigation electricity, accounting for 26.64% of the total amount of carbon emissions. The results indicate that the increased use of organic fertilizer, reduced use of organic fertilizer N and other agricultural chemicals and the establishment of a water-saving irrigation system for saving electricity are important measures to reduce carbon emissions in the process of vegetable production.(4)There is considerable nitrogen, phosphorus and potassium in 5 kinds of vegetable straw decomposing solutions, and among them, potassium content is the most, followed by nitrogen and phosphorus. In leaf decomposing solution, the nitrogen content is higher than that in stems, while the phosphorus and potassium content in stem decomposing solution are higher than those in leaves, indicating that straw decomposing solution is of certain fertility potential.(5)Pumpkin stem and leaf decomposing solution is of an integrated allelopathic inhibition effect on the growth performance of the seeds, and the response indexes are:-0.287,-0.230, while its inhibition effect strengthens as concentration increases. The integrated response indexes caused by the small pea stem and leaf decomposing solution to the growth of Chinese cabbage seeds are 0.263,-0.157, which respectively show the allelopathic promotion effect and allelopathic inhibition effect. But the average germination rates of cabbage seeds treated by four different decomposing solutions are all lower than the control group with the difference value of 19.81%. The results indicate that straw decomposing solution shall not be used when vegetable seeds just burgeon.(6) Although the root length and chlorophyll of cabbage treated by 1-time-concentration vegetable stalk decomposing solution is reduced by 23.45%,62.8% than that treated by conventional medium-concentration urea, and the volume of the root, stem height, stem volume, leaf length and width, yield and root activity are improved by 388%,61%,187%, 12.56%,13.8%,137.85%,47%. In terms of the yield components, the stalk decomposing solution can strengthen the activity and thickness of cabbage root, as well as promote the growth of stem, the stem volume, leaf growth and width and increase the leaf area.(7)Compared with conventional nitric-phosphoric acid compound fertilizer and carbamide, the content of soil available phosphorus treated by stalk decomposing solution increases by:11.96%,66.15% respectively, and the content of available K increases by: 54.13%,14.96% respectively, while the content of soil available phosphorus and K increases as the concentration of stalk decomposing solution increases. But for ammonium nitrogen, the enhanced effect is not obvious, which are only 136.96% and 56.61% of the conventional nitric-phosphoric acid compound fertilizer and carbamide. To sum up, the stalk decomposing solution is suitable for seedling growth of cabbage, and 1 to 1.5 acres of pumpkin straw decomposing fertilizer is suitable for planting 1 acre of cabbage to get a better returning-to-field effect.