| Greenhouse vegetable cropping system with high resource inputs is common in China, which caused severe environmental problems and received much attention. The present study was performed in typical greenhouse vegetable growing areas Shouguang city, in Shandong Province and outskirt in Beijing. With data from field survey and a large number of farm-level interview questionnaires, detailed analyses was performed on status of fertilization, irrigation, and pesticide inputs. And input-output balance method was used to estimate the economic benefit of greenhouse vegetable cropping system. In greenhouse vegetable production system, all processes including greenhouse construction, agricultural goods production and transportation, planting and harvest were involved in consumption of resources, energy and resulted in environmental problems. So environmental impact assessment of vegetable production system should not only consider the planting process, but also the other processes such as greenhouse construction and agricultural goods production. Therefore, the life cycle assessment (LCA) methodology was used to assement environmental impacts in greenhouse vegetable production system with 1 ton product and 1 hectare arable land as function unit, and to compare results in different scenarios. Based on spatial variability of farmer-level survey, the uncertainty of environmental impact assessment results was analyzed by kernel density curve, which provided data support and theoretical basis for compiling the greenhouse agricultural life cycle inventory data and unified quantitative environmental impact assessment method. The main results and conclusions are as follows:(1) There were serious problems in greenhouse vegetable cultivation on framer.1) Fertilizer inputs were excessive. In 2014, the single-season nutrient utilization rate in Shouguang greenhouse vegetable was between 5.76% and 47.0%. The total fertilizers applied were also much larger than the actual demand of nutrients by plant in 2015 of Beijing, which was between 2.48 and 31.3 times the latter. Manure application rate was also very large, which in single season in Shouguang and Beijing were 84.8 t·ha-1 and 50.4 t·ha-1 respectively. Organic fertilizer was main source of fertilizer. The organic N, P2O5 and K2O accounted for 70.7%,60.2% and 65.2% of the total inputs in Shouguang. In Beijing, 58.4%,56.9% and 52.3% of total N, P2O5 and K2O inputs were from organic fertilizer, respectively.2) A minority of farmers used drip irrigation. The proportion of farmers using drip irrigation was 26.4%, the average amount of single-season by which was 830 mm, which was 19.3%～27.4% less than traditional flood irrigation in Shouguang. The drip irrigation amount was average 385 mm, which was between 20.7% and 34.1% less than traditional, but only 5.88% of farmers used that in Beijing. In addition, irrigation was key factor for nutrient inputs, and there was a significant positive correlation between them under traditional flood irrigation conditions. Average fertilizer nutrient inputs by drip irrigation could save between 10.5% and 33.5% than the traditional.3) Amount of pesticide application was also big. The dosage of pesticides in autumn-winter solar greenhouse in Shouguang and Beijing were up to 46.5 kg·ha-1 and 40.4 kg·ha-1, respectively. This over-fertilization, unreasonable irrigation and experience pesticides applied will cause serious waste of resources and bring great pressure on environment. Therefore, greenhouse vegetable development mode must be accelerated to transform, to build modern cultivation methods, industrial and management systems and ensure its sustainable development.(2) Fertilizers, seeds, pesticides and plastic covering-film were major components for greenhouse vegetable production system cost. The total income and net income of greenhouse vegetable in Shouguang were higher than those in Beijing, but return rate was less, which mainly related to different cost inputs and vegetable market price. In Shouguang, yield was positively correlated with total nutrient inputs and organic fertilizer inputs, but not with chemical fertilizer. In Beijing, yield was positively correlated with organic fertilizer inputs. Farmers could not rely solely on expanding acreage to increase income. The greenhouse of 1-2 acres had the highest net income but below 1 acre with the highest return rate in Shouguang. The greenhouse of 1.5～2 acres was both the highest net income and return rate in Beijing, but proportion of that in survey was small.(4) Impact potential of per ton vegetables production in Shouguang solar greenhouse were 5285 MJ for energy depletion,246 kg CO2 for global warming,3.38 kg SO2 for acidification,1.49 kg PO43-for eutrophication,37.9 kg 1,4-DCB for terrestrial ecotoxicity,59.8 kg 1,4-DCB for Fresh water aquatic ecotoxicity, and 48.7 kg 1,4-DCB for human toxicity, respectively. On one hectare greenhouse field, environmental impacts for greenhouse tomato production system were the lowest among cucumber, eggplant and pepper. Impact potential of producing per ton tomatoin Beijing solar greenhouses were 6520 MJ for energy depletion,379 kg CO2 for global warming,4.46 kg SO2 for acidification,1.57 kg PO43- for eutrophication,55.5 kg 1,4-DCB for terrestrial ecotoxicity,96.7 kg 1,4-DCB for Fresh water aquatic ecotoxicity,51.5 kg 1,4-DCB for human toxicity, respectively, was higher than Shouguang, which mainly related to yield.(4) Planting process was key period for environmental acidification, eutrophication, and soil ecological toxicity. Main environmental problems caused by agricultural production were gobal greenhouse effect and potential human toxicity. Main environmental problems caused by greenhouse construction were energy consumption. LCA results on farmer-level survey showed that a positive skewed distributions, with a few growers extending the tail towards the highest environmental impact side, which indicated that to overall optimization the environment impacts in regional greenhouse production systems especially by reducing the impacts of those extreme growers located on the right upper tail of the distribution. From LCA results in different case scenarios, fertilizer reduction was the most effective to most environmental impacts, especially in GWP and ecotoxicity. Reduction of pesticides could significantly save energy and weaken the GWP, TAETP and FAETP. Extending the greenhouse life could significantly save energy and weaken the HTP. PVC could significantly save energy than EVA film. In conclusion, from the perspective of environmental protection, on the one hand, reasonable control in fertilizers and pesticides inputs should be performed. On the other hand, environmental impacts in stage of greenhouse construction should be reduced, such as extending the greenhouse lifespan and to use more environmental film such as PVC. |
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