Environmental Impacts of Progressive and Conventional Management in Winter Wheat Cropping System of Mayamey Plain in Shahrood, Using the Lifecycle Assessment Methodology

Food security in parallel with the preservation of environment and natural resources, has become a critical issue in the world. Wheat as the main food for human has allocated the high cultivation area each year in the world and in Iran as well. Agricultural systems due to the consumption of fossil fuels and chemical output has introduced as the biggest consumers of energy and natural resources, also it has contributed serious role in bio environment problems (Roy et al., 2005). The environment seeks a system to provide the necessities of current generation,   as well as prevention of resources s for the next generation.  To study the positive and negative effects of cropping systems, the researchers have introduced multiple methods to study bio environment effects. In this regard, one of the best method is the life cycle assessment (LCA). Management method plays critical role in bio environment effects of cropping systems. LCA study of wheat frequency has conducted in Iran and the world. This study compares two conventional and progressive cropping management systems of winter wheat in Mayamey farms in Shahrood city using the life cycle assessment method.

Life cycle assessment (LCA) was conducted using data of winter wheat fields in Mayamey, (Shahrood city) with two conventional and progressive management methods.  LCA includes four steps  (purpose definition, study practice area, assessment the effect of life cycle ,results integration and interpretation). At the first step,  the functional unit of one ton was determined,  then data was classified, normalized and weighted, finally the indices of global warming, eutrophication of agro ecology,  discharge potential for possible recyclable resources , poisoning and land use were analyzed .

The ecology index resulted from LCA method in progressive management is higher than conventional management.  The emission rate of effective greenhouse gases for global heating potential index in the studied cropping systems is 461.98, 309.48 units equal to CO2 kg for the conventional and progressive management of wheat fields respectively. Potential of acidification index in agroecosystems with different conventional and progressive managements are 4.43 and 3.13 units equal to SO2 kg per functional unit. Results shown that the bioenvironment effects of  eutrophication potential in  dry systems in winter wheat production was 33.35 in conventional agroecosystem and 23.75 for progressive agroecosystem per NOx kg dissemination . Results of discharge potential for possible recyclable resources shown the highest gas use is 2.54 m3.ha-1 in conventional agroecosystem and 1.53 m3.ha-1 in progressive agroecosystem respectively, while other non-renewable sources such as rock phosphate and potash were 6.75 and 3.39 in conventional afro ecology respectively and this amount was 5.25 for phosphate and 2.43 for potash in progressive agroecosystem. The study indicated that in conventional managed farm the poisoning effects of heavy metals cadmium for human and dry agroecosystem were 0.00033 and 1.40200, respectively, where it was 0.00030 and 1.28501 in agroecosystem for progressive management. The occupied land for each ton of wheat was computed as 1840 for progressive management and 1493.3 m3 for conventional management.

Results of LCA shown that phosphate resources depletion  for discharge potential index of renewable resources and eutrophication of dry agroecosystem has more bioenvironment effects than other  indices, also the results of both conventional and progressive management of winter wheat agroecosystem shown that  the bio environment effects of progressive management has been more than the conventional management, while it is shown higher yield and the higher use of inputs don't mean higher yield necessarily. Results may be important for farmers and agriculture managers in the region in case of a sustainable management procedure.