Comparsion of Ecological Footprint, Water Footprint and Environmental Impacts of Irrigated and Rainfed Wheat Production Systems based on Farm Size (Case Study: Boushehr Region)

Introduction:

Nowadays, agriculture plays a major role in environmental pollution, and knowledge regarding reducing input utilization in such systems can help us to decrease the limited input resource consumption and the consequent greenhouse gas (GHGs) emissions and environmental impacts. Environmental assessment is one of the accepted ways for achieving sustainable agricultural goals. Hence, life cycle assessment (LCA) is an appropriate way to study the environmental impact of a crop plant producing in its whole life cycle in production systems. Moreover, life cycle assessment (LCA) is an appropriate method for studying the environmental impacts of a crop product throughout its life cycle in production systems. Therefore, this research was carried out with the aim of evaluating the life cycle of irrigated and rainfed wheat productions based on the farm size in Bushehr region in 2016-17.

To conduct research, at first, 200 wheat fields were identified which 100 farms belonging to rainfed cultivation in the Genaveh region and 100 farms belonging to irrigated cultivation in the Dashty region were monitored. After data recording, farms in each method were classified into five groups in terms of size level, including very small (-1), small (2-5 ha-1), medium (5-10 ha-1), large (10-15 ha-1) and very large (>15 ha-1). For each impact category, correspond characterization factors were used based on cumulative energy demand (CED), cumulative exergy demand (CexD), greenhouse gas protocol (GGP), IPCC 2013 GWP 100a, ecological footprint (EF), and water footprint (WF) methods in SimaPro8.2.3 software.

The findings of this study demonstrated that all impact category of cumulative energy demand (CED), cumulative exergy demand (CexD), greenhouse gas protocol (GGP), IPCC 2013 GWP 100a, ecological footprint (EF), and water footprint (WF) in rainfed cultivation were significantly higher than irrigated cultivation. In addition, the impact category indices associated with the CML-IA non-baseline model, such as global warming 500a, acidification, eutrophication, ionizing radiation, malodorous air, ozone layer depletion 40a, human toxicity 100a, freshwater and marine aquatic ecotoxicity 100a in rainfed cultivation, were significantly higher than irrigated cultivation. Moreover, impact category of heavy metals emitted into the air (Pb, Cd, Zn, and Hg), heavy metals emitted into water (Cr, Zn, Cu, Cd, Hg, Pb, and Ni), nitrate into soil, metals into soil, pesticide into the soil, and emission of NOx, SOx, NH3, dust, COD, phosphorous and nitrogen in the rainfed method was much higher than irrigated cultivation. In irrigated planting method, with increasing farm size from very small to very large, all of the pollutants revealed a decreasing trend, but it was varied in rainfed cultivation, with the largest amount belonging to very small farms. According to the results, it is possible to improve productivity by reducing nitrogen and fuel consumption as well as mechanization of agricultural crops. Based on the findings, it can be argued that farmers in both systems consider economic efficiency in production and are less likely to pay attention to environmental sustainability. It seems that by reducing the government subsidies related to chemical inputs and promoting conservation planting systems, the gap created could be offset to increase economic and environmental productivity in wheat cultivation in the region.

The variability of these indicators based on farm size level in rainfed cultivation can be due to lower variation in output (yield) and all inputs from very small to very large fields. Therefore, these results show that the share of pollutants in irrigated cultivation is lower than in rainfed cultivation in the Bushehr region. This issue is of great importance from the ecological point of view because the source of non-renewable energies, which are mostly fossil fuels, and the reliance on these resources in the future, is fraught with great risks.