Nutrient Fluxes from Agriculture: Reducing Environmental Impact Through Optimum Application

Abstract

Unmindful of the increasing environmental risk exerted by agriculture, farmers are often liberal in application of chemical fertilizers, herbicides, pesticides in order to enhance farm productivity. Use of pesticide, herbicides like glyphosate has risen over the past few decades in most countries some of which are identified carcinogenic which affect human as well as many wildlife forms besides polluting freshwater resources. Agriculture mainly livestock sector also contributes to anthropogenic causes of NH3 emissions. Nutrient emissions from agriculture due to more and more fertilizer application have been the cause of major concern nowadays. Eutrophication is caused by accounting to excess nitrogen (N) and phosphorus (P) in the water bodies. Furthermore, paddy fields due to its water-loving character are much more vulnerable to nutrient outflows which results in eutrophication in water bodies. Nutrient balance method can be used as a land-based indicator for measuring the sustainability of agro-ecosystem. Various models like NUTMON have been developed for nutrient balance calculation, depending on the site-specific fertilization management practices of agriculture soils. Results across various countries including Vietnam, China and Thailand showed that nutrient loss through various means like infiltration, leaching and runoff from paddy fields is in significant amount, especially for N and P contributing more than 50\% of the total input. However, irrigating with the nutrient-loaded water minimized the use of fertilizer, especially N fertilizer up to 20\%. Furthermore, it was also found that use of sewage water for irrigation not only increased N uptake by 29, 23, 18 and 37\% in food grain, agroforestry, fodder and vegetable production systems, respectively, while the corresponding values were 28, 21, 29 and 35\% for P uptake but also increased soil microbial biomass carbon (MBC) and activities of dehydrogenase, urease and phosphatase. The results revealed that emphasizing on growing organic foods devoid of chemical input should be of priority to keep the soil health intact along with sound local environment. Further, it is recommended that two or more indicators should be accompanied for robust testing of sustainability of the agro-environment.