Nitrate leaching from intensive organic farms to groundwater

Abstract

It is commonly presumed that organic agriculture causes only minimal environmental pollution. In this study, we measured the quality of percolating water in the vadose zone, underlying both organic and conventional intensive greenhouses. Our study was conducted in newly established farms where the subsurface underlying the greenhouses has been monitored continuously from their establishment. Surprisingly, intensive organic agriculture relying on solid organic matter, such as composted manure that is implemented in the soil prior to planting as the sole fertilizer, resulted in significant down leaching of nitrate through the vadose zone to the groundwater. On the other hand, similar intensive agriculture that implemented liquid fertilizer through drip irrigation, as commonly practiced in conventional agriculture, resulted in much lower rates of pollution of the vadose zone and groundwater. It has been shown that accurate fertilization methods that distribute the fertilizers through the irrigation system, according to plant demand, during the growing season dramatically reduce the potential for groundwater contamination

Vadose Zone Monitoring as a Key to Groundwater Protection

“…In addition, contaminant spreading in the aquifer often results in very low concentrations on the edges of the contaminant plume, while contaminant concentration in the unsaturated zone often preserves the source's high concentrations, with only minimal dilution. Accordingly, pollution identification capability in the unsaturated zone is higher compare to the saturated zone (Gal et al, 2009;Dahan et al, 2014;Turkeltaub et al, 2016;Avishai et al, 2017;Moshkovich et al, 2017).…”

“…The potential for in-situ monitoring of the unsaturated zone has been demonstrated through several studies where the VMS was used to measure flow velocities, solute transport, and chemical transformation of contaminants across the unsaturated zone. It has been implemented in a variety of studies on water flow and contaminant transport including: (a) rainwater infiltration and groundwater recharge (Rimon et al, 2007(Rimon et al, , 2011a, (b) floodwater infiltration from stream channels and reservoirs (Shani, 2006;Dahan et al, 2007Dahan et al, , 2008Dahan et al, , 2009, (c) impact of agricultural practices on groundwater quality (Baram et al, 2012;Dahan et al, 2014;Turkeltaub et al, 2015bTurkeltaub et al, , 2016Weissman et al, 2020), (d) leachate generation and migration in landfills (Aharoni et al, 2017(Aharoni et al, , 2020, and (e) interactive remediation of contaminated sites (Dahan et al, 2017;Moshkovich et al, 2017;Levakov et al, 2019). Scientific and environmental implications from a number of these studies are presented here to demonstrate the capability to continuously monitor water flow and contaminant migration in the unsaturated zone.…”

“…Regulations that limit fertilizer application have been enacted in many countries, in an attempt to reduce nitrate pollution in aquifers (Macintosh, 2018;California Water Board, 2020). Yet, limiting the total nitrogen application does not necessarily lead to the expected reduction in nitrate pollution since nitrate leaching is dependent on fertilizer application regimes rather than the total amount (Dahan et al, 2014). Therefore, maintaining the delicate balance between agricultural productivity and groundwater quality can only be achieved through continuous measurements of the chemical composition of the water migrating from the root zone through to the deep unsaturated zone.…”

“…The data enabled identification of pollution processes in the vadose zone, long before groundwater pollution became evident. It enabled the linking of specific agricultural regimes to enhanced pollution processes (Dahan et al, 2014;Turkeltaub et al, 2015b), the calibration of transport models to long-term transient data from the vadose zone (Turkeltaub et al, 2014(Turkeltaub et al, , 2016, the identification of the mechanism controlling water and contaminant infiltration through clay sediments underlying dairy farms (Baram et al, 2012(Baram et al, , 2013(Baram et al, , 2014, and the acquisition of explicit information on the link between irrigation water salinity and increased nitrate transport from the root zone down to the groundwater (Weissman et al, 2020).…”

Feasibility Study of a National Web-Based GIS Application to Assess the Risk of Pesticide Drift in the U.S.

“…These two leach into and contaminate both surface water and groundwater, causing adverse health issues for plants, animals, humans and the environment [5] [6]. While organic farming can offset the contamination posed by conventional farming by increasing nutrient uptake and soil nitrogen, carbon and water levels, over-use of organic matter in organic farming has contributed to high ground water contamination, which can be managed by certain practices like crop rotation, soil aeration and timing of organic fertilizer application [7]- [9].…”