Public awareness of healthy food products that are free of chemical additives, along with a worldwide demand to reduce industrial pollution, has led in recent years, to the development of organic farming. It is commonly presumed that organic agriculture causes only minimal environmental pollution. But a new study conducted by researchers from Israel reveals a worrying trend.
Ben-Gurion University of the Negev and The Volcani Center has found that there is a dark side to organic farming: Intensive organic agriculture relying on solid organic matter, such as composted manure that is mixed in to the soil prior to planting, researchers find, 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.
While groundwater pollution is usually attributed to a large array of chemicals, the main cause for drinking-water well shut downs is a high nitrate concentration in the aquifer water.
The study compared the quality of the percolating water across the entire unsaturated zone under organic and conventional greenhouses using new vadose zone monitoring technology. The enhanced down-leaching of nitrate under intensive organic farming is attributed to unsynchronized nutrient release from the compost to the soil during the early stages of the growing season. In this stage, nutrient uptake capacity of the young plants is very low and down-leaching of nitrate to the deeper parts of the vadose zone and groundwater is unavoidable.
The study was done in commercial greenhouses on the southern part of the coastal aquifer in close cooperation with local farmers.
The study was conducted by Ofer Dahan and his student, Avshalom Babad, of the Zuckerberg Institute for Water Research at BGU, Naftali Lazarovitch of the French Associates Institute for Agriculture and Biotechnology of Drylands, Efrat E. Russak of the Department of Geological and Environmental Sciences and Daniel Kurtzman, Water and Environmental Sciences, Agricultural Research Organization, The Volcani Center.
Image of mushrooms on manure from Shutterstock