Wine-distillery waste compost addition to a drip-irrigated horticultural crop of central Spain: Risk assessment

•Risk evaluation of wine-distillery waste compost addition on aquifer NO3 pollution.•Measurement of NO3 leaching after compost addition under different irrigation rates.•Two different patterns were observed with respect to the irrigation rate.•An excess of irrigation contributes to increase the aquifer contamination.•It is crucial to adjust irrigation and compost doses to minimise the risk.

The assessment of environmental effects is important before agricultural use of organic wastes, especially in irrigated agricultural areas vulnerable to nitrate pollution. A field study with melon crop was conducted during 2011 and 2012 in central Spain, using different rates of wine-distillery waste compost to quantify nitrogen (N) leaching under two regimes of irrigation. To evaluate the groundwater pollution risk associated with these practices, some environmental indices were used to determine the variation in the quality of drinking water (Impact Index (II)) and in the nitrate concentration of the groundwater (Environmental Impact Index (EII)). To combine environmental together with yield parameters, the Management Efficiency (ME) was calculated. Considering II and EII, compost addition together with adjusted irrigation (90–100% ETc) do not represent a risk to increase groundwater contamination, and, in high doses, may contribute to remove nitrate from drainage water and improve the quality of the drinking water. In contrast, applying large amounts of compost together with an excess of water (120% ETc) increased N leaching significantly and poses a higher risk of groundwater contamination. The rate corresponding to 13 t ha−1 of compost together with an efficient irrigation is sufficient to achieve the highest yield, does not exceed the maximum allowable limits established by II and EII and has an adequate ME.