Soil water and nitrate distribution under drip irrigated corn receiving pig slurry

Intensive swine production in Catalonia (NE Spain) has great economic importance. Applying the resulting pig slurry as fertilizer is technically sound, but there is a risk of nitrate leaching. It is therefore important to determine the amount of pig slurry that will achieve an acceptable crop yield yet prevent environmental risks. In an experiment carried out in 2009 irrigation water and grain yield in a silt loam soil were compared for furrow and drip irrigation with two emitter spacings (30 and 50 cm). The results showed that using drip irrigation improved water use efficiency (WUE) and that WUE and corn yield were not significantly different for emitters spaced at 30 and 50 cm. Based on these results, in 2010 the irrigation was carried out using emitters spaced 50 cm apart. Two different pre-planting fertilization treatments (0 and 120 kg N/ha from pig slurry) were applied. In addition, each of those two treatments was subjected to ten different side-dress fertilization treatments, with the rate of nitrogen applied through fertigation ranging from 0 to 300 kg N/ha. Soil water distribution simulated with HYDRUS-2D showed good agreement with observed values.Most of the nitrate leaching was produced after physiological maturity associated with high precipitations that produced drainage and NO3−-N leaching, especially in the treatments that received excessive amounts of nitrogen.With relatively low initial soil nitrate content, side-dress application rates of 40–75 kg N/ha combined with pig slurry applied at pre-planting produced nearly maximum grain yield with minimum N leaching and did not contravene the existing EU directives on nitrate pollution. On the other hand, nitrogen applications over 150 kg N/ha during the growing season did not increase yield but did significantly increase the concentration of nitrate in the leached solution.

► The effect of different emitter spacings on a silt loam soil is examined.
► The effect of different fertilization strategies in corn is studied.
► Nitrate leaching for different fertilization treatments is estimated.
► 30 and 50 cm emitter spacings are acceptable in these soils.
► High rates of nitrogen at side-dressing increased nitrate leaching.