Band application of acidified slurry as an alternative to slurry injection in Mediterranean winter conditions: Impact on nitrate leaching

Abstract

The aim of the present work was to assess the impact of raw slurry injection and band application of acidified slurry upon nitrate leaching in two different soils under Mediterranean conditions. A lysimeter experiment with a winter crop (oat - Avena sativa) was performed over three years presenting significant inter-annual precipitation variability. Four fertilization treatments using dairy cattle slurry were implemented. Nitrate leaching was estimated using nitrate concentration in soil solution assessed through ceramic suction cups and drainage calculated using the Agricultural System Root Zone Water Quality Model (RZWQM2). Results show that the RZWQM2 was able to predict drainage with an average efficiency of 89%. Cumulative drainage averaged 69 and 65% of the precipitation for the sandy and the sandy loam soils, respectively. The application of acidified slurry did not lead to any increase of nitrate leaching relative to band application or injection of raw slurry. Soil incorporation following soil application of acidified slurry is highly relevant regarding nitrate leaching since it significantly reduced nitrate leaching in more than 50% in the sandy soil and close to 40% in the sandy loam soil. A severe risk of pollution swapping was observed with slurry injection since it led to an increase of nitrate leaching relative to band application of raw or acidified slurry (more than 100% in the sandy soil and around 30% in the sandy loam soil for the rainiest year). According to the results, band application of acidified slurry is an efficient alternative to raw slurry injection to minimize nitrogen losses by leaching. Nevertheless, soil incorporation of acidified slurry, not necessary in terms of ammonia emissions, is strongly recommended to reduce nitrate leaching.