Quemada, M.1, Alonso-Ayuso,M.1, Gabriel, JL.1
1 Technical University of Madrid (UPM), Ciudad Universitaria, Madrid, 28040. [email protected]
Nitrification inhibitors (NI) may increase the recovery of N fertilizer applied to a crop, but little is known about the effect on the soil N supply capacity over time and the recovery by the subsequent crops. During two seasons, a field experiment with maize was fertilized with ammonium sulfate nitrate (ASN) and DMPP blended ASN (ENTEC®) at two levels (130 and 170 kg N ha-1). A control non-fertilized treatment was included. Maize yield, grain quality, nutritional state and N use efficiency were evaluated. During a third experimental season, a non-fertilized sunflower was planted in the same plots to study the cumulative effect. Laboratory determinations were performed to elucidate possible sources of residual N. The second year, DMPP application allowed a 23% reduction of the fertilizer rate without decreasing crop yield or grain quality. In addition, the non-fertilized sunflower scavenged more N in treatments previously treated with ENTEC® than with ANS, increasing N use efficiency. After DMPP application, N was conserved in non-ready soil available forms during at least 1 year and subsequently released to meet crop demand. The potential N mineralization obtained from aerobic incubation was higher for soils from the ENTEC® treatments. A higher δ15N in the soil indicated larger non-exchangeable NH4+ fixation in soils from the plots treated with ENTEC® or ASN-170 than from the ASN-130 or the control. These results open the opportunity to increase N efficiency in crop rotations by taken advantage from the effect of NI on the soil residual N.