Resumen de Nitrate leaching in a silage maize field under different irrigation and nitrogen fertilizer rates

Mahdi Gheysari, Seyed Majid Mirlatifi, Mehdi Homaee, Mohammad Esmaeil Asadi, Gerrit Hoogenboom

• Quantification of the interactive effects of nitrogen (N) and water on nitrate (NO3) loss provides an important insight for more effective N and water management. The goal of this study was to evaluate the effect of different irrigation and nitrogen fertilizer levels on nitrate-nitrogen (NO3-N) leaching in a silage maize field. The experiment included four irrigation levels (0.7, 0.85, 1.0, and 1.13 of soil moisture depletion, SMD) and three N fertilization levels (0, 142, and 189 kg N ha-1), with three replications. Ceramic suction cups were used to extract soil solution at 30 and 60 cm soil depths for all 36 experimental plots. Soil NO3-N content of 0�30 and 30�60-cm layers were evaluated at planting and harvest maturity. Total N uptake (NU) by the crop was also determined. Maximum NO3-N leaching out of the 60-cm soil layer was 8.43 kg N ha-1, for the 142 kg N ha-1 and over irrigation (1.13 SMD) treatment. The minimum and maximum seasonal average NO3 concentration at the 60 cm depth was 46 and 138 mg l-1, respectively. Based on our findings, it is possible to control NO3 leaching out of the root zone during the growing season with a proper combination of irrigation and fertilizer management.

  Abbreviations AN30, sum of initial NO3-N for the 0�30 cm soil depth, N in irrigation water and applied N fertilizer;

  AN60, sum of initial NO3-N for the 0�60 cm soil depth, N in irrigation water and N fertilizer;

  Bd, bulk density;

  CNC, crop N content;

  CSC, ceramic suction cup;

  DAP, days after planting;

  ET, evapotranspiration;

  ETO, reference evapotranspiration;

  FC, field capacity;

  ID, applied water;

  NLIR, NO3-N leaching rate;

  NO3-NL30, total NO3-N leached out of 30-cm soil layer;

  NO3-NL60, total NO3-N leached out of the 60-cm soil layer;

  NO3-NL30G, NO3-N leached out of the 30-cm soil layer during crop season;

  NU, crop nitrogen uptake;

  NUE, nitrogen use efficiency;

  P-M, Penman-Monteith;

  PWP, permanent wilting point;

  SMD, soil moisture depletion;

  TN, soil initial N plus irrigation water N plus applied fertilizer N