Contribution of Anaerobically Mineralized Nitrogen to the Reliability of Planting or Presidedress Soil Nitrogen Test in Maize

SAINZ ROZAS, H.; CALVIÑO, P.A.; ECHEVERRÍA, H.E; BARBIERI, P.A.; REDOLATTI, M.

AGRONOMY JOURNAL

American Society of Agronomy Publication

Lugar: Madison, WI; Año: 2008 vol. 100 p. 1020 - 1025

0002-1962

The objective of this work was to evaluate if soil mineralizable N under anaerobic conditions (Nan) improves the reliability of preplant soil nitrate test (PPNT) and presidedress soil nitrate test (PSNT). Th e study was conducted under no-tillage (NT) in the southeastern Buenos Aires province, Argentina, in 26 site-years. In some site-years treatments were fi xed N rates (0, 70, 140, and 210 kg ha?1 or 0, 60, 120, 180, and 240 kg ha?1) applied at planting, whereas in others site-years N rates were determined by adding N to lead targets of N supply up to 120, 160, and 200 kg N ha?1. When sites were not separated by Nan, relative yield (RY) correlated with PPNT (r2 = 0.37) and reliability of PPNT did not increase when sites were separated by low (<48 mg kg?1) and high Nan (>48 mg kg?1). A high relationship between RY and PSNT (r2 = 0.56) was determined. However, when sites were separated by Nan, reliability of PSNT increased, mainly for sites with low Nan (r2 = 0.68 and 0.44 for sites with low and high Nan, respectively). Critical PSNT values for 94% of RY were 75 and 90 kg N ha?1 for sites with high and low Nan, respectively. Th e results show that PSNT was a better diagnostic method for maize (Zea mays L.) than PPNT. However, the separation of sites by its N mineralization capacity increased reliability of PSNT by indicating a lower N requirement to reach 94% of RY, decreasing the risk of overfertilization, an important feature from economical and environmental standpoints