The Pre-Sidedress Soil Nitrate Test and Nitrate Leaching from Corn
- Karl Guillard *,
- Thomas F. Morris and
- Kelly L. Kopp
The pre-sidedress soil nitrate test (PSNT) is recommended in many states as a best management practice (BMP) for corn (Zea mays L.). A 2-yr study was conducted in Connecticut on a Woodbridge fine sandy loam soil (coarse loamy, mixed, mesic Aquic Dystrochrept) to determine NO3-N concentrations and losses in soil water from corn managed with three different N fertilization regimes: (i) PRE, 196 kg N ha−1 applied preplant; (ii) PSNT-1, 90 kg N ha−1 applied at preplant and any remaining N needs estimated by the PSNT (0 kg ha−1 in 1995 and 45 kg ha−1 in 1996); and (iii) PSNT-2, no preplant N and all N needs estimated by the PSNT (34 kg ha−1 in 1995 and 123 kg ha−1 in 1996). Percolate was collected with zero-tension pan lysimeters. Flow-weighted NO3-N concentrations from the PRE treatment were 22.3 mg L−1 in 1995 and 17.4 mg L−1 in 1996; the PSNT treatments were <8.0 mg L−1. Losses of NO3-N as a percent of N applied in 1995 were 20%, 10%, and 12% for PRE, PSNT-1, and PSNT-2, respectively, and 31%, 21%, and 21%, respectively, in 1996. Greatest leaching losses occurred after corn harvest. Corn yields were not significantly (P > 0.05) different among N treatments. These findings suggest that a well calibrated soil N test can reduce excess fertilization and the potential for NO3 contamination of ground water.
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