Soil and tissue nitrate tests compared for predicting soil nitrogen availability to corn

Soil NO 3 concentration and soil N-supplying capability (NSC) at soil NO 3 levels below the critical level were not correlated well enough (r 2 =0.34) to use the predicted NSC for adjusting N-fertilizer recommendations. As a result, the best use of this test in Pennsylvania appears to be in identification of nonresponsive sites rather than predicting N-fertilizer rates. Use of this test by farmers in Pennsylvania will help minimize the practice of applying «insurance» N when N contributions from manure and legumes in rotations are uncertain