Evaluation of the presidedress soil nitrogen test for no-tillage maize fertilized at planting

Abstract

Soil N transformations under no-tillage (NT) could affect the utility of the presidedress soil nitrate test (PSNT), particularly where early season growing conditions are cool as in Balcarce, Argentina. The PSNT was evaluated for irrigated NT maize (Zea mays L.) with different N rates (Exp. 1) and for rainfed maize under NT and conventional tillage (CT) with different preceding crops and N rates (Exp. 2). In both experiments, N was surface broadcast as (NH2)2CO at planting. The reliability of the PSNT was evaluated when NH4/+-N was determined and when samples were taken up to a 60-cm depth in the first experiment. In this experiment, the relative yield (RY) was highly correlated (R2 = 0.61-0.86) with soil NO3/--N concentration (0-30 cm) at the six-leaf stage (V6). The reliability (R2) did not improve when NH4/+-N was determined or when sampling was done up to a 60-cm depth. In the second experiment, there was a good relationship between the RY and NO3/--N concentration (0-30 cm) at V6 (R2 = 0.47), and the R2 value increased (R2 = 0.61) when the preceding crop was wheat (Triticum aestivum L.). Soil NO3/--N critical concentrations ranged between 17 and 27 mg kg-1 and were associated with a RY of 0.92 or higher in both experiments. The results of this study show that the PSNT can be used to evaluate preplant N applications as a complementary method to N budget in maize under different management practices.