Response of Irrigated Corn to Time, Rate, and Source of Applied N on Sandy Soils
1972
Jung, P. E. | Peterson, Laurence A. | Schrader, L. E.
To maximize N recovery by corn (Zea mays L.) on irrigated sandy soils, establishing the proper time for and rate of N application are essential. Three sources of N (urea, NH₄,NO₃, and KNO₃) were applied to corn at four rates (56, 112, 168, and 224 kg/ha of N) and six times application in all combinations. ‘Wisconsin 273’ (85 R.M.) and ‘Wisconsin 433’ (95 R.M.) were grown. Response was measured as grain yield, tissue yield (aerial portion at early dent), percentage N in tissue, percentage N in grain, and N uptake The N applied during either the 5th, 6th, 7th, or 8th week after planting was the most effective as shown by increased grain and tissue yields. Nitrogen applied after the 8th week was associated with a distinct reduction in N uptake and grain and tissue yields. Generally, percentage N in the grain and tissue increased with later N applications. The responses to urea and NH₄NO₃ were similar and both sources were sig~fificantly better than KNO₃. Nitrate reductase (NR) activity in the leaves and percentage N in grain and tissue increased with increasing rate of applied N. Yields of grain and tissue for Wisconsin 273 and Wisconsin 433 leveled off at the 112 and 168 kg/ha rates of N, respectively.
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