Effect of Irrigation and Preplant Nitrogen Fertilizer Source on Maize in the Southern Great Plains

Table 2

Nitrogen fertilizer treatment structure applied to both irrigated and rain-fed plots in this study.

Treatment number	Preplant N rate	Preplant N source^a
	kg N ha^−1
1	0	—
2	90	UAN
3	90	AS
4	180	UAN
5	180	AS

UAN: urea ammonium nitrate (28-0-0); AS: ammonium sulfate (21-0-0); applied prior to planting and mechanically incorporated.