Nitrogen placement, row spacing, and furrow irrigation water positioning effects on corn yield

Furrow irrigation often leaches NO3-N. We hypothesized that banding and sid edressing N fertilizer on a nonirrigated side of a corn (Zea mays L.) row w ould maintain yield and decrease NO3-N leaching. In a 2-yr field study in s outhern Idaho on a Portneuf silt loam (coarse sitly, mixed, superactive, me sic Durinodic Xeric Haplocalcid), we evaluated the effects of (i) N placeme nt (broadcast vs. banded), (ii) row spacing (0.76 m vs. a modified 0.56 m), and (iii) irrigation water positioning (applying water to the same side or alternating sides of a row with successive irrigations) on field corn yiel d and IV uptake. We irrigated every second furrow nine times in 1988 and se ven times in 1989. Compared with broadcasting, banding maintained grain yie ld in 1988 and increased it by 11% in 1989. Where N was banded in 0.56-m ro ws in 1989, silage yield when only the nonfertilized furrow was irrigated w as 22.9 Mg ha(-1), which was 22% greater than when alternating furrows were irrigated. Compared with 0.56-m rows, the 0.76-m ro tss had no effect on 2 -yr average grain yield but tended to increase 2-yr average silage N. Bandi ng N on one side of a row, rather than broadcasting, and applying water all season to the furrow on the other side of the row maintained or increased grain yield, increased silage yield by up to 26%, and increased N uptake in silage by up to 21%, particularly from N-depleted profiles. Applying water to the same furrow, rather than alternating furrows, did not reduce yield or N uptake.