Methods of Placement for Increasing the Efficiency of N Fertilizers Applied in the Fall

In portions of the Prairie Provinces of Canada, fall-applied fertilizer N is often less effective in increasing yields of cereal crops than fertilizer N applied in the spring. Field experiments were conducted in northern and central Alberta on Udic Boroll, Boralfic Boroll, and Boralf soils to find if there was a consistent increase in yield and N uptake of barley (Hordeum vulgare L.) when fall-applied urea was placed in bands and in nests as compared to the conventional mixing into the soil. There were 14 field experiments with the fallapplications during 3 years, and 13 of the experiments were cropped. The crop was spring-sown barley. Fall-applied urea gave higher grain yield, recovery of N in grain and recovery of N in grain + straw when placed in 46 cm spaced bands, and more so in nests, than when urea was incorporated into soil in the conventional manner. Nests were obtained by placing the N fertilizer at a point in each area of 46 ✕ 46 cm and at a depth of approximately 5 cm. The average increases in grain yield from urea incorporated in the fall, from urea banded in the fall, from nest placement of urea applied in the fall, and from urea incorporated in the spring at seeding time were 810, 1220, 1530, and 1680 kg ha⁻¹, respectively. In the same order, the recoveries of fertilizer N in grain plus straw were 26, 40, 53, and 61% although values were similar for banding and nest placement in 5 of the 13 experiments. Nitrification of fall-applied N was slowed with banding and especially with nests, as compared to incorporation. With less nitrification, there was less over-winter loss of fallapplied N, apparently through reducing denitrification. As with urea, fall-applied aqua NH₃ placed in nests produced greater grain yield, N uptake by grain and N uptake by the whole plant as compared to aqua NH₃ injected in bands. There were six other cropped experiments where there was only spring application of nesting, banding, and mixing. With spring application, nest placement of urea was inferior to banding or mixing of urea, unless the spacing of nests was reduced from 46 ✕ 46 cm to 23 ✕ 23 cm or the application of nests was made 2 weeks before sowing with subsequent cultivation. Nest placement is an alternative to chemical inhibitors of nitrification with fall-applied N fertilizers.