Effects on barley and kale of NPK fertilizers containing differing proportions of urea and ammonium nitrate, and either triple superphosphate or mono-urea phosphate

Summary

Of eight experimental fertilizers (with %N; %P₂O₅; %K₂O ratios of 2:1:1) obtained, four contained triple superphosphate and four mono-urea phosphate; all contained muriate of potash. In the first four, urea supplied either 100, 66, 33 or 0% of the total N (ammonium nitrate supplied the remainder); in the second four, urea and ammonium nitrate supplied only the balance of the N, but in the same proportions.

For barley, each fertilizer was combine-drilled to give 0·5 or 1·0 cwt N/acre. In 1965, much rain fell after drilling, early growth was not harmed and yields from each fertilizer were the same. In 1966, dry weather followed sowing and all fertilizers checked growth; those containing urea killed many plants and diminished yields. Also, yields from the fertilizers containing urea phosphate were larger than from those containing superphosphate; thus urea phosphate was safer than urea alone. For kale, the fertilizers were broadcast in May to give 1·25 or 2·50 cwt N/acre. None seriously diminished plant number and yields from all were similar.

Increasing the proportion of urea in the fertilizers greatly increased %N in the barley grain in 1966, but not in 1965. The crops recovered more N from ammonium nitrate than from urea.