Nitrogen fertilizers for spring barley and wheat

Abstract

1. Ten experiments on spring barley (mainly Proctor) and four on spring wheat (mainly Atle) in 1954–6 compared 0·25 and 0·5 cwt. N/acre (as ammonium sulphate) when drilled with the seed, with dressings broadcast before sowing. Tests were also made of ‘Nitro-Chalk’ dressings given in mid-May. In heavier split applications seedbed dressings were supplemented by top-dressings of 0·5 cwt. N/acre. 2. Barley gave much larger average responses than wheat. For barley combine-drilling 0·25 or 0·5 cwt. N/acre gave consistently larger yields than broadcasting the same nitrogen dressing on the seedbed; for wheat combine-drilling gave slightly higher yields at the high rate of dressing only. 3. For both crops 0·5 cwt./acre of N drilled with the seed was almost sufficient for maximum yields, but where only 0·25 cwt. N was applied at sowing a mid-May top-dressing of 0·5 cwt. N/acre gave higher yields. 4. At most centres May top-dressings of ‘Nitro-Chalk’ gave lower yields than equivalent ammonium sulphate drilled with the seed. Yields were often reduced by lodging on plots which received seedbed dressings plus top-dressing or the heavier rates of top-dressing alone; these treatments also reduced the quality of the grain. Combine-drilled or broadcast seedbed dressings did not cause serious lodging or reduce grain quality. 5. 0·25 or 0·5 cwt. N/acre broadcast on the seedbed or combine-drilled had little effect on the percentage of nitrogen in the grain; equivalent topdressings in mid-May consistently increased nitrogen content. Seedbed dressings plus top-dressings supplying heavier total quantities of nitrogen continued to increase nitrogen percentage in grain without giving any increase in yield.