Experiments comparing concentrated and dilute NPK fertilizers and four nitrogen fertilizers on a range of crops

Abstract

1. In 1959 a concentrated granular fertilizer (15% N, 10% P₂O₅, 20% K₂O) was compared with an equivalent mixture of ammonium sulphate, superphosphate and muriate of potash (each supplying 0·75 or 1·50 cwt. N/acre) for potatoes. At Rothamsted (on heavy soil) the two fertilizers gave similar yields, but at Woburn (on light soil) the larger dressing of the concentrated fertilizer gave about 1 ton/acre more potatoes. In similar barley experiments a concentrated granular fertilizer (20% N, 10% P₂O₅, 10% K₂O) was compared with a dilute granular fertilizer (12% N, 6% P₂O₅, 6% K₂O); each was combine-drilled to supply 0·3 or 0·6 cwt. N/acre. At Rothamsted the two fertilizers gave identical yields, but at Woburn the concentrated fertilizer (at the double rate) gave significantly more grain.