The results of seventy-one field experiments to compare the effects on crop yields of the phosphate in Billingham nitrophosphates and in superphosphate are reported. The experiments tested nitrophosphates from a manufacturing process in course of development. The 1950 and 1951 products contained less water-soluble P2O5 and slaked less easily in water than the 1952 product.

All three Billingham nitrophosphates gave rather bigger increases in yields of grass and about the same increases in yields of swedes as superphosphate. The 1950 and 1951 products gave about 70% of the increases in yield given by super-phosphate on potatoes but the 1952 product gave about 90% of the increase with superphosphate. There was no evidence that powdery Billingham nitrophosphate was any more effective than granular material.

It is concluded that the phosphate in the 1952 Billingham nitrophosphate is, for practical purposes, as effective as that of superphosphate.

A continental nitrophosphate tested in 1952 gave poorer results than Billingham nitrophosphate. This product contained little water-soluble P2O6 and slaked very slowly in water.

Comment is made on the apparently poor average response of British grassland to phosphate fertilizer.