Effect of 8‐years fertilizer treatment on the ‘Protein‐nitrogen’ content of four cropped soils

Abstract ‘Protein‐nitrogen’ (α‐amino‐nitrogen released on acid hydrolysis), organic carbon and total nitrogen contents of four soil types which had been subjected to the same fertilizer treatments, cropping practices and weather conditions over 8 years are compared with values for similar unfertilized soils. In the case of a loam soil there were no significant differences in these values between fertilized and unfertilized soil, but with sandy loam, sand, and chalky sandy soils the three values were significantly lower in unfertilized than in fertilized soils. The differences in total nitrogen between fertilized and unfertilized soils were proportionally greater than were differences in protein‐nitrogen.