The determination of nitrogen in heavy clay soils

Abstract

In determining the nitrogen content of the heavy black cotton soil of the Central Provinces, India, by the Kjeldahl process it is important that the determinations be carried out on moist and not on air-dried soil. These soils apparently contain a cementing material probably containing iron which is insoluble in concentrated sulphuric acid and protects organic matter in the interior of the compound particles from the action of the acid.It may be that these soils are peculiar in this respect, but it would seem of importance that other workers should take into account the possibility of error in the estimation of nitrogen when using air-dry soils.In conclusion it is with great pleasure that I acknowledge my indebtedness to Mr F. J. Plymen and Dr H. E. Annett for their valuable suggestions and advice during the course of this work.