Effect of zinc on nitrogen transformation during composting process and in soil

Abstract

The influence of Zn on nitrogen partitioning in different organic fractions during plant composting and on nitrogen transformation in compost amended soil added with ammonium sulphate, was investigated. ¹⁵N labelled maize plants (stems and leaves) were composted with and without high level of ZnSO₄ so obtaining a Zn enriched compost, (4000 mg kg⁻¹ of Zn), and a low Zn compost (control compost). The carbon and nitrogen recovery in the alkali insoluble, alkali soluble-acid insoluble and alkali and acid soluble fractions showed that two different end-products were obtained. In fact the presence of Zn induced a decrease on the rate of carbon compounds humification and the lowering of alkali insoluble nitrogen level.

In order to study the mineralization rate of the two composts and to compare the effect of the Zn-enriched compost with the direct effect of inorganic zinc on nitrogen transformation in soil, two incubation experiments were conducted over 3 months under a controlled greenhouse, one without plants, the second with a test plant (wheat). At different incubation time KC1 soluble NO₃-N and NH₄-N, and biomass-N were determined in soil and yield and nitrogen concentrations were determined in plants.