BEHAVIOUR OF CERTAIN SLOW RELEASE FERTILIZERS IN SOILS

Abstract

A study •was carried Out to evaluate the possibility of using certain non conventional fertilizers ( represented by sulphur coated urea and superphosphate + sulphur ) and cerealin biofertilization under different conditions of soil moisture regimes, conventional fertilizers ( represented by ammonium sulphate, urea and superphosphate ) being also included. Such study was performed using three approac.hes involving incubation, p•ot and field experiments, both rice and wheat being grown under flooding and soil field capacity moisture conditions, respectively. The performed study was accomplished through tracing the behaviour of the concerned fertilizers in soil and reflections on certain phases of plant behaviour including response of growth and status of both nitrogen and phosphorus.

For incubation experiments, nutrient release from non conventional fertilizers of either sulphur coated urea ( SCU) or superphosphate+ sulphur ( SPS) was relatively slow for extended period compared to conventional ones, such behaviour being more' obvio\uS under flooding conditions. For pot experiments, both dry matter content arid nutrient status in rice plants as ellas residual effect in soil were improved with application of non • conventional fertilizers; both SCU and SPS were superior, ammonium sulphate ( AS ) being someti'mes suitable particularly when accompanied with ( SPS ). In spite of that, no significancy was encountered among wheat treatments at early studied growth period. A complete dose of applied fertilizers, whether non conventional or conventional, accompanied with cerealin inoc lation gave relatively high value of growth for the studied wheat plants along with their nutrient status, such responses were extended to be reflected on the soil along with conventional fertilizers. Finally, biofertilizer inoculation with cerealin was generally favourable when accompanied with slow release fertilizers, such e.ffect being sometimes favourable even with the half dose of applied non conventional fertilizers. Under field conditions, growth as well as nutrient status in the studied rice and wheat plants were most favoured by using SCU or SPS accompanied with cerealin :noculation, residual effect being generally• more pronounced with conventional fertilizers.