BIOGATION MODELING FOR MAXIMIZING INORGANIC FERTILIZER USE EFFICIENCY USING NUCLEAR TECHNIQUES

Abstract

A field experiment was constructed at the Experimental Farm of Soil and Water Research Department, Nuclear Research Center, Atomic Energy Authority, Egypt. This study aimed tofollowing direction of irrigation water movement horizontally and vertically in different depths of virgin sand soil, water scheduling and its correlation with nutrients movement, root distribution and microbial behavior under fertigation and biogation techniques. Common bean (Phaseolus vulgaris) cv Nebraska, was used as test plant to perform a proper management strategies of irrigation regime and fertilization rates and splitting through irrigating water (fertigation).Liquid broth of compatible Rhizobium inoculant was applied in irrigation water via drip irrigation system(biogation) technique. Un-inoculated and/or unfertilized control was also included.Labeled nitrogen fertilizer (15N) was applied in Ammonium Sulfate form with 2% 15N atom excess for tracing fertilizer behavior in soil and its use efficiency using fertigation technique. In addition, isotope dilution technique gave us the opportunity to estimate nitrogen derived from air (BNF) by common bean more accurately than other conventional methods. Fertigation and biogation techniques posed different patterns of nitrogen use efficiency and biological nitrogen fixed by different plant parts as affected by fertilizer rates and water regime. Neutron moisture meter was used to determine soil moisture before and after irrigation duration to estimate soil water depletion occurred in between as well as determination of active root depth. Interrelationship between soil moisture content and moisture retention as affected by biological behavior and nutrients movement in active absorption root zone of common bean was identified using Van-Genuchten model (1980). Depending on this model that can be estimated the losses of water through soil evaporation, those absorbed by root and those deeply leached to underground of active root zone. Keywords: BNF,Common bean, Fertigation,15N,Neutron gauge, Nitrogen use efficiency,Sand soil, Water movement,Water use efficiency.