Nutrient diagnostics and fertilizer prescription in Citrus: A perspective analysis

Productivity of a crop depends essentially on the two premier facts, nutrient balance and the biological activity. The biggest constraint in making soil analysis more purposeful is the non-redressal of spatial variation in soil fertility. Conjoint use of geoinformatics (Geographical Information System, Global Positioning System, Remote Sensing) and site specific nutrient management strategy have offered an easier method of combating such pivotal factor driving into reduced fertilizer use efficiency. Sensor-based technology (called proximal sensing of nutrients on real time basis) has further added a new dimension in providing the nutrient supply as per canopy size (Normali sed difference vegetation index) using programmable multi-channel fertigation. Rhizosphere properties vis-á-vis microbial and nutrient dynamics has dictated soil fertility management options in recent past, especially in many of the perennial fruit crops badly suffering through recurrent replant failures. Identification, isolation and characterization of rhizosphere speci fic microbes and later their up-scaling in consortium mode has given some definite edge, especially, with mycor rhiza-based microbial consortium, in overcoming the multiple soilfertility constraints on one hand and successfully addressing the replant issues on the other hand. Dev elopment of microbial consortium (microbial reactor) exploiting the native and natural microbial synergisms (with twin role as growth promoter and antagonistic to soil borne pathogens) is one of the popular methods of managing multiple soil fertility constraints occurring within the rhi zosphere. Such rhizosphere specific consortia (often called as crop-mi crobiome) could further engineer rhizosphere’s nutrient demand and supply through loading with organic manures in a much value added form using a widely accepted concept like integrated nutrient management (INM).