Nutrient management in Nagpur mandarin: frontier developments

Abstract

Citrus is considered highly nutrient responsive crop.  Occurrence of multiple nutrient deficiencies makes the redressal of such nutrient deficiencies all the more complex exercise. Site specific nutrient management studies find a greater weightage over conventional but classical progressive fertilization response studies, if constraint specific fertilization is to be worked out. Simultaneously use of integrated strategies viz., soil application of macronutrients (NPKS) and foliar application of micronutrients (Fe Mn Zn B); fertigation and integrated nutrient  management (INM) using rationale of organic manures fortified with microbial consortium based microbial reactor through isolation and characterization of native and dual purpose microbes and inorganic fertilizers have produced encouraging responses to improve production dividends underlying their undeniable utility. But, fertilizer requirement experiments have generated a vast variation in their recommendations depending upon orchard age, soil type and climatic features besides very limited information on micronutrients requirement. Application of these nutrients was substantially reduced (25-30%) using fertigation, thereby, adding an additional component of fertilizer use efficiency which could be effectively achieved through INM as well. There is a still a bigger constraint in form of non-availability of reproducible nutrient diagnostics to determine frequency distribution of nutrient constraints duly verifiable at orchard level.  Countrywide studies on development of nutrient diagnostics have suggested optimum range of nutrients based on leaf and soil analysis. For the optimum yield using DRIS (diagnosis and recommendation integrated system) based interpretation tool. Development of morphological descriptors and juice nutrient norms have further aid in defining the nutrient constraint more precisely.  Such studies strongly warrant refining diagnostics at regional, and still finer at orchard level, so that once the correct diagnosis of nutrient constraint is made, management becomes a comparatively easier task. Such management study starts with intervention of microbially loaded substrate as a part of rooting medium (rhizosphere engineering) in pre-bearing plants so that an adequate microbial pool of nutrients is built-up by the time plants enter into bearing stage in order to sustain quality production on one hand, and improve orchard longevity on the other hand.