New Soil Fertility Norms for Nagpur Mandarin from Summer Flush Using DRIS

The survey was undertaken and 10 to 13 years old 75 bearing orchards of Nagpur mandarin from summer flush from Western Vidarbha region of Maharashtra state were selected to establish soil fertility norms using diagnosis and recommendation integrated system (DRIS). DRIS norms as new ratings for 14 soil fertility parameters were derived from mean and standard deviation and divided into five classes, viz., very low, low, optimum, high and excess for diagnosis purpose. As per norms with an optimum range of nutrients, the optimum yield level of Nagpur mandarin ranging from 802 to 1433 fruits per tree was possible. The evaluation of orchard soils showed that the soil characteristics viz., pH, EC and organic carbon; major nutrients viz., K₂O, Mg and S as well as micronutrients viz., Fe, Mn, and Zn do not affect yield as they were in acceptable or adequate limit in soil. Low available N, P₂O₅, Ca and Cu; and higher CaCO₃ in low yielding orchard soils were found to be yield limiting. The new DRIS norms for yield showed that the yield level should be considered as ‘low’ when it is less than 801 fruits per tree in summer flush.