Abstract
Studies were carried out to determine the optimum soil property limits on fruit yield and quality of Nagpur mandarin (Citrus reticulata Blanco) grown under the hot sub-humid tropical climate of Central India. The optimum limit of various soil properties were soil pH 7.6; electrical conductivity (EC), 0.22 dS m-1; free CaCO3, 11.8%; sand, 25.5% silt 28.2%; clay, 46.3%; water soluble Ca2+, 171.1 mg L-1; Mg2+, 52.1 mg L-1; Na+ , 1.1 mg L-1; K+ 2.1 mg L-1 exchangeable Ca2+, 25.6 cmol (P+) kg-1; Mg2+, 10.2 cmol (P+) kg-1; Na, 1.4 cmol (P+) kg-1; K+ 5.2 cmol (P+) kg-1; cation exchange capacity, 42.4 cmol (P+) kg-1; available N, 118.1 mg kg-1; P, 10.2 mg kg-1; K, 220.1 mg kg-1; Fe, 14.1 mg kg-1; Mn, 10.5 mg kg-1; Cu, 2.2 mg kg-1; and Zn 1.0 mg kg-1 using multivariate quadratic correlation and regression analyses for the 0-15 cm soil depth. For the 15-30 cm soil depth, the optimum limit was soil pH, 7.5; EC, 0.18 dS m-1; free CaCO3, 14.6%; sand, 28.5%; silt, 20.5%; clay, 51.3%; water soluble Ca2+, 182.0 mg L-1; Mg2+, 62.5 mg L-1; Na+, 1.4 mg L-1; K+, 2.6 mg L-1; exchangeable Ca2+, 32.6 cmol (P+) kg-1; Mg2+, 9.2 cmol (P+) kg-1, Na+, 1.8 cmol (P+) kg-1; K+, 2.6 cmol (P+) kg-1; cation exchange capacity 46.2 cmol (P+) kg-1 available N 102.4 mg kg-1; P, 11.4 mg kg-1; K, 210.5 mg kg-1; Fe, 12.4 mg kg-1; Mn, 8.1 mg kg-1; Cu, 1.8 mg kg-1; and Zn, 0.82 mg kg-1. Beyond the 15-30 cm depth, the correlations were low. The presence of higher free lime in the form of concretions in montmorillonitic clay soils increased the yield and quality of Nagpur mandarin. The role of CaCO3 concretions was established to act as a source of regulated supply of micronutrients under the combined influence of argillo-pedoturbation and consistent use of farmyard manure.
