Determining the compositional nutrient diagnosis (CND) norms and main nutrient interactions in “Valencia” orange orchards on calcareous soils

Abstract

To establish compositional nutrient diagnosis (CND) standards, in “Valencia” orange orchards (Citrus sinensis L. Osbeck), the leaf nutrient concentrations and yields of 234 commercial orchards were determined. The orchards nutritional status was evaluated through the compatible principal component analysis (PCA). The CND reference norms were calculated as V*N = 2.766 ± 0.167, V*P = 0.093 ± 0.199, V*K = 2.574 ± 0.097, V*Ca = 2.970 ± 0.217, V*Mg = 1.415 ± 0.116, V*S = 1.250 ± 0.200, V*Fe = −1.503 ± 0.212, V*Mn = −3.626 ± 0.327, V*Zn = −4.096 ± 0.431, V*Cu = −5.231 ± 0.166, V*B = −2.979 ± 0.187, V*Rd = 6.368 ± 0.074. The corresponding optimum concentration values of nutrients were N = 2.504 ± 0.348, P = 0.175 ± 0.040, K = 2.059 ± 0.227, Ca = 3.101 ± 0.664, Mg = 0.646 ± 0.071, S = 0.554 ± 0.108 in percent and Fe = 355.929 ± 80.601, Mn = 44.071 ± 14.409, Zn = 28.500 ± 12.126, Cu = 8.500 ± 1.698, B = 80.429 ± 14.516 in mg kg−1. According to PCA analysis the lower production in the “Valencia” orange orchards was mainly due to lower leaf concentration of S, Ca, B and Mg and a higher leaf concentration of K, Zn, Cu and Mn, respectively. Also, increment of leaf N and P in the high yielding subpopulation and leaf Fe in the low yielding subpopulation had significant effects on the increasing of fruit yield, especially under saline and calcareous soil conditions.