Relationship between yield and mineral element contents in leaves of four early walnut cultivars

The contents of mineral nutrition elements in the leaves of early walnut trees their correlation with yields were studied by comparing the four early cultivars in Jiyuan City in 2010 and 2011. The contents of N, P, K, Ca, Mg, Fe, Cu, Mn and Zn. In the leaves of four early walnut cultivars were determined at five phonological stages. The results show that the mean contents of nine nutrient elements are in order of CaNMgPK, FeMnZnCu. In all the four cultivars, Mn contents show the maximum variations with a rang from 127.69 mg/kg to 169.53 mg/kg, and K show the minimum variation with a range from 2.19 mg/kg to 2.26 mg/kg. The contents of N, P and K are higher at the leaf-expanding stage (17.45 g/kg, 5.54 g/kg and 2.93 g/kg, respectively), and lower at the deciduous pro-stage (17.45 g/kg, 2.66 g/kg and 1.86 g/kg, respectively). The contents of Ca, Mg, Fe and Mn keep slow increasing, Cu and Zn chane slightly. Generally, the nutrient contents of walnut trees are stable from May to July. There are significantly positive correlations among N, P and K contents, but the cotents of N and P are significant negatiely correlate with those of Ca, Mg, Mn and Cu. The yields are significant corelated with the N, P and K contents in leaves at shoot rapid\|growing stage, the correlation efficient are 0.819, 0.843 and 0.895 respectively, indicating the shoot rapid-growing stage the optimal leaf sampling time for nutrient diagnosis.