A study on leaf nutritional diagnosis of olive

Abstract: 【Objective】In view of the fact that fertilization in domestic olive production areas is in a ca-sual way and that tree nutrition is prone to nutrient imbalance, it is necessary to establish leaf nutrition diagnosis standards so as to provide reference for balanced fertilization of olive.【Methods】A total of 66 representative olive orchards in fruiting period (15-18 a) in Longnan Wudu District, China's main olive production area, were selected as the sampling sites for the experiment. Mid and upper mature leaves of the current season branches of Leccino were collected from November to December. Optimum ratio range of diagnostic parameters of various nutrient elements in olive leaves was obtained by determining the contents of nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), copper (Cu), zinc (Zn) and iron (Fe) in leaves of mature shoots. With the DRIS method, the samples were divid-ed into the high-yield group and the low-yield group according to yield. Comprehensive method of diag-nostic fertilization (DRIS) was used to establish the nutrient diagnostic criteria for olive leaf, which was then used to diagnose the nutrition of the tested orchards and provide fertilization recommendations.【Results】The contents of nutrient elements in olive leaves with different yield levels were different. The mean leaf contents in the high-yield group were (17.23±1.756) g·kg^-1 for N, (1.20±0.214) g·kg^-1 for P, (6.93±0.92) g · kg^-1 for K, (11.49±0.673) g · kg^-1 for Ca, (0.91±0.084) g · kg^-1 for Ca, (0.010 6±0.002) g·kg^-1 for Zn, (0.121±0.055) g·kg^-1 for Fe, (0.030 0±0.007 5) g·kg^-1 for Mn, (0.020 6±0.006 9) g·kg^-1 for B and (0.005 8±0.005 3) g·kg^-1 for Cu. The coefficient of variation ranged from 5.86% to 91.34%. The mean leaf contents in the low-yield group were (13.30±2.239) g·kg^-1 for N, (1.14±0.235) g·kg^-1 for P, (6.29±0.82) g·kg^-1 for K, (10.64±1.289) g·kg^-1 for Ca, (0.94±0.098) g·kg^-1 for Mg, (0.010 4±0.006) g·kg^-1 for Zn, (0.123±0.065) g·kg^-1 for Fe, (0.033±0.009 8) g·kg^-1 for Mn, (0.020 9±0.006 1) g·kg^-1 for B and (0.004 0±0.002 8) g·kg^-1 for Cu. The coefficient of variation ranged from 10.38% to 73.58%. Except for Fe, the difference in nutrients between the two groups was significant. The coefficient of variation of each element was different in different groups. The coefficient of variation of N, P, K, Ca and Mg was between 12.06%-20.59%; that of Mn and B was 30%; and that of Zn, Fe and Cu was higher than 50%. N, P, K, Ca, and Mg were selected as the main elements for olive leaf nutrition diagnosis. F test was used to determine the difference between the two groups in ratios among 5 nutrient elements and 30 nutrient indicators. The results found that P/N, K/N, Ca/N, Mg/N, Ca/P, K/Ca, Mg/K and Mg/Ca, were significantly different, and htey were determined as the DRIS parameter calculated for the ol-ive leaf index, and the DRIS index of each element was calculated as follows: N index=1/4[-f(P/N)-f(K/N)-f(Ca/N)-f(Mg/N)], P index =1/2[f(P/N)-f(Ca/P)], K index=1/3[f(K/N)+f(K/Ca)-f(Mg/K)], Ca in-dex=1/4[f(Ca/N)+f(Ca/P)-f(K/Ca)-f(Mg/Ca)] and Mg index=1/3[f(Mg/N)+f(Mg/K)+f(Mg/Ca)]. The DRIS index was used to judge the profit and loss of nutrients and order in which olives need fertilizer in the 66 orchards tested. Both groups of olive orchards had coexistence of excessive and insufficient nutri-ents. The nutritional balance index (NBI) of the low-yield group was larger than that of the high-yield group; the high-yield group needed be supplemented with Mn, while the low-yield group with N.【Con-clusion】The results showed that the optimum concentrations of nutrients in leaves of olive trees were 1.6%-1.9% for N, 0.10%-0.14% for P, 0.6%-0.8% for K, 1.1%-1.22% for Ca, and 0.08%-0.10% for Mg. Both groups of olive orchards had cases of excessive and insufficient nutrients. Nutrient imbalance was the main factor for low yield. P and Mg were needed for most of the orchards in the high-yield group, while N fertilizer was needed for the low-yield group. DRIS method only provides the relative balance of elements, but does not reflect the specific index of the demand for an element, so it should be combined with other methods for evaluation of nutrients and for guidance of fertilization.