عنوان مقاله [English]
Quince with the scientific name "Cydonia oblonga Mill." is one of the most important horticultural products in the word including Iran. According to the average production from 1994 to 2020, Iran was the fourth largest quince producer in the world. Isfahan province is one of the most important centers of high quality quince production with 2432 hectares of cultivated area and annual production of 25986 tons. Most of the quince orchards are located in the cities of Natanz and Isfahan. Plant nutrition as an important factor in growth, is a function of nutrients and environmental conditions interactions. Assessing the nutritional status of plants is based on precise determination of nutrients and appropriate application method to diagnosis and interpret the results. Various methods have been used to evaluate the nutritional status of the plant, such as the Critical Value Approach (CVA), the Deviation from Optimum Percentage (DOP), the Diagnosis and Recommendation Integrated System (DRIS) and the Compositional Nutrient Diagnosis (CND). The CND method expresses interactions by considering the ratio of one element to the geometric mean of all elements. Then high and low functional groups are separated, by using mathematical and statistical methods and application of cumulative function of the variance ratio of nutrients and the chi-square distribution function. Finally, CND nutrients norms and indices such balance index are calculated step by step. Therefore, considering the importance of the quince production in the country and the lack of sufficient knowledge to determine its nutritional status, the present study was conducted with the aim of investigating the nutritional status of quince trees using the CND method and determining the nutrients norms for this product.
Materials and Methods
In order to evaluate the nutritional status of quince trees using the CND method, 28 orchards were selected in the cities of Isfahan and Natanz. The orchards were selected such a way that they had different ranges of yield. The geographical location was recorded for each orchard. Then random and composite sampling of leaves was done from branches without fruit in July 2018. Concentration of nitrogen phosphorous, potassium, calcium, magnesium, iron, manganese, zinc, copper and boron was measured in quince leaves. At the end of season, the yield was determined for each orchard. The orchards divided into two groups based on high and low yields. The CND norms, CND nutritional index and nutritional balance index (r2) were computed based on steps of Parent and Dafir. The balance index of nutritional elements (r2) was calculated by Keith-Nilson method based on the Chi-square statistical distribution function (K2) in Excel software.
Results and Discussion
According to results of cumulative distribution function of nutrient variance and considering the yield of 23 tons per hectare as the intermediate yield, 25% of the studied orchards were in the high yield group and 75% of the orchards were in the low yield group. After solving the third– rank cumulative function equations of the studied nutrients, the highest yield was obtained for potassium Fci (VK) = 21.98 and the lowest value was for nitrogen Fci (VN) = 15.37. CND standard norms of nutrients and residual value were described as: V*N= 2.91, V*P= 1.39, V*K= 2.91, V*Ca= 2.13, V*Mg= 1.35, V*Fe= -2.01, V*Mn= -3.12, V*Zn= -3.97, V*Cu= -4.85, V*B= -3.51 and V*Rd= 6.78. The CND nutrient index revealed that potassium and nitrogen had the most negative index among macronutrients in the low-yield orchard group. The low amount of soil organic matter and the high presence of sand can contribute to the negative nitrogen index. Among the micronutrients, the iron index was negative in 67.7% of the low-yield orchards. Zinc and copper had the next highest nutritional requirements in most orchards. The presence of calcareous conditions in the soil of the studied orchards may be one of the reasons for this observation. The estimation of the nutritional balance index indicated that the r2 value in orchards with low yield was 60.3% higher than that in high-yield orchards.
CND nutritional balance index (r2), specially in orchards with low yield was more than zero (20.85), indicating nutritional imbalance in these orchards. Proper management and balanced application of chemical fertilizers should be considered. This can increase the yield and quality of quince production.
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