Micronutrient Zn, Cu, Fe and Mn Indexation and Zn Nutrition Management in the Apple Orchards of Murree

Quality and yield of major fruits grown in country are far below their potential despite of favorable climatic conditions. Average yield of apple orchards in Pakistan is alarmingly lower than other apple producing countries in the world. In the fruit crops, either nutrient use is below optimum or in imbalanced proportions. Micronutrient disorder along with nitrogen, phosphorous and potassium deficiencies are of economic significance in this regard. It is estimated that Fe and zinc deficiencies are widespread occurring in about 30 to 50% of cultivated soils on the world scale. Murree is the only apple growing region in the Punjab Pakistan. Geo-statistics and GIS as diagnostic norms have not been used for nutrient indexation in the apple orchards and were neglected from nutrition management point of view. A field survey was conducted to examine the spatial dependence of micronutrients and to prepare the spatial distribution maps for the micronutrients in the soils. Field trials were conducted for site specific zinc nutrition assessment. The specific objectives of study were: (i) Micronutrients indexation (zinc, copper, iron and manganese) of soil and foliage of apple orchards in Murree (ii) Mapping and geo-statistical analysis of micronutrients in apple cultivated Murree area (iii) Impact of zinc nutrition on apple yield and fruit quality parameters. One hundred and eighty soil and associated foliage samples were collected from 30 selected apple orchards using grid of 6×6 m. General deficiency of plant available zinc prevailed in the orchard soils of Murree area followed by slight Mn deficiency. Widespread deficiency of zinc existed in the foliage of apple orchards followed by site-specific deficiency of manganese, iron and copper respectively. Plant available 2 zinc, copper and manganese were moderately spatial dependant in the surface and strongly spatial dependent in the subsurface and lower soil depth whereas moderate spatial dependence of plant available Fe at three depths was observed. Moderate to strong spatial dependence allowed us to prepare the digital maps for spatial distribution of micronutrients in the area. Moderate to strong spatial dependence of plant available micronutrient indicated a need for the development of variable fertilizer (micronutrient) rate technology by conducting field trials in various zones delineated in this study. Field trials were conducted by selecting 6 apple orchards, two from each low, medium and adequate in soil zinc but low in foliage zinc content. Treatment plan included T1= Zn 0 g/ tree, T2 = Zn 20 g/ tree, T3 = Zn 30 g/ tree and T4 = Zn 40 g/ tree with the basal dose of NPK per tree. Zinc fertilizer application resulted in increase in the apple yield and yield components. Thirty gram zinc produced maximum yield in the low zinc soils while twenty gram zinc resulted in optimum yield in medium and high zinc soils. Zinc fertilization increased size, number, yield and firmness of fruit. Zinc application decreased titratable acidity and relative electrical conductivity. Significant interaction between the treatments and location manifested differential response due to native zinc content in the soils.