Effects of Cow Manure, Ammonium Sulfate and Potassium Sulfate on Physico-Chemical Indices of Fruit and Leaf of Mazafati Date (Phoenix Dactylifera L.)

Date palm (Phoenix dactylifera L.) is one of the most important fruit species grown in Iran. This plant is mainly grown in the south of the country, where pH of soil is high, resulting in poor nutrient uptake. Furthermore, because of high yield and annual pruning of date palm, large amounts of macro and micronutrients are removed from soil. So, annual fertilizing should be applied for good performance. Research shows that use of manure alone or in combination with mineral fertilizers improves physico-chemical indices of fruits and leaves of palm trees. Regarding to high nutrition dependency of date palm, it is necessary to evaluate the effect of different fertilizers on physico-chemical indices of its leaf and fruit. The main objectives of this study were thus to evaluate the effect of cow manure, ammonium sulfate and potassium sulfate on physico-chemical indices in fruit and leaf of Mazafati date.
This study was conducted in bam zone, Kerman, Iran, in 2011- 2012. The area was located at 28°53′40′′N latitude, 58°37′18′′E longitude and 1050 m above sea level. A factorial experiment in a randomized complete block design was performed during month of March. Factors included ammonium sulfate (0, 500 and 1000 g/tree), potassium sulfate (0, 750 and 1500 g/tree) accompanied by cow manure (5 kg/tree). For leaf and fruit analysis, sampling was performed during month of June. Physico-chemical indices including nitrogen, potassium, iron, chlorophyll a, b and total, carotenoid, fruit weight, fruit diameter, fruit length, TSS and TSS/TA were evaluated. Chlorophyll was measured by using the method of Lichtenthaler (1987). Total soluble solid (TSS) was measured by using refractometer. Statistical analysis was performed using SPSS software and the treatment means were separated by Duncan’s multiple range tests.
Results showed that because of supplying nitrogen, sulfur and potassium and their significant effects on noted physico-chemical indices, the highest nitrogen and iron content, photosynthetic pigments of carotenoid and chlorophyll (a and total) of leaf, and fruit weight were obtained in treatments of ammonium sulfate (1000 g/tree) and potassium sulfate (1500 g/tree) combination with cow manure (5 kg/tree). The highest potassium content of leaf, TSS and TSS/TA ratio of fruit were obtained by using ammonium sulfate (500 g/tree) and potassium sulfate (1500 g/tree) in combination with cow manure. The general increase in physico-chemical indices of fruits and leaves of date palm by the application of cow manure plus mineral fertilizer might be due to the increase in the availability of nutrients especially available N, P and K in the soil. In many reports, the effects of mineral fertilizers on nitrogen, potassium and iron content of the plant tissues were discussed. For example, date palm (two cultivars including Zaghloul and Samany) treated by ammonium nitrate and nitrobean (a bio-fertilizer) had the highest amount of leaf nitrogen and potassium. The highest rates of nitrogen, iron and potassium in palm fruit were obtained from cow manure in combination with NPK. Nitrogen, iron and potassium contents of the date and pistachio were increased by using ammonium sulfate fertilizer. Fruit weight, length, diameter and dry weight increased, while fruit moisture content decreased by organic manures either alone or in combination with mineral NPK as compared to the mineral N. Higher fruit TSS was obtained by the application of organic manures alone or in combination with mineral NPK as compared with mineral fertilization alone. Nitrogen concentration can be increased by using nitrogen fertilizer, for example ammonium increased leaf nitrogen concentration more than nitrate. Mineral nutrient, especially sulfur and nitrogen supplied by ammonium sulphate and potassium sulphate, increased the content of chlorophyll and carotenoid due to their roles in the synthesis of these compounds. Higher potassium content of leaves promotes photosynthetic rate of chloroplast, phloem transport of photosynthates to sink tissues and finally improves quality and yield of the fruit, which is associated with high sugar content.
For feeding of date palm tree, cow manure fertilization alone is insufficient. Ammonium sulfate and potassium sulfate alone or in combination with cow manure could improve physico-chemical indices of leaves and fruits. This mixed fertilizer, supplying nitrogen, potassium and sulfur macronutrients, had significant effect on physico-chemical parameters, and subsequently improved the content of nitrogen, iron, potassium, photosynthetic pigments (a, b and total, carotenoid), TSS, TSS/TA ratio and the fruit weight.