Effect of Sulfur and Manure on Yield and Quality of Date Fruit c.v Barhee

Date palm is considered as one of the important fruit trees in Iran. According to agriculture statistic book of Iran (2015-2016), mature date plantation area and production of Iran are 230000 hectares and more than 1000000 tons, respectively. This crop usually is planted in south of Iran where the soils are calcareous with high pH. The high soil pH causes reduction of nutrient elements absorption and yield. Thus, finding a solution for this problem is necessary. The investigations indicate that application of elemental sulfur along with Thiobacillus inoculant in soil reduces local pH in rhizosphere area due to sulfur oxidation. The reduced pH of calcareous soil can increase the availability of other essential nutrients resulting in an increase in the nutrient uptake by plants. In addition, uncontrolled use of chemical fertilizers destroys soil structure and decreases organic matter resulting in a more dense soil. This research was conducted to assess the effects of sulfur along with manure on yield improvement and fruit quality as well as the consumption amount of chemical fertilizers. In order to evaluate the effect of elemental sulfur along with Thiobacilli bacteria and manure on quantitative and qualitative characteristics of date fruit, an experiment was carried out in randomized completed block design (RCBD) with six treatments and four replications on 24 fruitful, 25 years old date palm (cv. Barhee), in Ahwaz (Khuzestan Province). The treatments were: T1= Control (without any fertilizer), T2= (application of chemical fertilizer based on soil test for each date palm), T3= (application of 30 kg manure based on general recommendation for each date palm), T4= T3 + (application of elemental sulfur mixed with Thiobacillus inoculant) as 5% of manure, T5= T3 + (application of elemental sulfur mixed with Thiobacillus inoculant) as 10% of manure and T6= T3 (application of elemental sulfur mixed with Thiobacillus inoculant) as 15% of manure. Before the treatments application, soil and water were sampled and analyzed. In second treatment, macronutrient chemical fertilizers were also applied. Source of nitrogen, phosphorus and potassium were urea, triple super phosphate and potassium sulfate, respectively. The nitrogen fertilizer was split and applied in February and May (the next year). Furthermore, all phosphorus and potassium fertilizers were used in February. These treatments were carried out along with manure (30 kg) and chemical micronutrient fertilizers applied based on general recommendation (i.e. 150 g of zinc sulfate, iron sulfate, copper sulfate and manganese sulfate). In third treatment, manure (30 kg) was applied based on general recommendation for each date palm. In T4, T5 and T5 treatments, 500g of Thiobacillus inoculant was mixed with 25 kg of elemental sulfur and then consumed base on 5, 10 and 15% of manure, respectively. All treatments were undertaken during winter by local placement method (Chalkood). Agro-technical practices such as pollination, thinning and irrigation were done according to local practice. Each year, in May, 20-25 leaflets from middle of leaf in second row were picked up, and their mineral nutrients were analyzed. At harvesting time, yield, average of weight, length, diameter and volume of fresh fruit, weight of stone and weight ratio of fruit pulp to its stone, pH, acidity, brix, total and reducing sugars in fruits were determined. The obtained data were analyzed with MSTATC statistical program and mean comparison was conducted using the Duncan’s Multiple rang test. The results showed that using sulfur along with Thiobacillus bacteria and manure had significant effect on leaf phosphorus concentration at the 1% level and on yield and some quantitative characteristics such as weight, length, diameter, volume and pulp weight of fruit fresh and concentration of nitrogen at the 5% level. Sulfur application did not, however, significantly affect the leaf potassium concentration, stone weight, weight ratio of fruit pulp to its stone, pH, acidity, brix, reducing sugar and total sugar of fruit. As a result, application of 1500 g elemental sulfur (mixed with Thiobacillus inoculant) along with 30 kg manure for each date palm is recommended to improve yield and fruit quality and to reduce chemical fertilizer application.