Effect of mineral and organic fertilizers on the chemical characteristics and quality of date fruits

The study evaluated the effect of mineral and organic fertilizers with and without the supplementation of micronutrients on the chemical characteristics and quality of date fruits from two cultivars of date palm (Phoenix dactylifera L.) viz. Khalas and Khassab. Thirty date-palm trees from each of the cultivars, 6-7 years of age, were randomly selected and divided into 10 groups with 3 replicates in each group. The study was conducted in a completely randomized block design (RCBD) during the years 2002-2004 at Al-Fairoz Private Farms in Al-Batinah region, Sultanate of Oman. The fertilizers used were organic peat (80 L) either alone or with 1 kg of urea (divided into 4 & 5 equal N-doses) together with 500 g of triple super phosphate and 800 g of K₂SO₄ and with or without supplementation of micronutrients. The control did not include any fertilizers. The samples of date fruit were collected at " Rutab" stage (soft, ripe). Significant (P<0.05) differences were observed in the chemical characteristics and quality parameters of dates on different fertilizer applications as compared to control. The highest dry matter content was observed in both the date cultivars when mineral fertilizers (NPK, in 4-N doses) were supplemented with organic peat and micronutrients. The application of organic peat alone resulted in higher tannin and pectin contents but lower titeratable acidity (TA) in both the cultivars as compared to all other treatments. During the year 2004, both the cultivars showed lower pectin, tannin and moisture contents but higher pH values as compared to the years 2002 and 2003. Overall the application of organic peat over a period of 3 years in both cultivars increased the tannin contents, whereas the mineral fertilizers reduced it. The interactions between fertilizer application, year and stage of maturity were also significant (P<0.05) for DM, tannin and TA.