The effect of Chemical and Hand Cluster Thinning on Some Quantitative and Qualitative Characteristics of Date Palm Fruits cv. Estameran

The date palm tree tolerates high temperatures, drought and salinity more than the other fruit crops that is why date palm tree is named the tree of life in the desert. A conventional date palm management practices is fruit thinning. Fruit thinning allow the remaining fruits to develop larger sizes and better qualities. Also, fruit thinning helps to overcome the alternate bearing problems. The purpose of this research to assess the effect of chemical and hand thinning on several fruit properties of date palm cv. Estameran.

This study was conducted to investigate the effect of chemical and hand thinning on fruit characteristics of ‘Estameran’ date palm as randomized complete block design with three replications in an orchard with 1.5 hectares area, located at Ferdows village in Shushtar city. Experimental treatments included T1 (control), T2 (removal of 1/3 ends of spikelets at flowering stage), T3 (removal of 1/3 ends of spikelet in Kimiri stage), T4 (removal of 1/3 number of spikelets in Kimiri stage), T5, T6 and T7 (that were chemically thinned by spraying naphthalene acetic acid (NAA) at 50, 100 and 150 mg/l concentrations at flowering stage, respectively). The fruits were harvested at tamar stage and characteristics measured included: fruit length, diameter, fresh weight, fresh and dry flash fruit, seed length, seed fresh and dry weight, fresh flash weight to seed weight ratio, fruit volume, yield per spike, TSS, pH, total sugar, reducing sugar, non- reducing sugar and fruit color attributes (L*, a*, b*, hue and chroma).

The results showed that chemical thinning with 100 mg / l NAA concentration (T6 treatment) increased significantly fresh weight (10.56 g), dry weight (9.86 g), and volume (11.03 cm3) of fruit.The highest fruit flash to seed ratio (11.47) was obtained in chemically thinning by NAA at 100 mg/l (T6).The least seed length (2.33 cm) was acquired at removal of 1/3 ends of spikelet at the flowering stage (T2) but it was not significant with T3 and T5 treatments. Chemical thinning fruit by 150 mg/l NAA concentration at the flowering stage reduced yield per spike (T7). The highest amount of non-reducing sugars was obtained in T5 (46.19%) and T6 (43.13%) treatments. The maximum amount of L* indicator was obtained in T3 (19.32) and T1 (19.09) treatments. Moreover the highest amount of a* indicator (9.08) and b* indicator (11.75) were acquired in T2. The minimum amount of hue (27.62) was obtained in control (T1) and the maximum amount of chroma (15.02) was obtained in T2 treatments.

According to the finding of this research, both hand thinning and chemical thinning improved the fruit properties. Due to the fact that chemical thinning by 100 mg/l NAA concentration at flowering stage (T6) had a more effective impact on fruit characteristics, and also the chemical thinning is less expensive than hand thinning, it can be concluded that T6 treatment is more effective and it is recommended