Effects of Supplementary Irrigation Plus Humic Acid Application on Olive Production

A field study was conducted to investigate the effects of supplementary irrigation plus humic acid application on fruit yield, oil production and nutrient uptake of olive trees. Olive orchard located at Nabuls district, Palestine was used for conducting the field experiment during the growing period of 2011. Seventy-years-old olive trees “Souri cultivar” spaced at 10m×10m, were selected for the experiment. The field was divided into three treatments; with five replicates per each treatment. Each treatment has an area of one hectare with a plant density of 100 trees per hectare. Treatments consisted of application of three different irrigation water regimes as follows: Irrigation water plus humic acid, irrigation water only and no irrigation (rain-fed). Irrigation water was applied seven times at a rate of 430 l per tree, resulting in a total amount of three cubic meters per tree during summer months. Liquid organic fertilizer having 12% humic acid was applied with irrigation water once at a rate of 250cc per tree during the first irrigation application.
Results of this study indicated that, the fruit yield of treatment irrigated with water plus humic acid was 78kg per tree, and 56kg per tree for treatment irrigated with only water, while the rain-fed treatment gave only 36kg per tree. Moreover, the higher oil yield was observed under water plus humic acid application (16kg per tree), while the rain-fed gave only (6kg per tree). In addition to that, the mean fruit weight of treatment irrigated with water plus humic acid was 2.1g, and 1.6g for treatment irrigated with only water, while the rain-fed treatment was 1.1g.
The supplementary irrigation with three cubic meters of water per tree plus humic acid application have increased the fruit yield by 56.4% and oil yield by 62.5% compared to the rain-fed treatment.