Effect of soil application of humic acid and bio-humic on yield and fruit quality of “Kalamata” olive trees

Abstract

Abstract Background The present study was carried out during the two successive seasons of 2016 and 2017 on “Kalamata” olive trees (Olea europaea L.), at a private orchard located on Cairo-Ismailia Km 107 desert Road, Egypt. The trees were treated with four soil applications as follows: (T1) control (water only), (T2) organic matter of 10 kg chicken manure was added in both side of the tree under drip irrigation system at the 1st week of January, (T3) organic matter + 100 cm3 humic acid (Actosol®) for each tree, (T4) organic matter + bio-humic which contain 100 cm3 Actosol® and 150 cm3 of Azotobacter chroococcum, Bacillus megaterium, and Bacillus circulans in equal doses. Humic acid and bio-humic were added 3 times at the 1st week of March (full bloom), at 1st week of May (starting fruit set stage), and at the last week of July in the third stage of fruit development (70% of final fruit size) to study the effect of humic acid and bio-humic on the yield and fruit quality of Kalamata olive trees. Results The result showed that all treatments improve the nutrient status (N, P, K, Ca, Mg, Fe, Zn, Mn, Cu) of the leaves, yield (kg/tree) and fruit quality, i.e., fruit weight, volume, specific gravity, dimension, and shape index, as well as fruit moisture content percentage and oil percentage in FW and DW than the control. Within all treatments, the bio-humic treatment (T4) is recommended, since it had the highest value of these parameters in comparison with the other treatments or control. Conclusion It could be concluded that improving yield and fruit quality attributed to the positive effect of organic matter alone or in combination with humic or bio-humic in increasing the cation exchange capacity of the soil, reducing soil pH, enhancing the root development, increasing the root/shoot ratio, and production of root hairs of olive trees which increase the active uptake for most of the nutrients in the soil. In addition, bio-humic contains three bacteria that are now considered as plant growth-promoting rhizobacteria (PGPR) that play a great role in providing trees with NPK as bio-fertilizers and increased also the mineral status. Therefore, bio-humic positive effects reflected on improving the yield and fruit quality of Kalamata olive trees. In general, organic manure in combination with bio-humic had great effects on improving the yield and fruit quality of Kalamata olive trees than using organic manure alone or use organic manure combined with humic acid.