EFFECT OF HUMIC ACID ON GROWTH AND PRODUCTIVITY OF EGYPTIAN LIME TREES (Citrus aurantifolia Swingle) UNDER SALT STRESS CONDITIONS.

A field experiment was carried out during 2014/2015 and 2015/2016 seasons on Egyptian lime trees (Citrus urantifolia Swingle) at Baltim region, Kafr El-Sheikh governorate, Egypt, to study the effect of humic acid applications on soil properties, growth, yield, fruit quality and leaf nutrient content of Egyptian lime trees. Four treatments 0, 10, 20 and 30 ml/tree soil application were arranged in a randomized complete block design with three replicates.
The obtained results showed that application of Humic acid profoundly alleviated salinity effect by enhancing available nutrients and microbial activity. In addition, to it is induce a significant improvement of tree size and growth in terms of shoot length, leaves number/shoot, leaf area and canopy volume. Moreover, yield as kg/tree or number of fruits per tree was significantly increased with increasing humic acid level in both seasons. Fruit quality as weight (g), volume (cm3), juice% and SSC% were significantly increased by increasing humic acid levels, whereas acidity was slightly
decreased. Soil application of humic acid increased leaf N, P, K, Fe, Mn and Zn contents. The results suggested that humic acid treatment at 20 ml/tree have great potential in alleviating salinity stress on growth and productivity of
Egyptian lime trees under saline soil conditions.