Effect of Saline Irrigation Water and Humic Acid Application on Growth and Productivity of Two Cultivars of Cowpea (Vigna unguiculata L. Walp)

Two field experiment was carried out in the Experimental Farm of the Desert Research Center at Ras Sudr, South Sinai Governorate, during the two successive summer seasons of 2008 and 2009 to study the effect of the combinations between two cowpea cultivars, i.e. Kafr El- Shekh and Cream 7 with three saline irrigation water treatments, i.e., (3500, 4500 and 5500 ppm) and four levels of humic acid application (0, 2, 4 and 6 kg/ fed.) on growth, yield and its components, also chemical compositions of leaves and seeds of cowpea plants. Results revealed that: 1.Kafr El-Shekh cultivar surpassed than cream 7 cultivar in plant fresh weight, total pods yield, N, P, K uptake in addition to K/Na and Ca/Na ratio. Also, N, P, K, protein and carbohydrate content in cowpea seeds tissues. 2. The lowest values of plant growth, total pods yield N, P, K uptake and K/Na, Ca/Na ratio. Also, N, P, K, protein and carbohydrate content in cowpea seeds tissues were observed by the highest salinity level (5500 ppm). But this level significantly increased Na, Ca and Cl uptake by plant leaves, in addition to Cl and proline content in seeds tissues. 3. The effect of humic acid on the vegetative growth of cowpea plant i.e. plant height, number of branches, fresh weight, leaf area/ plant, total pods yield, N, P, K uptake and K/Na, Ca/Na ratio. Also N, P, K, protein and carbohydrate content in cowpea seeds showed significant increase with increasing the rate of humic acid application from 0, 3, 4.5 up to 6 kg/fed. 4. The interaction between cultivars and water salinity with humic acid application showed no statistical differences in both seasons.