Enhancing seed yield and quality of Egyptian clover (Trifolium alexandrinum L.) with foliar application of bio-regulators

Egyptian clover (Trifolium alexandrinum L.) is the most important winter legume fodder crop grown under irrigated conditions in Asia. There is a serious shortage of good quality seed of Egyptian clover due to poor seed yield production under hot and dry conditions prevailing during flowering and seed setting. Application of bio-regulators at pre-flowering stage is known to induce more flowering and increase seed production in many crops. A field experiment was conducted for three years (2008-2011) to investigate the effect of foliar application of five bio-regulators applied at different concentrations namely, sodium benzoate (NaC7H5O2) at 100 mg L−1 and 150 mg L−1, salicylic acid (C6H4(OH)COOH) at 50 mg L−1 and 100 mg L−1, calcium chloride (CaCl2) at 0.5% and 1.0%, potassium nitrate (KNO3) at 1% and 2% and naphthalene acetic acid (C10H12O2) at 25 mg L−1 on yield parameters and seed yield of two cultivars (BL 42 and BL 1) of Egyptian clover. Starting at flower initiation stage, three foliar sprays of each bio-regulator were applied at weekly interval. Cultivar BL 42 recorded significantly higher tillers plant−1, seeds head−1, green fodder yield and seed yield than BL 1. Foliar application of bio-regulators at different concentrations increased the seed yield of Egyptian clover by 13.2-32.5% compared to untreated control. Among all the bio-regulators, foliar application of salicylic acid at 50 mg L−1 and KNO3 at 2% recorded the maximum heads m−2, seeds head−1, 1000-seed weight, seed yield and seed quality (germination percentage and seedling vigor index), which were significantly higher than foliar application of the other bio-regulators (except 1% CaCl2) and the control. Sodium benzoate showed minimum effect on seed yield, but was significantly better than control.