Effect of phosphorus, chelated zinc and calcium on cotton seed yield, viability and seedling vigour

Stand establishment of cotton seedlings is one of the most critical stages in cotton production. Low-quality seed is a major contributing factor in stand failures. Cotton seed quality is affected to a large extent by its indeterminate growth habit which allows seed to set and develop over an extended period. Both seed size and seed density are correlated with planting seed quality in cotton. High seed quality and seedling vigour are thus requisites to consistent establishment of satisfactory stands. Plant nutrition using a balanced fertilisation programme with both macro and micro-nutrients has become very important in the production of high quality seed. In 1992 and 1993 at the Agricultural Research Center, Giza, Egypt, investigations were conducted on cotton cultivar Giza 75 (Gossypium barbadense L.), on the effect of soil P fertilisation (applied as calcium super phosphate. 15% P2O5 before the first irrigation three weeks after planting) rate (44 or 74 kg P2O5/ha) and foliar application of chelated zinc (applied twice, at 75 and 90 days after planting during square initiation and boiling stages at 0 or 40 ppm Zn, 960 l/ha) and calcium (applied twice at 80 and 95 days after planting at 0, 20, 40 or 60 ppm Ca, 960 l/ha) on seed yield, viability, and seedling vigour. Seed yield/plant and yield/plot, seed weight, seed viability (as indicated by first germination count, second germination count, and total germination count). seedling vigour (as indicated by length of hypocotyl, radicle and entire seedling, and seedling fresh and dry weight), and cool germination test performance (four, and seven day counts) increased as a result of the high P-rate (74 kg P2O5/ha), and from application of Zn, and Ca at different concentrations. No significant effect on germination rate index due to P-rates, application of Zn or Ca, was detected in either year. Most of the differences between the effects of Ca concentrations on the characters studied were not significant. There were no significant interactions between the variables involved in this study. Under the conditions of this study, applying P at 74 kg P2O5/ha and spraying cotton plants with Zn at 40 ppm and also with Ca at 60 ppm can be recommended to improve seed yield, viability, and seedling vigour.