Germination and growth of Pinus caribaea directly sown into containers as influenced by shade, phosphate and captan

Abstract

A split-plot factorial experiment was conducted, using three replications of the main treatments: shade and no shade after germination, superphosphate fertilizer with and without liquid captan fungicide. Five Pinus caribaea ra hondurensis seeds were sown in each polyethylene bag. Germination was 57 percent, but 26 percent of the seedlings did not survive. In the final result, 92 percent of the bags had at least one surviving seedling. Extra seedlings in bags containing more than one seedling were removed at the beginning of the experiment, equivalent to a loss of 57 percent of potential trees The highly concentrated phosphate treatment caused a slight reduction in germination. More important, there was an increase in mortality associated with the combination of captan and phosphate. However, the only consequence of the effects on germination and mortality was a linear reduction (11 percent maximum reduction with 8 kg of phosphate) in the number of seedlings with increasing phosphate concentration. Each test unit was given 50 percent shade during the germination period. Then, shade was removed from half the test units. The shaded seedlings grew taller but had a smaller diameter than seedlings exposed to full sunlight. The captan treatment stimulated plant growth, especially diameter growth. The reason for this is unknown, since the effect did not become apparent until after the captan applications were completed Seedlings in bags containing phosphate grew more in diameter but were no taller than seedlings in bags without phosphate. Seedlings in bags whose sides had been exposed to direct sun were smaller than those not exposed. There was a high correlation between height and diameter when the effect of shade was removed, possibly indicating a dependent-independent variable relationship.The methods used in this experiment produced seedlings ready for planting in the field 27 weeks after sowing.