Two experiments were conducted, the first laboratory experiment (incubation) was conducted to study the chemical Kinetics of phosphorous release, and the other was field experiment to study the effect of Triple super phosphate and different levels of humic acid in growth and yield of corn. Laboratory experiment was carried out to study the Kinetics of phosphorus release triple super phosphate with levels 0, 60, 80 and 100% P of recommended fertilizer dose and three levels of humic acids 0, 20, 40 Kg.h-1. After eight time of incubation, the available phosphorus was measured in the soil. The data were subjected to mathematical analysis using five kinetic equations.
The field experiment was carried out in silty clay loam soil to study the available phosphorus added from triple super phosphate to soil with humic acids and their impact on growth of corn cultivar (fijer 1), using factorial experiment with design of randomized complete block, with three replicates, and two factors: four levels of triple super phosphate 40, 60, 80, and 100% P of recommended dose of fertilizer and three levels of humic acids 0, 20, 40 Kg h-1. Results of the laboratory experiment indicated that decreased concentration of available phosphorus release with the time for all levels of phosphate fertilizer. The addition of humic acids at the levels of 20 and 40 kg ha-1 increase available phosphorus for any time of incubation. Second order equation gave the highest determination coefficient and the lowest standard error, the half time of phosphorus disappearance increased with the increased level of humic acid, it increased from 35.71 days to 38.46 and 41.66 days for 20 and 40 kg h-1 levels respectively. Results of the field experiment showed a significant increase in plant height, dry weight, plant yield, weight of 300 grains and total grain yield with increased levels of phosphorus and humic acid added. A significant increase were obtained in plant height, dry weight, plant yield, weight of 300 grains, total grain yield with increasing levels of humic acids for about 4.9, 9.99, 10.6, 3.82 and 10.61% respectively by adding the level of 40 kg h-1 comparing with control treatment