Effect of Source of Organic Matter Level and Phosphorous Level on Phosphorous Forms and Humic Acids Release in Gypsiferous Soil

Abstract

Abstract A laboratory experiment was conducted in the Department of Soil Sciences and Water Resources, College of Agriculture/Tikrit University for the year 2019 for the purpose of studying the effect of the source and level of organic matter and the level of added phosphorous on the level of phosphorous forms and humic acids in gypsum soil. A factorial experiment was conducted with three factors: The first factor: the type of organic matter (sheep manure and compost), the second factor: the level of organic matter as follows (0.5, 1.0, 1.5)% of the weight of the soil, and the third factor: it included phosphorous levels (0, 40, 80, 120) mg kg −1. The experiment was carried out in a complete randomization design (RCD) with three replications. To reach the field capacity to maintain the humidity of the experimental units, after the end of the incubation period (two months), the samples were air-dried, ground and passed through a sieve with holes (2) mm in diameter, then humic and fulvic acids, soluble, ready-made and organic acids were measured. With water and phosphorous prepared and organic by increasing the level of organic matter added, 1.5% was the best. It was also noted that the best level of phosphorous for the above indicators was the level (120) mg kg−1 compared to the rest of the levels, and that sheep manure outperformed the organic fertilizer in all the studied traits. Interventional treatment of 1.5% of the residual organic matter at a level of (120) mg kg−1 gave the highest significant effect, and the concentrations of humic and fulvic acid were (8.35 and 2.95) g kg−1 respectively. The treatment gave 1.5% organic matter for sheep manure and (120) mg kg−1 which is the highest value in the amount of water-soluble, ready-made and organic phosphorus with an average of (13.80, 71.35 and 167.44) mg kg−1 respectively.