Copper Fixation Kinetics in Semi-Arid Alkaline Soils of West Texas.

Total micronutrient concentration in soil is not often the best indicator of the plant available portion because of nutrient interactions with soil constituents resulting to its fixation. This study was designed to examine the fixation kinetics of added copper (Cu) in six semi-arid alkaline soils of West Texas. Findings indicated that on average, 35 and 39% of the added Cu was fixed after 14 and 90 days, respectively, indicating that majority of the added Cu was fixed within the first 14 days. The total amount of Cu fixed in the short term (first 14 days) was mostly influenced by organic matter (OM) content, while total amount fixed after 90 days was influenced by pH, OM, and calcium carbonate contents. The kinetics of the reactions (over 90 days) controlling Cu availability in these soils were better described by the power function model and poorly by the zero, first, and second order models, while reactions within the  first 35 days were better described by the second order model. Findings are important for understanding the fate of added micronutrient and its management in the semi-arid alkaline soils of West Texas.