Nutrient Availability to Corn From Dairy Manures and Fertilizer in a Calcareous Soil

The expansion of the dairy industry in southern Idaho has led to increased application of manures to meet crop nutrient demands that can alter the uptake pattern of both macronutrients and micronutrients. A greenhouse study was conducted to determine the effects of dairy manure, composted dairy manure, and fertilizer (monoammonium phosphate) application on soil test phosphorus (P), microbial activity, and nutrient uptake by silage corn (Zea mays). Two Portneuf soils, having either a low or high soil test P concentration, were amended with the three treatments at four application rates (25, 50, 100, and 200 mg P kg) with four replications of each treatment in a randomized complete design. Treatments were incubated for 2 weeks, then planted with corn grown for approximately 3 weeks. Soil samples were analyzed before planting, whereas plant samples were analyzed at the end of the growing period. Increases in Olsen P from P additions were greatest in the monoammonium phosphate and least in the manure-treated soils. Plant dry matter production and tissue P concentration did not differ with treatment. Tissue K increased with manure and compost addition, whereas tissue Ca decreased; there was also a decrease in tissue Mg with compost application. Tissue Zn increased with manure applications, whereas tissue Mn decreased with manure and compost application on the low-P soil. It is important to consider plant nutrient interactions when applying manure and compost to forage crops as imbalances in K, Ca, and Mg can have a negative impact on animal health.