Effects of Soluble Salts and Phosphorus From Dairy Manures On Idaho Soils and Potato Production.

In Idaho, potatoes are produced in fields with dairy waste application history. Dairy wastes are rich sources of potassium, calcium, magnesium, sodium and phosphorus, which can be applied in excess of plant demand. The objective of these field survey and greenhouse studies was to evaluate the current impact of dairy waste applications on soil soluble potassium, calcium, magnesium and sodium, sodium adsorption ratio, electrical conductivity, pH, Olsen phosphorus and potato production in Idaho. In 2009 and 2010, a field survey was conducted to determine soil soluble salts, Olsen phosphorus and grower reported yields in 84 south-central Idaho potato fields with history of dairy manure, dairy compost, dairy lagoon water and no dairy waste applications. A greenhouse study was conducted in 2010 to compare the effects of dairy manure, dairy compost and dairy lagoon water applied at or above typical rates and potassium, calcium, magnesium, sodium and phosphorus fertilizers on production of Russet Burbank potatoes grown in Portneuf silt loam. In the greenhouse study, soil soluble salts, Olsen phosphorus, plant nutrient uptake and tissue concentrations, plant and tuber dry matter, fresh tuber mass, tuber count, average dry matter per tuber and tuber specific gravity were measured. Results from the field survey and greenhouse studies demonstrate dairy waste applications increased both soil soluble potassium and Olsen phosphorus. In both studies, soil soluble calcium and magnesium were not significantly impacted by dairy waste applications. Dairy wastes did not increase sodium, sodium adsorption ratio, electrical conductivity, and pH to levels that would compromise potato yields or soil quality. In the greenhouse, potato plant potassium uptake increased with both lagoon water and compost applications, while only lagoon water increased potato plant magnesium uptake. Grower reported tuber yields, and greenhouse potato plant growth and tuber yield were not significantly affected by dairy waste applications.