Salt Accumulation & Potato Tuber Yield Response to Historical Dairy Manure Applications in South-Central Idaho

Dairy manure applications are common practice in southern Idaho. Questions have arisen regarding the salt accumulations commonly associated with dairy manure applications on salt-sensitive crops like potatoes. The objective of this 2-year study was to evaluate the impact of dairy manure, dairy compost, dairy lagoon water and fertilizer application on salt accumulation and tuber yields in south-central Idaho based on grower-reported nutrient applications and yields. Soil samples and grower-reported tuber yield information were collected midseason (during time period of July 1st-July 30th) from 84 cooperator potato fields in south-central Idaho in both 2009 and 2010. Soil samples were collected to a 30 cm depth and analyzed for soil electrical conductivity (EC), soluble K, Na, Ca, Mg, and pH. Information on manure application, cultural management practices, and total tuber yield was collected for each field. Average reported application rates (wet basis) of these amendments were: 128 Mg ha−1 dairy manure (28 fields), 29 Mg ha−1 dairy compost (11 fields), 415,000 l ha−1 dairy lagoon water (9 fields), or no manure applied (33 fields) over the 4 year period prior to the study. Mean soil soluble K for dairy manure (1.6 mmolc L−1) and dairy lagoon water fields (1.4 mmolc L−1) were significantly greater than dairy compost (0.6 mmolc L−1) or fertilizer fields (0.4 mmolc L−1). Manure application history had no significant treatment effect on soil electrical conductivity (EC), sodium adsorption ratio (SAR), soluble Na, Ca, or K, soil pH, or grower-reported total tuber yield. These overall findings suggest that current dairy manure, compost, and lagoon water application practices to potato production systems in south-central Idaho are not significantly influencing tuber yield or soil salt accumulations. However, significant soluble K accumulations in the soil suggest that dairy manure and dairy lagoon water applications should still be monitored to avoid potential salt accumulations and yield losses.

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