Dairy manure effects on sugar beet yield, quality, and nutrient uptake potential

Concentrated dairy production coexists with large-scale crop production in southern Idaho. This results in large amounts of manure available for crop production, but the suitability of manure for sugar beet production is not well understood. A field experiment was conducted to determine soil properties, sugar beet yield and quality, and economic value response to solid dry-lot manure applications. Research was conducted over an 8-year period with two manure application frequencies (annual and biennial) at dry-weight rates of (18, 36, and 52 Mg ha⁻¹) and a synthetic fertilizer-only and a non-amended check. Nearly all soil nutrients increased with increasing manure rates with particularly high levels of NO₃-N and Olsen-P at the highest rates. At the highest annual rate, soil electrical conductivity exceeded 2 dS m⁻¹, the concentration at which sugar beet growth is limited. Root yields were greater in manure treatments versus fertilizer and control treatments; however, beet sucrose concentration decreased, and NO₃-N and conductivity increased with higher manure application. Despite this, estimated recoverable sugar remained constant indicating similar payout for the grower. Results indicate the potential for manure usage in sugar beet production but convey concerns that may arise due to increased soil salinity alongside issues that exist in terms of crop quality.