Dairy manure influences soil properties, plant nutrient uptake, and tuber quality in potatoes

Dairy manure applications are a common practice in Idaho potato (Solanum tuberosum L.) production, however the impacts on tuber yield and quality are not well understood. Our objectives were to determine (1) how repeated dairy manure applications impact soil properties and plant nutrient uptake, and (2) how these changes influence plant nutrient interactions, tuber yield, and quality. Stockpiled dairy manure was fall-applied over a 6-year period to two adjacent potato production fields in Kimberly, ID. Eight treatments included application frequency (annual and biennial), manure application rate (18, 36, and 52 Mg ha⁻¹ application⁻¹ [dry weight basis]), fertilizer-only, and a non-amended control. Manure treatments were supplemented with fertilizer to prevent nutrient-limiting conditions. Compared to fertilizer treatments, mean soil organic matter, total N, and K were greater for annual manure by 53%, 47%, and 426%, and biennial manure by 24%, 23%, and 199%, respectively. For annual applications only, mean soil nitrate, P, and electrical conductivity were greater than fertilizer treatments by 247%, 431%, and 222%, respectively. Manure promoted P and K luxury consumption with increasing application rate and frequency. Foliage Ca, Mg, Zn, Mn, and Cu correlated negatively against foliage K, potentially due to cation competition and translocation disruption. Annual applications decreased mean tuber specific gravity from 1.078 to 1.073, which may be attributed to saline-sodic conditions and delayed maturity from late-season N mineralization. Our findings suggest that biennial manure applications may prevent specific gravity issues. Agronomic parameters related to N, K, and soluble salts should be closely monitored in these systems.