Removing Solids Improves Response of Grass to Surface‐Banded Dairy Manure Slurry: A Multiyear Study

Abstract

Removing solids from slurry manure helps balance nutrients to plant needs and may increase soil infiltration rate toreduce loss of ammonia. The long-term effects of applying the separated liquid fraction (SLF) of dairy slurry with surface banding applicators are not well known. This 6-yr study compared the yield, N recovery, and stand persistence of tall fescue (Festuca arundinacea Schreb.) receiving SLF at 300 (SLF300) and 400 (SLF400) kg ha(-1) yr(-1) of total ammoniacal N (TAN); whole dairy slurry (WS) at 200 (WS200), 300 (WS300), and 400 (WS400) kg TAN ha(-1) yr(-1); and mineral fertilizerat 300 kg N ha(-1) yr(-1). The slurries were applied four times per year by surface banding, a technique that reduces ammonia emission and canopy contamination. Grass yield and N uptake were significantly higher for SLF300 than WS300 atequivalent rates of TAN. At similar total N, yield and N uptake were much greater for SLF than WS (2 Mg DM ha(-1) and 75 kg N ha(-1), respectively). Apparent total N recoverywas 63% greater for SLF300 than WS300 due to less ammonia loss and less immobile N. The apparent recovery of total N was 31% higher for Fert300 than for SLF300. Yield and N uptake for SLF300 and WS300 were similar in Harvests 1 and4, but SLF had higher values under hot and dry conditions in Harvests 2 and 3. Using SLF rather than WS will increase crop yield and allow higher application volumes near barns, whichwill reduce hauling costs.