ESTIMATING NUTRIENT CONTENT OF ANIMAL SLURRIES USING ELECTRICAL-CONDUCTIVITY

Electrical conductivity was evaluated for estimating the nutrient cont ent of cattle and pig slurries. Slurry samples were collected in 1991 from the storage tanks of 48 cattle and 10 pig units on commercial far ms in Ireland. Samples were analysed for NH4+ and total concentrations of Na, K, Ca, Mg and P. Electrical conductivity (EC) was measured on raw slurries (EC(raw)) and on slurries diluted by 10 with water (EC(di lute)). Relationships between EC and nutrient content were examined by correlation and linear regression analyses. In both slurry types, NH4 + was the dominant cation with K+ second in importance on a molar basi s. Within each slurry type, the concentration of each of these cations was significantly correlated with EC. Using EC(dilute) gave more accu rate predictions of concentrations than EC(raw), but even EC(raw) was a better predictor than dry matter (DM) content. The linear relationsh ips between NH4+ or K+ and EC(dilute) explained > 82 % of the variance within each slurry type. The P content in slurries was related better to DM than to EC. Since EC measurement could be by cheap, robust mete rs, its potential for on-farm use deserves further investigation.