Dynamics of nematodes and protozoa following the experimental addition of cattle or pig slurry to soil

Abstract

An experimental system was used in which slurry could be placed in the central section of a tube, between two cores of packed, sieved soil. The system simulated the direct injection of slurry into soil and there was movement of water and substrate from the slurry into the surrounding soil. The effects of initial soil moisture, soil nitrate concentration and slurry type, on communities of nematodes and protozoa in soil sections adjacent to and away from the slurry were investigated. Protozoa increased rapidly in the soil layer adjacent to the slurry, but responded more quickly following the addition of pig slurry than cattle slurry. Pig slurry also specifically stimulated ciliates, especially larger Hypotrich ciliates. Nematodes, however, were stimulated to a greater extent by cattle than pig slurry. It is argued that pig slurry contained a greater proportion of readily-available C than cattle slurry. There was also a substantial increase in nematode numbers in soil up to 12 cm from the slurry. This was attributed to the migration of nematodes away from the soil section adjacent to the slurry. A separate experiment was conducted with gel-stabilised cattle slurry, which restricted the movement of water and substrate from the slurry. In this case there was no stimulation of microfauna in soil more than 2 mm from the soil-slurry interface, the largest changes occurred within the slurry phase.