Production and diversity of enchytraeids, earthworms and plants in fertilized hay meadow plots.
Random soil samples were used to estimate the number and weight of each species of enchytraeid and lumbricid at fourteen long-established experimentally fertilized hay meadow plots in Northumberland, England. Twenty-eight species of enchytraeids and seven species of lumbricids were found. Eight of the most abundant species of enchytraeids were maintained in laboratory cultures to measure rates of growth and survival and estimate the production of field populations.
The number, weight and production of enchytraeids was negatively correlated with soil pH, phosphorus added to the plots and the number of species of grass in the plots. The number and weight of earthworms was positively correlated with soil pH and the amount of farmyard manure (FYM) used. Although the weight of enchytraeids in the acid plots partly compensated for the low numbers, or absence of earthworms, enchytraeids comprised only approximately one tenth of the total weight of oligochaetes in plots above pH 5.0. The diversity of enchytraeids was related positively to soil pH and curvilinearly to plant yield and showed more complex relationships with nitrogen and phosphorus fertilizers.
When the total weight of oligochaetes was compared to the amount of food available estimated as average hay yield plus the amount of FYM added, those inorganic plots with low soil pH and consequently few earthworms, were found to support a low biomass of oligochaetes for a given quantity of food. The remaining inorganic plots, and plots receiving FYM annually, supported approximately 5 g dw m-2 oligochaetes for each 100 g dw m-2 food. Plots receiving FYM at infrequent intervals contained fewer oligochaetes than predicted from the estimated food supply. Oligochaete respiration was between 20% and 28% of litter input at the neutral inorganic plots and this was similar to some natural grazed grassland sites. Where oligochaete respiration was less than about 15%, litter accumulated as either a surface mat or, within soil, as organic carbon.