The soil Acari of barley plots with different cultural treatments

Sixty-four species of Acari were extracted by wet sieving and salt flotation from soil in four barley plots sampled on five occasions between 23 May and 15 August 1975. Over half the species were Prostigmata. The most abundant species wereScutacarus longiusculus (Karafiat) (Scutacaridae, Prostigmata),Bakerdania gracilis (Krczal) (Pygmephoridae, Prostigmata), andTyrophagus longior (Gervais) (Acaridae, Astigmata). Only three species (B. gracilis, T. longior andPseudopygmephorus sellnicki (Krczal) (Pygmephoridae)) contributed more than 2% of the individuals and occurred in more than 25% of the samples in all plots. Mean population densities ranged from 41 to 216 thousand/m2, with highest density occurring in a conventionally ploughed and cultivated plot and lowest in a direct drilled plot. Prostigmata accounted for 46–85% of the total populations in the various plots. Twelve species were recorded from decaying crop residues on the soil surface; these included some of the most abundant species recorded from growing barley in a related study. Soil and crop residues were the main sources of most of the dominant species colonizing the growing barley crop. The barley plots had greater numbers of Prostigmata and Astigmata but fewer Cryptostigmata and Mesostigmata than were extracted by a high gradient canister technique from adjacent grass ley pasture sampled in its second and third years (1976 and 1977). Biomass in the older ley was far greater than in the barley. There were higher numbers of species of intermediate relative abundance (0.1–5%) in the ley, indicating more mature communities than in the barley plots.