Effects of superphosphate and stocking intensity on grassland microarthropods.
Collembola and Acarina populations were sampled over two years from sites fertilized with three levels of superphosphate (0, 190, 380 kg ha-1yr-1) and grazed by sheep at three stocking intensities (12, 24, 36 ha-1). The sampling zone consisted of herbage to a height of 5 cm, the litter mat and soil from 0-5 cm depth. Superphosphate application led to a fourfold increase in the numbers of Collembola and Acarina. Numbers of microarthropods were related to the percentage of phosphorus in the litter. Litter nitrogen and sulphur contents were less effective in accounting for variation in numbers. Increased stocking intensity generally decreased numbers of Collembola and Acarina but the response was erratic in the higher fertilizer, high stocking intensity treatments. The hemiedaphic species Hypogastrura communis, Brachystomella parvula and Cryptopygus thermophilus comprised about 89% of the total Collembola, and H. communis responded most to superphosphate applications.