The effects of irrigation, cultivation and some insecticides on the soil arthropods of an East African dry grassland.
Investigations were made of arthropods in a silty, poorly drained, gray soil under dry grassland, irrigated sugar cane, and under natural grassland receiving water seeping from an irrigation canal. 1 Ib/acre dieidrin and 2 Ib/acre aldrin were applied, 27 and seven months before the investigation, to parts of the sugar-cane crop. The total number of arthropods under dry grassland was 14800/m2, 66% of which were acarines, Collembola comprised only 8%. Permanent moisture increased the total to 53, 600/m3, the number of acarines was doubled and Collembola were nine times more abundant than in dry grassland. On cultivated land the soil under the irrigation furrows was almost sterile; elsewhere, arthropod populations were slightly less than under moist grassland, mainly through the absence of ants whose nests had been destroyed. Aldrin and dieldrin had no detectable effect on arthropod populations.