Some Environmental Factors Affecting Earthworm Population and Sweet Potato Production in the Tari Basin, Papua New Guinea Highlands.

Abstract

Populations of the earthworm Pontoscolex corethrurus were measured in mounded sweet potato cultivation (lpomoea batatas (L.), Lam.), and mean values for the trial blocks ranged from 93 to 302 individuals per m (46.5 to 127. 7 g fresh weight). Populations were
higher on a drained peaty clay soil than on a drier, less organic alluvial soil. Mean sweet potato yields per block ranged from 324 to 776 g dry matter of tuber and 286 to 497 g dry matter of topgrowth per m. So,J moisture content was negatively correlated with crop production. There was no correlation between crop production and earthworm population for the whole trial, but mounds with less than 43 g of earthworm freshweight per m showed a positive and significant correlation with topgrowth production. In one block of the trial with a peaty clay soil, tuber production was negatively correlated with worm yield. In another block with an alluvial soil, topgrowth yields were positively correlated with worm yields. Weekly rainfall was positively correlated to earthworm population.