Impact of various organic mulches on the soil surface insect community in bean (Phaseolus vulgaris L.)

Mulching by spreading organic matter around plants has been shown to increase plant tolerance to insect pests. Also, mulches help in maintaining soil moisture required for plant vigor and thus improve soil water and nutrient status for plant growth. A field experiment was conducted to determine the impact of different kinds of mulches (pine bark, sunn hemp (Crotalaria juncea), sorghum-sudangrass (Sorghum bicolor x S. sudanense), cowpea (Vigna unguiculata), or non-mulched control) on the soil surface insect community. The five treatments were replicated five times in a randomized block design. Insects were evaluated every two weeks using two pitfall traps per plot. Soil surface insects were also sampled using other methods such as wooden board traps. The total number, order, and family of all arthropods found in the traps were recorded. Weeds, nematodes, and plant stand were also evaluated. Results showed that the effect of mulches on soil surface insects changes over time. In both pitfall traps and board traps, ants, Coleoptera, other insects preferred cowpea mulch early in the season. However, at the end of the season, when most of cowpea mulch had decayed, Collembola preferred sunnhemp mulch due to the continuous supply of organic matter from this more persistent material. The different kinds of mulches impacted weed counts as well.