| Two field experiments were initiated in summer 2006 to compare the effects of crop rotation, cover crops, living mulches, and intercropping on pest populations. Treatments consisted of cropping systems with summer fallow followed by fall and spring vegetables. Yellow squash and bell pepper were planted in experiment I during year 1 and rotated with broccoli and sweet corn in year 2. In experiment II, broccoli and sweet corn were planted in year 1, and squash and bell pepper in year 2. Cropping systems represented three levels of complexity. The simple cropping system was a summer fallow followed by sole fall and spring vegetables. Four intermediate cropping systems utilized summer cover crops of pearl millet (PM), sorghum-sudangrass (SS), sunn hemp (SH), or velvetbean (VB) followed by sole fall and spring vegetables. Two complex systems included either pearl millet-sunn hemp (PMSH) or sorghum sudangrass-velvetbean (SSVB) mixtures. In the complex systems, row middles of fall squash and broccoli were planted with rye-hairy vetch and crimson clover as living mulches, and bush beans were intercropped with spring vegetables. Weeds and nematode populations were monitored during each season and insect pests in spring only. Soil samples were collected annually for evaluating the weed seedbank. Systems planted with SS or PM increased root-knot nematodes while the SS system also increased ring and lesion nematode populations. Cropping systems failed to suppress aphid populations. PM and SS systems decreased thrips populations while PM and SH systems reduced whitefly populations in sweet corn. In experiment I, fewer grasses, broad-leaf weeds and total weed biomass were observed with the SSVB system than the WF system. In experiment II, the SSVB system resulted in fewer grass weeds between beds than the WF system; however, no differences were observed among systems for broad-leaf and sedge weed densities and total weed biomass. Cropping systems did not change the composition of the weed seedbank. Squash and sweet corn marketable yields were highest in the PM system while no differences were observed between complex and WF systems. In experiment II, bell pepper marketable yield was higher in complex than WF systems. Predicted population dynamics of southern crabgrass and Florida pusley indicated no differences among cropping systems. |
