Crop rotation effects on Cyperus rotundus and C-esculentus population dynamics in southern California vegetable production

Control options for Cyperus rotundus and Cyperus esculentus (purple and yellow nutsedge) were evaluated within three cropping systems in the low desert of southern California: (1) standard vegetable crop rotation (weed-free, uncontrolled nutsedge and cultivation) with spring cantaloupe (Cucumis melo) - summer fallow - winter broccoli (Brassica oleracea), (2) cover crop rotation (halosulfuron and smother crop) with spring wheat (Triticum aestivum)/corn (Zea mays) - summer sudangrass (Sorghum sudanense) - Winter Fallow, (3) rotation with solarization (non-solarization and solarization) with spring wheat - summer fallow/solarization - winter broccoli. After two growing seasons, broccoli was planted without Cyperus control, to study the effect on yield. Cyperus rotundus tubers increased from 0.66 tubers per m(2) to 1260 tubers per m(2) in the uncontrolled treatment over two seasons. Cultivation during the growing season reduced C. rotundus tubers by 93% compared with the uncontrolled plots. Cover crop rotation did not reduce the number of C. rotundus tubers significantly, despite the dense sudangrass canopy shading the soil during most of the summer. Cyperus rotundus was effectively controlled by the solarization treatment. All methods controlled C. esculentus, especially when there were no crops growing in the summer. When broccoli was grown after two years of various management strategies, the cultivation treatment showed a 44% yield reduction compared with the weed-free control, while the solarization treatment increased broccoli yield by 64% compared with the non-solarization treatment. Rotations that included sudangrass had low broccoli yield when either C. rotundus or C. esculentus were present.