An evaluation of cover crop-processing tomato (Lycopersicon esculentum L.) production systems, with an emphasis on weed managemen

The objectives of this study were to: evaluate several mixtures of cover crops to select a combination which takes advantage of beneficial species interactions; evaluate various methods of killing cover crops without chemicals; evaluate 4 different processing tomato production systems (with and without cover crops) which varied in the amounts of chemical inputs used, and; determine the mechanism of cover crop weed suppression.;The mixture selected from the screening (hairy vetch (Vicia villosa), crimson clover (Trifolium incarnatum), rye (Secale cereale), and barley (Hordeum vulgare)) provided a quick ground cover, produced substantial above-ground biomass (AGB) and N, had a C:N ratio of 22:1 which would limit immobilization of N after cover crop kill, overwintered consistently, killed easily by mechanical means, and demonstrated weed control potential.;An undercutter which severs cover crop roots and lays the residue intact on the soil surface was designed for use in this study. Cover crops suppressed more weeds when killed with the undercutter as compared to a flail mower, as the mulch was thicker and longer lasting.;In the systems study, the cover crop mixture produced high amounts of AGB (9570 kg/ha in Columbus, and 14,290 kg/ha in Fremont) and N (220 kg/ha in Columbus and 360 kg/ha in Fremont). The C:N ratio averaged 22:1. Larger plants and earlier fruit set contributed to higher yields from conventional plots in Fremont. The cover crop mulch conserved soil moisture and reduced soil maximum temperatures. The mulch suppressed weeds in this study as well as the herbicides did in the conventional plots. There were no differences in tomato diseases in spite of several fungicide sprays on the conventional and integrated plots, and there were no differences in insect populations between the plots. The no-input system had the highest economic return over variable costs in Columbus. In Fremont, the conventional system netted much higher returns than the other systems attributable to higher yields.;Weed suppression experiments demonstrated that a leached cover crop could be redried and used as a control for separating physical from allelochemical effects. Eastern black nightshade was allelochemically suppressed by crimson clover under field conditions.