Effects of tillage, inorganic N, and winter cover crops on sweet corn (Zea mays) were examined in 1994, 1995, and 1996. Tillage treatments were tillage or no tillage, and N treatments were the addition of inorganic N at 0 (N0) or 200 (N+) kg·ha-1 (0 or 179 lb/acre). Winter cover crops included hairy vetch (Vicia villosa), winter rye (Secale cereale), and a vetch/rye biculture. In the N0, rye treatment, the soil was N deficient in 1994 and highly N deficient in 1995 and 1996. When vetch shoot N content was ≥150 kg·ha-1 (134 lb/acre) (1994 and 1995), addition of inorganic N did not increase corn yields, and it only increased corn foliar N concentrations by 8%. Reductions in corn yields (29%) and foliar N concentrations (24%) occurred when vetch shoot N content was only 120 kg·ha-1 (107 lb/acre) (1996) and inorganic N was not supplied. In 1994, the vetch/rye biculture supplied sufficient N for maximum corn yields, but addition of inorganic N increased yields by more than 50% in 1995 and 1996. Under tilled conditions, the vetch N contribution to corn appeared to equal (1996) or exceed (1994 and 1995) 82 kg·ha-1 (73 lb/acre) of N supplied as ammonium nitrate, whereas a mean value of 30 kg·ha-1 (27 lb/acre) was obtained for the biculture cover crop (1995 and 1996). No significant effects of tillage on sweet corn population densities were detected following vetch, but no-tillage significantly reduced corn population densities following rye (17%) or biculture (35%) cover crops compared to tillage. No-tillage did not reduce yields from emerged seedlings (per plant basis) for any cover crops. Vetch appeared to be a satisfactory N source for sweet corn when vetch N content was ≥150 kg·ha-1, and it could be used with no-tillage without yield reductions.

Organic methods for managing striped cucumber beetles (Acalymma vittatum) and spotted (Diabrotica undecimpunctata) cucumber beetles were examined in the production of watermelon (Citrullus lanatus) and muskmelon (Cucumis melo) using sticky traps to monitor beetle populations. In 2002, the numbers of trapped striped and total (striped + spotted) cucumber beetles were significantly (P ≤ 0.05) reduced by the combined use of three companion plants thought to repel cucumber beetles [radish (Raphanus sativus), tansy (Tanacetum vulgare), and nasturtium (Tropaeolum spp.)] or by the combined use of three companion plants known to attract beneficial insects [buckwheat (Fagopyrum esculentum), cowpeas (Vigna unguiculata), and sweetclover (Melilotus officinalis)]. In 2003 and 2004, the single companion plant treatment consisted of the combined use of radish and buckwheat. In 2003, use of aluminum-coated plastic mulch (Al-plastic) or companion plants significantly increased muskmelon yields and vine cover, while significantly reducing numbers of trapped striped, spotted, and total cucumber beetles. The use of pyrethrin insecticide did not significantly affect muskmelon yields or vine cover. In 2004, the beneficial effects of companion plant and Al-plastic treatments on muskmelon yields and vine cover were also significant and similar to those in 2003; however, these treatments only affected early season numbers of trapped beetles. The use of rowcovers significantly increased muskmelon yields and vine cover in 2003 and 2004 and did not affect beetle populations after rowcover removal. It was concluded that use of companion plants and Al-plastic increased muskmelon yields and vine cover while reducing populations of cucumber beetles, particularly striped cucumber beetles. The use of rowcovers also increased muskmelon yields and vine cover.

A 4-year field experiment examined how monoculture and biculture winter cover crops were affected by prior inorganic nitrogen (N) fertilization of sweet corn (Zea mays) and by kill dates associated with tillage methods. Hairy vetch (Vicia villosa) biomass production and N content remained relatively constant with (N+) or without (N0) prior N application. In N+ treatments, biomass production of winter rye (Secale cereale) and a vetch-rye biculture were significantly greater than vetch biomass production. Rye responded to prior N fertilization and recovered N from residual inorganic N fertilizer at an average annual rate of 30 kg·ha-1 (27 lb/acre), excluding contributions of roots. Nitrogen contents of vetch and biculture cover crops were similar in most years and were significantly greater than those of rye. Nitrogen contents in vetch and biculture treatments were not increased by the residual inorganic N fertilizer addition of the N+ treatment. In the biculture treatment prior N application increased total biomass production but decreased the percentage of vetch biomass. Monoculture vetch biomass production was significantly increased by delaying cover crop kill dates for 8 days in mid-May. However, such delays also significantly lowered vetch foliar N concentrations and consequently did not significantly affect vetch N content. No significant effects of delays on rye or biculture cover crops were detected. It was concluded that prior fertilization of sweet corn with inorganic N affected various cover crops differently and that delaying vetch kill dates 8 days increased biomass production but did not affect N content.

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Organic weed control in direct seeded vegetables depends on management strategies that control weed germination or growth which depletes the weed seedbank. In 2004, a randomized complete-block experiment conducted on land transitioning to organic production examined the effects of tillage and control treatments on weed pressure in sweet corn [Zeamays (L.) cv. Silver Queen]. The two tillage treatments consisted of conventional (moldboard and rototill) and spader tillage. Weed control treatments included a weed free control, a spring-tine weeder, rolling cultivator, row flamer, stale seedbed, and corn gluten meal. In August, the weed infestation was primarily goose grass [Eleusineindica (L.) Gaertn.], crab grass [Digitariasanguinalis (L.) Scop.], giant foxtail (Setariafaberi Herrm.), and smooth pigweed [Amaranthushybridus (L.)] species. Dried weed weights indicated that smooth pigweed constituted about 80% of the total weed biomass in all but the control and flamer treatments. Plots managed with the spring-tine weeder or corn gluten had twice the weed biomass of those managed with the rolling cultivator and flamer. The rolling cultivator and control treatments produced equivalent husked corn yields (6.9 t·ha-1); yields were reduced by the other weed control methods. At 5.4 t·ha-1, yields in the flamer treatment were the lowest among all weed control methods. The flamer suppressed both weeds and the crop, which may preclude its utility for sweet corn production. Results demonstrated that the rolling cultivator provided the best weed control without negatively affecting potential yields.