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B. Warren Roberts and Jeffrey A. Anderson

Experiments were conducted from 1989 to 1991 to compare the effectiveness of various cultural techniques in reducing solar injury (SI) and increasing yield of bell pepper (Capsicum annuum var. annuum `California Wonder') in southern Oklahoma. Treatments included black plastic mulch, white plastic mulch, straw mulch, living rye, spunbonded polypropylene used as a plant canopy shade, and bare soil. Marketable yields from plots shaded with spunbonded polypropylene rowcovers were equal to or greater than those from other treatments each year. Two out of 3 years, plots with a black plastic soil mulch had marketable yields lower than those from other treatments. SI was reduced by rowcover shade.

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Wendy A. Nelson, Brian A. Kahn, and B. Warren Roberts

Several prospective cover crops were sown into 1-m2 monoculture plots on 9 Mar. 1987 and 10 Mar. 1988 at Bixby, Okla., and on 14 Mar. 1988 at Lane, Okla., after sites were plowed and fitted. Densities and dry weights of cover crops and weeds were determined in late April or early May of both years. Plots also were evaluated for degree of kill by glyphosate in 1988. Fourteen cover crops were screened at Bixby in 1987. Kentucky bluegrass (Poa pratensis L.) and three fescues (Festuca rubra L., Festuca rubra L. var. commutata Gaud.-Beaup., and Festuca elatior L.) were eliminated from further consideration due to inadequate cover density and inability to suppress weeds. Screenings of the 10 remaining covers were conducted at both locations in 1988. Annual ryegrass (Lolium multiflorum L.) and three small grains [rye (Secale cereale L.), barley (Hordeum vulgare L.), and wheat (Triticum aestivum L.)] were the most promising cover crops with respect to cover density, competitiveness against weeds, and degree of kill by glyphosate. Crimson clover (Trifolium incarnatum L.) and hairy vetch (Vicia villosa Roth) were the most promising legumes, but they generally were less satisfactory than the grassy covers in all tested aspects. A single application of glyphosate was ineffective in killing hairy vetch at both locations. Chemical name used: N-(phosphonomethyl)glycine (glyphosate).

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Wenhua Lu, J.V. Edelson, Jim A. Duthie, and B. Warren Roberts

Factors of crop management such as irrigation, cultivation, cultivar selection, and control of insect pests and plant diseases play important roles in watermelon production. To gain a better understanding of how intensity of crop management affects yield, we conducted a comparative study contrasting high and low intensity management in 1997, 1999, and 2000. High-intensity management (HM) included the use of trickle irrigation, black plastic mulch, insecticides, and fungicides, not used under low-intensity management (LM). We examined the effects of management intensity on watermelon productivity, the variation in such effects among watermelon cultivars, and the mediating effect of survival of watermelon plants, abundance of insect pests, and incidence of anthracnose (% leaves with anthracnose lesions). The results indicated that HM produced 100% greater marketable fruit yield per area and marketable fraction of total fruit than LM in 2 out of 3 years. The effect of management intensity on plant survival was related to this effect on yield in 1 out of 2 years, and contributed to the latter by increasing weight and number of marketable fruit per plant under HM. We detected no significant effect of abundance of insect pests and incidence of anthracnose on yield. There was variation in the effect of management intensity on yield among watermelon cultivars in 1 out of 3 years. The triploid `Gem Dandy' showed great differences in yield between HM and LM in 2 years, producing on average 28.9 Mg·ha-1 of marketable fruit yield under HM compared to 14.0 Mg·ha-1 under LM. `Gem Dandy' also produced 100% higher yield of marketable fruit per area, per plant, and marketable fraction of total fruit than the open-pollinated diploid `Allsweet' or the diploid hybrid `Sangria.' Each year during the 3-year study, all three cultivars had a similar density of insect pests, incidence of anthracnose, and plant survival after transplant and at harvest. This study provided information on the collective impact of multiple aspects of watermelon management on yield.