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  • Author or Editor: Joseph Aguyoh x
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Sweet corn (Zea mays L.) growers in the upper midwestern U.S. have used clear plastic mulch to improve early yield and advance crop maturity. Results of this practice have been inconsistent because of early season temperature variability and inadequate information on cultivar adaptation. Our objective was to improve the performance consistency by investigating earliness techniques with the early, sugary-enhancer (se) cultivar Temptation planted at two sites. Treatments were bare soil or clear plastic mulch, rowcovers or none, and direct-seeded or transplanted plants. Transplants were produced in the greenhouse in either 50-cell plastic trays or peat pot strips, 2.3 inches × 4.0 inches deep (6 × 10 cm) and were evaluated according to transplant age and cell size. In the cold springs of 1996 and 1997, the use of clear plastic mulch shortened maturity of sweet corn by 1 and 10 days, respectively, for the silt loam site; but no maturity advantage was observed for the loamy sand site. Clear plastic raised the minimum soil temperature by 3.8 to 4.0 °F (2.1 to 2.2 °C) at both sites. The 2-week-old 50-cell tray transplants matured 6 days earlier than the peat pot strip transplants or direct seeded at both locations in 1997. Marketable yield from the transplants was inconsistent by location and year. Four-week-old transplants did not withstand field stress and performed poorly regardless of type of container. Ear quality as indicated by row number, ear diameter, ear length, and tipfill was lowest with transplants.

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Cowpea [Vigna unguiculata (L.) Walp.] is an important component of most traditional cropping systems in the semiarid tropics. It provides both leaf vegetable and/or grain. Dual-purpose production of cowpea is most common in subsistence farming systems. Little is, however, known about the effects of cowpea leaf harvesting on tissue nitrogen composition and productivity of most cowpea-based cropping systems. A four-season study was carried out at the National Dry Land Research Center, Katumani, Kenya, to establish the effects of cowpea leaf harvesting initiation time and frequency on 1) tissue nitrogen content of cowpea and maize in a dual-purpose cowpea–maize intercropping systems; and 2) cowpea and maize yield and the overall productivity of a cowpea–maize intercrop measured by land equivalent ratio (LER). Cowpea leaf harvesting was initiated at 2, 3, or 4 weeks after emergence (WAE) and continued at 7- or 14-day intervals until onset of flowering. Cowpea tissue nitrogen content was highest in the control treatment and lowest in cowpea subjected to leaf harvesting from 2 WAE or at 7-day intervals, whereas maize tissue nitrogen content showed the reverse trend. Harvesting cowpea leaves from 3 WAE or at 7-day intervals gave the highest leaf vegetable yield, whereas grain yields were highest when no leaf harvesting was done. Maize yields were significantly improved by harvesting of leaves of the companion cowpea. Harvesting cowpea leaves for use as leaf vegetable increased productivity per unit area of land as measured by LER with the highest productivity achieved when leaf harvesting was initiated at 4 WAE or done at a 14-day interval.

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Integrated weed management strategies maintain sub-threshold levels of weeds. The remaining weeds may impact the feeding and habitation patterns of both potato leafhoppers and bean leaf beetles in a snap bean agroecosystem. The objective of our study was to determine the effect of interference between snap beans (Phaseolus vulgaris L.) and either redroot pigweed (Amaranthus retroflexus L.) or large crabgrass (Digitaria sanguinalis L.) on populations of potato leafhopper [Empoasca fabae (Harris)] and bean leaf beetle [Cerotoma trifurcata (Forster)]. Plots were seeded with redroot pigweed or large crabgrass at either the same time as snap bean planting (early) or when snap bean had one trifoliate leaf open (late). The weed density averaged two plants per meter of row. Bean leaf beetle populations, snap bean pod damage, and leaf defoliation were lower in weed-free plots compared to those with either early emerging pigweed or crabgrass. Leafhopper nymphs and adults were 31% to 34% less in plots with crabgrass emerging with snap beans compared to those in weed-free snap bean plots. Thus, the effect of sub-threshold densities of pigweed and crabgrass on insect pests in snap bean varied depending on the species and should be considered when deciding to integrate weed management approaches.

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