Field experiments were conducted to determine the effect of large crabgrass densities of 0.5 to 8 plants m−1 of row and emergence time on snap bean yield. Large crabgrass was planted either along with snap beans (early) or when the first trifoliate leaf of snap beans was opening (late). Observed yield loss ranged from 46 to 50%, and predicted yield loss ranged from 53 ± 29.3% to 63 ± 18.3%. Relative leaf area was correlated to snap bean yield (r 2 = 0.88 to 0.92). The relative damage coefficient (q), an indication of the competitiveness of large crabgrass with snap bean, was 1.65 ± 1.03 and 1.26 ± 0.72 for early- and late-emerging large crabgrass, respectively. Early-emerging large crabgrass reduced snap bean biomass 10 to 28% and snap bean pod numbers 44 to 60%, depending on the density. Because of intraspecies competition, leaf area index and number of seed for large crabgrass were reduced with increasing density. Emergence of > 2 plants m−1 of large crabgrass with snap beans should be controlled to avoid significant yield loss.

Continuous cultivation of farms has led to decline in soil fertility due to constant removal of nutrients leading to reduction of carrot (Daucus carota L.) yields. A field study was carried out at Egerton University, Horticulture Research and Teaching field in two seasons (October 2010 to January 2011 and February to May 2011) with the aim of investigating the effects of decomposed cattle bio-slurry manure on carrot growth and performance. The experimental design was a Randomized Complete Block Design (RCBD) with 3 replications. Treatments comprised four levels (0, 2.6, 5.2 and 7.8 t/ha) of decomposed bio-slurry manure. Growth, yield and quality parameters were recorded and used to discern the treatment effects. Application of bio-slurry manure generally improved growth, yield and quality of carrots. Application of 7.8 t/ha of bio-slurry increased yields by 8.8% in season 1 and 23.5% in season 2 compared to the control. Leaf numbers, plant height, dry weights of shoot and roots and root volume were also generally higher for the 7.8 t/ha treatment compared to other treatments. Total Soluble Solids of roots from plant treated with 7.8 t/ha were higher by 12.7% in season 1 and 13.2% in season 2 compared to the control. The study recommends 7.8 t/ha of bio-slurry manure for enhanced yield and quality of carrot.

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.

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.

Two studies were conducted in Kenya during 1993 and 1994 to determine the yield responses of kale (Brassica oleracea var. acephala D.C.) intercropped with beans (Phaseolus vulgaris L.) under different redroot pigweed (Amaranthus retroflexus L.) densities. Redroot pigweed significantly reduced both kale and bean yields, the reduction being greater in 1993 than in 1994, and being greater for beans than for kale. Redroot pigweed growth was suppressed more by beans than by kale. Food output per unit area, measured by Land Equivalent Ratios, was increased by 22–115% by intercropping kale with beans and the increase was greater under weedy conditions (38–115%) than under weed-free conditions (22–74%). The presence of beans did not affect the leaf yield of kale. The presence of kale did not affect the seed yield of beans in 1994, but consistently reduced it by about 50% in 1993, though the difference was not significant.

A field study on the growth and yield characteristics of African nightshades was conducted at Kisii Agricultural Training Center for two seasons in 2006/2007. The three species studied were Solanum villosum Miller, S. americanum Miller and S. scabrum Miller. The experiment was carried out under randomized complete block design (RCBD) with three replications. Of the three species tested, S. villosum was the tallest in both seasons by between 34% and 58.7% compared to S. americanum and S. scabrum. The internode lengths of both S. scabrum and S. americanum were also shorter compared to that of S. villosum. The edible yield of the African nightshade species was seasonal, with S. americanum giving the highest yield of 4.12t/ha in season 1, but the lowest yield of 2.31t/ha in season 2. S. americanum with the highest yield during rainy season (Season 1) coupled with average height and branching ability would be preferred for vegetable production, especially where rainfall is above 1200mm per annum

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Cowpea [Vigna unguiculata (L.) Walp.] is a vital component of traditional cropping systems in the subtropics and tropics, grown both for high-protein grain and nutritious fresh leaves. Th e objectives of this study were to determine the eff ects of (i) cropping regime and (ii) leaf harvesting initiation time and frequency on yield and yield components of dual-purpose cowpea. Studies were conducted at the Kenya National Dry land Research Center-Katumani over four seasons. Cowpea cultivar 'K80' was grown as a monocrop or intercropped with maize. Leaf harvesting was initiated at 2, 3, or 4 wk aft er emergence (WAE) and thereaft er done at 7-or 14-d intervals. Control plants remained intact with no leaf harvesting. Th e number of lateral stems per plant, pods per plant, seeds per pod, unit seed weight, and vegetable and grain yields were monitored throughout each season, and plant productivity was found to be lower in intercropped than in monocropped cowpea. Leaf harvesting reduced all yield components. Initiating leaf harvesting at 3 and 4 WAE resulted in the highest leaf and grain yields, respectively. Harvesting leaves at a 7-d interval was associated with higher leaf yield, while a 14-d interval led to higher grain yield. Overall, yields were highest under treatments with no leaf harvest and lowest when leaf harvesting was initiated 2 WAE. Results of this study can help dual-purpose cowpea growers optimize yields according to their production goals.