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Francis M. Itulya, Vasey N. Mwaja, and John B. Masiunas

Field experiments were conducted in 1992 and 1993 to determine the effect of N fertility, cropping system, redroot pigweed (Amaranthus retroflexus L.) density, and harvesting frequency on collard (Brassica oleracea var. acephala D.C) and cowpea [Vigna unguiculata (L.) Walp.] growth. The N fertilization regimes were 0, 80, 160, and 240 kg·ha-1, applied as urea in a split application. Four weeks after crop planting, redroot pigweed was seeded at 0, 300, and 1200 seeds/m2. Between weeks 6 and 12, collard leaves were harvested at 1- to 3-week intervals. Year, N fertility, and cropping system interacted to determine collard leaf number and mass. For example, in 1992, with N at 160 kg·ha-1, collards intercropped had more total leaf mass than those monocropped. Pigweed density had no effect on collard yields, which were greatest from the 3-week harvest frequency. Cropping system and pigweed density interacted to determine cowpea vine length, shoot dry mass, and branching. The high density of pigweed caused a 56% reduction of cowpea dry mass in 1992.

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Ana Regia Alves de Araújo Hendges, Jose Wagner da Silva Melo, Marcelo de Almeida Guimaraes, and Janiquelle da Silva Rabelo

populations of the M. persicae aphid; and 3) to evaluate the economic benefits of intercropping by the total fresh weight of kale produced under the different cropping systems (monocrop and intercrop). Material and Methods Characterization of the study area

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Ravneet K. Sandhu, Nathan S. Boyd, Lincoln Zotarelli, Shinsuke Agehara, and Natalia Peres

lowers the chances of complete crop failure, as it is highly unlikely that two or more crops have the same susceptibility to pest and disease incidence, and the method thus ensures crop stability ( Boudreau, 2013 ). Monocrops are more likely to be

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John R. Teasdale and Aref A. Abdul-Baki

Hairy vetch (Vicia villosa Roth), crimson clover (Trifolium incarnatum L.), and rye (Secale cereale L.) and mixtures of rye with hairy vetch and/or crimson clover were compared for no-tillage production of staked, fresh-market tomatoes (Lycopersicon esculentum Mill.) on raised beds. All cover crops were evaluated both with or without a postemergence application of metribuzin for weed control. Biomass of cover crop mixtures were higher than that of the hairy vetch monocrop. Cover crop nitrogen content varied little among legume monocrops and all mixtures but was lower in the rye monocrop. The C:N ratio of legume monocrops and all mixtures was <30 but that of the rye monocrop was >50, suggesting that nitrogen immobilization probably occurred only in the rye monocrop. Marketable fruit yield was similar in the legume monocrops and all mixtures but was lower in the rye monocrop when weeds were controlled by metribuzin. When no herbicide was applied, cover crop mixtures reduced weed emergence and biomass compared to the legume monocrops. Despite weed suppression by cover crop mixtures, tomatoes grown in the mixtures without herbicide yielded lower than the corresponding treatments with herbicide in 2 of 3 years. Chemical name used: [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one](metribuzin).

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Emily R. Vollmer, Nancy Creamer, Chris Reberg-Horton, and Greg Hoyt

crop biomass production compared with their respective monocultures ( Sainju et al., 2005 ). When compared with a legume monocrop, grass–legume mixtures can provide equivalent N release while improving N use efficiency of a subsequent crop by moderating

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Jose G. Franco, Stephen R. King, Joseph G. Masabni, and Astrid Volder

peanut, pepper, okra, and cowpea monocrops, respectively. On average, the presence of watermelon reduced weed biomass by 81%, 83%, 88%, and 92% compared with peanut, pepper, okra, and cowpea monocultures, respectively. However, in 2012, watermelon did not

Open access

Ravneet K. Sandhu, Nathan S. Boyd, Shaun Sharpe, Zhengfei Guan, Qi Qiu, Tianyuan Luo, and Shinsuke Agehara

becomes a major challenge when two critical growth stages of the crop plants occur at the same time ( Coolman and Hoyt, 1993 ). For example, tomatoes relay cropped with okra had reduced yields compared with monocrop production ( Olasantan, 1985 ). However

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Roger Francis and Dennis R. Decoteau

Southernpea and sweet corn can be intercropped effectively. When simultaneously planted, sweet corn appears to be the dominant crop in the mixture, with intercropped southernpea producing a supplemental yield to intercropped sweet corn. Increasing intercrop plant densities increased the amount of sweet corn yield and reduced the amount of southernpea yield. The reduction in light intercepted by southernpea and sweet corn in the intercrop situation probably contributed to the reduction in yield by these component crops as compared to the yield of these crops as monocrops. The total system LER (LERsouthernpea + LERsweetcorn) for the high-population intercropping system, where plant densities for each crop were comparable to the densities of these crops as monocrops, was 1.26. This suggests that intercropping southernpea and sweet corn at this density gave a yield advantage of 26%, or that 26% more land planted in equal proportion of each component crop would be required to produce the same yield as the intercrop. A N application rate of 125 lb/acre (140 kg·ha-1) was optimum for intercropped sweet corn, and there was no advantage of a 2-week delayed planting of sweet corn in this intercrop system.

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V. A. Khan, C. Stevens, J. Y. Lu, J. E. Brown, E. G. Rhoden, M. A. Wilson, M. K. Kabwe, and Z. Haung

An early planting (January) of 8 wks. old collards (Brassica oleracea (L) var. acephala `Georgia Collards') and subsequently followed by `Crimson Sweet' watermelon transplants (April) on clear and black polyethylene mulches and bare soil plus VisPore row cover (VCM, VBM, VBS), clear and black polyethylene mulches and bare soil (CM, BM, BS) in combination with drip irrigation were transplanted on the same plots. Marketable yield of collards (March) was significantly greater for mulched and row cover treatments than bare soil. Watermelon (harvested June 7th, 1990) total and marketable numbers and yield were significantly greater when grown on mulched treatments than bare soil. Mono-cropping of watermelon were profitable under VCM, VBM, CM and BM treatments and collards when grown as a mono-crop was not profitable under any system. By sharing the costs of production under a double-cropping system the profitability of watermelons increased when grown under VCM, VBM, CM, BM VBS and for collards under VCM and VBM treatments.

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M. Mergo, E. G. Rhoden, and M. Burns

Intercropping is a management system that maximizes production per unit area of land. Intercropping has to be carried out with crops that are compatible in order to ensure increased productivity. An intercropping study was conducted to determine a suitable planting pattern for corn (Zea mays), an overstory crop, and sweetpotato (Ipomoea batatas), an under-story crop. Five relative planting dates were established for each component crop (3 week; before, 3WB; 2 weeks before, 2WB; simultaneous, SIM; 2 weeks after, 2WA; and 3 weeks after, 3WA planting the other crop). Monocrop of each component was also planted. The marketable yields of sweetpotato were reduced by 48, 57, 75, 76 and 74% when sweetpotato was intercropped with corn and planted 3WB, 2WB, SIM, 2WA and 3WA corn, respectively. Corn grain yields were reduced 28, 28, 26, 57, and 66% when intercropped with sweetpotato beginning 3WB, 2WB, SIM, 2WA and 3WA sweetpotato, respectively. Although yields of individual component crop were reduced in intercrop, there was no significant difference in land utilization. Land equivalent ratio, area time equivalent ratio, and competition ratio were not significantly affected by planting date. Intercropping corn and sweetpotato was compatible when both crops were simultaneously planted.