The effectiveness of cover crops as an alternative weed control strategy should be assessed as the demand for food and fiber grown under sustainable agricultural practices increases. This study assessed the effect of fall cover crops on weed populations in the fall and spring prior to sweet corn planting and during sweet corn growth. The experiment was a split-plot design in a pea cover-cover crop-sweet corn rotation with fall cover crop type as the main plot factor and presence or absence of weeds in the sweet corn as the split-plot factor. The cover crop treatments were a control with no cover crop (no-cover), oat, cereal rye (rye), oilseed radish (OSR), and oilseed radish with rye (OSR+rye). In the fall, at Ridgetown, weed biomass in the OSR treatments was 29 and 59 g m 22 lower than in the no-cover and the cereal treatments, respectively. In the spring, OSR+rye and rye reduced weed biomass, density, and richness below the levels observed in the control at Bothwell. At Ridgetown in the spring, cover crops had no effect on weed populations. During the sweet corn season, weed populations and sweet corn yields were generally unaffected by the cover crops, provided OSR did not set viable seed. All cover crop treatments were as profitable as or more profitable than the no-cover treatment. At Bothwell profit margins were highest for oat at almost Can$600 ha 21 higher than the no-cover treatment. At Ridgetown, compared with the no-cover treatment, OSR and OSR+rye profit margins were between Can$1,250 and Can$1,350 ha 21 and between Can$682 and Can$835 ha 21 , respectively. Therefore, provided that OSR does not set viable seed, the cover crops tested are feasible and profitable options to include in sweet corn production and provide weed-suppression benefits. Nomenclature: Cereal rye, Secale cereale L.; oat, Avena sativa L.; oilseed radish, Raphanus sativus L. var. oleoferus Metzg. Stokes; pea, Pisum sativum L.; sweet corn, Zea mays L. Key words: Catch crops, vegetable production, profit margins, cost-benefit analysis, species richness, Simpson's index.La efectividad de los cultivos de cobertura como una estrategia alternativa para el control de malezas debe ser evaluada, en vista del incremento en la demanda de alimentos y fibras cultivadas bajo prácticas agrícolas sustentables. Este estudio evaluó el efecto de cultivos de cobertura de otoño en las poblaciones de maleza en la misma estación, en la primavera anterior a la siembra y durante el crecimiento del maíz dulce. El diseño del experimento fue de parcela divida con la rotación de chícharo-cultivo de cobertura-maíz dulce, con el tipo de cultivo de cobertura de otoño como factor principal de la parcela y con la presencia o ausencia de malezas en el maíz dulce como el factor de la parcela dividida. Los tratamientos de cultivos de cobertura fueron: un testigo sin cultivo de cobertura, avena, centeno, rábano oleaginoso, y rábano oleaginoso + centeno. En Ridgetown, durante el otoño, la biomasa de la maleza con los tratamientos de rábano oleaginoso fue 29 y 59 g m-2 m...

The increase in fertilizer costs as well as environmental concerns has stimulated growers to re-evaluate their fertilizer applications to optimize nitrogen use efficiency (NUE) while maintaining crop yields and minimizing N losses. With these objectives, field trials were conducted at seven sites with five N rates (0 to 220 kg N/ha) of ammonium-nitrate applied preplant broadcast and incorporated as well as a split application treatment of 65 + 45 kg N/ha. In three contrasting years (i.e., cool/wet versus warm/dry versus average), N treatment had no observable effect on grade size distribution or brine quality. Based on the zero N control treatment, the limited yield response to fertilizer N was the result of sufficient plant-available N over the growing season. In the N budget, there was no difference between N treatments in crop N removal, but there was a positive linear relationship between N applied and the quantity of N in crop residue as well as in the soil after harvest. As expected, apparent fertilizer N recovery and N uptake efficiency were lower at 220 versus 110 kg N/ha applied preplant or split. The preplant and split applications of 110 kg N/ha were not different in yield, overall N budget, or NUE. Considering the short growing season, planting into warm soils, and the generally productive, nonresponsive soils in the region, growers should consider reducing or eliminating fertilizer N applications in machine-harvested cucumber.