The EI can be reduced by reducing herbicide rates or applying herbicides that have a lower EI; the environmental impact quotient can help determine the relative risk of various herbicide programs. The EIQ is a calculated potential risk based on physiochemical and toxicological properties of a herbicide. Toxicological data are gathered on the potential risk to the farm worker, consumer, and ecosystem, and include variables such as acute and chronic toxicity, toxicity to birds, aquatic species, and beneficial insects,as well as soil half-life, leaching potential, and the half-life of the chemical within the plant . The EIQ is then multiplied by the application rate to determine the EI.Farmers must ensure they are producing an economically sustainable crop in addition to herbicide efficacy, herbicide cost, crop safety, and EI.

The commercial release of DR soybean provides additional weed control strategies that need to be compared with traditional two-pass weed management strategies in soybean.The objective of this study was to evaluate herbicide programs for their crop safety, weed control efficacy,mobile grow system profitability, and EI in DR soybean produced with conventional tillage. A partial profit analysis compared the profitability of the herbicide treatments.The profitability of each treatment was determined by subtracting the costs of the herbicide and herbicide application from the gross economic return. Gross returns were determined by multiplying the plot yield by the average Ontario soybean price for the month of October in 2014 and 2015 . Annual herbicide costs were calculated based on the herbicide retail prices provided by AGRIS ,and the cost of the herbicide application was based on the Ontario Field Crop Budgets . Retail prices for some herbicide programs included in this study were not available, so those products were excluded from the profit analysis.

Profitability data were transformed using a square root transformation before analysis. There was no difference in partial profit among herbicide programs. All herbicide treatments produced similar partial profits. Glyphosate was the lowest cost weed management program and was 33% of the cost of the second lowest cost weed management program. The low cost of glyphosate combined with only one application cost contributes to why this treatment demonstrated the highest partial profit in this study. It is important to note, however, that if a single POST application of glyphosate was not applied in a timely matter, soybean would be exposed to a longer period of early-season weed interference, potentially causing greater yield losses which may result in lower partial profits. Additionally, infields where higher weed pressures exist, or where one or more difficult-to-control or GR weeds are present, glyphosate may not adequately control the weed population, which could also contribute to greater yield losses and lower partial profits. The development of glyphosate resistant weeds is a topic of concern; from a stewardship perspective, a herbicide program consisting only of glyphosate should be avoided to reduce the risk of selecting for GR weed biotypes.

Since there were no differences in partial profits between the glyphosate-only herbicide program and other two-pass weed control programs with multiple modes-of-action, it is recommended that a two-pass weed control program be employed. Alfalfa is a perennial, cool season, C3 forage species cultivated throughout the world and is primarily used for hay, pasture, silage, and cover crop . Alfalfa and its mixtures make most of the hay production in the US, with nearly 7 Million ha planted in 2017 . Alfalfa makes cropping system sustainable by reducing soil erosion, enhancing soil quality, and fixes atmosphere icnitrogen in the soil . As a perennial crop, alfalfa persists for multiple years, reducing the cost of establishment. Several biotic and abiotic factors pose challenges to alfalfa seed germination, emergence and seedling growth in the establishment phase. Weeds compete with alfalfa for light, water, and nutrients and consequently reduce yield and forage quality . Newly established stands are especially more vulnerable , but older stand sand frequently cut stands are also affected. Therefore, the first year of planting is very crucial in terms of crop establishment, biomass yield, and stand persistence of alfalfa.