Whole Farm and Field Corn and Alfalfa Yield Variability on a CAFO Dairy Farm.

Dairy farms in New York produce a large percentage of forages for cows on the farm itself, while importing remaining nutrients in the form of concentrates. Whole-farm nutrient mass balances (indicator of environmental footprint) and farm profitability can be improved by increasing the percent homegrown forage. To improve forage production, accurate yield records are needed. Such yield records can be used to evaluate trends over time, which can be used to identify high versus low yielding fields as well as high versus low yield stability (year-to-year variability). In this study, fourteen years of yield data from a 1000-cow western New York dairy farm were used to evaluate field- and farm-scale yields, and yield stability of corn silage (Zea mays L.) silage and alfalfa (Medicago sativa L.) and grass mixtures. The specific objectives were to: (1) determine temporal variability of forage yields over time; (2) determine yield stability (year to year variability) across all fields, and (3) evaluate soil physical and chemical properties as potential indicators of yield and yield stability. Yield varied temporally and spatially. Corn silage yield increased between from 13.3 Mg DM ha^-1 in 2000 to 17.8 Mg DM ha^-1 in 2013, while hay yield averaged 8.6 Mg DM ha^-1 without a trend over time. Year-to-year yield variability was impacted by timing and amount of rainfall. Field drainage was the most significant soil physical factor impacting yield performance and stability. High yielding and stable fields averaged 18-20 Mg kg^-1 Morgan soil test P and 2.9-3.2% organic matter versus 9 Mg kg^-1 Morgan soil test P and 2.7-2.8% organic matter for low and variable yielding fields. Results suggest management practices that increase organic matter, improve drainage, and provide soil fertility levels in optimal ranges will result in higher and more stable yields that are less impacted by weather extremes.