A whole-farm nutrient mass balance (NMB) is a useful measure of the nutrient status of a dairy farm. Research is needed to define and determine a feasible NMB range for dairy farm systems in New York State (NY). The objectives of this study were to (1) document the distribution of N, P, and K mass balances of 102 NY dairy farms (including 75 small, 15 medium, and 12 large farms); (2) establish initial NMB benchmarks based on what 75% of the farms achieved; (3) determine the maximum animal density that allows an example NY dairy farm to balance cow P excretions and crop P removal without exporting crops or manure; and (4) identify opportunities to improve NMB over time. Nutrient mass balances of the 102 farms ranged from -39 to 237 kg of N/ha for N without including N2 fixation (N1), from -14 to 259 kg of N/ha when N2 fixation was included (N2), from -7 to 51 kg of P/ha, and from -46 to 148 kg of K/ha. Seventy-five percent of the farms were operating at NMB less than 118 kg of N/ha for N1, 146 kg of N/ha for N2, 13 kg of P/ha, and 41 kg of K/ha (75% benchmarks). Farms with the highest nutrient use efficiencies (lowest NMB per unit of milk produced) operated with less than 8.8 kg of N/Mg of milk for N1, 11.8 kg of N/Mg of milk for N2, 1.1 kg of P/Mg of milk, and 3.0 kg of K/Mg of milk. The biggest contributor to the NMB was the amount of imported nutrients, primarily feed purchases. The example farm assessment (assuming no export of crops or manure) suggested that, when 70% of the feed is produced on the farm and P in feed rations does not exceed 4 g of P/kg of DM, cow P excretion and crop P removal were balanced at a maximum animal density of 2.4 animal units (AU)/ha (~0.97 AU/acre). Dairy farms operating with animal densities <2.4 AU/ha typically had NMB below the 75% benchmark, whereas most dairies with more than 2.4 AU/ha needed to export manure or crops to meet the 75% benchmark. Opportunities to reduce NMB on many farms, independent of size and without changes in animal density, are possible by more tightly managing fertilizer and feed imports, increasing the percentage of farm-produced nutrients, implementing precision feeding, and exporting crops or manure.

Northeastern U.S. (New York, Pennsylvania, and New England states) dairy farmers are increasingly interested in improving soil health, nutrient sequestration, and dry matter production. Consequently, farmers ask about managing winter cover crops (WCCs) in corn silage (Zea mays L.) rotations. In this literature review we identify WCCs most suitable to the Northeast, and summarize studies on (i) fall and spring N accumulation, (ii) nitrogen fertilizer replacement value (NFRV) for the next corn crop, and (3) environmental and management variables that aff ect N uptake and NFRV. We also discuss the literature on use of WCCs as forage commodity crops. Overwintering species most suitable for corn silage rotations are wheat (Triticum aestivum L.), cereal rye (Secale cereale L.) and triticale (X Triticosecale Wittm.). Clover (Trifolium spp.) and vetch (Vicia spp.) can add N but require inter-seeding in the Northeast. Th e NFRV for vetch typically exceeds that of clover, while the NFRVs of winter cereals tend to be low or negative. A few studies suggest cover crop termination with herbicides compared to tillage incorporation can, when no fertilizer N or manure is added, result in slower decomposition and more gradual N release. Research on the eff ects of tillage on NFRVs of cover crops is inconclusive. When seeded aft er corn silage, cereal rye is most eff ective in N uptake in fall and spring. A corn rotation that includes cereal rye or triticale that can be harvested has the potential to reduce soil erosion, capture residual N, increase annual forage yields, and provide quality forage.

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Animal manure is typically applied to meet the N needs of crops. This can lead to overapplication of P and K. We evaluated the impact of a change from N‐based applications of manure and compost without incorporation to a P‐based (crop‐removal) management system with immediate incorporation of manure on (i) silage corn (Zea mays L.) yield and quality, and (ii) soil test NO3, P (STP), and K (STK). A 5‐yr field study was conducted with annual spring applications of composted dairy solids (46 and 74 Mg ha−1), liquid dairy manure (68 and 196 kL ha−1), and inorganic N fertilizer (0 and 112 kg ha−1). Shifting from N‐ to P‐based manure and compost management reduced the corn yield by 7 to 13% and protein by 8 to 9%, suggesting that fertilizer N is needed for P‐based management. Shifting from N‐ to P‐based manure management reduced soil NO3–N at silage harvest by 39% vs. 21% for compost. After 5 yr, STP increased four‐ and sixfold and two‐ and fourfold for N‐ and P‐based manure and compost management, respectively, reflecting positive P balances (lower than anticipated yields). Soil test K increased three‐ and twofold with N‐ and P‐based manure and compost management, respectively. Both STP and STK remained unchanged with inorganic N fertilization. We conclude that a shift from N‐ to P‐based compost and manure management, with immediate incorporation of manure, leads to reduced soil P and K buildup and, for manure, also soil NO3, but supplemental inorganic N fertilization is required to ensure that crop N needs are met.