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.

Weather extremes in 2012 and 2013 impacted corn silage and hay yields for many dairies in the northeastern United States and prompted a growing interest in double cropping of winter cereals for harvest as high quality forage in the spring. Here we report on (1) forage yield ranges of cereal rye and triticale in corn-cereal rotations in New York in 2012-2014, and (2) survey results of 30 New York farm managers who grew winter cereals as double crops with corn silage in 2013. Yields averaged 3.62 and 4.88 Mg ha -1 for cereal rye and triticale, respectively. On average, the surveyed farmers planted 8% of their tillable acres to winter cereal with the intent to harvest as forage. Triticale was the most frequently seeded double crop (70%). Most stands were established with a drill (57%). Manure was applied to 37% of the fields. Fertilizer nitrogen (N) was applied at dormancy break by 79% of the farmers with a median application rate of 67 kg N ha -1 . The biggest challenge with the double-crop rotation, identified by the farmers, was timely seeding of the double crop in the fall given late corn silage harvest and early onset of frost in the Northeast. Despite challenges encountered and questions about the impact of harvest of the winter cereal on the main crop, 83% of the surveyed farmers planned to continue to grow double crops.

Core Ideas Corn silage and grain yield monitors collect yield data of relevance to farmers. Evaluation of quality of yield monitor data is essential, especially for silage. A data cleaning protocol, consistent across fields, farms, and years, is needed. Semi‐automation is needed for quick and consistent processing of whole‐farm data. Yield monitor data are being used for a variety of purposes including conducting on‐farm studies, assessing nutrient balances, determining yield potential, and creating management zones. However, standardization of raw data processing is needed to obtain comparable data across fields, farms, and years. Our objective was to evaluate the impact of data cleaning protocols on corn (Zea mays L.) grain and silage yield data at the whole field (with and without headlands) and within field (soil map unit) scales. Corn silage data from 145 fields (three farms) and grain data from 88 fields (three farms) were processed. Comparisons were made to evaluate yields among three levels of cleaning: (i) none; (ii) automated cleaning (“Auto”) with filter settings derived for 10 fields per farm; and (iii) automated cleaning with manual inspection for unrepresentative patterns, after the automated cleaning step was completed (“Auto+”). The Auto+ cleaning process was conducted separately by three individuals to evaluate person‐to‐person differences. Spatial Management System software was used to read raw data and transfer to Ag Leader format. Yield Editor software was used to clean data (Auto and Auto+). Results showed the necessity of data cleaning, especially for corn silage. However, considering less than 5% deviation between methods at three spatial scales, the Auto and Auto+ cleaning resulted in similar output, as long as (i) each field or subfield included at least 100 harvester measurement points, and (ii) a moisture filter was applied for corn silage data.

Forage double cropping can be a beneficial practice for dairy farmers in the northeastern United States, providing an additional, harvestable crop plus many environmental benefits. Triticale (× Triticosecale Wittm.), winter wheat (Triticum aestivum L.), and cereal rye (Secale cereale L.) are forage double crop options in New York that require nitrogen (N) management. From 2013 to 2016, 62 N‐rate trials were conducted across New York with five N rates (0, 34, 67, 101, and 135 kg N ha−1) applied in four replications at spring dormancy break. Forage was harvested at flag‐leaf stage in May (Feekes stage 9). Soil samples were taken prior to N‐application at dormancy break. Management practices and field characteristics were evaluated as predictors (using classification tree analyses) for yield and the most economic rate of N (MERN) at dormancy break, determined using a quadratic plateau model. Approximately one‐third of the sites did not respond in yield to spring N application, averaging 4.3 Mg DM ha−1. Of the remaining sites, ∼80% had MERNs ranging from 47 to 112 kg N ha−1, averaging 77 kg N ha−1, with yields at the MERN from 2.2 to 6.9 Mg DM ha−1, averaging 4.2 Mg DM ha−1. Yield could not accurately be predicted statistically. However, low‐yielding sites lacked fall manure application and well‐drained soils. We conclude that forage winter cereal fields with well‐drained soils, recent manure applications, and timely planting may not need additional N at dormancy break, while others require approximately 19 kg N ha−1 per Mg DM ha−1. Core Ideas N management is needed for optimum performance of forage winter cereal crops in New York. Yields of 1.0 to 6.9 Mg DM ha−1 were found in New York (4.1 Mg DM ha−1 average). Winter cereals required approximately 19 kg of N per 1 Mg DM for optimum forage yield. Soil drainage, manure history, and planting date affected N needs. Nitrogen rates beyond plant needs for optimum yield can increase crude protein.

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