What Do New York Corn Fields Really Yield? The Case for Using Yield Monitors

Quirine Ketterings1, Karl Czymmek1,2, Tulsi Kharel1, and Sheryl Swink1
Cornell University Nutrient Management Spear Program1, PRODAIRY2

Corn silage and grain yields have steadily increased since World War II (Figure 1) with a slightly greater increase per year for corn grain than for corn silage, possibly reflecting an emphasis on corn grain improvement by plant breeders in the past decades.

Figure 1: New York State average corn silage and grain yields over time show a steady increase 1948 – 2015 in both silage and grain yields but also large year-to-year variation. Yield data source: New York State Agricultural Statistics Service.

With an increase in yield comes the question: has the ability of improved crop varieties to explore the soil for nutrients kept up with higher yield or do we need to supply more N fertilizer to meet N needs? Further, we need to look at what differences in field traits (within and between) affect yield beyond the hybrid selected and the N fertilizer or manure that was applied. Nationwide evaluation of N use shows that overall, farmers are using the same average fertilizer N rates even while yields have been increasing.  Does that hold true for New York? With increasing focus on the water and air quality impacts of nutrient losses from agriculture, combined with higher risk of loss when nutrient applications are in excess of plant need, these questions are more important than ever for the future of agriculture in New York.

Before we can answer these questions, we need to know the actual yield levels for corn grown for grain and also for corn grown and harvested for silage. We also need to know how stable yields are from year to year as fields that deliver stable yield results will likely require different management from fields that yield low one year and high the next, depending on the growing season.

With a growing number of choppers joining the fleet of combines with yield monitors we now have the opportunity to summarize large yield datasets to help update several important issues: these include the ability to generate an updated general yield potential database, the opportunity for farms to develop and maintain their own yield potential database, and the ability to more quickly test if higher yielding fields, zones within fields, or specific varieties need higher N applications to meet or exceed potentials.

Figure 2: A consistent data cleaning process is essential for creation of reliable multi-field and multi-year yield maps.

The first requirement when working with yield monitors, is to make sure they are calibrated regularly. However, even with well-calibrated equipment, yield data from monitors need to be combed for obvious errors through a cleaning process, especially for silage yield monitors (Figure 2). To ensure we use the best possible data, cleaning protocols were developed recently for both grain and silage that now allow for fairly quick checking and cleaning of data for all corn grain and silage yield data in a particular harvest year. A manual that will help producers or consulting companies do this will be released in early 2018.

With this new data cleaning process, the Nutrient Management Spear Program in partnership with farmers and consulting firms, is now analyzing data from test farms located in Northern New York through a grant supported by the Northern New York Agriculture Development Program. The hope is to expand this beyond the farmers currently involved and thus create a statewide database for corn grain yield and for corn silage yields per soil type in the coming years. Once data are cleaned, we can create yield frequency histograms (Figure 3).

Figure 3: Histogram of yields of Hogansburg soils (N=43) in northern New York. Blue are fields harvested in the year of reporting. In green are all fields of this soil type harvested and recorded to date, previous years included.

These types of histograms show the range of yields and how many fields with this soil type provided a certain yield. For example, in the case of 43 fields with the Hogansburg soil shown in Figure 3, the average yield was 19.9 tons/acre while 5 fields out of 43 yielded more than 25 tons/acre and one field averaged 27.5 tons/acre (maximum reported for the example shown in Figure 3). These histograms allow for determination of means, medians, ranges in yields, etc. and they can help us (1) quickly update the yield potential database for corn grain that is the foundation for the basic N guidelines; and (2) develop an independent database for yield potentials for corn grown for silage.

Stay tuned for further updates! A call for participating will be shared with farmers and farm advisors as funding to proceed at a larger scale is granted.  The protocols for data sharing are available through the NMSP website (http://nmsp.cals.cornell.edu/NYOnFarmResearchPartnership/YieldDatabase.html). The data-processing protocol will be added to this page once completed.


We thank the farmers and farm consultants that have participated in the yield potential evaluation project to date. For questions about these results contact Quirine M. Ketterings at 607-255-3061 or qmk2@cornell.edu, and/or visit the Cornell Nutrient Management Spear Program website at: http://nmsp.cals.cornell.edu/.

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