By Dennis Pennington, Wheat Systems Specialist

Many growers have invested in yield monitor systems that have been standard equipment on combines for a number of years. Data from these systems can provide valuable information on areas of the field with significantly lower yield. This information, especially with data collected over a number of years with different weather conditions, can be used to address problem areas and improve yields. Yield monitor data is increasingly being used in precision agriculture to develop precision for fertilization, spraying and variable rate planting.

Importance for Water Quantity Management

Crop productivity is highly dependent upon soil moisture, often the most limiting yield factor in production. Crop production takes place on fields that are made up of many different soil types. Yield maps can give us insight into the potential benefits of investing in better drainage for heavy soils, or perhaps irrigation on lighter soils. Good data must be collected over a number of years, as yields on fields with variable soils will vary significantly in wet vs. dry years.

On irrigated crops, accurate data can be used to evaluate changes in yield due to variable irrigation rates across the field. Comparing yields in dry corners can be used to evaluate benefits of irrigation for that year. 

Uniformity tests many times show significant differences in application rates across a pivot, and with accurate yield data, the impact of the different rates over the season can be determined. Accurate yield monitor data can also be used to show impact of variable nitrogen (N) rates with irrigation.

Importance in Crop Production

Accurate yield monitor data are especially important in helping to understand which factors are impacting corn yields. Accurate yield maps also help to identify areas of the fields where we may want to manage inputs such as N or seeding rates to help reach top potential yields on different soil types.

One of the most important inputs in corn production is N. Since N availability is highly dependent upon environmental loss (leaching, denitrification and volatilization) and mineralization of organic matter, correlation of yields to soil type given a season’s rainfall may help us to better manage timing and type of applications to maximize returns when managing inputs. On lighter soils, sulfur availability is playing an increasingly important role in maintaining productivity in corn, and economic response to fertilizer sulfur will most likely be highly related to soil texture and organic matter levels at any given location in the field.

Finally, we know there are a lot of choices of hybrids we can raise. Experience with university variety trials shows there can be large differences between hybrids performance between companies and even within a particular company’s product line (20 bushels and more). The decision on what seed to plant has been important for a long time. Now, we are moving into an era where herbicide-resistant weeds are becoming more common in Michigan and Bt traits are facing more significant challenges in controlling some important insect pests.

To state it plainly, good pest management is poised to become much more complex over the next several years. It is likely to take multiple applications of herbicide, insecticide and stepped up scouting to provide the same level of crop protection we have become accustomed to. Accurate yield mapping allows growers to evaluate different hybrids, traits and pest control strategies on their farm relatively painlessly by planting or spraying strips in a field. The added effort can pay off big if you can find ways to more cost effectively manage pests or select high yielding varieties for your farm.

Importance for Soybeans

Like many other crops, soybean yields can vary significantly within any given field. To maximize yield and income from their fields, growers need to identify and track poor-yielding areas in each field and identify the factors responsible. Some of the common yield-reducing factors occurring in Michigan are soybean cyst nematodes (SCN), sudden death syndrome, white mold and manganese deficiency.

Yield monitors can be especially beneficial in identifying early SCN problems as soybean yields can be reduced by 10-15 bushels per acre before above-ground symptoms are visible. Also, if the yields of SCN-resistant varieties are declining over time in SCN-infested locations within the field, growers should suspect the existing SCN population is able to reproduce on the current variety and should submit a soil sample to Michigan State University Diagnostic Services for SCN-type testing.

Many soybean planters and air seeders are equipped with variable-rate seeding technology, enabling producers to change soybean seeding rates on the go. Yield monitor data can help growers develop seeding rate prescriptions based on the rule of thumb that soybean seeding rates should be lower in highly productive areas and higher in less productive areas. Potential benefits of prescription soybean seeding rates are: reduced seed costs, higher yields, reduced lodging and less white mold.

For more information about how to calibrate a yield monitor, see the accompanying MSU Extension article, “Yield monitor calibration procedure.”