By Angie Peltier
Whenever a growing season ends, a lidded rubber box that houses my scouting supplies moves out from my vehicle's trunk and gets moved into the my office to make way for the lidded box holding my winter weather survival gear. Come spring, the scouting box gets restocked and switches place with the survival gear indicating that the growing season (aka scouting season) is upon us!
It is important to come prepared for the task at hand whenever you plan to scout your fields. My scouting box contains the following items: a pair of work gloves, some disposable gloves (for checking insect traps), a notebook and pen, a collapsible shovel, a machete, some large seal-able bags and a hand lens. Hard (or digital) copies of insect, weed and disease ID guides are also handy to have as is a pocket knife.
Whenever you scout a field, plan to look at plants away from border rows in at least 5 different areas of the field.
Scouting begins before and at planting. Typically farmers will visit a field before planting to measure soil temperature at planting depth and determine whether the soils are dry enough to cultivate or plant. During planting, folks will sometimes climb down from the tractor and check whether the cab monitors match reality – is the planter dropping seeds at the desired depth and plant population?
Scouting for seedling emergence and assessing plant population. In the next couple of weeks, depending upon soil temperature and moisture conditions, you'll be watching for seedling emergence. A lot can happen between planting and seedling emergence, including freezing temperatures, crusted soil, or cool, moist soil conditions and seedling disease. In order to be sure that you have an adequate plant population to reach realistic optimum yield for a particular field it is important to estimate plant stands in both corn and soybean.
With its inherent ability to compensate for thinner than planned stands, as long as there are no large bare patches soybean populations can be as low as 100,000 plants/acre and still be able to develop a full canopy to intercept all of the sunlight needed to produce high yields. Corn is less able to compensate for poor stands and is more vulnerable to sustaining yield losses due to uneven emergence than soybean. On productive soils in Illinois, corn stands around 34,000/acre are near optimal.
If you planted in corn in 30 inch rows, plant stands can easily be estimated by counting the number of plants in 17 feet 5 inches of row and multiplying by 1000. Purdue University has a nice handout on how to estimate soybean stands.
U of I has a handy corn replant calculator that takes into account: the realistic optimum yield for the field, the original planting date, the current plant population, the date that you might be able to realistically replant the field and the current price of corn. It crunches all of this data together to help you to determine whether there would be an economic incentive to replanting and whether any potential yield increase due to larger plant stands might be large enough to cover the cost of replanting.