This “spring,” the weather has gone from snow and 24 degrees to sunny and 80 degrees within one week. This unusual weather leaves many of us wondering what’s in store for the remainder of the growing season.
In general, unfavorable weather conditions tend to affect soybean yield much less compared to corn yield. In 2012, when we experienced a hot, dry summer, corn yield was reduced by 23% while soybean yield was only reduced by 8% (see the table below). However, under more optimum weather conditions, corn yield gains are much greater compared to soybean. With more ideal weather in 2013 and 2014, corn yield increased 12-14% while soybean yield only increased 2-8%.
Table 1. Corn and soybean grain yield averages for Ohio compared to the 5-year average (data from USDA National Agricultural Statistics Service).
Despite the weather, the state soybean yield does not tend to fluctuate much. Soybean vegetative and reproductive stages overlap allowing the soybean plant to compensate for short periods of stress (see the figure). In 2012, while plants were stunted and there was an increased number of flower abortion due to hot/dry weather conditions, soybean yield was “saved” in many areas of the state due to rainfall in August and September promoting seed fill. (This was especially true of our later maturing varieties.)
With the weather forecast calling for “slightly-above” normal temperatures and “slightly below precipitation” for the remainder of April and similar conditions for May, this year offers an opportunity to plant corn at optimum calendar dates for yield. The recommended time for planting corns across Ohio is mid-April through about the first week of May. Grain yield and test weight are increased by early plantings, whereas grain moisture is reduced, thereby allowing earlier harvest and reducing drying costs. In central Ohio, yields decline approximately 1 to 1.5 bushels per day for planting delayed beyond the first week of May. Early planting generally produces shorter plants with better standability. Delayed planting increases the risk of frost damage to corn and may subject the crop to greater injury from various late insect and disease pest problems, such as European corn borer and gray leaf spot. With earlier planting, vegetative growth is usually complete and pollination initiated prior to the period of greatest moisture stress in July and grain filling occurs during the periods when solar radiation is high which promotes greater accumulation of dry matter in the grain.
No-tillage corn can be planted at the same time as conventional, if soil conditions permit. In reality, however, planting may often need to be delayed several days to permit extra soil drying. Corn should be planted only when soils are dry enough to support traffic without causing soil compaction. The yield reductions resulting from “mudding the seed in” may be much greater than those resulting from a slight planting delay. Moreover, given the weather projections for drier and warmer conditions than normal, even with such delays, the crop may be planted before the optimum plant date window ends.
There have been occurrences in past years when early to mid-April planting were adversely affected by an abrupt transition from warm, dry conditions to freezing rains and snow. When dry corn seed absorbs cold water as a result of a cold rain or melting snow, “imbibitional chilling injury” may result. Such injury in corn seed can lead to delayed seedling growth and reduced stands so planting right before such large temperature swings should be avoided.
Appropriate planting depths for corn vary with soil and weather conditions. There is a perception that shallow planting depths (less than 1.5 inches) are appropriate for early plantings — when soil conditions are usually cool and moist — because seed will emerge more rapidly due to warmer soil temperatures closer to the surface. However, planting shallower than 1.5 inches is generally not recommended at any planting date or in any soil type. Recent Ohio studies that evaluated corn response to seeding depth provide no evidence to support shallow plantings. For normal conditions plant corn at 1.5 to 2-inches deep to provide frost protection and allow for adequate root development. When corn is planted 1.5 to 2 inches deep, the nodal roots develop about 0.5 to 0.75 inches below the soil surface. At planting depths less than 1 inch, the nodal roots develop at or just below the soil surface. Excessively shallow planting can cause slow, uneven emergence due to soil moisture variation, and rootless corn (“floppy corn syndrome”) when hot, dry weather inhibits nodal root development. Shallow plantings increase stress and result in less developed roots, smaller ears and reduced yields.