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Late Planting of Small Grains and Corn

Joel Ransom

Extension Agronomist - Cereal Crops

May 21, 2003

In last week�s Crop and Pest Report, I expressed my concern that planting of cereal crops not already in the ground could be delayed beyond their optimum dates if rains continued. The heavy rains during the past week have in fact delayed or stopped planting in a wide area of the state. We are now at the point in the season where any new plantings or replantings of cereal crops will be "late". Late planting will almost always result in reduced yields. The optimum window for maximum yield in barley and spring wheat is between the middle of April and the middle of May. Delays in planting small grains generally result in a 1% reduction in yield for each day delay after May 15. The optimum planting date for corn is around the 1^st of May for North Dakota. Not only does the yield of corn decline after this date, but moisture content at harvest increases and test weight decreases if full season hybrids are planted. In this issue, I will briefly describe potential options for managing the problems associated with late plantings.

The yield reduction associated with late planting small grains is largely a result of the higher temperatures during early plant growth causing accelerated plant development which reduces tillering and head size. When seeding rates below 900,000 seed per acre were planned, the lower yield potential of late planted small grains can be partially offset by increasing the seeding rate. For every 10 days delay beyond May 15, increase your seeding rate by 5 to 10% up to a maximum of 20%. There is probably little advantage at this point in changing varieties to one that is earlier or to one with known tolerance to late planting unless you already have it on hand. You should avoid planting varieties developed for Canada, as they tend to be more photo period sensitive and typically do poorly when planted late. Although there is urgency in getting the crop in, it will probably pay to exercise some patience, as working a wet field can result in clods, compaction and potentially poor emergence.

Late planting often results in higher protein. You should adjust nitrogen applications to more closely match the lower yield potential of your delayed plantings. This is particularly important in barley that is intended for malt, where high protein may result in the loss of malt quality.

Full season corn varieties planted near May 1^st are the most productive. A full season hybrid will almost always out-yield a earlier hybrid. In late planting situations, however, a full season hybrid has a high probability of having high moisture content and low test weight at harvest. The cost of drying a full season hybrid planted late should be considered before deciding on whether or not to stay with a full season hybrid. Data from a hybrid trial conducted in Carrignton in 2002 demonstrates the effect of pushing the maturity of a hybrid beyond the heat units required for it to fully mature and dry down before harvest (see Table 1). These data demonstrate the potential yield advantage of a later maturing hybrid, but they also show that the value of the crop, even if yield is greater, can be less due to the cost of drying the extra moisture from the grain. Earlier hybrids can often be more profitable to produce than later ones, particularly for late plantings.

Table 1. The effect of corn hybrid maturity on grain moisture content at harvest, yield, and market value, Carrrington, 2002 growing season.