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Monday, February 5, 2007

Hybrid Maturity for Southern Minnesota

D. R. Hicks and T.R. Hoverstad, University of Minnesota

There's a strong relationship between maturity of hybrids and grain yield such that normally one wants to choose hybrids with maturities that use the entire growing season for maximum grain yields. In the past few years, the price of drying has increased substantially because of higher LP Gas prices. We used yield data from the Minnesota Corn Performance Tests of 1998-2006 to determine the optimum hybrid maturity based on two corn selling prices and two drying costs.

The relationship between relative maturity (RM) and kernel moisture at harvest is given in Figure 1. Moisture content continues to increase as RM increases through the range of maturities that are adaptable to southern MN. The figure is not shown, but the same relationship occurs for the central MN tests.

Figure 1. Relationship between Kernel Moisture and Relative Maturity for the Southern Zone of the Hybrid Performance Tests, 1998-2006.
The yield relationship to RM for the southern MN tests is given in Figure 2. We fit a curvilinear line to the data; that line is drawn through the open circles in the figure. The maximum yield on the curvilinear line occurred at a RM of 104. A similar figure (not shown) for the central MN test shows the maximum yield occurred at 98 RM. We used this kind of analysis to calculate gross returns per acre and the economic optimum RM based on two drying costs and two corn selling prices. Those values are given in Table 1 for both the southern and central zones of MN.

Figure 2.Relationship Between Corn Grain Yield and Hybrid Relative Maturity for the Southern Zone of the Hybrid Performance Tests, 1998-2006
Table 1. Economic Optimum Hybrid Maturities for Differing Drying Costs and Corn Prices.

Drying Cost
Corn Price
Economic Optimum Relative Maturity
Central Zone
Southern Zone

The drying cost of 2.8 cents per point of moisture is the energy cost to dry corn on the farm while 4 cents per point is a normal custom drying charge. Selling prices of $1.85 and $3.25 were used to reflect "normal" selling prices of years past and that expected in the next few years.

The economic optimum RM (EORM) ranges from 92 to 94 for the central zone and from 97 to 101 for the southern zone of MN which is lower than the RM that growers could use in both growing zones. But, maximum return after drying costs should be a growers' objective rather than maximum yield per se. The EORM depends on drying costs and selling price. As one would expect, the EORM goes up as corn selling price increases at either drying cost. That is, as corn price increases, more money can be made with higher yields which are usually associated with higher RM's. And at either corn price, the EORM goes down as drying cost increases. For all combinations of drying cost and corn price, the EORM is lower than the RM's we have recommended in the past years for maximum profit per acre.

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