Manitoba Agriculture, Food and Rural Initiatives

Introduction to Corn Production

In Manitoba, field corn is grown for grain for human and livestock products, and as a silage for animal feed. Manitoba producers provide most of the high quality corn required by the distillery at Gimli. Corn silage is fed to dairy and beef cattle.  Corn is also processed and used for hog and poultry feed.

Adaptability to Manitoba

The three main climatic variables that affect adaptation in Manitoba are day length, temperature (both heat and frost-free period), and rainfall. Day length and temperature affect development, i.e., flowering and maturity; and temperature and rainfall affect growth, i.e., yield.

Air and soil temperatures are very important because the rates of growth and development increase as temperatures increase from 10 to 30ºC. In early spring, soil temperature is more important than air temperature because the growing point stays below the soil surface until sometimes in June.

Corn Heat Units

In Manitoba, as well as other parts of Canada, cumulative temperatures such as Corn Heat Units (CHU) are closely related to development. CHU are better than calendar days for measuring time between stages because, in warmer regions, more CHU are accumulated per day so that corn develops faster per day than in cooler regions.

When calculating the CHU for each day for corn, there are several considerations:

• day and night temperatures are treated separately

• no growth is assumed to occur with night temperatures below 4.4ºC or day temperatures below 10ºC

• maximum growth occurs at 30ºC and decreases with higher temperatures

CHU for each day are calculated by the formula:

CHU = 1.8 (Tmin - 4.4) + 3.3 (Tmax -10) - 0.082(Tmax -10)²
                                    2

where: Tmin = Daily minimum temperature (ºC) and
          Tmax = Daily maximum temperature (ºC)

Average accumulation of CHU’s for agro-Manitoba is presented in Figure 1. Local factors such as soil type, slope of land, elevation, and shelter will modify the growing conditions. Corn hybrids sold in Manitoba are given a CHU rating, providing a base for selecting hybrids for a particular location. CHU ratings for corn hybrids are available from Manitoba Agriculture, Food and Rural Initiatives offices and from the Manitoba Corn Growers Association.

A water shortage occurring at any time during the year can cause yield decreases.  Drought stress early in the growing season can reduce growth, thereby affecting the photosynthetic area.  Drought during pollination may decrease yields by affecting silk elongation.  If water stress occurs during grain filling, kernels may abort or not fill out, reducing yield and quality.

Moisture stress is the greatest problem on coarse-textured (sandy) soils, while excess moisture is a more common problem on fine-textured, compacted or poorly drained soils.