Choosing one’s maize variety
Choosing one's maize varieties
To choose one’s maize variety is to compromise among several factors: earliness adapted to local climate, consistent productivity, and tolerance to stressors such as lodging, drought, or disease.
Importance of Earliness when Choosing One’s Varieties
Earliness is one of the traits that contribute to yield and its consistency, as well as to threshing quality and grain drying. It is an indicator of flower initiation, kernel moisture content, and dry matter (D.M.) content in the whole plant. It also determines the length of the growing season and the dry-down rate of the kernel.
The length of the growing season is the time between sowing and the crop’s physiological maturity (which is attained at 30-32 percent kernel moisture or 32-33 percent D.M., in feed corn), during which the yield is formed. A late hybrid will have a longer growing season and will produce more if there are no limiting factors in terms of temperature and water.
With grain maize, a later variety will generally produce yield gains of 0,5 to 2,5 q/hectare for each earliness point – an advantage that is however offset by the extra cost of drying. Later varieties can produce yield gains when the planting dates and temperatures of the year allow it. In temperature or water stress situations in the final stages of kernel growth, earlier varieties perform proportionally better.
With feed maize, the choice of earliness will allow for more flexibility in terms of harvest dates, establishment of the next winter crop, and feed value. A variety that is too early for a given region will underuse the available climate and soil conditions and will produce less biomass per whole plant. If harvested too late, it will accumulate levels of starch that will be too high for a proper use by dairy cows if their ration is not adjusted with roughage. A later feed maize variety has the advantage of a yield gain of 0,2 tons of DM/hectare/earliness point; however, that potential will only express itself if the planting dates and the temperatures of the year allow it.
Yields and Consistency
Yield potential differences among varieties – attenuated by earliness degrees at harvest – remain an important selection criterion. Production result consistency is assessed on the basis of the previous years, by making comparisons to other regions, and by the consistency of trials carried out during that year.
In the case of identical earliness, a difference of 5 percent in grain yield will trigger a commensurate difference in rations. With feed maize, a difference of 5 percent means an increased number of rations or a longer period of feeding based on maize silage.
With the exception of the earliness and stalk posture effects that the different varieties have, the traits that contribute to yield steadiness are more difficult to bring out. They merge, they combine with one another and they cancel out various behaviour impacts caused by temperature stress and the wide range of water stress scenarios and crop management methods. Therefore, the consistency of the results needs to be assessed through comparisons among trials carried out in multiple areas and over multiple years.
Lodging and Disease Tolerance in Risky Situations
Lodging resistance is another important criterion when choosing one’s varieties. Not only does it have a bearing on the yield, but it is also key to how easily one can harvest, and when. The quality of the stalks in the plants’ final stages (which may be affected by such things as the hollow stalk symptoms, which have physiological and pathological causes), although not always indicative of all types of lodging, will provide additional information.
Given the early planting practices and the pest risks at the beginning of the growing season, early vigour will provide useful information.
In vulnerable areas, one should consider disease tolerance, as it, too, contributes to yield expression and regularity.
UFL: a Synthetic Criterion in the Livestock Industry
The differences in energy value among varieties, expressed by the UFL value (which is the ability to turn feed intake into milk) should be taken into account: thus an UFL difference of 0,01 allows for an average daily milk gain of 0,3 l per dairy cow, if the animal receives a balanced ration. The digestibility of non-starch organic matter (dMOna) and of plant cell wall fibres (dNDF), along with the degradable starch percentage are complementary criteria, which are useful when establishing the feeding rations for ruminants. With high-potential dairy cows, it is recommended to use varieties that present a good balance between these three quality components.