Managing a corn crop is not one of the most complex tasks compared to the other agricultural crops grown in our country. Obviously, corn has certain obstacles, but farmers have not faced serious problems growing it. However, the scenario experienced by many livestock producers has been somewhat bleaker. Why? Many livestock farms do not have specialized equipment or trained labor to manage corn during the agronomic phase. On top of these problems, there is also a lack of focus on this stage. In other words, much is discussed about the nutritional aspects of corn silage and very little (almost nothing) about the agronomic side.
Although transgenic hybrids account for most of our fields, many of them require insecticide applications throughout the cycle, as can be seen in Figure 1. On the other hand, some pests have no established control and, therefore, there is nothing to be done (Figure 2). Many hybrids are also susceptible to late-season diseases and require fungicides (Figure 3). In many areas, especially where there is no no-till system, weeds infest the crop and herbicides are needed.
As for the fertilization program, there is fertilization at planting and, later, side-dress fertilization, which must be carried out at predetermined periods. All of these agronomic aspects (control of pests, diseases, weeds and fertilization) must be performed during the rainiest period in the central region of the country. In other words, management will not always happen whenever a pest needs to be controlled or a herbicide applied, because the weather interferes.
So corn silage with high nutritional value and reduced cost ends up being for the few. In the livestock environment, a habit has developed of discussing corn silage, which is a forage, as if it were a concentrate ingredient. Many nutritionists who formulate diets simply go to the silo face, collect a sample, send it to the laboratory and then criticize the report because of the low nutritional value of the silage. I invite these professionals to take part in choosing the hybrid, follow the planting and all the other stages involved in managing the crop and producing the silage. Corn silage requires intense attention and dedication from start to finish, that is, from choosing the hybrid to the feed bunk. A big-picture view of the system is needed.
Therefore, agronomic planning is considered a priority when choosing a corn hybrid for silage. Its nutritional value also has its due importance, but should be considered secondary. Hybrids that perform well during the agronomic stage should be preferred by livestock producers, since the great difficulty in producing corn silage lies precisely in this period. Ensiling per se (harvesting, compaction, etc.) is well known to livestock farms and holds no great secrets.
Table 1 shows the variation in forage production and the economic efficiency of eleven corn hybrids grown in Lavras, in southern Minas Gerais. The agronomic cost was calculated based on the commercial value of each hybrid's seeds, fertilization (planting and side-dress), weed control, as well as whether or not insecticide and/or fungicide applications were needed. There was a difference of 6.4 tons of dry matter/ha between the lowest and highest forage production. The agronomic cost varied by two hundred and ninety-five reais per hectare. These variations resulted in different forage production costs (R$ 116.9 and 88.2 as maximum and minimum, respectively). The difference between the highest and lowest cost results in a difference of three cents per kg of forage produced. Since the animal eats a large amount of silage in its diet (~50%), this difference (R$ 0.03) can be decisive between profit and loss on a dairy farm, for example. Therefore, knowing the agronomic history of the hybrid to be planted becomes essential for livestock farms that intend to produce corn silage.
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