Researcher explains the impacts of drought and cold on safrinha corn crops

The scientific researcher at Embrapa Maize and Sorgo in Sete Lagoas-MG, Paulo César Magalhaes, is a specialist in production physiology and participates in the XVI National Seminar on Safrinha Maize as a speaker with the theme “Ecophysiology: Impacts of the Environment on the Plant”.

In his line of research, Magalhaes analyzes the main effects of drought and cold on the safrinha corn crop. According to him, the corn plant's first line of defense in the face of drought is the closure of the stomata, which, in turn, causes a decrease in CO2 absorption and, consequently, in photosynthetic rates.

The researcher remembers that drought is critical in two phases of corn cultivation: flowering and grain filling. During flowering, drought can cause problems with grain pollination, resulting in failed ears and, consequently, lower production.

Another critical period is grain filling. During this period, the metabolic activity of plants is intense. There is a great demand from photoassimilates for carbohydrates that will be displaced to fill the grains. Less photosynthesis implies compromised biomass and lower grain production.

In general, drought in the corn harvest will result in smaller, lighter grains and, therefore, less productive. Low temperatures, in turn, prolong the cycle because they reduce metabolic activities in the plant. In case of frost, the effects are more drastic, especially if you take the plant during the flowering or grain filling phase.

Magalhaes explains that frost burns those leaves that have a high photosynthetic rate compared to the others that are superimposed. When frost occurs at the end of the cycle, a large part of the plant's productive potential will already be satisfied, and it is not as problematic. The reasoning is the same as in drought, the plant needs the leaf area to produce photoassimilates potentially available for the grains.

Production system  

For Magalhaes, an ideal technological package to minimize risks must consider the correct sowing time and the choice of genetic material. Off-season corn, when planted within the correct window, considerably reduces the risks inherent to its cultivation.

The choice of a good cultivar, adapted to the region in which it will be cultivated, is also recommended by the researcher. He notes that there are already cultivars on the market adapted to each producer's region. Population density, soil management, including fertilization and conservation practices are also added to the production system.

Among the various technologies made available to farmers for good weed control and adequate management of pests and diseases are emerging technologies. Magalhaes brings, as an example, biostimulants. “BiomaPhos is a liquid inoculant that contains bacteria that will proliferate in the soil and make phosphorus available”, he says.

If the producer is in a late window, he can opt for the Antecipe technology, a system of intercalary sowing of corn between the soybean rows, before harvesting the oilseed crop. “With this technology, the farmer gains 20 days in the cycle and the corn affected when soybeans are harvested recovers quickly because its growing point is still below the soil surface”, he explains.

The weather

Water and temperature are essential for corn to reach its full productive potential. The Ministry of Agriculture, Livestock and Supply (MAPA) made available the ZARC – Agricultural Zoning of Climate Risk, which predicts the correct sowing time in all planting regions.

For Magalhaes, the ZARC is extremely important as it takes into account all the characteristics inherent to each region, including soil conditions, and signals the correct time so that risks are minimized. Another important factor in minimizing risks is the choice of cultivar.

According to the researcher, the hybrid must have rusticity and production consistency even in the face of climatic adversities. In addition, it must have good resistance to pests and diseases, tolerance to lodging and breakage and good straw formation. The farmer must pay attention to the precocity (cycle) of this material.

Super or hyper

Due to the off-season being a risky activity, many farmers question whether they should always use super or hyper-early materials. The researcher observes that, in general, early materials produce more than super early materials which, in turn, are recommended where the planting window is very short and with very low temperatures at the end of the cycle. Rio Grande do Sul is an example. 

According to Magalhaes, seed companies place several genotypes on the market each year. They are adapted, productive materials that accept the use of technology. “They have a robust plant genetic improvement program that makes these new materials available to farmers in general every year,” he notes.

Knowing how to identify each stage of the plant and its respective demands is another important factor for the success of safrinha corn crops from Magalhães' point of view. “In the past, it was used to adopt some technologies according to days after sowing, but this is no longer used. Currently, any type of crop management is carried out according to the phenological stage of the plant”, he explains.

Different stages, different demands. Magalhaes reinforces that the farmer must monitor the development of the plant on a daily basis and, if there is a problem, he must be able to identify the stage of the plant in order to obtain technical guidance more easily. “Plant stages can be reached on different days depending on the agricultural year and climatic behavior. This is why phenology is very important”, he concludes.