New method is capable of predicting the occurrence of frost in Mato Grosso do Sul

Danilton Flumignan, researcher at Embrapa Agricultural West (MS), developed a method capable of predicting the occurrence of frosts in the southern region of the state of Mato Grosso do Sul well in advance. It is possible to know in December the approximate minimum temperature that will be reached in June. This information is updated in the month of May, when the occurrence of frost is confirmed or not. The researcher reveals that, according to data collected so far, the region should not suffer from frost this year.

Flumignan points out that, especially in the month of June, frosts are a cause for great concern for off-season corn producers. “That month, corn is still in a sensitive phase of its development andfrost can be harmful to the crop”, explains the scientist, stressing that the extent of the damage is associated with the intensity of the frost.

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The system uses rainfall data measured at the Guia Clima agrometeorological station at Embrapa Agropecuária Oeste, located in Dourados (MS), and sea surface temperature data provided by the American agency National Oceanic and Atmospheric Administration (NOAA).

With a confidence level of 95%, the system is capable of predicting in December, and with a known margin of error of ±2,3ºC, what the minimum temperature should occur in June, in the south of Mato Grosso do Sul. Based on At this predicted temperature and on the scale in Table 1, it is possible to predict whether frost will occur and with what intensity.

No frost this year According to the researcher, for 2019 the specific frost forecast system for the south of Mato Grosso do Sul showed that the minimum temperature predicted for June is 10,9 ºC. “Considering the uncertainty associated with the mathematical model that makes the prediction, it is estimated that the temperature could be between 8,6 ºC and 13,2 ºC. Frosts generally occur at temperatures below 4ºC, and only below this level can they be classified as weak, moderate or strong”, explains Flumignan. In 2018, the published forecast was a risk of moderate frost in June, with a minimum temperature forecast of 5ºC, which could fluctuate between 2,7 and 7,3ºC. The data released by the forecast was confirmed and the minimum temperature recorded in June 2018 was 6 ºC, in Dourados, and 5,2 ºC, in Rio Brilhante.

No frost this year

According to the researcher, for 2019 the specific frost forecast system for the south of Mato Grosso do Sul showed that the minimum temperature predicted for June is 10,9 ºC. “Considering the uncertainty associated with the mathematical model that makes the prediction, it is estimated that the temperature could be between 8,6 ºC and 13,2 ºC. Frosts generally occur at temperatures below 4ºC, and only below this level can they be classified as weak, moderate or strong”, explains Flumignan.

In 2018, the published forecast was a risk of moderate frost in June, with a minimum temperature forecast of 5ºC, which could fluctuate between 2,7 and 7,3ºC. The data released by the forecast was confirmed and the minimum temperature recorded in June 2018 was 6 ºC, in Dourados, and 5,2 ºC, in Rio Brilhante.

As frost represents a risk factor for productivity in the field, Embrapa Agropecuária Oeste has been analyzing some forecasting methods.

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The Embrapa Agropecuária Oeste Climate Guide maintains organized information from the last 40 years in the municipality of Dourados. The historical series shows that 25,4% of frosts in the region occurred in June. “Of these, the majority, 77,8%, were of medium or strong intensity, causing damage to crops and losses to producers”, says Flumignan. Since 1979, in June, frosts have occurred in 21 years, totaling 38 episodes.

In other months, the risk of frost is not a concern for off-season corn producers. This is the case of July, which, despite having more frequent frosts (51% of records), is a time when crops are in the final phase of their cycle or have already been harvested, which reduces the potential for damage. In May, in turn, frosts are rare (4% of records) and, when they occur, they tend to be weak in intensity.

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Second-crop corn is the main winter crop in Mato Grosso do Sul. In 2018, around 1,7 million hectares of second-crop corn were cultivated in the state. Approximately 70% of these crops were in the southern region of Mato Grosso do Sul.

Agricultural Climate Risk Zoning (ZARC) establishes that, in this region, off-season corn must be sown by March 10 in order to minimize the risk of crop losses.

Embrapa agronomist Gessi Ceccon, a specialist in safrinha corn cultivation, explains that there are three types of corn hybrid cycles: super early, early and normal. In the case of crops with super-early corn hybrids, frost in June does not cause damage because the corn will have already formed grains, ready for harvest. “However, for those with an early and normal cycle, frost in June causes less grain filling and, consequently, lower productivity”, highlights Ceccon.

In general, the analyst emphasizes that it is very difficult to predict the potential damage that frost could cause to corn, if it occurs in June. “Many variables are involved, such as the terrain of the property, planting time and hybrid cycle. However, in general, it is possible to state that even if the frost occurs in June and is strong, there will not be a complete loss of the crop, as the off-season corn is sown in a staggered manner on rural properties in Mato Grosso do Sul, in other words, it occurs gradually as the soybean harvest is carried out”, he adds.

He draws attention to the extent of the damage in specific situations. “In the event of a strong frost, in a crop located in a lowland, with a hybrid with a normal cycle, the loss will certainly be great.” He emphasizes that even though there are severe losses in the plantation, the cereal can be harvested and provided as food for animals, as it is a rich source of energy. This way, it is possible to minimize losses.