February 22, 2012

Mato Grosso Soybeans - Too Much Rust and Too Little Sunshine

Author: Michael Cordonnier/Soybean & Corn Advisor, Inc.

According to the Mato Grosso Soybean and Corn Producers Association (Aprosoja), the statewide soybean yields in the state should be 2% to 5% lower than the record yields achieved last year. The principal reason for the slight decline in yield is the widespread presence of soybean rust as well as the lack of sunshine during the month of January. In their February report, Conab estimated the Mato Grosso soybean yield at 3,190 kg/ha (46.2 bu/ac), which is unchanged from the statewide yield achieved in 2010/11. If Aprosoja's estimate is correct, then the soybean yields will be down approximately 1-2 bu/ac compared to last year.

Soybean rust has been a bigger problem in the state this year then the last several years especially in central and northern Mato Grosso along highway BR-163. The heavy rains during January allowed the disease to spread while it hindered farmer's efforts to control the disease. Most of Mato Grosso has only been growing soybeans for the last 25 to 30 years, so accurate weather records don't go very far back, but many farmers in the state say this was the rainiest January that they can remember since they have been farming in Mato Grosso.

Up until last week, Mato Grosso had the most confirmed cases of rust in Brazil but now the state of Goias has more cases with 103 followed by Mato Grosso at 82. These two states combined now account for 77% of the 240 cases of rust in Brazil. After two years of relatively low levels of rust infestation, many farmers in the state were complacent about applying a preventative fungicide application. Instead, they waited until the disease appeared in their vicinity before they started to apply fungicides, similar to what they have done for the last several years. Unfortunately, that was probably the wrong decision this year.

Once the presence of the disease was confirmed, they had to play catch up with their control measures, but the wet weather prevented much of their spraying activity and the disease got ahead of them. Some producers are reporting that they had to apply up to four applications of fungicides, whereas in the last few years, two applications were sufficient to control the disease. Rust is probably the main cause for the slight yield reduction this growing season.

The impact from the cloudy conditions during the month of January is harder to quantify. Ideally, soybeans would like to have adequate soil moisture coupled with bright sunshine in order to maximize photosynthesis. If it is constantly overcast during the pod filling period, soybean yields generally tend to be lower than expected. That is apparently what happened in central and northern Mato Grosso this year.

Even with the slightly lower yields, the state is still going to produce a soybean crop that is approximately 7% larger than last year (22 million tons vs. 20.5 million tons). The increased production is the result of farmers in the state planting 400,000 more hectares of soybeans in 2011/12 for a total acreage of 6.8 million hectares. The majority of the increased soybean acreage came from the conversion of degraded pastures to additional row crop production.