Argentina Corn Update: Heat and Dryness Reduce Estimated Yield

USDA's 2005/06 February estimate for Argentina corn production has been decreased to 15.5 million tons, down from 16.8 million last month, and down from last year's record of 19.5 million.  The harvested area forecast has also been revised downward this month to 2.3 million hectares, from 2.4 million in January. While Argentina's corn yields have generally increased since the early 1990's, the particularly inopportune weather during the vulnerable stage of tasselling this year, specifically the significant dryness in December and extremely hot temperatures in January, have significantly damaged the corn crop and reduced yield forecasts. 

Argentine farmers typically plant corn for on-farm livestock demands. When harvesting, on-farm silage demands are usually met first, then the remaining corn is harvested for grain to be sold for domestic consumption or export. Due to last year's record production, many farmers exceeded their on-farm needs and decreased their 2005/06 planted area.  Coupled with the oversupply from last year, was a general shift from grains to oilseeds due to the increased profitability of oilseeds. While USDA's corn area estimate for the 2005/06 Argentine corn crop has reflected these factors, the February corn area estimate was further decreased to reflect December and January weather conditions. 

The largest corn producing provinces are Córdoba, Buenos Aires, and Santa Fe, which comprise the corn belt (see above figure on right). The optimal window for planting corn in Argentina is from September through December.  Typically the northern provinces finish planting after the southern provinces.  During November, crop establishment in the corn belt was good; however, dryness in December threatened yields. Decreased yield potential was realized when dryness was coupled with extreme maximum temperatures during the first ten days of January.  Soybeans, which are grown in much of the same area as corn, evaded yield damage because they were in the vegetative stage of development, while much of the corn crop was tasselling, the most vulnerable stage of development, during the extreme temperatures.  Medium resolution satellite imagery indicates that corn in Marcos Juarez was entering the tasselling stage at the end of December. The deeper shades of red in the AWIFs image show that much of the corn had already tasseled by January 19.  While significant precipitation was received following the heat wave, corn yield potential had already been reduced.

Assuming that 1200 growing degree days (GDD) are necessary for corn to enter the silking stage, growth stage models indicate that as much as 50 percent of Argentina's corn was tasselling during the extremely hot weather temperatures of 38ºC (100 ºF) or greater in early January. Temperatures of 38ºC or greater can kill corn pollen, but corn has agronomic adaptations to avoid complete pollen loss and subsequent yield damage.  One adaptation is that pollen may be shed for up to two weeks, thus avoiding damage during days of extreme heat.  A second adaptation is that pollen is typically shed in the morning hours when air temperature is cooler. While up to 50 percent of Argentina's corn area was tasselling during the heat wave, perhaps half of this area reached effective pollination. Nonetheless,  damage and stress was incurred given the severity of these conditions such that the corn yield forecast was decreased by 4 percent this month to 6.74 tons per hectare.

This year's weather-affected crop notwithstanding,  corn yield in Argentina has been generally increasing for the last fifteen years. The strongest local increases have occurred in the corn belt, e.g. southern Santa Fe, northern Buenos Aires, and eastern Cordoba. There are four major factors for this phenomenon; the first is an increase in no-till agricultural practices.  No-till farming is very effective at retaining soil moisture, thus decreasing soil moisture variability during dry periods. For those producers that have switched to no-till, the typical early-January dry periods have had less of an effect on yield than they had in the past.  A second factor resulting in higher yields is increased plant densities. Because of the shift to no-till practices and subsequent increased soil moisture retention, producers have been able to plant corn at higher densities.  Thirdly, seed varieties have played a major role in boosting corn yields.  Seed companies have been influencing farmers to plant dent varieties instead of flint varieties.  This shift has largely occurred in the 1990's.  While flint varieties typically yield between 4 - 9 tons per hectare and are useful for poultry feed and corn flakes, dent varieties yield 8 - 15 tons per hectare.  The proliferation of genetically modified corn which uses the Bt gene have also boosted yield by decreasing damage due to corn borer. The fourth factor for an increase in yields has been the increase in fertilizer consumption especially in Argentina's corn belt.  

Official USDA area and production estimates for grains and other agricultural commodities are available at www.pecad.fas.usda.gov.