With below-average precipitation in much of the corn belt for the past three years, subsoil moisture is low heading into 2013, maintaining risk for below average crop production, explains Iowa State University climatologist Elwynn Taylor. “A year as extreme as 2012 is seldom followed by a full return to normal.” Though likely better, 2013 could be our fourth straight year of below-trend yields.
It’s one impact from what he terms a “double-barreled drought,” meaning both short and long term droughts. Short-term droughts hurt crop production. Long-term is a hydrological drought — the water table is drawn down and waterways dry up. The current drought has “given us both barrels: Short and long term drought.”
While something extraordinary might happen to recharge soil quickly, recognize that:
- La Nina patterns suggest persistent drought and erratic crop yields
- 2010 was the second strongest La Nina pattern on record (130 years)
- The 2012 drought started in 2010
- Since then, water recharge in much of the corn belt has been below average
- Which means the long-term drought persists.
This can have significant impacts, including lack of normal flow on the Mississippi River continuing to affect shipping, he notes. Plus the potential for farms and cities to see a shortage of water.
Dr. Taylor reviews data and weather events going back more than 100 years, looking for patterns. In an age of La Nina, for example, we see erratic yields, while El Nino typically brings favorable Midwest yields. Since 1976, El Nino has been dominant. Then 2010 launched the second strongest La Nina on record; the strongest occurred in 1955. The 50s represented record dry years in Texas and Oklahoma, he says, and were disastrous for crops. Similarly, Australia saw disastrous weather in the 50s with significant flooding — just as it did three years ago with the start of the La Nina pattern. While the current La Nina ended in March 2012, we typically see stronger events — drought, severe flooding, tornadoes associated with La Nina. “In 2011 we saw the second year of this La Nina drought – and the Missouri River had its worst flood since the mid-50s.”
If we’re back in a pattern of more volatile weather and potential for severe weather events, there’s more crop risk. The trend line for corn yields is an increase of 2 to 2.5 bu/a every year. Before 2010 we had six years above trend line — the longest in history in Iowa. For the past three years, yields were below trend — 20% below in 2012, coming in at 123.4 bu/a compared to the trend line average of 160 bu/a.
With below-average soil moisture, crop risk continues. But pay attention to the coming spring weather. Consider this data: Normal October to May precipitation is 12 inches. The normal subsoil deficit is seven inches. The 2013 deficit is 16 inches. We have at least five feet of soil to recharge and the soil at two feet won’t correct until after the first foot of soil is corrected, the professor states.
If we have a wet spring followed by dry weather, crops will have shallow roots and we could see a dramatic drop in yield. Consistent weekly rains could provide near-normal yields because the crop won’t rely on subsoil moisture. Still, the subsoil moisture deficit will persist. Farmers, feeders, grain buyers and merchandisers, and barge companies will be paying attention.