Corn and Soybean Practices following Severe Drought Roger Elmore and Andy Lenssen Department of Agronomy, ISU
Shawn Macha
2012 growing season Corn & Soybean Dry fall, 2011 & spring 2012. Early-planting opportunities 2012. Hot temperatures sped crop maturation reducing yield potential. Localized rain resulted in extreme variability in crop yields. Early 2012 maturity, faster drydown.
Corn water use Irrigating Corn http://ianrpubs.unl.edu/fieldcrops/g1354.htm
Yield (bu/acre) 200 180 160 30 - Year Corn Yield Trends, With October 2012 Yield Forecasts. Iowa and U.S.A. from USDA-NASS y = 2.602x - 5054.3 R² = 0.6764 140 120 100 80 60 40 y = 2.0088x - 3881.8 R² = 0.7246 Iowa U.S.A. IA Oct 12 U.S. Oct 12 20 0 1980 1985 1990 1995 2000 2005 2010 2015
2012 - Corn Many producers are pleased that yields are better than expected. Yields were across the board. Corn following corn yield penalties likely very high Jury is still out on drought-tolerant hybrids. Transgenic hybrids protect yield potential, they don t add to it.
Corn: Concerns/Possibilities going into 2013 Corn: nitrate carryover depends on rainfall. Dry Fall 2012 encouraged greater than normal fall field operations Iowa farmers not likely to plant ultra-early hybrids. Producers will not likely seek out more drought tolerant crops or drastically change up their cropping system. Dry soils may lead to poor germination and crop stands. Corn on corn acres may be reduced Seed supply of some hot hybrids may be limited. Hybrid selection dilemma: How much to weight 12 data? Fall NH3 applications: Not enough equipment, time, or supply to do it all in the spring.
Our specific calling here crop insurance policy has language about following "good agronomic practices." the question is, does a drought year change that definition, both in the drought year and the year following? Dr. William Edwards
Thinking of the future (1) What are the practices we should consider changing in corn and soybean production systems? Rotations Tillage Resistance management Prevention or delay of resistance
Thinking of the future (2) Continuous corn Yield drag compared to rotation with soybean or other crops Western corn rootworm populations have overcome Bt corn in many locations, often resulting in greater insecticide use than prior to Bt corn introduction. (research by Gassmann et al.) Rotation to a non-host is a sensible solution.
Thinking of the future (3) Fungicide use with specific targets Strobilurin fungicides are now recommended when plant diseases are not present. Cercospora pathogens of soybean and sugar beet are already resistant to strobilurin mode of action. (Cercospora leaf spots) Integrated pest management is not being used. When we need them they may not work for us.
Thinking of the future (4) Northern corn root worm and extended diapause Rotation to a non-host usually prevents damaging populations from building up. Some populations have extended diapause. Two-year rotation of corn-soybean may not prevent damage in this case. Fisher (USDA, ARS) selected in lab for extended diapause of up to 7 years.
Thinking of the future (5) Goss Wilt Many producers utilize excessive tillage to destroy corn residue and primary inoculum. Planting Goss Wilt-resistant hybrids is a sensible solution. Rotation to a non-host is a sensible solution.
Thinking of the future (6) Rotation does not prevent soybean aphid infestations. Gary Munkvold (ISU-Plant Path & Micro) has a neat rotation study that will provide excellent results on the effect of years out of soybean and buildups of several diseases. SDS, SCN, Phytophthora root rot, other root pathogens
Iowa Tillage Systems Tillage is done to manage weeds and prepare seedbeds. Tillage is typically done with disk-chisel, offset disk, tandem disk, field cultivator, and even moldboard plow.
Tillage Tillage results in less residue on soil surface, increasing potential for erosion Iowa leads US in planted acreage of corn and soybean Iowa leads US in average per acre yields of corn and soybean Iowa leads US in highest soil erosion rate
Tillage (1) Tillage of wet soils causes soil compaction & stand establishment issues. Tillage during dry periods breaks of soil aggregates. Soils with compaction zones or less aggregation have slower water infiltration rate, allowing more runoff after intense rains. Slower infiltration rate results in slower recharge of dry soils.
Tillage (2) Less recharge means inadequate water may be available during July and August, times when crop water use typically exceeds rainfall in Iowa. During July and August, corn and soybean rely on stored soil water to supplement inadequate rains. In 2012, farmers found roots and moist soil at 8 -depths.
Tillage (3) The first physiological process affected by drought in soybean in nitrogen fixation. N fixation is typically responsible for onehalf of the protein in a soybean crop. Once N fixation stops, it rarely is reinitiated. Once N fixation stops, soybean yield is fixed.
The Future To attain average corn yields of 300 bu/acre we must increase corn water use and light capture. This will not happen without increased soil water capture and storage. To attain average soybean yields of 100 bu/acre we must increase soybean water use and light capture. This will not happen without increased soil water capture and storage.
Questions for the Audience Does the insurance industry: consider crop rotation? consider tillage system? consider prophylactic pesticide applications?