Agronomic lessons learned from the drought
Al-Kaisi and his Iowa State colleagues identified several additional agronomic lessons that were learned from the 2012 drought:
• Crop residue retention with no-till systems improves water infiltration rate and conserves soil water content by reducing soil cracking and crusting and preserving soil structure.
• Corn following corn suffered greater yield losses than corn following soybean. Continuous corn typically does not yield as well as corn after soybean, but the yield differential was much greater in 2012.
• Cover crops can accumulate residual NO3-N, thus decreasing losses from the root zone. Much of the N accrued in cover crops will become available to subsequent crops.
• The reduction of corn plant growth and grain fill during drought led to high NO3 accumulations in vegetative plant tissues, particularly in the lower corn stalk. Testing corn silage or baled stalks was important in 2012 to determine if NO3-N levels were safe for livestock.
• Corn N fertilization rates necessary to provide optimum yield typically are lower in years with below-normal rainfall. This effect can persist across multiple years of dry conditions, even with a return to normal rainfall. Therefore, effects of dry conditions should be considered in decisions for N application rates to 2013 corn crops.
• Corn silage harvest results in greater P and K removal than grain harvest alone since most of the aboveground plant is harvested. This increased removal rate from grain-only harvest should be considered in nutrient plans for subsequent crops.
• Dry fall conditions can impact soil test results. Predicting nutrient availability during drought is difficult. Sampling after fall rainfall occurs or sampling in the spring improves soil test reliability.
• Drought revealed that genetics may have a limited role in protecting yield without optimum moisture availability in the absence of an integrated crop management system. Significant rootworm feeding damage was observed in 2012 on hybrids with Bt rootworm resistance. Decreased root volume following root pruning results in lower water use under drought conditions, more crop stress, and reduced yields.
• The jury is still out on drought-tolerant hybrids. Unfortunately, results of scientifically valid comparisons of similar genetics with and without drought tolerance are not yet available.
• Planting a range of hybrid maturities will help spread risk, but plant only hybrids adapted to your area. Non-adapted hybrids may have neither the yield potential nor disease resistance of adapted hybrids.
While the drought could continue in some portions of the Cornbelt in 2013, some good lessons have been learned that may help prevent a recurrence of poor yields that resulted from a lack of drought management. Damage to the soil in drought conditions can occur from tillage, which breaks up soil structure and reduces infiltration of rainwater, preventing it from getting to the subsoil.
Allowing more residue to remain on the soil surface will help retain moisture and improve moisture infiltration; and the use of cover crops will retain moisture, provide livestock feed, and retain soil nutrients.
Source: FarmGate blog