By Mahdi Al-Kaisi, Department of Agronomy
Tillage as a soil management practice has the potential to have a significant effect on crop production and environment (i.e., soil quality and water quality) in Iowa and the Midwest. Tillage can contribute to soil erosion, sediment and chemical runoff from farms, on-farm energy use, and fertilizer and pesticide use. Intensive use of tillage can significantly affect agricultural sustainability and economic return, commodity production and input cost per acre. Tillage and crop rotation can influence the sustainability and resiliency of our agriculture systems in lieu of the unpredictable trend of climate changes resulting in extreme cyclic wet or drought conditions.
The increased use of intensive tillage may accelerate such effects due to release of greenhouse gases, primarily CO2 and N2O, from fossil fuel during tillage operations and the oxidation and mineralization of organic matter. Generally, organic matter consists of stored carbon that is not available to contribute to greenhouse gases in the atmosphere as a carbon dioxide or nitrous oxides unless it is subjected to oxidation process through soil disturbance. These changes not only have an effect on the climate, but are also major contributors to depleting soil of its essential productivity.
Trends in adopting no —till
Conservation tillage, and especially no-till, is a proven practice in protecting soil quality in corn and soybean cropping systems. The trend in adopting no-tillage (NT) is gaining some momentum over the past few years, but at a very slow pace. The general trend in adopting NT in the U.S. was estimated to be at 1.5 percent per year for corn and soybean according to the USDA's Economic Research Service (ERS) report of November 2010, where NT has increased from 23.5 to 29.5 percent for the period of 2005 to 2009 for corn production. That means approximately 70 percent of corn crop land is under some degree of tillage. However, the percentage of soybean acreage going into NT is much higher, at 45.3 to 50 percent for the period of 2006 to 2009, respectively (Table 1).
The trend of increase in soybean acreage is similar to corn acreage at 1.5 percent per year. Generally, soybean acreage will be tilled as it goes into corn for the following year. Therefore, the high percentage of NT soybean acres reflects NT at that year only, as indicated by the percentage of NT corn of 23.5-29.5 percent, which means 20 percent of soybean acreage goes back to conventional tillage for corn after soybean the following year. Therefore, defining true NT is critical, where continuous NT should be implemented for the entire rotation from year to year regardless of the following crop.
In the Midwest the rate of increase of NT under corn crop was 1.9 percent compared with an increase in soybeans of 3.8 percent per year. However, in Iowa the rate of increase in NT under both corn and soybean was much greater, at 3.8 percent for corn and 4.5 percent for soybean per year. In Iowa, according to USDA-ERS estimates there is noticeable progress in NT corn from 7.8 percent in 2001 to 22.8 percent in 2005, while NT acreage under soybean moved from 22.7 percent in 2002 to 40.8 percent in 2006. However, this increase in NT soybean does not represent a permanent increase; it is only an increase in the years in which soybeans are grown. The drop in NT acreage to 22.8 percent under corn following soybean, reflects the challenges associated with NT corn production in Iowa and the Midwest in general.
The progress made in adopting NT is relatively slow when 70-80 percent of row crop lands are under one form or another of tillage. The tillage and crop rotation research at Iowa State University documented the lack of yield and economic advantages for soybean production under conventional tillage regardless of where in the state. However, corn production is more challenging and requires additional management to have a successful NT system.
To achieve an efficient no-till system, consider the following
• Efficient drainage system in poorly drained areas to remove excess water
• Include filter strips and grass water ways to reduce surface erosion
• Ground water management to utilize water more efficiently under drought conditions
• Proper residue management attachments (i.e., residue cleaners set for removing residue from the row with minimum soil disturbance) to increase soil surface temperature
• Proper adjustment for planters for proper down pressure and seed depth
• Combine adjustment for uniform residue distribution
• Proper fertilizer application equipment to minimize soil disturbance
• Corn following soybean to help build soil biodiversity
• Continuous corn (C-C)—if C-C is used residue cleaner should be set to manage corn residue with minimum soil disturbance
• Other extended crop rotations—if forage crop used with NT in the rotation, consideration for minimizing soil disturbance needs to be included when forage is terminated
Proper fertilizer program
• Soil testing—soil testing is essential regardless of the tillage system to insure adequate availability of nutrients
• Timing of application is critical to avoid nutrient loss, especially nitrogen
• Starter fertilizer can help provide initial boost for plant growth and development
• Days for maturity—this is important especially, if planting delayed due to soil moisture conditions
• Climate and soil conditions are different in different regions in the state. Therefore, selecting proper hybrid for NT should take in consideration such conditions
Integrated crop management program
• Pest and disease control—this is important for NT in cold, poorly drained soils
• Weed control—timing of controlling weeds is important by applying chemicals to minimize potential yield loss
• Potential input cost for selected tillage system needs to be factored in determining net return
• Potential yield of site—selection of any tillage should take in account the soil site potential productivity
• Compliance with conservation plan—this is important for those who have a conservation plan contract with a conservation agency
These considerations are essential for treating NT as a comprehensive system that requires an integrated approach of management practices. The adoption of NT can be valuable for managing crop production and increase the resiliency of row cropping systems in adapting to unpredictable weather changes. It is also important to recognize that a successful NT system may require a diversified cropping system along with other practices such as: cover crop, grass waterways, and filter strips to maintain soil productivity.
Mahdi Al-Kaisi is an associate professor in agronomy with research and extension responsibilities in soil management and environmental soil science. He can be reached at firstname.lastname@example.org or (515) 294-8304.