The environmental and economical values of conservation practices far exceed the perceived negatives or challenges associated with such systems. The environmental value of well-managed conservation systems is in terms of water and soil quality by protecting soils and reducing sediment transport, which is the main contributor to the water quality problems in Iowa. Conservation systems demonstrated the benefits of improving soil organic matter significantly over conventional systems that utilize extensive tillage mono-cropping systems. On average, research showed the no-tillage system with a crop rotation of corn-soybean can contribute annually close to 0.5 ton of total carbon to the soil organic matter. This improvement in soil organic matter is coming from two sources:
- The stability of the system. The conservation system, no-tillage in particular, keeps the soil system intact, enhancing soil structure and microbial populations and reducing the loss of organic matter and nutrients to soil erosion.
- The amount of residues left on the soil surface, which provides protection to the soil surface and is a source of slowly released carbon and nutrients to the soil system.
One of the challenges with a conservation system is the management of crop residues. The way residues are managed on the field after harvest is very critical to the success of providing a good soil seedbed environment for planting. Cutting residues at 12 inches or more will provide better residue orientation for trapping snow and uniform distribution of it across the field. Many farmers have gotten into the habit of chopping corn stalks after harvest. This can present a significant management problem, as well as other potential production problems that are associated with low soil temperature early in the spring, potential soil diseases, and early germination problems just to name a few. Chopping residue also can reduce the effectiveness of it in protecting the soil surface from potential water erosion, especially during high intensity rainfall events, where residue will be washed away with the surface runoff. Chopped residue is no longer anchored into the soil and is more prone to plugging tillage implements or planters used in subsequent operations.
While cutting residue after harvest is one technique for managing crop residue, it is possible to avoid this step altogether. This can be accomplished by calibrating the combine properly to ensure a uniform residue distribution on the soil surface. A few adjustments and fine tuning of a combine prior to harvest can pay off significantly in having uniform residue cover across the field.
The misconception about conservation systems and no-till as an obstacle is widely used to avoid the adoption of these systems. The success of farmers who have been using no-till for many years shows that such systems can pay off economically and environmentally. Studies show that tilling corn residue prior to soybean planting did not improve soybean yield (see the April 3, 2006, Integrated Crop Management article, Is tillage needed for your soybean crop?). Removing residue for any purpose needs to be balanced with the potential impact that may take place--especially from water and soil quality perspectives. Although standing residue in the field is sometimes viewed negatively, it actually presents fewer problems for equipment or seedling establishment than chopped, detached residue.
Conservation systems are the right choice and offer significant services to the environment. Understanding conservation systems and the proper way of managing them is the key to a successful outcome. Conservation systems should be managed in a system approach that includes a diversified cropping system, a balanced nutrient management program, the use of the right equipment, and, above all, understanding the system.
Mahdi Al-Kaisi is an associate professor of agronomy with research and extension responsibilities in soil management and environmental soil science.
This article originally appeared on page 270 of the IC-498(24) -- October 1, 2007 issue.