Tillage is a tool for managing many things that can go wrong on a given field. It breaks compaction (if done at the right soil moisture), improves drainage (again if done at the right soil moisture), and manages inoculum loads from residue borne insects and pathogens that impact corn, soybean, and wheat. Just like pesticides and fertilizers – too much tillage also can bring another set of problems, a compacted plow layer, but more importantly, soil erosion. With any agronomic practice, including tillage, there are benefits and drawbacks.
Below is a list of potential problems associated with no-till fields.
High levels of disease from pathogens that survive on and in crop residue: This year in 2016, we have had outbreaks of a number of pathogens that cause ear molds and leaf blights on corn, leaf spots and seed rots on soybean. The likes of what we have not seen for some time. All of these pathogens will overwinter during the 2017 cycle – so they will be ready to go and infect next season’s crop – the higher the inoculum the more disease that the 2017 season will see.
Similar to pathogens, insects can also survive on and in crop residue. Some of the top culprits are true armyworm (which like the grassy weeds and cover like rye), and fall armyworm (which prefer broadleaf weeds). The populations of caterpillars are usually tough to predict since they are migratory and their presence in the spring depends on flight patterns. In addition, higher slug populations are often associated with fields that have a lot of residue. Some of these issues in no-till fields could be controlled by appropriate weed management and good spring scouting.
Most weeds are controlled adequately in no-tillage systems with the currently available herbicide systems. Tillage can be an effective option for management of biennial and perennial weeds – primarily those that have simple root systems (e.g. deep taproots). Tillage can also help with control of perennials with creeping roots or rhizomes, but primarily when integrated with an herbicide application. A combination of fall and spring tillage operations, or even thorough spring tillage alone, can control marestail for at least the current growing season. Tillage must completely uproot emerged marestail plants and uniformly mix the upper few inches of soil. The spring tillage should ideally occur as close to planting as possible. Be aware also that in fields where the soil seedbank is heavily infested with marestail seed, tillage can turn up seeds to the soil surface where germination and emergence is more likely.
Consider soil drainage. In poorly drained fields, tillage can help reduce yield losses from late planting. Tilled fields will warm up and dry out quicker in the spring. In well-drained fields, no-till is often a better option with many benefits including conservation of soil moisture, reduction in erosion and soil crusting, and reduction in fuel and labor. Corn response to tillage is strongly influenced by soil type and crop rotation. No-till cropping systems are more likely to succeed on poorly drained soils (like those in Northwest Ohio) if corn follows soybean or forage legumes rather than corn or a small grain, such as wheat. On the poorly drained silty clay loam soils, where corn follows soybean or meadow, yield differences between no-till and plowed soils are reduced. Crop rotation with soybeans generally has much less effect on corn response to tillage on the well-drained silt loam. This yield advantage to growing corn following soybean is often much more pronounced when drought occurs during the growing season.