With the price of fertilizer as high as it is, cycling nutrient-rich crop residue back into the soil will be the difference in growing a crop economically or not. A healthy soil with balanced fertility is the key to long-term crop production. Baling straw without returning it and the manure back to the field means you’ll have to increase your fertilizer rates to compensate. Same when you burn.
Straw management is one of the keys to maintain nutrient levels and healthy soils. Healthy soil has good tilth, balanced fertility, good water holding capacity yet good drainage, and a balanced microbial population. Rhizosphere ecology is the new study of the interaction between microbes and plants. This is the motor that runs plant production.
Building organic matter in the soil creates a positive environment for microbes to live. It provides food, shelter, moisture and air — everything a living organism requires to survive. The problem with our agricultural system is that we are killing off our microbes in the soil. High rates of fertilizer, soil compaction, and heavy use of non-host plants such as canola are reducing the beneficial microbes in our soils. I am not organic, but there are some principles we can use in conventional production systems that will make our management easier.
BUILD ORGANIC MATTER
First is to build organic matter in the soil. This comes from growing taller crops and doing a better job of managing the trash. That means ensuring the straw chopper is set properly and is well maintained. Chaffer spreaders are a must on conventional combines. They spread the chaff more evenly across the cutting width of the combine. Using smaller cutting widths also helps to spread residue more evenly. The rule of thumb is to spread the chaff and straw at least three quarters of the cutting width.
Once you develop a good ground cover, you need to manage it. Salford Farm Machinery has a tillage tool that fits the bill. It is called a RTS (Residue Tillage Specialist), and I’ve demo’ed one for the past two falls. RTS has a bank of wavy coulters, a set of heavy harrows, and a rolling harrow. It is very low draft, and recommended to be used at fairly high field speeds.
Coulters cut the trash and soil, causing some mixing which will get some soil on the trash. Microbes in the soil will then start breaking down the trash. Heavy harrows spread the trash evenly over the field, which then gets pressed into the soil surface by the rolling harrows actually crimping the trash like a haybine. It does not do a dramatic job of breaking down residue, but when the microbes have time to work on the stubble, it really speeds up the time of decomposition of the trash. Plus the trash is evenly distributed across the field.
A heavy harrow alone will spread straw. The RTS advantage is its coulters. They provide some vertical tillage to the unit. The vertical tillage will encourage some drainage, break up hard-
pans, and allow some aeration in the soil profile. Aerating the soil is going to promote growth of “good” microbes, which will happily breakdown the trash for you. In spring, a quick pass with this will warm the soil quicker meaning a quicker emergence of your crop, improved nutrient uptake, and higher rates of fertilizer efficiencies.
INOCULATING THE SOIL
If you have high soil disturbance in your system, use a fair amount of canola in your rotation, burn stubble or use conventional summer-fallowing, you may see a response to using mycorrhizae inoculation in the soil. Mycorrhizae are a beneficial fungus in the soil that works symbiotically with the plant. They act as extra roots for the plant to extract more nutrients out of the soil. Forage stands tend to build up fairly high levels of mycorrhizae, usually within a few years. Crops seeded into a broken up forage stand are better than those without forages in rotation, assuming proper fertilizer has been applied to the forage rotation crops. Premier Tech Biotechnologies is a Canadian company that has been providing greenhouses with mycorrhizae for many years. Now they are looking at the agricultural field. Testing to date looks very promising for Prairie farmers.
Rhizosphere ecology is an emerging field of crop research. Anyone going to university may want to consider entering this discipline. Soil activity and productivity is based on the microbes in our soil. They are sensitive and have a very complex network that we are just starting to understand. Past management has decreased the variety and numbers of the microbes allowing more toxic species to start dominating and creating other management problems. To change the direction our soils are going, we are going to have to change our management.
Kevin Elmy operates Friendly Acres Seed Farm, along with his wife, Christina, and parents, Robert and Verene, near Saltcoats, Sask. You can contact him at 306-744-2779 or [email protected]