Production | Summer 2010
Bring your soil back to life.
By Jennifer Barber
Where should you start when bringing back a field that’s been out of production for a while or has had its nutrients depleted? Or even if you’re putting new land into production, what’s the first step in bringing soil to life?
According to Dr. Ross McKenzie, agronomy research scientist with Alberta Agriculture and Rural Development in Lethbridge, the first step is to soil test. Although this is simple and inexpensive, only about 15 per cent of Alberta’s irrigated farm operators and 10 per cent of dryland producers test their soil on a regular basis.
"Fertilizer use is quite widespread on the prairies and is essential to replace nutrients removed by crops each year," says McKenzie. "But that doesn’t mean we are using fertilizer efficiently. Soil testing is the number one way to systematically measure not only fertility status but other physical and chemical characteristics of the soil that can affect crop growth and yield."
Ideally, McKenzie says, the rule of thumb is to test all fields every year, but often this is not practical for growers with a large land base. They may cut back by sampling specific fields they feel are representative of their land base. Larger growers with varying topography and soil types may need to sample from different areas of specific fields to develop fertilizer recommendations for uniquely different soil areas within one field. He recommends testing for nitrogen, phosphorus, potassium and sulphur levels every year. Micronutrients might need to be checked only once every five years if levels are adequate to high.
While micronutrients should be included as part of a soil test about every five years, he advises caution in how they are used. Micronutrient fertilizers tend to be costly and should be used only if there is a reasonable chance to economically increase crop yield. He adds that for most prairie soils, depending on crop and soil composition, they aren’t necessary. And sometimes they can even harm a crop.
"There are times when micronutrients are required, especially in nutrient-depleted land that is intensively cropped," says McKenzie. "For example, copper fertilizer can make a significant difference on wheat and barley when grown in central Alberta on black or gray-black transition soils that are sandy, have been intensively cropped and have low soil copper levels. Some micronutrients such as boron applied to canola, however, can actually be toxic even at a rate of only 3 lb/ac, depending on application method and and soil pH."
Right now, he adds, Alberta has a good database of fertilizer recommendations accessible to growers. The computer program called Alberta Farm Fertilizer and Information Recommendation Manager (AFFIRM) is an online, interactive source for growers to develop their own recommendations based on crops grown, a farm’s soil-climatic region, management practices, crop value, fertilizer prices and soil test results. However, he says, the challenge is in maintaining that knowledge base.
"With higher yield targets, continually evolving farming practices and changing varieties, we have to constantly modify and develop new recommendations," he says. "Farmers develop a feel for what their soil needs based on experience, but when they have a new field, or they are new to the business themselves, it helps to have a place to turn for information."
