Soil testing may be the secret to a successful harvest
by Jane Caulfield
For growers across Saskatchewan, the end of harvest marks the beginning of the planning season. Soil testing can be one of the most important pieces of information for planning when it comes to determining what and where to plant in the upcoming
“It is a means of predicting the nutrients that are available in the soil,” says Dr. Jeff Schoenau, Professor and Ministry of Agriculture Strategic Research Chair, Department of Soil Science, University of Saskatchewan. “This kind of prediction can inform and enable better decisions regarding crop rotation and fertilizer requirements for the following year.”
There are several factors that alter the amount of available nutrients in soil and influence nutrient uptake and removal — from weather during the growing season, to the kind of crop that was previously in the field. Soil testing can reveal the amounts and supply of plant available nutrients such as higher-than-normal available nitrogen, which will inform decisions for the upcoming season.
The best time to test the soil is as close to seeding as possible. But often, that kind of timeline is not realistic.
“When you do test, you want to make sure are taking samples when the soil has cooled enough for the nutrient turnover processes to have slowed down to similar levels that you would see in the spring,” says Schoenau.
The philosophy behind how much to sample is simple – test often to account for influences of variations in crop, management, and environmental conditions. Make sure you are taking enough samples to adequately represent the area you intend to seed and apply fertilizer to.
“It may not be feasible to test every field, every year, but I think it is a good idea to be doing some kind of fertility evaluation every year,” says Schoenau. “Sampling areas that are representative and typical is important, especially for benchmarks.”
According to Ken Panchuk, Provincial Specialist, Soils with the Saskatchewan Ministry of Agriculture, a strong working relationship with the scientists testing your soil can be incredibly helpful.
“It is always a good plan to work with your agrologist when soil sampling and reviewing soil test recommendations,” says Panchuk. “Review the nutrient plans again in spring just before seeding because soil moisture conditions may have changed, meaning the target yields would have changed too, or to do some crop switching to better match the market conditions.”
Soil Testing for Pulses
When it comes to pulse crops, knowing the amount of available nutrients in the soil when seeding can lead to greater yields and a successful harvest.
“Apart from dry beans, which have poor nitrogen fixation capability, pulse crops are legumes that have the capability of fixing most of their nitrogen needs in symbiotic relationship with crop specific Rhizobium bacteria species,” says Panchuk. “But, if a
field has more than 35 pounds of nitrogen per acre in the top foot, the onset of nodules and the fixation process will be delayed.”
Conversely, knowing that a field shows lower-than-normal levels of nitrogen will help inform immediate seeding decisions and can even impact long-term planning.
“If a stubble is low in available nitrogen, it would be a good candidate for a pulse, as this will enable more of the plant’s requirement for nitrogen to be derived from fixation rather than soil or fertilizer,” says Schoenau. “The nitrogen fixation process in
pulses is an external source that can help replenish nitrogen levels in the soil for future crops in the rotation.”
Just like any other crop, there is more than one nutrient that plays a role in producing vigorous plants and larger yields.
“Pulse crops require phosphate for early, uniform, and healthy root growth, which is the first step in ensuring early onset of nodules and nitrogen fixation,” says Panchuk. “It is also needed for the energy intensive nitrogen fixation process, so it is important that phosphate levels be adequate.”
With snow already blanketing many fields across the province, it may be too late for soil testing this year. But, as the snow begins to melt, make sure to take a few core samples and send them to get tested. After all, “understanding your soil means better yields,” says Schoenau.
Labs that do nutrient analysis of soil and plant tissue can be accredited by the North American Proficiency Testing Program (NAPT).
2136 Jetstream Road
London, ON N5V 3P5
2910 12 Street NE
Calgary, AB T2E 7P7
The address and phone number given is for AGAT’s agriculture lab — called their “environmental” division — in Calgary. The company also has ag labs and sample drop off points in Edmonton, Red Deer and Grande Prairie.
604 Highway 15 W, P.O. Box 510
Northwood, ND 58267
Western Ag Labs
#3-411 Downey Road
Saskatoon, SK S7N 4L8