But there are other steps for ensuring a good potato crop beyond tillage and forming good hills and seed beds. Testing the fertility of the soil and applying early-season nutrients if necessary, as well as other agricultural practices like planting cover crops, can all play an important role in ensuring your crop gets off to a good start.Growers, like boy scouts, know it’s important to be prepared. Each spring, potato fields across the country are cultivated to varying degrees, depending on the soil, and the earth carefully shaped prior to planting.
We asked a trio of experts — McCain Foods agronomist Scott Graham, former Canadian Potato Council chair Joe Brennan, and soil fertility extension specialist John Heard — to share their thoughts on best practices for preparing fields for potato production.
Joe Brennan retired from farming just last year, but before that he spent 20 years growing potatoes at a farm near Bath, New Brunswick. The soils in that area of the province are very heavy, so Brennan found it useful to till his fields in the fall in preparation for a potato crop the following spring.
“We do moldboard ploughing here, as we’ve found it works the best in this type of soil. It turns the top of the soil upside down, so if your rotation crop is clover or grain stubble, it’ll put that down,” he says, adding the top foot or so of the soil is turned over this way.
“The main purpose of the tillage in the year before you plant, is to loosen up that top root zone of the ground so the roots can penetrate into the soil and pick up moisture and nutrients.”
Brennan says many growers in his area will go back in the spring and till once more to a depth of eight inches or so. This helps to incorporate any crop residue left over from the previous crop from the fall before, and also loosens and breaks up lumps in soil so it can form a good, even bed to plant the next crop in.
Scott Graham says the soils in most potato-producing areas of Manitoba can also benefit from fall tillage when it comes to ensuring a high-quality crop. If the soil type is sandy loam to loamy and imperfectly drained with compaction issues, he recommends growers till the soil to depth of nine to 12 inches, starting one inch below the compaction layer in the fall.
According to Graham, this will break up any hardpan layer in the potato fields and will improve root development, accessibility to water and nutrients, the tilth of soils and the infiltration of water through the soil profile by reducing levels of soil compaction in fields.
In some regions, he adds, it’s important to be wary of tilling too deep and pulling up salts and subsoil to the surface. “When you go back in there with your implement in the spring, you don’t want to exceed the depth of your fall tillage because that will bring up new lumps [which] will end up there all through the summer time and into harvest,” Graham says, “and that will cause bruising issues.”
John Heard says there are a couple of reasons why planting cover crops after potatoes can benefit farmers.
“If there does happen to be some residual nutrients like nitrogen in the soil, a cover crop like rye can take that up and immobilize it vegetatively,” he explains. “But probably even more important is that it’s used for erosion control.”
Heard maintains farmers who use cover crops to protect their fields may have “completely different objectives” depending on the geography and differing soil types.
“What may be important in Eastern Canada is catching nitrogen, but for us [in Western Canada], it’s a higher priority to provide cover,” he says, referring to fierce winter windstorms that can strip soil from unprotected fields.
Brennan says cover crops aren’t a widespread practice among potato producers in his neck of the woods, but it’s currently being looked at on a trial basis in New Brunswick.
“It’s not in full swing here yet,” he says. “It’s being tried and there’s been some very interesting results.”
Graham says sampling soils for nutrient levels prior to planting enables potato producers to make more informed decisions, matching nitrogen supply with crop demand and improving nitrogen efficiency, reducing nitrogen losses in the environment.
“Every fall or spring, it’s recommended to do a soil test to see where your fertility levels are, so you know how much nutrients you’ll have to supply that crop throughout the growing season,” he says. “In-season soils tests after extreme amounts of rain are a good indicator to help you determine if adequate nitrogen levels are available to finish off the crop.”
“Understanding how much nitrogen is available is critical as too much nitrogen can have negative effects on tuber yield and quality. Too much late season nitrogen may also delay tuber maturity and subsequently reduce storability and quality, including specific gravity,” Graham says.
According to Heard, “soil testing is the initial inventory of the main nutrients but also the micronutrients in the soil. The current soil supply of nutrients helps trigger fertilization practices, not just what rate they’re going to use but … [also] the timing and source and placement.”
Heard says soil testing if frequently done after harvest, is important so the results are available for farmers to discuss with their agronomists during the off-season.
“The time you want to strategize a fertility program is in the winter, not necessarily a week or two before planting, so most of the soil testing will be done in the fall,” he says.
Applying fertilizer is one of the soil amendment practices often used by farmers to make their land more productive.
Soil testing can help identify which nutrients are required and/or the best place to put them within a field, but there are a lot of different ways to actually apply fertilizer. The best methods for this, like many agricultural practices, depend on specific field conditions and where you live in Canada.
Graham says in Manitoba, growers often apply a portion of crops nitrogen requirement at pre-planting or planting. “That’s going to help your crop with early growth combating disease,” he explains. “It’s usually broadcast up front, and depending on the farm, they’ll do different amounts.” Graham adds it’s common to do another nitrogen application pass at hilling time and nitrogen applied with irrigation is an effective way to supplement the crop during the growing season.
“Applying phosphate with the planter is also a good idea,” he says. “That provides the potatoes with early root growth development, which is essential to get that crop to a good start to uptake the other nutrients.”
Brennan says growers in New Brunswick will often apply nutrients in the fall and then sometimes again in the spring just prior to planting potatoes. “Potash would be a typical example,” he says. “We could broadcast some potash onto the ground, and that spring cultivation would also incorporate that fertilizer into the soil and even it out.”