New crop rotation studies aim to help growers boost their profits for fields in non-potato years.
Most potato growers understand the value of rotating spuds with other crops in a rotation spanning three years or longer, as a vital tool for fighting potato diseases and pests.
Some farmers, facing shrinking margins and other factors such as a declining agricultural land base and high costs for adding fields, are tempted to grow potatoes one in every two years, despite the deleterious effects of shorter crop rotations. Potatoes are a high-value crop, so the profitability of alternative crops in non-potato years in the rotation is another important consideration.
Research is showing that canola is poised in some areas of Canada to become the crop with possibly the highest profit potential next to potatoes. Before we take a closer look at new potato rotation studies that involve canola and other crops, here’s a look at what producers are planting in non-potato years in some areas of the country — and why.
Prince Edward Island
Brian Beaton, potato industry co-ordinator for the Prince Edward Island Department of Agriculture and Fisheries, says farmers in the Maritimes are under pressure to make more money in non-potato years.
“The cost of most things on the farm goes up a bit each year, so you have to find ways to keep up,” he notes. P.E.I.’s agricultural Crop Rotation Act specifies a three-year rotation unless a grower develops a management plan approved by the province to ensure acceptable soil losses over the shortened rotation.
Beaton says a concern for producers with non-potato crops is disease and soil conservation. Potatoes, soybean and canola, for example, are all susceptible to sclerotinia disease. Some non-potato fall cover crops can leave plant debris behind which helps prevent both wind- and water-related soil erosion, where others do not.
In terms of what farmers are choosing to grow in their fields in non-potato years, Beaton says much of that are grains like barley and wheat, with some brown mustard, ryegrass and buckwheat being used as cover crops.
“We are also growing more soybeans and corn in rotation with potatoes,” Beaton notes. “The price of soybeans and corn was higher the last few years, which increased the acres of those crops, but those prices have come down some over the last year or so.
Ontario Potato Board member Bert Tupling says the main rotational crops for Ontario potato growers are wheat, corn and barley, with roughly two-thirds of producers following a three-year rotation in their fields and one-third doing a two-year rotation.
Tupling grows 1,500 acres of potatoes every year with his family outside Shelburne near Toronto, with more land supporting other rotational crops. He says there is definitely more pressure nowadays on producers to maximize every field’s profit potential in non-potato years.
There is definitely more pressure to make more money in non-potato years. Margins have shrunk, and other crops have to pay their way.
– Dan Sawatzky
“Land prices are very high, and with the range from $10,000 to $15,000 an acre, you need to grow a profitable crop every year, not just potato years,” says Tupling. He adds that figuring out a correct rotation for their crops is an individual thing for farmers, with factors such as heat units, soil types, and disease and pest pressure all coming into play.
Tupling notes that corn in the rotation provides many benefits through the corn stover (crop debris left over on the field after harvest), as a ground cover to help prevent wind and soil erosion and as added organic material to the soil. He notes that for most Ontario potato operations, canola isn’t considered a viable non-potato crop, due to the fact that it adds little organic matter to the soil.
In Manitoba, the vast majority of potato growers follow a three- or four-year crop rotation. In non-potato years, they mostly grow wheat, canola, corn, soybeans and rye, says Dan Sawatzky, manager of the Keystone Potato Growers Association (the province’s processing potato producer organization).
“There is definitely more pressure to make more money in non-potato years,” he says. “Margins have shrunk, and other crops have to pay their way.”
In Alberta, potato growers utilizing irrigation are able to include a large variety of specialty crops in their rotations, all of which provide quite a good return, according to Terence Hochstein, executive director of Potato Growers of Alberta.
“Finding another profitable crop to complement potatoes is not as critical here because there are many more options with irrigated land,” he says. “Irrigation is not just in southern Alberta. The northern seed areas of the province around Edmonton have some irrigation as well.”
About 40,000 acres of irrigated potatoes (out of 53,000 potato acres in total) are grown in the province each year, in rotation with non-potato crops include corn, sugar beets, seed canola, hemp, lentils, chickpeas, sunflowers and vegetables such as peas and onions.
Most years there generally isn’t a great deal of concern around water shortages, Hochstein says, but that can change without warning. He notes many improvements made by the irrigation industry over the last 10 years have greatly reduced water wastage in the province.
Another important factor is land availability. Hochstein notes that because the province’s potato producers do a lot of farmland rental exchanges (basically trading fields with neighbours), they’re able to do at least a four-year crop rotation. Some farmers have four, five or six years between potatoes, he says, with the longer crop rotations having a significant impact on reducing disease.
“We are very conscious of disease,” says Hochstein. “For example, there is very little viral disease in the province, and we’re aiming for zero. We do have the cool nights, which really helps as well, but there is more of an emphasis here on making a conscious decision to widen the rotation to keep disease down and potato crops protected rather than to maximize total profits by planting potatoes more often. That’s a risk growers here are not pressured to take and we are fortunate about that.”
Ramona Mohr, a sustainable systems agronomist at Agriculture and Agri-Food Canada in Brandon, Man., led an extensive potato rotation study from 1998 to 2011. Canola, alfalfa, oat and wheat were included in two-, three- and four-year rotations.
In general, Mohr and her colleagues found rotation had little effect on tuber quality, likely because factors that influence quality were consistent among rotations within a given year. The presence of canola in the two-year potato-canola rotation promoted some diseases such as potato early dying while suppressing others like fusarium dry rot when compared against the potato-wheat rotation.
Having a perennial alfalfa crop in the rotation appeared to increase the potential for sclerotinia, even in four-year rotations, as both canola and alfalfa are sclerotinia-susceptible. Having alfalfa in the rotation also resulted in an increased occurrence of sweetclover, medic and residual alfalfa in other crops, according to the study.
Overall, from this study we can say that there was less disease risk and more consistent yields in three- or four-year rotations compared to the two-year rotations.
– Ramona Mohr
Where wheat preceded potato, Mohr says there were more wireworm larvae, and in most cases, a higher percentage of damaged tubers as a result. However, where canola was grown prior to potato, the wireworm populations were lower. Mohr notes that this was likely due to the application of thiamethoxam to canola seed and the production by the canola plant of glucosinolate degradation products, both of which may deter wireworms and click beetles. Wireworms also prefer crops other than canola.
Mohr’s study found that in overall economic terms, potato-canola-wheat was among the highest revenue-generating rotations. Because of the high value of potatoes, the two-year potato-canola rotation had the highest net revenue at first, but beginning in 2007, Mohr says two-year rotations produced a markedly lower potato yield than three- or four-year rotations.
“It happened quite suddenly,” she recalls. “Overall, from this study we can say that there was less disease risk and more consistent yields in three- or four-year rotations compared to the two-year rotations.”
There are two major potato rotation research projects (within a larger five-year initiative) currently underway in Eastern Canada that being spearheaded by the P.E.I.-based Eastern Canadian Oilseed Development Alliance (ECODA) and funded through Agriculture and Agri-food Canada and industry partners. The projects finished year two of field trials in 2015.
The objective of one study in P.E.I. being led by AAFC research scientist Aaron Mills is the evaluation of the effect of canola and soybean crops on potato yield and quality during a three-year rotation.
“The project is extensive and we are looking at several factors that have not been previously evaluated,” Mills says. “In addition to the regular suite of agronomic measurements that would include yield and quality of all crops, we’re also measuring parameters such as microbial community, labile carbon and nematode community changes.”
According to Mills, labile carbon is a form of organic carbon in soil that’s been shown in certain recent rotation studies to be a good predictor of crop vigour and yield. “It’s a relatively inexpensive test that can be run in the spring. If we can nail down measurements of a suite of things that correspond with changes crop yield and quality, we can pass on good information to growers for use when making management decisions,” he says.
In addition, Mills and his team are hoping to determine how particular crops or different crop management strategies affect different microbial groups such as bacteria, fungi and mycorrhizae — all of which have an impact on soil health. The nematode community profile data will also provide a picture of how the soil is functioning under different rotations.
Andre Gagnon, an independent researcher with a firm called Progest based in Sainte-Croix Que., is also conducting ECODA canola and potatoes rotation research. Gagnon and his team are studying 18 different rotation patterns, including different lengths of rotation and different rotational combinations, such as canola planted after or before the potato crop in a two-year rotation.
“We will get a good sense whether or not there is a disease transfer issue with canola, for example, sclerotinia,” Gagnon explains. “Each year, yield and quality of all crops are being assessed and at the end, a comparative economic analysis will be done.”
WHERE ON THE WEB:
For more information on the Eastern Canadian Oilseed Development Alliance crop rotation studies, visit ecodainc.ca.