AgronomyCrop Rotations

    Crop Rotations


    [deck]Creating a positive connection between economical and environmental sustainability.[/deck]

    The effect of sensible crop rotation on pest and pathogen populations in potato crops is coming under increasing scrutiny these days, and is a matter that most commercial farmers in Canada carefully consider when planning for the next cropping season.

    In fact, many growers regard crop rotation as a primary cornerstone of their sustainability strategies. In addition, studies in Canada, the United States and several European countries consistently confirm the importance of crop rotation systems in optimizing potato yields and quality.

    Brian Beaton, potato crop co-ordinator with the Prince Edward Island Department of Agriculture and Forestry, maintains that “crop rotation is a critical component to any cropping system to maintain sustainability. The goals of crop rotation can vary depending on the crop and soil conditions but the goal of rotation is to reduce the impacts of pests and diseases and maintain or build soil quality.”

    Beaton points out that crop rotations can reduce pests and diseases by breaking the pest cycle, by providing a crop that is not a host to that organism. In addition, herbicides not available for use in potatoes can be utilized in certain rotation crops to control problem weeds.

    Proper crop rotations can also enhance soil fertility, help maintain soil structure, increase soil organic matter and conserve soil moisture. According to Barbara Pleasant, author of Maintain healthy soil with crop rotation, crop rotations act to help maintain the balance of nutrients, organic matter, and microorganisms necessary for healthy soil. “Of these three, the invisible world of soil-dwelling micro-creatures is the one that most benefits from crop rotations,” she writes.

    “In addition to interrupting disease cycles, rotating crops prevents the depletion of nutrients. Nitrogen-fixing legumes often take no more nitrogen from the soil than they replace, and their presence stimulates the growth of beneficial soil microorganisms.”

    A crop rotation systems study for Atlantic Canada prepared by the Eastern Canada Soil and Water Conservation Centre evaluated the economical and environmental performance of different crop rotation systems in that region’s potato industry. The authors of Crop rotation: The future of the potato industry in Atlantic Canada stress that potato production systems must achieve both economical and environmental sustainability.

    Soil Improvement

    The study notes that from an environmental perspective, soil quality, as well as surface and groundwater protection, are the main challenges of the potato industry in Atlantic Canada. And crop rotation, it maintains, is an effective management strategy to meet these challenges.

    Other studies related to crop rotation have shown that production systems where potatoes are grown no more than one year out of two and that include cereals and/or forages in a crop rotation can improve soil and crop productivity. More frequent potato cropping, such as planting potatoes two years out of three or not using other rotation crops at all, degrades the soil and lowers both total and marketable potato yields.

    The authors of the Atlantic Canada crop rotation systems study maintain that soil represents about 30 per cent of a potato farm’s assets: “Its protection, through the adoption of better rotations and other conservation practices, will most certainly influence the sustainability of the potato farm. By conserving the productive capacity of the land, producers will maintain and may even improve their ability to produce, and thus to meet their financial obligations.”

    By changing from continuous potatoes to a three-year rotation system, it is possible to increase potential marketable yield of a farm’s potato crop by 31 per cent, according to the report. The study further found that frequent potato production can result in low long-term levels of stable organic matter in the soil, especially if erosion is occurring.

    Increasing the organic matter content in soil can also boost its ability to resist compaction caused by wheel traffic of heavy field equipment used for potato production. This compaction makes soil less productive by inhibiting root penetration and negatively affecting soil aeration, soil moisture and temperature regimes  — all of which reduce potato yield.

    In a paper entitled Cropping sequence and rotation: Impact on potato production and soil condition, potato specialists at the University of Idaho maintain one of biggest pitfalls of growing potatoes too frequently in one location is the likelihood of the buildup of pests that either seek tubers as their primary host or are difficult to control in potato crops. Rotational crops can provide an opportunity to more effectively and/or inexpensively control certain pests.

    Richard Gorrill runs a large farming operation in the western part of Prince Edward Island. He agrees that the implementation of a sound crop rotation plan has proven value for soil health as well as pest and disease suppression, but points out that there are at least two practical realities which growers are faced with.

    “One reality is that any rotation strategy needs to take into account the fact that enough land is available for implementation. Secondly, it is a challenge to find a rotation crop that is economically profitable. Options are limited,” Gorrill says.

    According to Beaton, brown mustard is a rotation crop that is showing up more frequently in P.E.I. “Although there is still a lot of research to be done with this rotation crop, the goal is to reduce soil-borne diseases such as Verticilium wilt and reduce populations of wireworms in fields,” he says. “The brown mustard, when properly incorporated into the soil, produces a bio-fumigant in the soil which can reduce the population of the wireworms.”

    Beaton says thousands of acres of brown mustard were planted in 2014 as part of the battle against wireworm and diseases, compared to just a few hundred acres planted in 2013.

    It is clear that crop rotation is a good example of the positive connection that can be established between economical and environmental sustainability. An effective crop rotation strategy can bring significant benefits at all levels of a potato production operation. But on a cautionary note, producers also need to be aware of any factors at play that could hinder their ability to employ rotation strategies that make good financial sense for their operations.

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