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“Deciding on the ‘right’ time (one of the 4Rs of nutrient stewardship) for application will depend on the situation and will be driven by agronomic, economic, environmental or neighbour considerations,” says Trevor Wallace, nutrient management specialist with the Alberta government.
The ‘right’ or optimal time for application in a field depends on:
- operational factors such as cropping plans, past nutrient applications, manure storage capacity and regulatory requirements
- site-specific factors such as soil conditions and soil nutrient level
- environmental conditions such as the season, weather and runoff risk potential, and
- social factors such as neighbours and local events
“To maximize nutrient use efficiency and reduce the risk of nutrient loss, it is best to apply the nutrient source as close to crop needs as possible. This ensures there is adequate time for nutrient release and plant uptake.”
While spring application may be ideal for annual crops, it is not always achievable. In Alberta, the option for spring application is limited by our short growing season. Applying in the spring adds to an already busy season and can delay seeding if manure application is hampered by road restrictions, wet soils or equipment availability. Thus more often manure is applied later in the year, into the fall, when soils are generally drier and more time is available; but the risk for nutrient loss is greater because crops are not actively taking up nutrients and the absence of ground cover increases the risk of runoff potential.
“When possible, apply manure or compost in the late summer or early fall. This allows manure nutrients to infiltrate the soil and stabilize with the soil. The later the manure is applied, the greater the risk of nutrient loss via snowmelt and spring runoff. The risk of nutrient loss from fall applied manure and compost can be reduced by incorporation or injection as well as ensuring application setbacks are followed.”
Several operational changes can be made to widen the window of opportunity for manure or compost application. Through the adoption of new practices, crops or technologies or by working with neighbours, an operation may find opportunities to expand in-season manure application windows.
“Post seeding or in-crop application of manure or compost are additional windows for manure application. Research is showing that liquid manure dragline application can be done until a corn crop reaches the V-4 leaf stage without harming the corn crop stand. To find out more about this research, read this article from Ohio State University. Solid/liquid separation technology can be used to separate solids, allowing the liquid portion of the manure to be applied through irrigation systems into growing crops."
Forages or winter cereals can provide additional in-season windows for application as they capture readily available nutrients, reducing the risk of nutrient loss and spreading out the workload.
The least optimal time for manure application is on frozen or snow-covered ground. The risk of nutrient loss is much greater as infiltration is limited and plants are not growing to utilize applied nutrients. This is why new or expanding confined feeding operations and those operations modifying their facilities are required to have a minimum 9 months of manure storage to help eliminate the need for winter spreading. In addition, confined feeding operators must obtain permission from the Natural Resources Conservation Board (NRCB) before applying.
“A full or imminently full manure or compost storage may force an emergency application on frozen or snow-covered ground. If it appears you may have to spread manure on frozen or snow-covered ground, please contact the NRCB field office nearest you to ensure that you are complying with the regulations and minimizing environmental risks and neighbour conflicts. For more information, check out the NRCB’s fact sheet (PDF, 295 KB).”
Understanding the trade-offs associated with decisions about timing of application is key to ensuring producers are getting the most beneficial return from available manure or compost resources, while minimizing potential environmental impacts and neighbour conflicts.
“Remember no matter what time of year, plan to minimize risks and conflicts, notify the appropriate authorities if required to do so, and ensure you follow manure spreading requirements,” says Wallace.
Connect with Trevor Wallace for more information:
Email: [email protected]
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