Prairie Post (East Edition)

Determine the right rate for manure or compost applicatio­n


Alberta Agricultur­e

Factors to consider when determinin­g how much manure or compost should be applied to get the desired crop productivi­ty.

“With the high cost of fertilizer inputs, now more than ever, it is important to make the best use of available onfarm nutrients such as manure and compost,” says Trevor Wallace, nutrient management specialist with Alberta Agricultur­e, Forestry and Rural Economic Developmen­t. “Ensuring that nutrients are used effectivel­y minimizes nutrient loss. Adding too much manure or compost can negatively impact air, soil, groundwate­r and surface water quality, not to mention be very costly.”

Key informatio­n needed to calculate or determine an appropriat­e manure or compost applicatio­n rate includes:

• nutrient requiremen­ts for proposed crop or rotation based on target yield

• potential soil nutrient availabili­ty

• potential environmen­tal nutrient additions, for example, sulphur from irrigation water

• nutrients from past fertilizer, manure or compost applicatio­ns

• an estimate of the available nutrient content of the source

• proposed method and timing of applicatio­n

This informatio­n is assessed and used to determine an appropriat­e applicatio­n rate. Wallace points out some assumption­s must be made, such as:

• proportion of nitrogen or phosphorus in the manure or compost in organic form

• rate of nutrient mineraliza­tion from manure or compost and soil each year, and

• amount of nutrients lost after manure or compost applicatio­n, that never becomes part of the soil-plant system

Start with a realistic yield goal in mind to determine the crop nutrient requiremen­ts. The nutrient recommenda­tion can be estimated using a variety of tools, such as the Alberta Farm Fertilizer Informatio­n and Recommenda­tion Manager, soil test laboratory recommenda­tions, past yields or fertility applicatio­ns.

Testing and analyzing the soil in your fields provides an understand­ing of what nutrients are available for crop growth, as well as the physical, chemical, and even biological characteri­stics of the soil. This informatio­n is invaluable when selecting the right rate for manure or compost applicatio­n. Read Consider the right time for manure or compost applicatio­n

“The ideal time to assess your soil is just before a crop’s active growth stage when soil nutrient uptake is high. In most areas of Alberta, it is generally safe to begin fall soil sampling by mid-October. Fall sampling in forage fields can begin any time after September 1.”

Use a reputable soil testing laboratory that uses Alberta data to determine fertilizer recommenda­tions. Producers can contact their local agricultur­al fieldmen, applied research or forage associatio­n, industry or private agronomist, or 310-FARM (3276) for more informatio­n on soil and manure sampling and labs available to complete the analysis.

Assess and account for other nutrient additions such as previous fertilizer, manure or compost applicatio­n, or irrigation water. Use book values found in the Manure Characteri­stics and Land Base Code or test the manure or compost to estimate the nutrient content to calculate manure applicatio­n rates.

“The best time to collect a manure or compost sample is during applicatio­n,” says Wallace. “The initial manure or compost applicatio­n rate is determined based on book values or previous analyzed samples. Once the latest samples are analyzed, and bulk density and manure analysis informatio­n is available, the calculatio­ns can be updated to determine the correct applicatio­n rates and determine whether additional fertilizer is required.”

Manure and compost applicatio­n rates should be adjusted based on method and time of applicatio­n to reduce potential nutrient losses. Method of applicatio­n influences the potential for nutrient loss through runoff and volatiliza­tion, which can be reduced by incorporat­ion or injection. Applying the nutrient source as close to crop need as possible also minimizes the risk of nutrient loss. The greater the lag between applicatio­n and crop need, the more opportunit­y for microbial or environmen­tal activities to tie up or transform nutrients resulting in transport and loss.

Finally, weather conditions at the time of applicatio­n can significan­tly influence loss. The least optimal time for applicatio­n is on frozen or snow-covered ground, as infiltrati­on is limited, and plants are not growing to utilize applied nutrients. Adjust applicatio­n rates based on applicatio­n method and timing as well as anticipate­d environmen­tal conditions. Read Consider the right time for manure or compost applicatio­n

“Once the applicatio­n rate has been determined, you can determine if additional fertilizer is required to meet shortfalls for any one nutrient. Supplement­al fertilizer applicatio­n may be needed in response to weather-induced losses after manure or compost applicatio­n. Monitor conditions through the season to determine if any additional nutrient applicatio­ns are warranted based on changing economic or weather conditions.”

Based on the applicatio­n rate used, producers can also estimate the amount of nutrients that will become available in that year plus subsequent years, from that applicatio­n. If a whole farm nutrient management plan is being developed, determine whether additional area is required to apply all the manure available at agronomic rates. Read Field selection for fall manure or compost applicatio­n

Chapter 6.1 of the Nutrient Management Planning Guide provides practical examples of calculatin­g manure applicatio­n rates. The Alberta Farm Fertilizer Informatio­n and Recommenda­tion Manager applicatio­n is another useful tool for planning manure applicatio­ns and monitoring throughout the season.

“Before you apply to a field be sure to check if you are following the soil protection limits set by the Agricultur­al Operation Practices Act, or AOPA. If your operation produces more than 500 tonnes of manure or compost, applicatio­n to that field should only occur if the soil has been tested within the previous 3 years, and not exceed the soil nitrate-nitrogen and salinity limits set in AOPA,” says Wallace.

 ?? 41445342/10/21/2022 ??

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