Estimating Forage Yields on Salvaged Grain Crops

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 When conditions are dry, livestock producers often acquire crops that are not harvestable for grain production to supplement their forage and grazing stocks. It is strongly recommended to estimate the crop’s yield potential before striking an agreement to salvage a crop for feed. A hands-on, field-level yield estimate goes a long way towards preventing a discrepancy that may arise from differences in rough estimates, best guesses, "eyeballing" or "ball parking" the crop.

Measure what’s there
Swathing an area of the crop, baling it, and weighing the bales can provide a measure of forage yield. The area of crop baled can be extrapolated to a field level yield estimate.

Another method is to cut and weigh square meter samples from the crop to determine yields. If this is done in 10 areas of the field and the weights are averaged, then this should provide a reasonable estimate of the average moist yield of the field.

Convert moist yield to a dry matter basis
The moisture content of standing crops can vary significantly. In order to create a solid footing for a bid and offer, moist yields should be converted to a dry matter basis. Moisture levels can be determined by using the microwave method.

Microwave oven method for determining moisture content of forages

  1. Weigh out approximately 100 g sample of the forage (W1), excluding the weight of the container. Weigh to the nearest gram.
  2. Spread the weighed forage sample on a paper plate or place it in a paper bag and put it in the microwave oven.
  3. Place an 8 oz glass three-quarters full of water in the oven to prevent igniting the sample.
  4. Heat at 80 to 90 per cent of maximum power for four minutes.
  5. Remove the sample, mix it and weigh it.
  6. Continue to reheat for two minute intervals, re-weighing each time. To prevent burning use a lower power level and 30 second time intervals as it approaches being dry. If the sample weight does not change after two or three drying intervals, then it is 100 per cent dry. This is the final dry weight (W2). A slightly charred sample should not affect accuracy of the moisture determination. Repeat the test if the sample burns.
  7. Calculate moisture content as follows:

Other agronomic considerations
Many fields in crop production are not suitably fenced for grazing. Constructing a perimeter fence can be done easily with electric fence, it also allows for limiting access to the whole field. Cross-fencing reduces wastage and encourages livestock to consume the whole plant.

Swathing a grain crop prior to grazing prevents the crop from becoming too mature because forage quality decreases as crops mature. Limiting access to the swaths similarly reduces wastage and encourages livestock to eat the complete plant.

Analyze stressed crops for nitrates to prevent nitrate poisoning when feeding salvaged crops.

Click here to download this AgriProfit$ Technical Bulletin.

Dale A. Kaliel 1

Sr. Economist: Production Economics
Economics & Competitiveness Division

1 Revised from "Determining Yields of Droughted Crops", by Arvid Aasen, Pasture Agronomist, Alberta Agriculture and Rural Development (2002)
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For more information about the content of this document, contact Anatoliy Oginskyy.
This document is maintained by Shukun Guan.
This information published to the web on August 28, 2009.
Last Reviewed/Revised on September 18, 2017.