Estimating Forage Yield on Salvage Grain Crops

From the Sept 14, 2009 Issue of Agri-News


	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. . "Swathing an area of the crop, baling it, and weighing the bales can provide a measure of forage yield," says Dale Kaliel, senior economist: production economics with Alberta Agriculture and Rural Development. "The area of crop baled can be extrapolated to a field level yield estimate." Another method of measuring what's in the field is to cut and weigh square metre samples from the crop to determine yields. If this is done in 10 areas of the field and the weights are averaged, this should provide a reasonable estimate of the average "moist" yield of the field. 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. One method that can be used to determined dry matter is the microwave method for determining moisture content of forages: weigh out approximately 100 g sample of the forage (W1), excluding the weight of the container, weigh to nearest gram spread the weighed forage sample on a paper plate or place it in a paper bag and put it in the microwave oven place an 8-oz glass that is three-quarters full of water in the oven to prevent igniting the sample heat at 80 to 90 per cent of maximum power for four minutes remove the sample, mix it and weigh it 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) when the sample weight does not change after two or three drying intervals, it is 100 per cent dry and this is the final dry weight (W2) (a slightly charred sample should not affect accuracy of the moisture determination, however you must repeat the test if the sample burns) calculate moisture content as follows: "There are a few other agronomic considerations that can affect the harvestable forage yield and should be taken into account," says Kaliel. "Many fields in crop production are not suitably fenced for grazing. However, 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." Forage quality decreases as crops mature, so swathing a grain crop prior to grazing will prevent the crop from becoming too mature. Limiting access to the swaths similarly reduces waste and encourages livestock to eat the complete plant. If crops have been stressed by frost, be sure to analyze these stressed crops for nitrates to prevent nitrate poisoning when feeding salvaged crops. Contact: Dale A. Kaliel 780-427-5390

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