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Pulse crops are a group of annual grain legumes that includes field pea, lentil, chickpea, faba bean, dry bean and lupin. These crops form a unique, beneficial relationship with certain bacteria isolated from the soil known as rhizobia. These rhizobia are found on root nodules and, as a result, these plants produce their own nitrogen from the air.
"The most obvious economic positive of pulse crops in the rotation is that they fix nitrogen for themselves from the air,” says Mark Olson, provincial pulse industry development specialist with Alberta Agriculture and Rural Development, Edmonton. “Nitrogen is by far the most important nutrient for crop growth, and the nutrient required in the largest quantity by all crops. Crops that are not legumes, such as wheat, barley and canola, must have high rates of manufactured nitrogen, as well as other nutrients, applied which is a cash output for growers and affects profitability.”
For example, a 40 bushel per acre field pea crop (the average Alberta yield) would require an equivalent of 120 lbs per acre of nitrogen for growth, but since field pea is a legume crop, 90 per cent (0.9) or 108 lbs per acre is made by the crop itself under optimum conditions in Year 1. The general rule is that for every bushel of field pea harvested the ‘nitrogen equivalent’ of approximately 1.0 lb of nitrogen per bushel is available.
“This same 40 bushel per acre field pea crop would provide an additional nitrogen equivalent benefit of 40 lbs per acre for the crop following,” says Olson. “Combing the savings of Year 1 (108 lbs) with the nitrogen equivalent benefit in Year 2 (40 lbs) would equate to approximately 150 lbs per acre of actual nitrogen savings over course of two years. At a nitrogen price of 0.60 (60¢/lb actual N) this is $90 or $45 per acre per year.”
Another economic advantage is the yield increase for crops following a pulse crop in the rotation. A review of the research literature examining yields following a pulse crop is abundant and clear. In Western Canada, researchers have conclusively seen higher yields of canola (15 to 96 per cent increase), wheat (20 to 47 per cent increase) and barley (41 to 52 per cent increase) in the year following grain legume crops compared to growing the crop on it own stubble kind. Unfortunately, this economic gain is more often not attributed to the pulse crop. Additionally, there is an increase in protein of the crop that is placed on pulse crop stubble and, in the case of wheat where protein premiums are paid, this results in increased profits to the grower.
“The environmental benefits stem from the reduction in nitrogen fertilizer use in the year of growing the pulse and in the year following the pulse crop,” says Olson. “Overall, the need for manufactured nutrients is substantially lower reducing greenhouse gas emissions associated with the manufacturing of fertilizer, transportation of fertilizer, and application of fertilizer by tractors that burn fossil fuels thus minimizing the crop’s energy footprint.
“Moreover, 80 per cent of the grain legume crops in Alberta are grown in a reduced tillage system, meaning fewer tillage passes in the field, again further reducing the impact of agricultural practices on the environment.”
Increased use of pulse crops will significantly reduce greenhouse gas emissions from cropping systems, including reduced CO2 emissions, as well as, N2O, CH4, NO and NO2 emissions at the different steps of manufacturing, transportation and application of products.
A last point to be made for pulse crops and the resultant food products are the indirect benefits to human health. Pulses have a low glycemic index which is particularly beneficial for people with diabetes. In addition, researchers have attributed anti-carcinogenic effects to various components contained within pulse crops including dietary fibre and folate. Regular consumption of pulses may contribute to reduced serum cholesterol and triglycerides which are the two major risk factors in cardiovascular disease. Eating grain legumes regularly may also reduce the risk of heart disease via favourable effects on blood pressure, blood glucose and insulin moderation and the likelihood of obesity.
“In conclusion, growers should consider including pulses in the crop rotation as there are multiple benefits to themselves as well as greater society,” says Olson. “It will not only make their farms more profitable, but also help save the environment and contribute to better human health.”
Contact: Mark Olson 780-422-3825
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