Effect of an oat companion crop on irrigated alfalfa yield and economic returns in southwestern Saskatchewan

Companion crops are not recommended for use in the establishment of alfalfa (Medicago sativa L.) stands on dryland areas in southwestern Saskatchewan because of competition for soil water. However, their use has been common with irrigated alfalfa to control weeds and produce economic yields in the establishment year. The objective of this study was to determine the effect of an oat companion crop on forage yield and economic returns for irrigated alfalfa. In four irrigated trials at Swift Current, Saskatchewan, alfalfa was planted with and without a companion oat (Avena sativa L.) crop. The direct-seeded alfalfa produced harvestable yields in three of four trials, with forage yields ranging from 2584 to 6248 kg DM ha−1. Stands of alfalfa established with the oat companion crop exhibited 33% lower forage yields at first harvest in the first year after seeding in three of the four trials. The persistence of this treatment effect over time varied among the three trials. Economic returns for the establishment treatments differed considerably among trials and depended on the prices for oat grain and forage hay. In three of four trials, net margins for the establishment year were highest for alfalfa grown with an oat companion crop which was harvested for hay when the ratio of oat hay to alfalfa hay price was greater than 0.5. Further, it was generally more profitable to harvest the oats for grain than for hay when the ratio of oat grain to oat hay price was greater than 1.3. In the remaining trial, direct-seeded alfalfa provided the highest net margin during the establishment year. When evaluated over the 3-yr study periods, however, there was generally little consistent difference in economic rankings among the alfalfa establishment methods. Economic returns were generally higher for direct-seeded alfalfa or for alfalfa seeded with an oat companion crop that was harvested for hay when the ratios of alfalfa hay and oat hay to oat grain price were greater than 1.2 and 0.9, respectively. The study concluded that the use of an oat companion crop has both agronomic and economic merit for producers establishing alfalfa on irrigation areas in this semi-arid region of Saskatchewan.