INFLUENCE OF PREVIOUS CROP TYPE ON YIELD OF SPRING WHEAT - ANALYSIS OF COMMERCIAL FIELD DATA

Although rotational benefits of non-cereal crops have been observed in small plot research trials, few quantitative data are available on a field scale. In this study, field data of farmers from the Manitoba Cr op Insurance Corporation were analysed to compare yield of wheat (Trit icum aestivum L.) following different crops. The yield of wheat follow ing wheat was used as a basis of comparison among crop sequences. The yield data were collected between 1982 and 1993 from fields 64 ha in s ize, located throughout the province of Manitoba. During this period, the yield of wheat following flax (Linum usitatissimum L.), peas (Pisu m sativum L.), and canola (Brassica napus L.), on average was 16%, 11% , and 8% higher, respectively, than wheat following wheat. In one year , the yield of wheat was increased by as much as 41% following a field pea crop.