Winter Wheat-Soybean Intercrop
WADO
1. To evaluate agronomic performance of relay soybean in winter wheat
2. To determine if different nitrogen management systems (100% in fall vs 50% in fall and 50% in
spring) affect soybean nodule development
Selection of a cropping system depends of several interrelated climatic, agronomic and economic factors. Compared to monocrop, intercrop systems involving a legume usually result in more benefits such as residual nitrogen, biological control of pests and diseases, weed suppression, improvement of soil organic matter and control of soil erosion. Based on timing and design of crop species, intercropping can be divided into several categories: mixed, strip, row and relay (Goldmon, 1991). Relay intercropping is where a second crop is planted into land area already occupied by the first crop such that the two species overlap for a portion of the same growing season. In Canada, winter wheat is usually seeded by mid-September (fall) and insurance seeding cut off dates depending on the region or zone. Soybean is seeded in May and is initially slow in growth and development compared to wheat as a result of cooler soil temperatures in spring. Performance of wheat and soybean in an intercrop system is largely influenced by the time of interplanting the soybean crop (Khokhar and Jeffers, 2001). Successful relay cropping of soybean is dependent on a range of factors that include: variety attributes, row spacing, soil conditions at planting and during the growing season, soil moisture availability and fertility (Goldmon, 1991). Various fertility management systems can be utilized in wheat and soybean with some producers preferring application of nitrogen in fall while conservative producers opt for split application in fall and spring to account for fertilizer losses. Another concept that measures the success of an intercrop is Land Equivalence ratio, which is a measure of the yield obtained from an intercrop in relation to yield obtained from the monocrop (Mead and Willey, 1980; Delmar, 1994). This study seeks to address possible benefits of winter wheatsoybean intercropping system with respect to yield, nodulation and land equivalence ration.