Wheat Residue Management for Soybean Production on the Northern Frontier.

Soybeans are an expanding crop in Manitoba, planted on over 1 million acres for the past three years.  The expansion of soybean has mainly been in areas with shorter growing seasons, where minimum or no-till systems are traditionally used.  To accommodate the lengthy soybean growing season, these minimum or no-till systems have been abandoned for increased tillage to facilitate fast soil warming.  The purpose of this study was to compare wheat residue management techniques that could reduce tillage before planting a soybean crop, and compare them to current tillage practices.  The following wheat residue management treatments were established in the fall of 2013 and 2014 near Carman, Manitoba: conventional till (disc), strip-till, no-till short stubble (15 cm stubble height), no-till tall stubble (40 cm stubble height), and a fall rye cover crop. A soybean test crop was planted the following spring in 2014 and 2015.

Surface soil temperature at 5 cm was found to have a significantly higher daytime temperature before and after soybean planting in the strip-till treatment compared to all other residue management treatments.  No-till treatments had a cooler daytime temperature compared to strip-till and conventional tillage, however the no-till treatments still produced soil temperatures above the recommended average soil temperature for planting soybean (10^oC) before soybean planting occurred (May 28, 2014 and May 22, 2015).  Soil moisture was recorded for the soybean growing season at 5 and 30 cm, and was found to be conserved under no-till treatments throughout the entire growing season.  Soybean yield was not significantly different for strip-till, disc, short and tall stubble treatments in 2014.  Results from the first soybean test crop year indicate that tillage can be reduced prior to planting soybeans in Manitoba.