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The optimum killing time of a rye (Secale cereale) cover crop is an important management decision and can determine the yield of the subsequent soybean (Glyane max) crop The objective of this research was to study a rye cover/soybean system. Soybeans were grown on sandy (Delhi) and loam (Woodstock) soils (1989/1990) with mulch on the soil surface obtained by killing rye approximately 1 and 2 wk before soybean planting. A conventional tillage treatment was used as a control. Soil water content, soil temperature, rye mulch amount and soybean growth were monitored over the season. Rye mulch amount for the late killing (LK) date was always larger than for the ear y killing (EK) date. LK decreased soil water content at soybean planting time at Delhi in 1989. The rye mulch produced with the LK increased soil water content early in the soybean growing season in 1990. A substantial decrease in the amount of mulch was observed during the growing season and resulted in little difference between mulch and no mulch soil water and temperature conditions later in the season. Extreme temperatures were more frequent under the bare soil, but these were limited to a small percentage of hours, and did not translate into differences in soybean development rates. Reduced soybean growth observed early in the season in one out of four location-years vanished as the season progressed. Number of seeds per pod and nodule number were increased due to rye mulch, but no difference in soybean yields were observed among treatments. Key words: Rye (Secale cereale), cover crop, mulch, soybean (Glycine max)
Wagner‐Riddle et al. (Fri,) studied this question.