Comparative response of canola, field pea and wheat to zero tillage

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Poppe, Sylvia
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Knowledge of the relative responses of different crop species to zero tillage is important for rotation planning in conservation farming systems. The performance of Katepwa wheat, Westar canola, and Victoria field pea was investigated under zero and conventional tillage on a sandy loam at Carman, MB, and on a clay loam soil at Portage la Prairie, MB in 1989 and 1990. Parameters under investigation included dry matter accumulation, crop development, evapotranspiration (ET), soil water extraction, water use efficiency (WUE), plant water stress, yield and quality. An additional study was done at Portage in 1990 examining the response of field pea and canola to zero tillage under simulated early season drought. Effects of zero tillage on establishment, growth, yield, yield conponents and grain quality of these crops were limited. For grain yield, location and year were more important than tillage regime. Differences in ET among crop species in response to zero tillage was greater in 1989, a dry year, than in 1990, a relatively wet year. The trends for ET were reflected in soil water depletion trends. In 1989, canola extracted more water at all depths under zero tillage compared with conventional tillage. However, zero tillage increased soil water extraction below 50 cm in field pea, and above 50 cm in wheat, compared to conventional tillage. At both sites in 1990 the trend was for less water depletion below 90 cm under zero tillage. Higher WUE under zero tillage occurred three of 16 times and was attributed to a higher transpiration:ET ratio. A reduction in tillage enhanced WUE in field pea more frequently than in canola or wheat. Relative water content measurements indicated that tillage affected the water status of canola and field pea more often than wheat. For canopy and leaf temperature measurements positive responses to zero tillage were more frequent at Carman than at Portage, possibly due to the sandier soil at Carman. Only one response to tillage was observed for leaf conductance. It can be concluded that these crops are all well adapted to production under a zero tillage system.