Response of spring barley and weed communities to lime, phosphorus and tillage

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Abstract
Soils under permanent pasture in eastern Canada are often characterized by acidic conditions and low P availability. A 3-yr experiment was initiated in the spring of 1988 to evaluate the feasibility of using conservation tillage practices and fertilization to improve the fertility of old, poorly managed pastures taken into cereals. The effects of tillage, liming and P additions on weed communities and spring barley (Hordeum vulgare L.) yields were measured on a Joseph sandy loam (Humic Gleysol). The tillage systems were 1) moldboard plowing in the fall, with disc harrowing in the spring; 2) chisel plowing in the fall, with disc harrowing in the spring; and 3) minimum spring surface tillage. Liming and P applications favoured growth and yields of barley. Weeds competing with barley were unable to derive benefits from either liming or increased P availability, despite their potential capacity to respond positively to this nutrient. Increasing soil fertility was generally detrimental to weeds, but this effect decreased with a reduction in tillage intensity. Yield response to improved fertility also decreased as tillage intensity was reduced. Despite a fertility status comparable to that found in the moldboard-plow treatment, conditions in reduced-tillage systems were less conducive to the competitiveness of the crop and, thus, favoured the development of weed infestations, particularly under minimum tillage. Optimum crop management that can maximize the competitiveness of the crop needs to be applied if benefits of fertilization in reduced-tillage systems are to be fully realized. Key words: Conservation tillage, reduced tillage, minimum tillage, lime, phosphorus, weeds

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