The nature of the competition between cereal crops and annual weeds

Abstract

In continuation of earlier work, a study has been made of the factors controlling the competition between spring-sown cereals and annual weeds. During the years 1934 and 1935 some eighteen replicated trials were carried out in widely different localities. In six experiments, observations involving some 20,000 counts were made on the cereal development. Competition between Brassica arvensis (yellow charlock) and spring barley primarily reduced the number of tillers and fertile shoots; competition on the other hand with Raphanus raphanistrum (white charlock) diminished in addition ear size. The presence of R. raphanistrum in spring oats may decrease panicle size to the same extent as shoot number. In four out of six experiments the addition of nitrogen to both the weedy and clean crop had similar effects, greatly increasing tiller production in barley and both panicle size and shoot number in oats.In six experiments nitrogenous manuring raised the yield of the weedy crop (containing either B. arvensis, R. raphanistrum or Chrysanthemum segetum (corn marigold)) to or above the level of the clean crop; n i four the yield increases were greater in the weedy than in the weed-free crop. In one experiment doubling the amount of nitrogen applied to the weedy crop did not increase the yield of oats more than the single rate, although the final yield level was considerably below that of the weed-free oats. In four other experiments additional nitrogen did not raise the yield of the weedy crop; but in only one was the yield of the clean crop increased by nitrogenous manuring.

Competition between weeds and irrigated wheat in the Nigerian Sahel zone

“…This probably could be interpreted to mean that weed interference was not severe enough from emergence up to tillering and panicle initiation of the crop. According to Blackman and Templeman (1938), cereals and annual weeds primarily compete for nitrogen and light. Nitrogen significantly increases the number of tillers and panicles.…”

The biology of Canadian weeds. 132. Raphanus raphanistrum L.

“…The initial flush of germination followed by sporadic germination throughout a long growing season contributes to herbicide control problems in Australia (Donaldson 1986). Frankton and Mulligan (1987 In UK studies, R. raphanistrum reduced tiller number, number of fertile shoots, head size and 1000-kernel weight in barley and oats (Avena sativa L.) (Blackman and Templeman 1938). In a 3-yr study of spring-sown cereal fields in southern Sweden, wild radish, with an average abundance of 35 plants m -2 , was along with hempnettle (Galeopsis spp.…”

Influence of soil moisture on the competitive ability and seed dormancy of Sinapis arvensis in spring wheat

“…Sinapis arvensis L. is an annual broad‐leaved weed, which is indigenous throughout most of the temperate regions of the world ( Mulligan & Bailey, 1975) and is considered to be one of the most competitive species of spring‐sown crops ( Welbank, 1963; Courtney & Johnson, 1988). Previous work has suggested that the presence of such weeds has a greater depressing effect on cereal yields in a wet spring than in a dry spring ( Blackman & Templeman, 1938). As S. arvensis has been shown to be a strong competitor for water ( Blackshaw & Dekker, 1988), drought conditions (i.e.…”