Competition between annual weeds and vining peas grown at a range of population densities: effects on the weeds

Abstract

Resum^: ZasammenfassungLinear regression of dry weight of weeds against crop density, together with the use of diversity indices and principal component analysis were used to derive inforniLition about changes in the behaviour of annual weeds over the growing season and in response to a wide range of crop densities in vining peas Pi.sum sativunt L. Using linear regression it was possible lo quantify reductions in weed dry weights per unit increase in crop plant density. The "weed loss" factor was acceptably consistent between experiments. Indices examining richness and evenness showed that numbers of weed species declined with increasing crop density and as the season progressed, but although species evenness became less at successive sampling dates the presence of a pea crop, whatever its density, did not radically alter [he composition ofthe weed flora. Principal component analysis demonstrated that although there was competition wiihin the weed flora, ihe crop did not replace the dominant weed spwcies on high density plots, but reduced growth of all weed species alike. Concurrence entre les mauvaises herhes annuelles et les pois industriels cultires a diverses den.sites: effet.% sur les mauvaises herbesLa regression lineairedu poids sec des mauvaises herbes par rapport a la densite de la culture a ele utilisee. en association a des indices de diversite el a l'analyse en composantes principales. pour obtenir des donnees sur les modifications dans le comportement des mauvai.ses herbes annuelles lout au long de I'epoque de vegetation ainsi que par rapport a une large gamme de densites culturaies des pois industriels (PMH/JI sativum L.). L'emploi de la regression lineaire a permis d'evaluer avec precision les reductions dans le poids sec des adventices par unite d'augmentation de la densite des plantes cultivees, Le facteur'perte due aux adventices' est reste assez constant d'une experience a l'autre, Des indices relatives a la richesse et la repartition florisiiques ont revele que les nombres d'especes adventices diminuaient au cours de la saison et a mesurequ'augmentait la densite de la cullure; mais tout en admeltant que la repartition des especes devienne moins cgale a chaque nouveau prelevement. la presence d'une culture de pois. quelle qu'en fut la densite. n'a point modifie foncierement le cortege florislique. L'analyse en composantes principales a fait voir que. malgre une concurrence parmi les especes adventices. la culture n'u pas rempiacc I'espece dominante sur les parcelles a haute densite culturale. Au contraire. elle a amene une diminution pareille chez toutes les especes adventices. Konkurrenzkrafiverschiedener Dichwn der Erhse (•Pisum salivum L.I gcgeniiher einjahrigen Unkrautern

Wild mustard (Sinapis arvensis) response to field pea (Pisum sativum) cultivar and seeding rate

“…Nelson and Nylund (1962) Increasing field pea plant density significantly reduced weed biomass in 2 of 3 yr. Several studies have shown that increasing field pea populations reduce weed biomass (Marx und Hagedo* 196l; Lawson and Topham 1985; iownley-Smith-and Wright 1994), but none reported significant di-fferences among cultivars' In this study, while the The cultivar-by-seeding-rate interaction was significant n^J994 and 1995 only, while the cultivar 2n4 segling rate effects were significant in 1993. In all 3 yr, seed /ields increased with field pea plant density.…”

Weed community responses in a corn‐soybean intercrop

“…The significant difference between the weed biomass in the replacement intercrop and in the additive intercrop confirms the observation that weeds decrease as crop density and biomass increases. Similar results on the relationship between crop density and weed biomass were reported by Lawson & Topham (1985). In a review of the literature on the effects of intercropping and crop rotation on weed productivity, Liebman & Dyck (1993) reported mixed results (unfortunately based on a flawed vote-counting approach; see Gurevitch & Hedges 1993) on the success of intercrops in suppressing weed biomass.…”

Weed management in organic agriculture: are we addressing the right issues?

“…Obviously, in this case, the crop sowing date can be used as a weed management tool only in those environments where the farmer can actually choose whether to sow wheat in autumn or in spring and not, for example, in Mediterranean‐type environments, where wheat can only be sown in autumn. In vining pea ( Pisum sativum L.), an increase in the seeding rate may turn into a higher competitive ability, but often to the detriment of grain yield because of the concurrently higher intraspecific competition (Lawson & Topham, 1985). Similarly, in potato ( Solanum tuberosum L.), a higher planting density may turn into a crop competitive advantage but may also decrease tuber quality and increase crop susceptibility to diseases (Litterick et al ., 1999).…”