Abstract
<p>This study, lasting from 1999 to 2006, was conducted at the Research Station in Tomaszkowo, which belongs to the University of Warmia and Mazury in Olsztyn. The experiment was set up on brown rusty soil classified as good rye complex 5 in the Polish soil valuation system. The analysis comprised weeds in fields sown with pea cultivated in two four-field crop rotation systems with a different first crop: A. potato – spring barley – pea – spring barley; B. mixture of spring barley with pea – spring barley – pea – spring barley. Every year, at the 2–3 true leaf stage of pea, the species composition and density of individual weed species were determined; in addition, before harvesting the main crop, the dry matter of weeds was weighed. The results were used to analyze the constancy of weed taxa, species diversity, and the evenness and dominance indices, to determine the relationships between all biological indicators analyzed and weather conditions, and to calculate the indices of similarity, in terms of species composition, density and biomass of weeds, between the crop rotations compared.</p><p>The species richness, density and biomass of weeds in fields with field pea were not differentiated by the choice of the initial crop in a given rotation system. In the spring, the total number of identified taxa was 28 and it increased to 36 before the harvest of pea plants. <em>Chenopodium album </em>and <em>Echinochloa crus-galli</em> were the most numerous<em>.</em> <em>Chenopodium album, Echinochloa crus-galli, Sonchus arvensis</em>, <em>Fallopia convolvulus </em>and<em> Viola arvensis </em>were constant in all treatments, regardless of what the first crop in rotation was or when the observations were made.</p><p>The species diversity and the evenness and species dominance indices varied significantly between years and dates of observations. Species diversity calculated on the basis of the density of weed species was higher in the rotation with a mixture of cereals and legumes, while that calculated on the basis of weed biomass was higher in the system with potato. The similarity indices, which express the convergence of floristic composition as well as of the density and biomass of weeds growing in pea fields in the two crop rotation systems compared, were within a broad range (42–86%). The biodiversity of weed communities was more closely correlated to total precipitation than to air temperature.</p>
Highlights
Weeds are an omnipresent component of phytocenoses formed in agricultural ecosystems
The purpose of this study was to evaluate the degree of weed infestation of pea grown in crop rotation systems with a different first crop, taking into account the density and biomass of weeds, indices of dominance and diversity as well as indices of similarity
This study proved that the density of weeds in the said phytocenoses did not change much in response to a different first crop in a rotation system
Summary
Weeds are an omnipresent component of phytocenoses formed in agricultural ecosystems. Loss of yields of leguminous crops due to weeds may range between 5 and 30%, depending on the degree of infestation [11]. Crop rotation is this element of agronomic practice which does not incur additional costs, protects crop yields and is an eco-friendly way to control weeds [8,12,13]. There is still little interest in growing leguminous crops, either sown as pure plantations or mixed with cereals, which might become an important element in the field production of high protein feeds
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