Changes in spring wheat (Triticum aestivum ssp. vulgare L.) and persian clover (Trifolium resupinatum L.) biomass under the influence of plant competition and density

The influence of sowing method and plant density on the biomass of spring wheat and Persian clover was evaluated. In a pot experiment conducted in three series during the years 2010–2012, plants were cultivated as mixed and pure crop at higher (consistent with agronomic recommendations) and lower density, decreased by 20% compared to it. Dry mass accumulation tests for both species were conducted during the following wheat growth stages (BBCH): leaf development (12–14), tillering (21–23), stem elongation (31–32), inflorescence development (54–56), and ripening (87–89). Based on the results obtained, the biomass growth rate for both species in question was also determined. It was shown that the mass of shoots of spring wheat cultivated as mixed crop was lower than that of wheat shoots grown as pure crop during the stem elongation and ripening stages. Mixed sowing limited aboveground accumulation in the heads and grain the most and in the stems the least. During the leaf development and stem elongation stages, the wheat presented a more pronounced response to the presence of clover expressed by biomass decrease in case of the treatment with lower plant density and during ripening in the treatment with recommended plant density. In case of both sowing methods and plant densities, the mass of wheat roots was similar. Biomass accumulation in Persian clover shoots and roots in mixed sowing was lower than in pure crop during the entire growing period. The wheat limited biomass accumulation of Persian clover in inflorescences the strongest and in the roots the least. The spring wheat growth rate in both sowing methods was similar as opposed to Persian clover in the case of which a decrease in the growth rate was observed in the mixed crop during the generative development period