Maria Wanic

Effect of a sowing regime and water conditions on nitrogen content and accumulation in the aerial biomass of spring barley (Hordeum vulgare L.) and Italian ryegrass (Lolium multiflorum Lam.)

Competitive interactions are common in plant communities, but the underlying mechanisms and effects of competition have not been fully elucidated to date. A pot experiment (3 series in 20092011) was conducted to evaluate the effect of a sowing method of spring barley and Italian ryegrass, and different water condition on the nitrogen (N) content and accumulation in the aerial biomass of plants at different stages. The experimental factors were as follows: 1) sowing regime – pure sowing and mixed sowing – spring barley undersown with Italian ryegrass, 2) water supply – plants supplied with water to meet their full requirements and 50% water supply reduction. The N content of the aerial biomass of plants was determined at five phenological development stages of spring barley grown in a pure stand under optimal soil moisture conditions: leaf development, tillering, stem elongation, heading and ripening. Nitrogen uptake was determined based on the N content and dry matter accumulation in plants. Nitrogen concentrations in the aerial biomass of barley and ryegrass varied throughout the growing season. Nitrogen content was particularly high in leaves, and it decreased steadily during plant development. Neither the sowing regime nor the water supply exerted significant effects on the N content of the aerial biomass of spring barley. In Italian ryegrass, under optimal water supply, mixed sowing with spring barley decreased N concentrations in shoots only during tillering. In spring barley, mixed sowing reduced N uptake by biomass, and the observed decrease was exacerbated under water deficit. In Italian ryegrass, reduced water supply decreased N uptake, but the effect of competitive interactions between the analyzed species was usually stronger than the influence of water deficit. Differences in N accumulation in aerial biomass were determined by the dr hab. inż. Marta K. Kostrzewska, Chair of Agroecosystems, University of Warmia and Mazury in Olsztyn, 10-718 Olsztyn, Pl. Łódzki 3, e-mail: marta.kostrzewska@uwm.edu.pl * The study was supported financially by the Ministry of Science and Higher Education in 2009-2012 (grant No. N N310 082836).

Competition for nitrogen, phosphorus, potassium and magnesium between spring wheat and Persian clover depending on the density of plants

A pot experiment completed in 2010-2012 analysed the relationship between spring wheat and the undersown Persian clover in the competition for nitrogen, phosphorus, potassium and magnesium depending on the plant density during the spring wheat growth stages of inflorescence emergence (BBCH 54-56) and ripening (BBCH 87-89). A mixture was composed according to the additive pattern. The analyses covered the aerial parts and roots of both species. The species were cultivated in a mixture and pure sowing at higher density (consistent with agricultural technology recommendations) and a density 20% lower than recommended. Based on the measurements of dry mass of the aerial organs and roots, as well as the content of N, P, K and Mg in the plant parts, the uptake of these elements by both species was calculated. The above data were the basis for computing the relative yield (uptake) – RY, relative yield total (uptake) – RYT, index of competitive balance (Cb) and relative efficiency index (REI). It has been shown that spring wheat and Persian clover competed for the whole pool of nitrogen and potassium and almost the entire content of phosphorus and magnesium. Wheat was a stronger competitor in obtaining the nutrients than clover. It showed the strongest competition against undersown clover for magnesium and the weakest one for nitrogen. Wheat competed more intensively with Persian clover for phosphorus and potassium in the treatment where the density was lower than recommended during the inflorescence emergence stage and for nitrogen and magnesium during the ripening stage.