Relationship between concentration of crude protein in spring barley (Hordeum vulgare L.), white goosefoot (Chenopodium album L.), charlock (Sinapis arvensis L.) and prickly grass (Echinochloa crus-galli (L.) Beauv.)

Abstract

Laboratory bioassay was carried out at the Laboratory of Agronomic and Zootechnical Research of the Lithuanian University of Agriculture (Aleksandras Stulginskis University) at 54°89’N and 23°83’E during 2004–2005. The field experiment from which plant samples were taken for the laboratorial bioassay was performed in 2003–2004 in spring barley Aura crop at the Experimental Station of the Lithuanian University of Agriculture at 54°52’N and 23°49’E. The Lithuanian territory occupies an intermediate geographical position between the west European oceanic climate and the Eurasian continental climate. Lithuania belongs to the western region of the Atlantic Ocean continental climatic area with the average annual precipitation of 675 mm (572–978 mm) and temperature of 6–7 °C. The change of crude protein concentration in weeds affects accumulation of crude protein in spring barley. The aim of the experiment was to establish the dependence of spring barley biomass crude protein concentration on crude protein concentration in white goosefoot, charlock and prickly grass biomass from the same agrophytocenosis. The plant biomass taken from organic and conventional agriculture crops was evaluated for crude protein concentration by the Kjeldahl method. The highest concentration of crude protein in the biomass was established in the conventional agriculture system: 20.5% in spring barley and 21.7% in white goosefoot, 20.5% in spring barley and 20.4% in charlock. In the organic agriculture system, the highest concentration of crude protein in the biomass was established in prickly grass (18.9%) and spring barley (12.8%). The increase of crude protein concentration in white goosefoot, charlock and prickly grass induced the crude protein concentration increase in spring barley. The following relationship between the crude protein concentration was described by a linear correlation-regression analysis: in spring barley and white goosefoot r = 0.898 (p < 0.001), in spring barley and charlock r = 0.909 (p < 0.05), in spring barley and prickly grass r = 0.657 (p > 0.05). However, increase of the accumulated mass of crude protein in white goosefoot decreased the accumulated crude protein mass in spring barley: in the organic agriculture system y = 0.710–8.174 x, r = –0.74 (p < 0.01) and in the conventional agriculture system y = 0.856–0.834 x, r  =  –0.07 (p  >  0.05). The estimated negative dependence of the white goosefoot crude protein mass on the spring barley crude protein mass was in conformity with the Law of Crop Productivity.