IMPACT OF NON-CHEMICAL WEED CONTROL METHODS ON SOIL AND SUGAR BEET ROOT CHEMICAL COMPOSITION

A short-term, stationary field experiment was carried out at the Experimental Station of the Aleksandras Stulginskis University (ASU) in 2015-2016. The soil under the experiment was silty loam Planosol (Endohypogleyic-Eutric - Pie-gln-w). The research objective was to determine the influence of different non-chemical weed control treatments on soil and sugar beet root chemical composition under organic farming conditions. Six weed control methods were tested: inter-row loosening (CT, control treatment), cutting and mulching with weeds (MW), Persian clover (MC), white mustard (MM) and spring barley (MB), inter-row steaming (ST). According to the results of the investigation, during the two plant growing seasons, the accumulated biomass of inter-row plants positively influenced the content of nitrogen, phosphorus and potassium in the soil, but decreased the proportion of magnesium and sulfur. Inter-row loosening (control treatment) positively affected nearly all the tested soil chemical properties (especially total nitrogen and magnesium), except for the content of sulfur. Although inter-row mulching with weeds drastically decreased the content of phosphorus, the concentration of potassium increased. Mulching with the Persian clover improved the contents of total nitrogen and available potasshim. However, this impact was common. Mulching with white mustard significantly increased the contents of potassium and magnesium. Similar results were found in the plots with spring barley living mulch. In the steamed plots, due to the lack of plant residues, the soil properties did not improve and the losses of phosphorus and magnesium were the highest in the entire experiment. Different non-chemical weed control methods decreased the yield and the sucrose content in sugar beet roots. The content of potassium, sodium and alpha amino nitrogen in the roots did not significantly depend on the methods of weed control.