The use of biopreparations in the control of soybean endangered by pathogenic soil-borne fungi

A field experiment was conducted in the years 2003-2004 on a field of 10-years’ soybean monoculture, with naturally accumulated infection material in the soil. Soybean of ‘Mazovia’ was the object of studies. Before the sowing the seeds were dressed, and at the beginning of anthesis the plants were sprayed with biopreparations Polyversum, Biosept 33 SL and Biochikol 020 PC. The experiment considered the combination with dressing the seeds by means of Zaprawa Oxafun T (a.s. carboxine 37.5% + tiuram 37.5%) and spraying the plants with fungicide Bravo Plus 500 S.C. (a.s.: chlorotalonile 50%). The seeds that were not dressed constituted the control. During the vegetation the number and healthiness of soybean plants were determined twice (in the seedling phase and at anthesis), at the same time a laboratory mycological analysis was carried out. After the harvest the studies established the size and quality of the seed yield of soybean growing in particular experimental combinations. The best number of plants was obtained in the combination with Biosept 33 SL, slightly weaker after applying Polyversum or Zaprawa Oxafun T, and the worst in the control combination. Biosept 33 SL and the fungicide were the most effective in protecting the plants from infection by soil-borne fungi. Polyversum and Biochikol 020 PC also showed a good protective effect. The greatest seed yield was collected from soybean plants after applying Biosept 33 SL, while the lowest – from control plants. Soybean plants were mainly infected by Fusarium spp.,A. alternate, P. exigua, R. solani and P. irregulare. Those fungi were most frequently isolated from control plants, and the least frequently after applying Biosept 33 SL or Polyversum. The proportion of pathogenic fungi (P. sojae, Fusarium spp., S. sclerotiorum, P. exigua) in seed infection of soybean was the smallest in the combinations with Biosept 33 SL or Zaprawa Oxafun T, while the biggest in the control.