Effect of predecessors on the productivity and phytosanitary condition of hull-less oats in organic farming

Abstract. On a certified organic field a trial of the hull-less oat variety Mina was conducted, sown after peas-sunflower mixture, maize for silage, and fallow. The aim of this experiment was to evaluate the effect of predecessors on the productivity and phytosanitary condition of hull-less oats in organic farming. The study was conducted in the period 2012 – 2014 under field conditions on leached, moderately loamy to slightly clayey smolniza at the Institute of Agriculture in Karnobat, Bulgaria, on a field certified for organic farming. The trial was conducted with spring hull-less oat, variety Mina. Predecessors – peas-sunflower mixture, maize for silage and fallow. Phytosanitary monitoring was conducted. The insect reporting was performed through direct investigation for plant pests. The weed reporting – species composition and density of weed infestation by a quantity-weight method, at the end of tillering and beginning of ear formation stage. Disease infestation was determined by walking through the plots during crop vegetation, by the route method, by inspection of the plants. The best predecessor for hull-less oats was fallow, followed by peas-sunflower mixture. The yield was high and the level of weed infestation was comparatively lower than after maize for silage. During the studied period a tendency for the effect of predecessor on disease infestation was not formed. The predecessors did not affect the species composition but mainly their density