Weed infestation in the stand of milk thistle and infestation in sustainable crop rotation

Milk thistle – Silybum marianum (L.) Gaertn. can be a winter annual or a biennial medicinal plant. This study was focused onmilk thistle as a weed in the sustainable farming system with the crop rotation of maize for grain, common pea for grain, durum wheat and milk thistle. The assessment of the occurrence of Milk thistle in sustainable crop rotation was conducted at the Experimental Base of Faculty of Agrobiology and Food Resources, Slovak University of Agriculture in Nitra in the years 2013–2015. An actual weed infestation of maize, common pea and durum wheat stands with milk thistle was evaluated before preemergence application of herbicides, in the spring time. Second screening of actual weed infestation of all stands in sustainable crop rotation with milk thistle was done before crops harvest. Screening of each field was made on 1 m2 area with three replications. The three randomly established sample quadrants were situated minimally 10 m from field margin and apart from each other, respectively. The level of infestation was evaluated according to average density of weeds per square meter. Obtained data were statistically analyzed by software Statistica 7.0 by Analysis of variance (ANOVA), LSDtest (P = 0.05). According to statistical analyses, in the year 2014 maize stands was infested with the highest and highly significant amount of Silybum marianum (7.8 plants per m2). Stands of pea for grain in the second year after milk thistle cropping were infested only with 1.23 plants per m2. Durum wheat stands were infested with 0.96 milk thistle plants per m2. The originality of this paper is in testing the introduction of a new perspective crops in sustainable crop rotation. Milk thistle not infestation fields within the reporting unit. Dominant weed species in canopy of Silybum marianum are: Echinochloa crus galli, Chenopodium album, Amaranthus spp. (retroflexus, powelli), Atriplex spp. (patula, acuminate, prostrata), Avena fatua, etc. All dominant weed species belongs to the group of annual early and late spring weeds. Next very dangerous group are perennial weeds Cirsium arvense, Convolvulus arvensis and Sonchus arvensis.