The goal of the study was to evaluate the effect of a tillage system and plant cover on the intensity of P and K losses due to surface runoff in a six-year research period, taking into account tillage stages and development of the plant cover. A two-factor field experiment was carried out during the six-year research period. The investigated factors included no-tillage system (NT) and conventional tillage system (CT) as well as the cultivated plant: horse bean, spring wheat and winter oilseed rape. The results demonstrated that the content of P and K in the soil was 9.5% higher in the NT system than in the CT system. The NT system showed better soil-protection effectiveness preventing P and K losses from soil. Significant differences between the NT and CT systems were observed in the period without plant cover when soil in the CT system was subjected to tillage treatments, as well as in the period from sowing to 50% cover of soil by plants. It was observed that differences in P losses between the systems were lower in the initial period of the research than in the years that followed, namely the difference in 2008 was 11.6%, in 2009 57.3%, and from 59.5 to 65.4% in the years 2010-2013. Similar results were obtained for K, as the differences between the systems in in K losses were: 25.6% in 2008, 64.1% in 2009, and from 66.0 to 70.9% in the years 2010-2013. The investigated plants can be ranked according to soil-protection properties in the following order, starting from the most effective one: winter rape>spring wheat>horse bean.  

25.3.2020