Wplyw zróznicowanej uprawy roli i nawozenia organicznego ziemniaków na plon bulw oraz zawartosc azotu ogólnego w glebie | Effect of soil tillage methods and organic fertilization on growth and residual soil nitrogen in poatao crops

The aim of the present study was to determine the influence of soil tillage operations and organic fertilizers on crop productivity of potato and content of total nitrogen (N) in the soil. Two field experiments were conducted in 1996-2003 on a leached brown soil in East Poland (50°42' N, 23°15'E) employing a split-plot design with four replicates. Experiment I ( 1996-2000): three methods of soil tillage were tested (A, B, C) and type of organic fertilization as cattle manure in dose 30 ton per hectare. Methods of soil tillage: A - conventional soil tillage ( cattle-manure, ploughing - 20 cm, pre-winter ploughing- 25 cm); B - autumn ridge tillage ( cattle-manure, ploughing -20 cm, forming 20-25 cm ridges with a furrow plough ridger); C - spring ridge soil tillage ( cattle-manure, ploughing - 20 cm, in spring potato planting and forming 20- 25 cm ridges with a planting machine). Experiment II (2001-2003): three methods of soil tillage were tested (D, E, F) and type of organic fertilization as straw of spring Triticale (in dose 5 ton per hectare, with count out: 1 kg ofN in form urea pro 100 kg of straw) and catch-crop of white mustard. Methods of soil tillage: D - summer ridge soil tillage ( straw + urea, plough skimming - 10 cm, ridge forming - 25 cm, seeding of white mustard); E - autumn ridge soil tillage ( straw + urea, plough skimming - 10 cm, seeding of white mustard, cultivation 15 cm, ridge forming); F - spring ridge soil tillage ( straw + urea, plough skimming - 10 cm, seeding of white mustard, in spring potato planting and forming 20-25 cm ridges with a planting machine). Using the tillage with forming ridges in autumn gained the highest total and commercial yield of tubers. The different soil tillage methods also had no significantly effect of the total N content in the soil (0-25 cm), however forming ridges in autumn decreased the N content in the 25-40 cm layer of the soil. Straw fertilizati9n and mulching ridges with white mustard (Sinapis alba) not only reduced the N leaching, but also prevented soil erosion.