Undersowing Italian ryegrass diminishes nitrogen leaching from spring barley

Nitrogen (N) leaching from spring barley with and without undersown Italian ryegrass was studied in Jokioinen, south-western Finland during five years (summer 1993-spring 1998) in 1.7 m deep lysimeters (empty set 0.9 m) fille d to 1.1 m with clay, silt, sand and peat soil. Tillage was performed in mi d-October or in May, before sowing of the barley and ryegrass for the next season. In the second, third and fourth years of the experiment, total N le aching from barley without undersown ryegrass was 15, 7.9, 32 and 38 kg ha( -1)y(-1) in clay, silt, sand and peat soil, respectively. Undersowing reduc ed N leaching by 52, 31, 68 and 27%. The reduction in N leaching from clay and sand when barley was undersown with ryegrass was nearly the same as the increased total uptake of N (barley + ryegrass). In sand soil, ryegrass wa s able to diminish the NO3-N concentration of the drainage water well below the limit for acceptable drinking water. Spring tillage reduced N leaching only on peat soil (16%). Slight competition between the main and the under sown crop was indicated by lower N contents of the barley yield.