Grass species as a living mulch – impact of sod and its weediness on apple trees

The relationship between a cover of four grass living mulches in an apple orchard and the weed cover as well as its impact on the fruit tree yield, growth, and fruit quality was estimated at the Fruit Experimental Station of the Wrocław University of Environmental and Life Sciences in Wrocław (Poland). The experiment was established in a young orchard of ‘Chopin’ cv. apple trees grafted on rootstock MM 106, i.e. one of the strongest semi-dwarf rootstock. One year after, the tree planting soil was covered by blue fescue, red fescue, Kentucky bluegrass, and perennial ryegrass in tree rows and tractor alleys. The apple trees showed a similar degree of adaptation to the changing cultivation conditions in four different living mulches despite the varied share of the area covered by weeds. However, they did not avoid competition from different grass sods and their weediness, which was reflected in their low yield and low crop efficiency coefficient. The perennial species composition and the percentage share of the most common weeds differentiated the sod of the studied grasses. Among several perennial weed species, Trifolium repens L. was found to be the most competitive in all grass living mulches. The dynamic development of this species in time was stimulated by a rapid increase in precipitation in the orchard. The lowest soil surface cover by the total weeds was noted soon after the perennial ryegrass emergence due to the rapid development of the grass. Red fescue spread the most efficiently among all the studied grasses, and its coverage allowed effective reduction of the presence of weeds. This cover crop also maintained high purity of grass sod, especially in the tree rows, until the end of the experiment period.