Field experiments with bark humus MoDo-Mylla

This preliminary 3-year field experiment with bark humus MoDo-Mylla revealed that an application of 28 tons d.m./ha of bark humus to a sandy soil increased the content of organic carbon by about 0.5 % and that application of 56 tons d.m./ha increased the organic content of the topsoil by about 1%. Corresponding increases in organic carbon were obtained following application of 30 and 60 tons d.m./ ha MoDo-Mylla to a clay soil. The largest yield increase resulting from bark humus was obtained in the first year on the clay soil in Uppland. This increase amounted to 81 per cent at 30 tons d.m./ha and 108percent at 60 tons d.m./ha, in comparison with treatments without bark humus. Positive effects were also obtained in the second year in oats, while in the third year (winter wheat) the yield was similar in all treatments. In the first year of the experiment on sandy soil in Dalarna there was no yield promoting effect from the bark humus, probably because the experiment had been laid out on a newly ploughed ley. Positive effects of the bark humus appeared in the second and third years in the potato yields which were 10 % and 5 % higher in the third year at 56 tons d.m./ha of MoDo-Mylla than in the treatment without MoDo-Mylla. No directly yield-promoting effects were noticed on the yield of straw. The determinations of bulk weight and 1 000-kernel weight revealed a clear trend towards increased kernel weight in the treatments with bark humus at both experimental sites. The chemical analyses of grain and straw show that on the clay soil the addition of MoDo-Mylla resulted in decreases in the contents of nitrogen, phosphorus and potassium in the grain and, in addition to these, calcium in the straw. On sand soil the situtation is the reverse for nitrogen and potassium as an increase in these nutrients can be obtained following an application of bark humus. These differences in the nutrient content are probably linked with the yield levels.