The paper presents the results of investigations carried out in 2003-2006 aimed to assess the influence of intercrops, stubble catch crops and spring barley straw on some chemical constituents of potato tubers. The experiment included: I. Intercrop fertilization: control object (without intercrop fertilization), farmyard manure, undersown crop (birdsfoot trefoil, birdsfoot trefoil+Italian ryegrass), stubble catch crop (oil radish) and II. Straw fertilization: without straw, with straw. Plants of potato table cultivar Fianna were cultivated in the first year after organic fertilization. In the collected samples of tubers contents of the following constituents were measured: starch, reducing sugar, total sugar and total protein. The results indicated that intercrop fertilization significantly influenced the contents of the all the four constituents, whereas straw fertilization only affected the contents of starch and total protein. The highest starch content characterized the potatoes fertilized with the mixture of birdsfoot trefoil with Italian ryegrass, or with oil radish, both in combinations with or without straw. The highest content of total protein was found in the potatoes fertilized with birdsfoot trefoil alone or in combination with straw. The lowest content of reducing sugars and of total sugar was recorded with potatoes fertilized with the mixture of birdsfoot trefoil with Italian ryegrass with or without the addition of straw.
