DECOMPOSABILITY OF BARLEY STRAW - EFFECT OF COLD-WATER EXTRACTION ON DRY-WEIGHT AND NUTRIENT CONTENT

Mature spring barley (Hordeum vulgare L.) straw, cut to a length of 5 cm, was successively extracted with cold water. The influence of leaching on dry weight, nutrient content, and decomposability was investigated in fresh and in partially-decomposed straw. The loss in dry weight was 6% after one extraction, increasing to 9% after 3 successive extractions. Incubating the straw between extractions increased losses of dry matter and N, whereas losses of ash, K, P, Mg and Ca were not affected by the intervening incubations. Three successive extractions removed 58% of the ash, 87% of the K, 59% of the P, 34% of the Mg and 25% of the Ca. The loss of N increased from 20% without intermittent incubations to 43% for straw samples incubated at 15.degree. C between the extractions (total incubation period, 66 days). The respiration losses of untreated straw samples incubated for 203 days at 5.degree. and 15.degree. C were 9 and 23%, respectively. Extracting the straw before incubation reduced initial respiration losses. After 203 days, the cumulative respiration loss of leached straw incubated at 15.degree. C was 11% of initial straw by weight, whereas the loss at 5.degree. C was similar to that of untreated straw.