Effect of sampling date on nitrogen mobilization during incubation experiments
SummaryThe influence of time of sampling on nitrogen mobilisation in incubation experiments at 20°C with humus and mineral soil samples has been systematically investigated. After five and seven samplings, respectively, during the years 1967 and 1968, it has been established that the amounts of mineral nitrogen formed vary considerably more after incubation than other characteristics investigated in samples taken at different times.The variation is great in both humus layer and mineral soil (0–5 cm) and decreases somewhat when the incubation time increases from six to nine weeks.The dry weight, density, ignition loss and Kjeldahl nitrogen of the sample vary relatively little on different sampling occasions, usually with a variation coefficient by about five per cent.The mineral nitrogen after incubation showed rather large coefficients of variation (up to 57 per cent) for the years investigated.For this reason the time at which samples are collected for incubation experiments cannot be considered irrelevant.
Studies on nitrogen mobilisation in forest soils
Incubation experiments were performed on samples from various horizons of middle Swedish podzol profiles, stored under aerobic conditions at room temperature for up to two and a half years. More than one-third of the organic matter in the mor sample from a good site disappeared during two years' incubation at room temperature. Twenty-four to twenty-six per cent of its nitrogen content was simultaneously mineralised, the largest part as ammonia. The loss of organic matter was somewhat lower in samples from three poor sites (between 20 and 30 per cent) and the release of nitrogen was also lower (12 to 17 per cent). Both the breakdown and the release of nitrogen were generally lower in A, and A, samples and much lower in B horizon samples. Liming decreased nitrogen release in mor samples (often to nil) but increased release in B horizon samples. Liming also increased nitrate formation.
D'une application pratique des indices bio-météorologiques
Abstract The purpose of the author is to determine statistically in what part of Switzerland maize could be cultivated with certain chance of rentability. The author gives first the method he used for determining the biometeorological index of four species of maize which were selected by the Swiss agronomical research stations. He has considered two possibilities for the growing period: ( a ) raising-ripening (l'approche globale); ( b ) raising-flowering, flowering-ripening (l'approche fractionee). From the biometeorological index, he calculated retrospectively the ripening time of these four species in the years 1901–1965. Assuming a priori that maize should be harvested before October 15th at the latest, he calculated, for a number of meteorological stations, the relative number of years when such conditions were fulfilled. Dividing the country in regions of similar mesoclimates and sorting these stations per region, it is possible to average the maximum altitude where maize can ripen at least 7, 8, 9 and 10 times within 10 years. Finally, taking into account the exposure and ground slope, he draws maps of the theoretically possible extension area, which maps are more reliable and detailed than the ones derived from actual means.