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.
The effect of nitrogenous fertilizers on the nitrification of forest soils
The effect of fertilization with urea and ammonium nitrate on nitrogen mineralization was studied in a series of laboratory incubation experiments. The samples (humus layer) were collected from field experiments with different applications of fertilizers during a period of 11–14 years. The nitrogen fertilization influenced some chemical properties of the humus layer such as pH, N-Kjeldahl content and the content of inorganic nitrogen, especially in the samples from North Sweden. Nitrate nitrogen was formed in humus samples classified as non-nitrifying in several cases, usually after urea fertilization.
A New Method for the Study of Water Movement in Soil
Abstract A method is described for studying the movement of soil water by application of a weak solution (e. g., one per cent) of NH4SCN. After a suitable interval a profile is dug up, and sprayed with a strong solution (e. g., 20 per cent) of FeCl3. All parts of the profile containing thiocyanate then become deep red.