Humusbalans i odlad jord

Authors

• Jan Persson Lantbrukshögskolan, Institutionen för markvetenskap, avdelningen för växtnäringslära, 75007 Uppsala 7, Sverige 

DOI: https://doi.org/10.23986/afsci.71882

Abstract

Studies of the organic content and biological activity of the soil have been made on two farms belonging to the Agricultural College of Sweden. The soil analyses on the two farms were compiled during the 1930’5, and the samples taken at the time, as well as the maps used during the sampling, have been preserved. Some parts of the farms were again sampled in the early 1970’s. The samples from the two series have been analysed for organic carbon. In some of the samples the biological activity was determined in incubation experiments and the organic matter was fractionated. The areas chosen for the investigation represent different soil types and have different cropping backgrounds. Some of them have been cultivated for several hundred years while others have only recently been brought under the plough. The determinations of organic carbon show that the humus content in the recently broken soils decreased considerably during the 40 years separating the samplings. The magnitude of the decrease partly depends on the extent of the decomposition at the first sampling, partly on the moisture conditions. In some cases decreases of the humus content were also registered in the older fields. This may be due to intensified soil cultivations and improved drainage. The amount of easily decomposable substances in the initial samples was larger than in the later ones. This difference maybe partly due to changes taking place during storage, and the results suggest that to some extent it may also depend on a higher biological activity in the soil at the initial sampling.