Metla Project 7110

Circulating nutritious residues in forests

Duration: 2002-2008 Keywords: compost, fertilization, growth and yield, nitrogen, wasteproduct
Research project group: Distinct projects 1 - Structure and function of forest ecosystems

Objectives

In this project we study the effects of fertilization with some nutritious composted wasteproducts. The study is based on one single but rather large field experiment. The benefits of fertilization will be described with measurements of growth reactions of all trees in the experiment. Possible harmful effects that we study include leaching of nutrients into ground water and increased concentrations of heavy metals or other harmful compounds in plants, soil and water. 4 different wasteproducts were used in levels of nitrogen ranging from 100 to 450 kg /ha. Unfertilized plots are used for comparison as well as a normal fertilization of 150 kg/ha with a standard mineral fertilizer.

Results

2004 2005 2006

A review 2004

Concentrations of different elements has been studied with samples taken every year since fertilization. After two growing periods there were quite clear changes in the top soil and slightly increased nitrogen concentrations in the soil water. There were no sign of increased heavy metal concentration in neither soil, mosses nor Vaccinium leaves. After one growing season the needles showed only slightly increased concentrations of nitrogen. At this stage the nitrogen status was such that a growth increase could have happened only in plots with standard fertilization. The nitrogen in the wasteproducts is bound to organic compounds and will be released only gradually over a longer period. The ground vegetation has, however, already become more eutrophic on plots with the highest wasteproduct nitrogen fertilization.

A review 2005

Some results were presented at a seminar in Vaasa in november 2005. The conclusions remained quite as before. However, a clear increase in the needle nitrogen content was now found also on plots, which had received large amounts of compost. This increase was after three growing seasons and will probably lead to an increase in tree growth as well.
The effects on the environment were still regarded as small. Concentrations of nitrogen and other compounds should yet be tranformed to absolute amounts kg/ha in fertilizers, humuslayer and soil water in order to detect the actual flow of nutrients.

Large amounts of the compost products were spread out because the nitrogen content was so low. Therefore leaching of organic matter was detected especially one year after fertilisation. In the long run this should lead to an improvement in the water- and nutrient retention capability of the soil. This could be of importance in situations where the biomass harvesting is at a high level (logging residues, stump, whole tree harvesting).

The sligtly raised concentrations of nitrate-nitrogen in soil water should be futher examined as nitrification is a process increasing soil acidity.

Expecting 2006

The growth reactions will be determined if funding is arranged.

Project leader: Karlsson, Kristian
The Finnish Forest Research Institute, Kannus Office, Silmäjärventie 2, FI-69100 KANNUS, FINLAND
Phone: +358 10 211 3413 Telefax: +358 10 211 2103
E-mail: kristian.karlsson@metla.fi

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Updated 31.12.2011
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