Nitrogen and energy balance of a short-rotation poplar forest system.

The mean annual dry matter production of a short-rotation poplar forest in the Netherlands was 14.4 tonnes ha-1 during a 5-year growing period. During the growing period trees took up 542 kg N ha-1 of which 64 % was in the bole and branches. In the 5th year denitrification was measured in undisturbed columns in the field by the acetylene-inhibition technique. An annual denitrification rate of 18 kg N ha-1 was estimated on the basis of the observed N2O profile. The system needed an annual input of 122 kg N ha-1 to balance the nitrogen budget. The energy balance showed that at the present dry matter production the system had a net output of 54 GJ ha-1 year-1. An increase in dry matter production to a maximum of 25 tonnes ha-1 year-1, possible by planting the trees at a higher density, would raise the net energy output to 97 GJ ha-1 year-1, in spite of higher energy inputs associated with fertilizer applications. (Abstract retrieved from CAB Abstracts by CABI’s permission

Accumulation and distribution of mercury in Dutch soils.

The eleven soils investigated were placed in the following groups: (1) foreland soils from the river Rhine with Hg contents ranging from 10.43 to 0.10 ppm, corresponding to a decreasing clay content from 40% to 2%, with increasing distance from the sea; (2) soils used for bulb culture, which had been treated with Hg fungicides and showed a Hg content of about 0.15 ppm in the top 20 cm; (3) soils used as permanent pastures for over 20 years which, despite widely differing soil characteristics show, with one exception, the same Hg content (about 0.09 ppm) in the top 20 cm; these soils were chosen as references. It appears that organic Mg-containing fungicides when added to soils are slowly transformed to metallic Hg, which escapes from the soil mainly by evaporation.[116.49]. (Abstract retrieved from CAB Abstracts by CABI’s permission