Stig Ledin

Willow coppice systems in short rotation forestry: effects of plant spacing rotation length and clonal composition on biomass production.

Abstract Above ground biomass production was determined for ten Salix clones grown in pure and mixed stands at a square spacing of 1 m and seven rotation periods (1 to 6 and 8 years), and of one clone grown at four square spacings (0.5, 0.6, 0.7 and 1 m), with rotation cycles of 1 to 5 years. Most clones reached a maximum mean annual increment (8 to 14 tons dry matter ha −1 yr −1 ) under a rotation period of 4 to 5 years. Densely spaced stands exhibited a higher production than wider spacings during the first harvests under the shortest rotation periods. Neither in later harvests of short cycles (1 to 3 years) nor in any harvests of longer cycles (> 3 years) did spacing affect biomass production. Some clones suffered from leaf rust and grazing by roe deer. Clone mixtures showed a higher biomass production in the later stages due to the compensatory effect of the successful clones which, when growing in mixtures, could fill out the gaps left by individuals that suffered from impacts other than competition. We conclude that extremely short rotations (1 to 2 years) are unsuitable for Swedish conditions, and that 4- to 6-year rotations perform best. In such longer rotations, biomass production of stands with 2 × 10 4 plants per hectare equals the production of denser stands.

Willow wood properties, production and economy

Abstract Over the last few years, selected and genetically improved willows have been introduced as a new crop on farmland with short-rotation coppice systems. The willow wood is used mainly as a biomass fuel. The introduction of willow plantations has been fast in a few areas in northwest Europe and there is still a lot of research and biological and technical development needed for further improvement. Since large-scale willow plantations for biomass fuel constitute a new crop and the willow species come from a very old and wide-spread genera, the potential for improvement is large. The water content in stems at harvest is around 50%, and may be reduced to 25–30% in non-chipped stems after drying during one summer. The calorific heat value of willow wood has been determined to be 19.7 MJ/kg. The ash and sulphur contents are low, 1.0–1.2% and 0.03%, respectively. Nitrogen, phosphorus and potassium in the wood constitute about 0.5%, 0.09% and 0.3%, respectively. Among the metals, cadmium seems to be somewhat higher in willow wood than in wood from conventional forests, namely in the range of 0.8–2.9 mg/kg as compared to

CHANGES IN PHYTOAVAILABILITY AND CONCENTRATION OF CADMIUM IN SOIL FOLLOWING LONG TERM SALIX CROPPING

Cadmium concentrations in Salix (willow) shoots are generally high and Salix can therefore potentially remove significant amounts of Cd from soil. The aim of this study was to investigate how long-term Salix cultivation had affected total and plant available Cd concentrations in agricultural soil. The study was made in 8 to 30 yr old plantations. Soil profiles down to 65 cm depth were sampled and conditions within the plantations were compared to those in nearby reference areas. When consideration was given to certain pH differences, concentrations of exchangeable Cd throughout the soil profiles were significantly lower in the Salix stands than in the reference areas. However, the effect on concentrations of total Cd was negligible. The yield levels proved not to be optimal and Cd concentrations in shoots were lower than average in the investigated stands. Data on exchangeable Cd show that uptake occurs throughout the soil profile and the Cd pool involved is thus large. These facts may explain why total concentrations were only slightly influenced. The conclusion reached was that Salix cultivation reduces the amount of plant-available Cd in the soil. However, more investigations are needed to evaluate how this effect can be optimized by choice of clone and other management measures.

Comparison of four low-technology composting methods for market crop wastes.

Four methods for composting, pit-cover (PC), pit-open (PO), above ground-open (AO) and above ground-covered (AC), were compared for their effect in accelerating compost maturity using market crop waste (MCW). The composting process was monitored through determining changes in temperature and pH, with compost maturity indices measured in terms of variations in water-soluble carbon (WSC), ammonium-N (NH(4)(+)-N) and nitrate-N (NO(3)(-)-N), and C/N, NH(4)(+)-N/NO(3)(-)-N, WSC/organic N and WSC/total N (TN). Total organic carbon (TOC), nitrogen (TN), potassium (TK) and phosphorus (TP) were also determined. Temperature rapidly increased from mesophilic to thermophilic and gradually reduced through maturation phases. A similar pattern was recorded for pH, which reached a slightly alkaline level at maturity. Composting significantly (p<0.05) decreased the concentrations of TOC, TN, TP, TK, NH(4)(+)-N and WSC and increased that of NO(3)(-)-N. All four low-technology composting methods used in this study produced mature composts within 63 days. Suitable maturity indicators for MCW compost were C/N ratio<12, WSC<1%, NH(4)(+)-N<400 mg kg(-1), NH(4)(+)-N/NO(3)(-)-N<0.2, WSC/TN, WSC/organic-N<1. On the basis of these indicators, the AC method generally enhanced maturity faster than the AO, PC and PO methods. Pit methods require less investment and are recommended for the smallhold farmers.

Effect of nitrogen fertilization on growth in a Salix viminalis stand using a response surface experimental design

In order to find a nitrogen fertilization regime that is economically feasible in commercial short‐rotation forest stands of basket willow (Salix viminalis L.), a field trial was established on a clay soil near Vasteras, central Sweden, in early 1990. A response surface design was used in which three levels of treatment were chosen for each single year: year 1—0, 30, 60, kg N ha−1; year 2—0, 60, 120, kg N ha−1; year 3—0, 90, 180, kg N ha−1; year 4—0, 60, 120, kg N ha−1. Thirty‐two combinations of these levels, out of 81 possible, were chosen and divided into four blocks. Thus, eight unique treatments were randomized to the plots within each block, providing no replicates at the end of the experimental period. This gave us a more flexible and informative experiment than many of those used earlier with rather few treatments, although they were replicated. After 4 years the willow stand was harvested and the accumulated stem production of each treatment was assessed. The effect of nitrogen fertilization on a...

Effects of Iron Precipitation and Organic Amendments on Porosity and Penetrability in Sulphide Mine Tailings

This paper evaluates the effects of organic amendments and ironprecipitation on pore size distribution and mechanical resistancein sulphide mine tailings, as related to plant habitat requirements. Unaltered tailings, oxidised tailings collected from untreated, fertilized and sludge-amended plots in the field,and mixtures of unaltered tailings and organic amendments prepared in the laboratory, were analysed for pore size distribution. The organic amendments (sewage sludge, peat mossand paper mill sludge) were each applied at the rates of 0, 16 and 33% by volume. A difference in pore-size distribution between untreated and treated samples was shown in both field and laboratory samples. Both inorganic and organic amendments caused a decrease in pores holding water at soil water potentials–10 to –60 kPa, but increased the pores holding water at tensions below –60 kPa. This resulted in a decreased or unchanged content of plant available water (Wa) in all laboratory samples and in the fertilized field samples. Penetration studies in the field showed that additions of fertilizer, without any organic matter, had resulted in hardpans in the oxidised tailings that significantly increased themechanical resistance in the surface horizon. Thus, this studyindicates that the physical influence of the oxidation processestaking place in sulphide mine tailings can be magnified by additions of soil amendments. The aggregation of iron oxides and negatively charged particles such as organic substances orphosphate anions may cement the tailings, which can result inimpeded root growth.

The energy forestry production systems

Abstract When growing and using energy forests a long chain of steps is taken: choice of site, site characterization, amelioration, choice of plant material and spacing, land preparation, planting, management, harvest and handling, transport, conversion, production of hot water and electricity. The economics of energy forestry must be improved to make the whole concept viable. Although the economics need strengthening, it has been agreed that energy forestry is one of the most promising alternatives to cereal crops on farm land. There are two main ways to improve the economics: to increase production of stemwood per area and time, and to lower the costs of production. Good achievements along these routes have been reached over the last three years. Improving each step in growing is being achieved gradually. Lowering the costs is a more stepwise process, for example as was the case when a modified maize harvester proved to work surprisingly well as an energy forestry harvester. Introductary work done during the three-year period indicates that expert systems or decision support systems may play an important role to share and use the knowledge on energy forestry production systems. For immediate use, a handbook on how to grow short rotation forests has been made published.

Bamboo as bioresource in Ethiopia: management strategy to improve seedling performance (Oxytenanthera abyssinica)

Seedling emergence and subsequent survival and growth are vital for natural forest restoration or plantation establishment by means of seeds. Such information is lacking for the African bamboo species. Two experiments were carried out in a greenhouse to evaluate the influence of seed orientation and sowing depth of the lowland bamboo Oxytenanthera abyssinica on seedling emergence, survival and growth. A randomised complete block design was used. Seedling emergence in the seed orientation experiment followed the order embryo-end-up>lay-flat>embryo-end-down. Survival rate after 62 days decreased in the order lay-flat>embryo-end-down>embryo-end-up. Mean seedling height and number of leaves per seedling followed a similar pattern. Seeds sown on top of the soil surface and at 2.5 mm depth achieved faster and higher seedling emergence than those sown at 5 and 10 mm depths. However, mean seedling height and number of leaves per seedling were higher in 5 and 2.5 mm depths than surface and 10 mm depths. There were significant quadratic relationships between sowing depth and seedling height (p=0.034) as well as number of leaves per seedling (p=0.032), both peaking around 5 mm soil depth. Lay-flat orientation, which is the most frequent position in broadcast sowing, is recommended at 5 mm sowing depth for the lowland bamboo based on overall performance in seedling emergence, survival and growth.

Biomass Production and Nutritive Composition of Cratylia argentea Under Different Planting Densities and Harvest Intervals

ABSTRACT Effects of planting density (10,000, 20,000, and 40,000 plants ha−1) and harvest interval (8, 12, and 16 weeks) on production and nutritive composition of biomass of Cratylia argentea were studied for two years in Nicaragua. Further, properties related to use of the bio-mass as animal feed were investigated. Dry matter (DM) yield increased from 8.7 to 18.2 Mg ha−1 yr−1 as the harvest interval was prolonged from 8 to 16 weeks. The density of 40,000 plants ha−1 gave the highest DM yield (18.2 Mg ha−1 yr−1). All planting densities showed the highest DM yield at 16 weeks harvest interval. Crude protein content decreased (219 to 185 g kg−1 DM) and acid detergent fibre content increased (341 to 391 g kg−1 DM) as harvest intervals and planting densities increased from 8 to 16 weeks and from 10,000 to 40,000 plants ha−1, respectively. Planting densities and harvest intervals had no significant effect on neutral detergent fibre content (529 g kg−1 DM). In conclusion a planting density of at least 40,000 plants ha−1 with a harvest interval of sixteen weeks resulted in a high total DM yield and an acceptable crude protein content.

Effects of the herbicides propaquizafop and primisulfuronmetyl on Salix plants and weeds in energy plantations

Abstract The foliar-acting, post-emergence herbicides Agil (active ingredient propaquizafop) and Tell (active ingredient primisulfuronmetyl) were tested in two different Salix plantations during the first and second growing seasons. The residual effects on Salix plants and weeds in the year after application were also assessed in one plantation. Overall-spraying of Agil did not result in any visible damage to Salix plants, and stool weight was not negatively affected. Couch grass was controlled by Agil. The use of Tell resulted in severe damage to Salix plants when applied during the first growing season. The damage was expressed by an abnormally high sprouting frequency from the leading shoots as well as retarded growth in the leading shoots. Treatment with Agil combined with Tell resulted in very good weed control, but it increased the growth disturbances to Salix plants compared to Agil or Tell by themselves when applied early during the year of planting, as well as in the one-year-old plantation. An additional effect of the treatment with Agil in combination with Tell in the established Salix plantation was an increased susceptibility to frost damage in the year after application.