Southern Tablelands Farm Forestry Network |
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STFFN newsletter - May / June 2001
Fertilising pines - aids to decision making By Dr Clive Carlyle, CSIRO Forestry and Forest Products. From ‘Onwood’, Research updates from CSIRO Forestry and Forest Products, Autumn 2001 No 32 New findings from CSIRO's Plantation Forest Research Centre at Mt Gambier, South Australia, are helping decision-making by radiata pine plantation managers on mid-rotation fertiliser application. Applying nitrogen or phosphorus fertiliser, or both, five to eight years before harvest can significantly boost the economic return from a plantation. As well as increasing wood production, the resulting extra growth lifts the price obtained per cubic metre if logs move into a larger diameter class. The relatively rapid return on the investment in fertiliser is a further advantage. The growth response of plantations varies greatly, however. Economic analyses have shown that internal rates of return from mid-rotation fertilisation range from negative figures -reflecting a negligible effect on tree growth -to a very healthy 28%. Managers need to predict the response, and generally base their estimates on analyses of nutrient levels in the foliage. With nitrogen, for example, readings below 1.2% suggest trees will give a good response to fertilisation. Above 1.5% the response is likely to be weak or non-existent. Unfortunately, most plantations fall into the marginal range for nitrogen -1.2-1.5% -where predictions are highly uncertain. A similar situation exists with the other key nutrient, phosphorus. In experiments set up in collaboration with industry at 18 sites in South Australia, Victoria and Tasmania, Dr Clive Carlyle of CSIRO Forestry and Forest Products found the growth boost from mid-rotation nitrogen fertilisation ranged from zero up to an impressive 30%. Conventional foliar analysis proved a poor predictor of the outcome, explaining only about 30% of the variation in response. Its success rate in predicting the impact of phosphorus fertilisation was about the same. A key aim of the research has been to develop better prediction tools, and results to date are highly promising. Carlyle found that analysis of the balance of nitrogen to phosphorus in foliage gives a much better indication of the potential of a plantation to respond to nitrogen fertilisation than nitrogen readings alone, explaining about 65% of the variation in response. For phosphorus, linking foliar analysis with a measure of the amount of foliage in a plantation lifts the figure to a similar level. Concerns about accuracy have not been the only problem with foliar analysis; it also presents practical problems. Selecting representative samples of the foliage is difficult, and collecting them from tall trees is expensive as limbs have to be shot down. So, as well as investigating ways to improve foliage-based tests, Carlyle and his colleagues are researching alternatives. Excellent results have been obtained in early trials of one soil-based test. Carlyle found that analyses based on an index of nitrogen and phosphorus availability in the soil explained about 90% of the variation in response to mid-rotation nitrogen fertilisation. A forest company has begun using the method to guide its fertiliser applications. Other outcomes of the research are suggesting ways to ensure mid-rotation fertilisation produces the maximum possible economic response. The CSIRO team has found that any limitation in phosphorus nutrition, even where trees would not normally be considered phosphorus deficient, will prevent trees responding to their potential to nitrogen additions. The CSIRO team can now quantify this limitation, enabling managers to objectively decide on the need to apply nitrogen alone or in combination with phosphorus. The research also raises important considerations about the way in which nitrogen and phosphorus fertilisers are currently applied to plantations. The research has been conducted in collaboration with Auspine Ltd, ForestrySA, Green Triangle Forest Products, and Norske Skog. New Zealand Farm Forestry Association (NZFFA) 45th Annual Conference By Rebecca Blundell The New Zealand Farm Forestry Association (NZFFA) was formed in 1957, and currently has over 4000 members managing over 200,000ha of forest worth approx. $2 Billion. These forest areas consist of Radiata Pine, Cypresses, Eucalypts, Douglas Fir, Blackwood, Poplars as well as a range of North American hardwoods and indigenous NZ species. Around 800 of NZFFA members will on average harvest 12.7ha over the next 5 years. These mature forest plantations have a market value of approx. $300 million. The Hawke’s Bay Branch of the NZFFA hosted the 45th Annual Conference. Hawke’s Bay is a region of diverse land use – from pines to vines and everything in between. The region is home to 114,000 hectares of Pine plantation and 36 wineries. Landforms range from mountains, down to hills and through to river valleys, terraces and coastal plains. Unlike Australia, the soils are generally fertile, however the rainfall in parts of Hawke’s Bay is a familiar 700mm per year. 385 people attended the conference from New Zealand, Australia, Santiago Chile and Nevada USA. The conference’s theme was Balancing Diversity and field excursions explored the diverse reasons for planting trees in Hawke’s Bay:
The farm foresters of Hawke’s Bay are leading the way in creating sustainable land use patterns, with a mosaic of productive plantations, sheltering highly productive pastures and healthy stock. The silvicultural management of radiata pine in Hawke’s Bay is aimed at sawlog production. Plantations are typically pruned to 6 metres and thinned to 200-250 stems per hectare. There are local and export markets for pulp, and sawlogs through Pan Pac Forests Products just north of Hawke’s Bay, and the port of Napier. Although it may seem that New Zealand is leaps and bounds ahead of Australia in farm forestry, it needn’t be disheartening, but inspiring. Many New Zealand farmers were told they were crazy planting various trees on their properties with no guaranteed markets or returns. Dairy farmers were told their cows would become lazy with too much shade, lying down all day instead of eating grass! Now, the majority of farmers who have planted trees for various reasons are laughing all the way to the bank. So, the message from NZ is ‘don’t give up’ and focus on high quality high value products. The main focus, in any discussion about pruning P. radiata, is usually on techniques, equipment and cost. Little attention is given to the most important variable, that of the trees themselves. This is a little suprising as the characteristics of the individual tree affects the cost more than any other factor. Trees which are expensive to prune and will yield the least clearwood are ones which have;
These trees are difficult to prune and are adversely affected by the removal of branches as there is often less green material above the target DOS than the tree needs to quickly recover from the pruning. If the stocking is high enough these are the trees which are rejected and are unpruned. The ideal tree has the following characteristics;
These trees are easy to prune and are less affected by the removal of branches because they have relatively more green material above the pruning. The branch occludes quicker and as a result the defect core is closer to the DOS than is the case for trees with large branches. The angle of the branch makes a great deal of difference to the pruning operation. High angle branches are difficult to remove and can be dangerous as they fall. Contract pruners are expert in identifying easy and difficult trees, this of course, is part of the expertise which is used to assess the costing of the work Given these factors are so important to pruning one may have expected that material which has the desired characteristics would be routinely planted by those who need to prune their trees. That is small growers in regions where there is no pulp market or growers aiming for peeler logs. The technology to produce such plants is well known. It has been possible to produce cuttings with the desired characteristics for some time. The extra price of such material is more than compensated for in the cost of pruning and the concomitant increase in clearwood. This hidden aspect of pruning should be given far more attention by growers, before planting, than it has to date. Potassium can boost young pines By Dr Philip Smethurst, CSIRO Forestry and Forest Products. From ‘Onwood’, Research updates from CSIRO Forestry and Forest Products, Autumn 2001 No 32 Research in Tasmania has shown that fertilisation with potassium can be important in achieving maximum growth in young radiata pine plantations on ex-pasture land in drier regions of Australia. Dr Philip Smethurst and colleagues from CSIRO Forestry and Forest Products and the CRC for Sustainable Production Forestry, including Arthur Lyons from Private Forests Tasmania, found trees showing needle yellowing in a 2 year old plantation had very low potassium concentrations in their foliage –about half those considered necessary for good growth. Concentrations in trees that were still relatively green were only about two thirds the acceptable levels. In a subsequent experiment at this site they found that, after one year, a combination of weed removal and potassium fertilisation dramatically improved tree colour, foliar potassium concentrations and tree growth. Removing weeds had a considerable effect on its own, presumably through reducing competition for the potassium in the soil; foliar concentrations rose to the levels commonly accepted as adequate. However, addition of potassium had a further substantial impact. Together, weed control and potassium fertilisation more than doubled tree growth rates. Smethurst suggests these results highlight the difficulty of diagnosing potassium deficiency using commonly accepted critical concentrations. "Where visual symptoms are evident, a comparison of concentrations in foliage of healthy and unhealthy trees might be more instructive than the commonly used method of comparing concentrations in the foliage of unhealthy trees with a critical concentration developed in different circumstances," he says. He does not find the discovery of potassium deficiency in plantations on ex- pasture sites surprising, noting that the nutrient is not normally applied to pastures, and the continual removal of large amounts in animal and plant products must deplete soil supplies. He says drought can exacerbate the problem, because adequate soil moisture is needed for nutrients to move readily through the soil to roots. While potassium deficiency in forest plantations has not been observed in Tasmania previously, it was documented about 30 years ago in Gippsland, Victoria, where it was also most noticeable on ex- pasture sites. Recently, potassium deficiency has been suspected in Eucalyptus globulus plantations on ex-pasture land in WA, and research is planned to check this. Smethurst suggests that, where potassium addition is needed, the appropriate fertiliser regime may be a light application of muriate of potash at planting followed by a further application at about age two years when the canopy is rapidly developing. The rate of fertilisation required will depend on conditions at the site. Biology and Ecology of Essigella californica (Essig) Trudi Wharton In 1998, it was discovered that the hills were alive with the exotic aphid Essigella californica, a pest of Pinus radiata. It made its first fatal mistake by climbing on the arm of an entomologist at CSIRO who alerted Dr Mary Carver, the CSIRO resident aphid taxonomist. Further investigation discovered that E. californica was happily sucking away in the P.radiata plantations out there, and has since been found in all States and Territories where P.radiata is grown. Naturally the Forest industry were a little disturbed about the idea of an aphid running loose in their forests and have funded my project, with the aim of answering some of the questions on E. californica’s biology , ecology, and insect-plant interactions. Pinus radiata is a native pine of California and has been increasingly used as a plantation timber world wide. As P. radiata has spread, so it seems has E. californica. Despite this, E.californica has not been studied to any degree in the USA or elsewhere, so there was little information available when E.californica turned up on pine here. E.californica feeding causes P.radiata needles to turn yellow, and when shed, result in a yellow carpet effect especially in older plantations. Needles along the main trunk and upper crown are damaged in 4-6 year old trees. Older trees (20-25 year old) damaged in the upper third to quarter of the tree. Needle loss results in reduced photosynthesis and hence lower growth rate in P.radiata plantations, resulting in a loss to the Industry of 17.3 million dollars per year. Essigella californica, exhibits parthenogenetic (asexual) reproduction and has a short generation time. This allows them to increase their population size rapidly. The aptera (wingless morph) is spindle shaped with grey green thorax and lime green abdomen. It’s body length is 1.5-2.0mm. It is an extremely excitable and active aphid, and will move rapidly and evasively at the slightest disturbance, usually to the base of the needle, or it will drop off the tree. Surprisingly these aphids have only 3 larval forms, compared with 4 larval forms in other aphids. The difference in the number of larval forms may be a consequence of the earlier evolution of aphids living on Gymnosperms compared with the later expansion of aphids onto Angiosperms. Bioenergy Australia Bioenergy Australia is a group of 34 Australian government and private sector organizations formed to promote the development of biomass energy in Australia. On Tuesday 10th April the Joint Venture Agroforestry Program and Bioenergy Australia held a seminar on the aspects of growing, harvesting and the economics of short rotation woody crops (SRCs) for energy generation in Australia. It was an opportunity to hear of the progress of the Bioenergy Task Force, in particular Task 17; Short Rotation Crops for Bioenergy. Biomass as an energy source is plant and animal materials that can be used to supply heat, electricity and fuels. It is viewed as a renewable alternative to coal, oil and natural gas. Types of Biomass employed as an energy source include wood and wood wastes, agricultural residues, oil seeds, sewage sludge and animal manure. In Australia, biomass accounts for less than 5% of our energy supply, the global figure is about 14%. The interest in biomass came about through concerns for global warming, largely resulting from release of ‘greenhouse gases’ by coal, oil and natural gas combustion. According to the International Energy Association (IEA) Bioenergy, energy derived from burning or conversion of woody crops, biomass residues and wastes, could be a cost effective and sustainable way of meeting an increasing part of the world's energy needs in the next century. If power plants fuelled by biomass contributed 1000 megawatts (MW) of Australia’s electricity generating capacity (an achievable level), this would displace an equivalent capacity of coal-fired power plant and net carbon dioxide emissions would fall by about 7.4 million tonnes a year. It is hoped that many of the agro-forests being planted all over Australia today could be used for energy production in the future. STFFN will keep all its members up-to-date on the future of this exciting new opportunity for forest growers. More information on Bioenergy is available at: http://renewable.greenhouse.gov.au/technologies/biomass/biomass.html |