COMPOST MADE OF FOREST DEBRIS: ITS QUALITY AND PROSPECTS AS A SEEDLING MEDIUM

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1 The Balance between Biodiversity Conservation and Sustainable Use of Tropical Rain Forests COMPOST MADE OF FOREST DEBRIS: ITS QUALITY AND PROSPECTS AS A SEEDLING MEDIUM M. Hesti Lestari Tata, Nina Mindawati and Diana Prameswari ABSTRACT Sustainable forest management involves various silvicultural techniques, such as continuous seedling availability and fertiliser application. Fertiliser is used to increase soil productivity and assist the growth of seedlings. Fertiliser demand is increasing, but its application is expensive. The waste from forest industries and forest debris is increasing but it has so far been little used. This waste can be converted into compost. The present study was carried out to study the effectiveness of compost made of forest debris, sawdust and sludge from a pulp factory as a seedling medium. The forest debris was treated for 4 to 6 weeks, after which the material was ready for use. This condition was indicated by the C/N ratio (around 20 to 26), stable temperature and normal acidity (around 5 to 6). The ph of the material during treatment increased from less than 3.5 at the start to 5.0 after composting was achieved. Compost made of sludge did not reach a C/N ratio below 20 during the treatment. Compost may be used as a fertiliser, but also as a growth medium for seedlings. The growth medium obtained from Shorea spp. leaf litter gave the best results. The average height of seedlings grown on soil: unchopped Shorea spp. compost 1:1 and 1:2 was ± 2.52 cm and ± 2.27 cm, respectively. The quality index of the seedlings grown on the two media was 0.18 ± 0.03 and 0.14 ± 0.01, respectively. Soil as a control gave the best quality index for seedling growth. This indicated that the higher the C/N ratio of the compost, the more difficult it is for the nutrient to be absorbed by the plant. Keywords: seedling, compost, EM-4, forest debris, Shorea selanica INTRODUCTION Sustainable forest management involves various silvicultural techniques, such as continuous seedling availability and fertiliser application. Fertiliser is used to increase soil productivity and growth of seedlings. In relation to this, fertiliser demand is increasing but its application is expensive. Waste from forest industries and forest debris is increasing but hitherto unused, whereas it can be converted into compost. Continuous seedling availability needs not only good seed from a good provenance, but also a medium for propagating and growing plants. Topsoil is commonly used as a propagating medium, but using topsoil as a seedling and propagating medium in large plantations is not recommended. The latter need bulk soil that may degrade land, because the soil is carried from the forest to nursery. Meanwhile, compost may be used as seedling and propagating medium. Mixed with soil, compost adds organic matter (Hartman and Kester, 1983). 211

2 The Tropenbos Foundation, Wageningen, the Netherlands Composting can be defined as the biological decomposition of bulk organic wastes under controlled conditions (Hartmann and Kester, 1983; Polprasert, 1989). Naturally, some microorganisms, such as bacteria, fungi and actinomycetes, work as a decomposer. In a controlled aerobic process, composting was carried out by successive microbial populations combining both mesophilic and thermophilic activities (Polpraset, 1989). Effective microorganisms-4 (EM-4) is a trade name for a fermenting solution of mixed microorganisms, consisting of Lactobacillus spp., yeast, photosynthetic bacteria and Actinomycetes. The microorganisms work as decomposer, blocking soil pathogens and increasing the activity of indigenous non-pathogenic microorganisms (Higa and Parr, 1994). The objective of the study was to investigate the differential response of seedling growth to compost as a planting medium and to the composition of the medium. MATERIALS AND METHODS Seeds of S. selanica were collected from Haur Bentes Experimental Garden, Jasinga, Bogor. They were sown on a sterilised silt in a greenhouse for four weeks. The study was carried out in a greenhouse of the Forest and Nature Conservation Research and Development Center (FNCRDC) Bogor, Indonesia. Some forest debris has been composted in aerobic conditions using EM-4, as described by Mindawati et al. (1998). The materials were treated for 6 weeks, and each week the temperature of the material, ph, humidity and C/N ratio were measured. Seedlings were planted in mixed soil with some compost made of forest debris and soil as a control. The soil used in this experiment was a red-yellow podzol collected from a 0-20 cm depth under a Dipterocarpaceae stand at Jasinga, Bogor. Plants were harvested eleven months after transplanting (MAT), the shoot and roots were dried at 70 o C and weighed. The quality index of the seedling was calculated using Dickson s equation (1960, cited by Bickelhaupt, 1980). This experiment used a randomised factorial design with two factors, i.e.: 1. Composition of mixed soil and compost, consists of two levels; 1:1 (S1) and 1:2 (S2) 2. Kind of compost consists of 5 levels; - Unchopped Litter of Shorea spp. (K1) - Mixed Litter of Shorea spp. + sawdust (K2) - Chopped Litter of Shorea spp. (K3) - Sawdust (K4) - Sludge from a pulp factory (K5) Each treatment was replicated twice. The parameter measured was the growth of seedling height and stem diameter. Analysis of variance was performed in all combinations in a factorial design. 212

3 The Balance between Biodiversity Conservation and Sustainable Use of Tropical Rain Forests RESULTS AND DISCUSSION Status nutrient of the compost The forest debris was treated during 4 to 6 weeks, after which the material was ready to use. This condition was indicated by C/N ratio (around 20 to 26), stable temperature and normal acidity (around 5 to 6). The ph of the material which was obtained from sludge, increased during treatment from less than 3.5 at the start to 5.0 after composting was achieved (Mindawati et al., 1998). The quality of the compost is indicated by its nutrient status, particularly the macronutrient content. Compost made of sludge has relatively the highest nutrient content. The nutrient content of some compost made of forest debris is represented in Table 1. Based on Perhutani s standardisation (1997), good compost has a C/N ratio below 20. Compost may be used as an organic fertiliser or planting medium, because compost adds organic matter to soil, which increasing the soil nutrient content, improving soil texture and feeding indigenous soil microorganisms. Table 1 Nutrient content of some compost made of forest debris (Mindawati et al, 1998) Kinds of Compost Nutrient content (%) C/N Ratio N P K Ca Mg Unchopped Litter of Shorea spp Litter of Shorea spp. + sawdust Chopped Litter of Shorea spp Sawdust Sludge from a pulp factory Height and Diameter Growth Height growths of S. selanica seedlings were not affected by different planting media. The best height of S. selanica (21.04 ± 2.27 cm) was obtained from mixed soil and unchopped litter of Shorea spp. (1:2). Whereas the height of seedlings which were grown on mixed soil and sludge compost (1:1) varies widely, as indicated by the high standard deviation (Table 2). Table 2 The effect of interaction between compost and composition of medium on the height and diameter growth of S. selanica seedlings at 11 months after transplanting (MAT). No. Treatments Height (cm) Diameter (mm) 1 Soil : litter compost (1:1) ± 2.52a 3.39 ± 0.21b 2 Soil : litter + sawdust compost (1:1) ± 1.89a 2.94 ± 0.36b 3 Soil : chopped litter compost (1:1) ± 2.63a 4.91 ± 1.95a 4 Soil : sawdust compost (1:1) ± 1.98a 3.06 ± 0.06b 5 Soil : sludge compost (1:1) ± 18.29a 3.14 ± 0.53b 6 Soil: litter compost (1:2) ± 2.27a 3.45 ± 0.17b 7 Soil: litter + sawdust compost (1:2) ± 1.58a 3.09 ± 0.03b 8 Soil: chopped litter compost (1:2) ± 1.47a 3.20 ± 0.01b 9 Soil: sawdust compost (1:2) ± 2.74a 3.20 ± 0.19b 10 Soil: sludge compost (1:2) ± 0.19a 3.03 ± 0.12b 11 Soil (control) ± 1.52a 3.19 ± 0.10b Means followed by the same letter in the column are not significantly different by DMRT at the 5% level 213

4 The Tropenbos Foundation, Wageningen, the Netherlands S. selanica which was grown on mixed soil and litter of Shorea spp. sawdust compost (1:1) had the biggest stem diameter growth, while mixed soil and sludge compost had the smallest stem diameter. Seedlings which were grown on sludge compost tended to have slow growth, although the nutrient content of the sludge was sufficient. It may have been due to its C/N ratio (> 20), which indicated the maturity of the compost. The lower the C/N ratio, the more mature the compost. Shoot-to-root ratio The different interaction of composition medium and kinds of compost (Table 3) affected the shoot-to-root ratios of S. selanica seedlings. The ratio was based on the dry weight of the seedling. The total dry weight of a plant represents the net gain in photosynthate. Shoot-to-root ratio reflects a concern for the balance of the seedling (Bickehaupt, 1980). Table 3 shows the shoot-to-root ratio of S. selanica seedlings on different planting media. Litter compost as a seedling medium tended to increase the growth of seedlings, while sludge compost tended to cause slow growth, especially at a of soil: compost composition of 1:2. The sludge compost should be decomposed for longer than 6 weeks until it is mature. Table 3 Shoot and root ratio of S. selanica seedlings at the age of 11 MAT on different planting media No. Treatments Shoot dry wt Root dry wt Shoot: root gram Soil: litter compost (1:1) ± ± ± 0.16abc 2 Soil: litter + sawdust compost (1:1) ± ± ± 0.59ab 3 Soil: chopped litter compost (1:1) ± ± ± 0.51abc 4 Soil: sawdust compost (1:1) ± ± ± 0.44abc 5 Soil: sludge compost (1:1) ± ± ± 2.83c 6 Soil: litter compost (1:2) ± ± ± 0.17ab 7 Soil: litter + sawdust compost (1:2) ± ± ± 0.13a 8 Soil: chopped litter compost (1:2) ± ± ± 0.05bc 9 Soil: sawdust compost (1:2) ± ± ± 1.77a 10 Soil: sludge compost (1:2) ± ± ± 0.50abc 11 Soil (control) ± ± ± 0.27ab Means followed by the same letter in the column are not significantly different by DMRT at the 5% level QI of S. selanica seedlings Index quality 0,25 0,20 0,15 0,10 0, ab 0.14abc 0.12bc 0.10c 0.18abc 0.16abc 0.14abc 0.10c 0.13bc 0.11bc 0.21a S1 S2 0,00 K1 K2 K3 K4 K5 K0 Kinds of compost Figure 1 Quality index of S. selanica seedlings at the age 11 MAT on different planting media. K indicates compost of forest debris (0, control; 1, unchopped litter of Shorea spp.; 2, litter of Shorea spp. + sawdust; 3, sawdust; 4, chopped litter of Shorea spp.; 5, sludge). S indicates soil and compost composition (1, 1:1; 2, 1:2). Means followed by the same letter in the column are not significantly different by DMRT at the 5% level. 214

5 The Balance between Biodiversity Conservation and Sustainable Use of Tropical Rain Forests Quality index The quality index (QI) has been correlated with the soil nutrient status and has been used to revise the fertiliser recommendation (Bickelhaupt, 1980).The quality index of S. selanica seedlings, which were grown on different seedling media, is shown in Figure 1. The best quality index is shown by the control (soil). This reflected the fact that compost treatment in this experiment did not increase soil nutrient content. Mixed compost with soil added organic matter. This was related to the characteristics of the compost. The more mature the compost, the more easily its nutrients are absorbed by seedlings. Composts made of forest debris in this experiment were not sufficiently decomposed. Even though the nutrient content of the compost is sufficient, its nutrient may not be absorbed by the seedling. The organic matter which is added to the soil may improve the soil texture. CONCLUSION Compost made of forest debris has a sufficient nutrient status. It tends to increase soil organic matter. The more decomposed the compost, as indicated by the low C/N ratio, the more easily it is absorbed by the plant. It can play a role as a fertiliser to enhance plant growth. The purposes of adding compost (organic matter) to soil is not only to increase soil nutrient status, but also to increase soil texture and to feed indigenous microorganisms. Some forest debris, such as litter and sawdust, decompose more easily than sludge. Since compost made of sludge has a higher C/N ratio, it might not increase the height and diameter growth of the seedlings. Compost made of litter gave better results in this experiment. REFERENCES Bickelhaupt, D.H. (1980). Nursery soil and seedling analysis methodology. North American Forest Tree Nursery Soil Workshop, pp USDA Proceedings. Syracuse, N.Y., USA. Hartmann, H.T. and Kester, D.E. (1983). Plant propagation. Principles and practices. 4 th ed. Prentice-Hall, Inc., New Jersey, USA. Higa, T and Parr, J.F. (1994). Beneficial and effective microorganisms for a sustainable agriculture and environment. International Nature Farming research Center. Atami, Japan. Mindawati, N., Tata, M.H.L., Sumarna, Y. and Kosasih, A.S. (1998). The effect of some kinds organic wastes materials to compost quality and process by using effective microorganisms 4 (EM-4). Forest Research Bulletin 614: (in Bahasa Indonesia). Polpraset, C. (1989). Organic waste recycling. Asian Institute of Technology Bangkok. John Wiley and Sons. N.Y., USA. 215

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