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Open Access
Standardisation of planting stock production techniques for teak (Tectona grandis Linn.f.)
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2020) Vijayalakshmi, K P; KAU; Jamaludheen, V
The study was undertaken at Tree Nursery of College of Forestry to compare the effect of different pre-treatment methods on seed germination and optimization of fertigation intervals and seed sowing at different spacing for quality teak stump production. Attempt was also made to select ideal potting media and to standardize container type and size for producing quality teak seedlings. The treatment combination of termite scarified seeds + Alternate wetting and drying (AWD)-3 days gave the highest germination percentage (92.33 %). This resulted in 18.56 % increase in germination percent against the 73.77 % in the AWD 7 days alone (Standard Pre-treatment followed). The dual advantages of the treatment combination of termite scarified seeds + AWD-3 days with respect to both high a germination percentage and the lesser number of days required for the pre- treatment of teak seeds is an important highlight. Termite scarified seeds gave the highest collar diameter of 1.46 mm as against the control treatment (0.81 mm) after 30 days of germination. The superiority of this treatment was evident, in most of the seedling growth characters in the nursery also, as in shoot length (6.43 cm), root length (13.04 cm), total seedling length (19.48 cm), dry weight (0.20 g) and vigour index (14.91). Mechanical scarification also has shown advantage over the untreated seeds as it followed as the next best treatment in germination percentage and in most of the early seedling growth characteristics. Hence, in situations where the suitable subterranean termite cannot be assured, mechanical scarification using the mechanical scarifier is recommended. For quality teak stump production, at 180 days, the maximum collar diameter (23.31mm) showed by Fertigation at 7 days interval was significantly superior to all other treatments. Moreover, at 180 days, all the fertigation treatments reached the minimal collar diameter criteria of 1-2 cm were statistically distinct from the no fertigation (control) treatment. All the fertigated treatments attained collar diameter of 2-3 cm criteria for better teak stump production. It is also proved that even the least frequent fertigation at 21 days application resulted in the collar diameter of (22.66 mm) at 180 days of growth period. Hence, fertigation with 0.2 % N: P: K (19:19:19) in equal proportion at 21 days interval can be recommended for producing seedlings for better stump production. Seed sowing at 10 cm x 10 cm also reached required collar diameter for stump production. That means, 1000 numbers of utilisable seedlings are available for stump production from a standard nursery bed of 10 m x 1m at 180 days of seedling growth. At 180 days, the treatment interaction F1 X S3 (Fertigation at 14 days interval X Spacing at 30cm X 30cm) showed the maximum collar diameter (34.88 mm) followed by F2 X S3 and F3 X S3 (32.00 and 31.75 mm), these two were on par with each other. Taking into account the number, the treatment combination S1 X F3 (10 cm X 10 cm with 21 days intervals of fertigation) is recommended as it produces 1000 numbers of seedlings fit for better stump production from a standard nursery bed size of 10 m X 1m. The treatment S1 X F4 (10 cm X 10 cm) with no fertigation also reached the minimal collar diameter (11.51 mm) criteria of 1-2 cm. Good correlation existed between root growth potentials and most of the seedling characteristics needed for good quality teak stump with six months of seedling growth. Among the potting media the maximum seedling length (138.00 cm), collar diameter (8.77 mm), total dry weight (17.77 g) and the highest quality index (0.98) recorded in M3-Soil+ Rice husk+ Vermicompost in the ratio of 2:1:1 as against the standard potting media M5 (Soil+ Sand+ FYM) normally used for raising seedlings. Apart from the observed improvement in plant growth, the production cost of planting stock was found comparable for M3 (soil+ rice husk+ vermicompost) 2:1:1 mixture (₹ 9.09 / plant) as against the cost for standard potting mixture (₹ 9.01 / plant) and the treatment M4-Coir pith+ vermiculite+ perlite was found as the costliest (₹ 13.02 / plant). Both from the seedling quality and from the economic point of view, the treatment M3- Soil+ rice husk+ vermicompost was emerged as the best. Among the polythene bags, 30 cm x 25cm (T1) raised seedling exhibited maximum number of leaves (15.25), leaf area (4025.95 cm2), shoot length (106.89 cm), collar diameter (13.50 mm), the number of primary lateral roots (58.12), length of primary lateral roots (38.96 cm) maximum root length (48.74 cm), total dry weight (60.37 g) and quality index (4.56) at 90 days after transplanting. Among the different root trainers, 300 cc raised seedlings showed maximum number of leaves (11.12), leaf area (435.08 cm2), collar diameter (6.91 mm), shoot length (27.09 cm), root length (23.80 cm), total seedling length (50.90 cm), number of primary lateral roots (51.25), length of primary lateral roots (19.80 cm), leaves dry weight (2.11 g), shoot dry weight (3.46 g), total dry weight (6.61 g) and quality index (0.84) as against the T6-Root trainer of 150 cc (Standard size/control). The production cost of planting stock was found (₹ 9.09 and ₹ 7.89 / plant) for T4-Root trainer of 300 cc and T5-Root trainer of 200 cc and T6-Root trainer of 150 cc - Standard size/control (₹ 6.99 / plant). From the results of the study, it is advisable to adopt root trainer of 300 cc only if the additional cost of ₹ 2.10 can be spent per seedling, otherwise go for the standard size of 150 cc for there was no distinct advantage of adopting the next bigger size of 200 cc. The prominent managerial inputs form this study for teak nursery production forestry include development of standard protocols for pre-treatment, seed sowing spacing, potting media, size of the polythene bags and root trainers. The package for quality teak stump production was also standardised.
Open Access
Optimization of fertilizer regimes and understorey productivity in four-year-old Swietenia macrophylla King stands
(Department of Silviculture and Agroforestry, College of Forestry, Vellanikkara, 2018) Vikas Kumar; KAU; Kunhamu, T K
Extensive field study was carried out to investigate the effect of fertilizer treatment and intercrops on the growth and productivity of 4-year-old Swietenia macrophylla King. The study was carried out in a S. macrophylla plantation that was established at Mala, Thrissur during 2009 at a spacing of 2.5 x 2.5m. The fertilizer cum intercropping trial was superimposed on the existing S. macrophylla plantation in a split plot design with fertilizer levels as main plots and intercrops as sub plots during two consecutive years (2014-2016). The various N, P, K fertilizer combinations were viz. F1: 0:0:0; F2-50:25:25 (68:78:26 g per tree); F3- 100:50:50 (136:156:52 g per tree) and F4-150:75:75 (205:234:78 g per tree) kg ha-1 year-1 N, P2O5 and K2O; equivalent to 0:0:0, 50:10.75:20.75, 100:21.5:41.5 and 150:32.25:62.25 kg ha-1 per year elemental N, P and K, respectively. The fertilizers were applied to the mahagony trees at a basal ring of 50 cm radius just after the pre-monsoon rains. The various intercrops selected were shade tolerant ginger (Zingiber officinale Roscoe), wild turmeric (Curcuma aromatic Salisb) and turmeric (Curcuma longa L.). There were total 16 combinations of treatments with three replications (total 48 plots). The main plot size was 40 x 10 m and sub plot 10 x 10 m. The growth observation of the S. macrophylla tree after the fertilizer application showed consistent increase with increasing fertilizer dosage. Tree growth in terms of height, diameter, basal area and volume showed characteristic increase with increase in fertilizer levels. For instance, the stand basal area increased from 8.69 (F1: unfertilized) to 14.87 m2 ha-1 (F4: heavily fertilized). Similarly the tree volume also showed increase with fertilizer application. The difference in basal area for the higher fertilizer regimes were on par (F3, 14.50 m2 ha-1 and F4, 14.87 m2 ha-1) suggesting F3 as the optimal fertilizer regime if basal area production is the objective. However, the volume production was the highest under F4 regimes (105.28 m3 ha-1) which was significantly different from F3 (93.31 m3 ha-1). Hence tree management at F4 fertilizer regime would be ideal for optimal volume production for S. macrophylla. The biomass production results also showed positive response to applied fertilizers. Total mean tree biomass production was in the order 52.24, 60.62, 64.32 and 83.62 kg per tree for F1, F2, F3 and F4 fertilizer dosage regime respectively. The corresponding stand level biomass (per ha basis) was in the order 83.59, 97.00, 102.91 and 133.80 Mg ha-1 for F1, F2, F3 and F4 fertilizer dosage regime respectively. The highest fertilizer dosage plots showed almost 60 per cent increase in biomass production as compared to unfertilized control. Among the biomass components, stemwood represented almost 50 % of the total biomass production for all fertilizer regimes followed by roots which accounted almost 18 % of total biomass production. Branchwood biomass represented roughly 14-15 % of total biomass. Biomass accrual by the various components in the decreasing order was: stemwood> roots> branch wood >leaves>twigs. Mean tree and stand level carbon sequestration showed positive response to fertilizer application for 6 year old S. macrophylla. The total mean tree carbon stocks ranged from 29.1 kg (F1) to 46.66 (F4). The total carbon sequestration on per hectare basis was 74.66, 57.24, 54.31, and 46.56 Mg ha-1 for fertilizer regimes F4, F3, F2 and F1 respectively.Among the various biomass components, stemwood accounted bulk of the biomass carbon which was roughly 50% followed by roots (17 %). Nutrient partitioning S. macrophylla suggests that in general, nitrogen and potassium concentrations decreased in the order leaves > stem > branch > roots > twigs for N, P and K. However, tissue phosphorus concentration followed the order branches > leaves > roots > twigs > stem. Various components stored considerable amount of nutrients in their biomass. The total N stock in the standing biomass ranged from 0.428 (unfertilized control) to 0.716 Mg ha-1 (F4; heavily fertilized). The stock of phosphorus in the biomass was 0.174 (unfertilized control) to 0.223 Mg ha-1 (F4; heavily fertilized) while the corresponding stock for potassium was 0.090 (unfertilized control) to 0.144 Mg ha-1 (F4; heavily fertilized). Root distribution studies using logarithmic spiral trench technique in 6-year-old S. macrophylla showed increase in rooting intensity with fertilizer application for total roots and root class <2.5 mm. Fine root (< 2.5 mm) represented approximately 58 to 62 % of the total roots. Hence the increase in fine root count in high fertilized plots suggest higher nutrient uptake and there by higher tree growth for S. macrophylla. The present study showed the maximum foraging zone for S. macrophylla was at rhizosphere volume of 2.17 m lateral distance and 40 cm soil depth. At the present stocking this leads to considerable overlapping of the rhizosphere of S. macrophylla and intercrops and thereby limits the prospects of intercropping. Hence the possible optimal spacing suggested for 6-year-old S. macrophylla would be 5.5 m x 5.5 m for effective intercropping. Effect of intercrop on the tree growth in all the fertilizer treatment plots suggested non-significant response. Despite the overwhelming effect of fertilizer on tree growth and yield, the presence of intercrop had only very modest influence on tree growth. Interestingly some of the S. macrophylla tree growth variables were marginally better in the intercropped plots suggesting possible complementary interaction between the intercrop and trees for applied fertilizers. The intercrops viz. ginger, wild turmeric and turmeric showed better growth in fertilized plots as compared to unfertilized control. Also the biometric growth and rhizome yieldswere higher in the treeless open control plots as compared to S. macrophylla intercropped plots. Nevertheless the growth differences were lower in the heavily fertilized plotsas compared to open control. The better growth and rhizome yields during the second year for all the three intercrops was due to improvement in understory light regimes consequent to uniform tree pruning.
Open Access
Bamboo (Dendrocalamus strictus (Roxb.) Nees) based agroforestry system: planting density effects on biomass accumulation, carbon sequestration, root distribution pattern and understorey crop productivity
(Department of silviculture and agroforestry, College of forestry, Vellanikkara, 2014) Bhimappa Kittur; KAU; Sudhakara, K
A field experiment was undertaken at Vellanikkara, Thrissur in a seven year old bamboo (Dendrocalamus strictus (Roxb.) Nees) stand planted at 4x4, 6x6, 8x8, 10x10, and 12x12 m spacings to assess rhizosphere competition and understorey (turmeric, ginger and chittaratha) productivity, to explore the root activity and distribution pattern in bamboo, to determine the understorey photosynthetically active radiation (PAR), leaf area index of bamboo (LAI) and aboveground biomass production, nutrient uptake and carbon sequestration as a function of planting density. Detailed investigation on the physico-chemical attributes of the soil was also done. Results reveal that understorey turmeric and ginger height, shoot length, number of tiller and leaves were significantly lesser due to close spacings (4x4 and 6x6 m) of bamboo, but NPK uptake, dry matter production, rhizome yield and oleoresin content were significantly higher in wider spacings (10x10 and 12x12 m) of bamboo. The chittaratha responded better in control plot followed by widest spacing (12x12 m) of bamboo. Due to competition of bamboo about 89% decline in 32P absorption by turmeric at closest spacing (4x4 m) of bamboo as compared to sole turmeric plot. The recovery of 32P by bamboo from the treated turmeric was significantly decreased with increasing distance from the turmeric beds. The recovery of 32P by bamboo in > 8x8 m spacings was nil. The other factors attributed to reduction in growth and yield of understorey crops may be high LAI of bamboo and low understorey PAR. The LAI of bamboo in 4x4 m spacing was 678 % higher compared to 12x12 m spacing. At 12 noon the understorey PAR increased from 107 µmol/sec per m2 in 4x4 m to 1019 µmol/sec per m2 in 12x12 m spacings of bamboo against the overstorey PAR (1033 µmol/sec per m2). The maximum rooting intensity of bamboo was within 0-30 cm soil depth and up to 4.45 m lateral distance under all the spacings. However, in wider spacings (10x10 and 12x12 m) the roots were distributed beyond 30 cm depth and spread laterally up to 8.75 m. The deeper spread of roots in wider spacings may enable clumps to capture nutrients that would otherwise be leached from the upper horizons of the soil profile. The root activity of bamboo was studied by 32P at varying depths (50 cm and 1 m) and lateral distances (50 cm, 1 m and 2 m). At closest spacing (4x4 m), the 32P absorption by bamboo (15th DAA) at 50x50 cm depth and lateral distance was significantly higher (809 cpm) which gradually decreased by placing 32P beyond 1 m (448 cpm) and 2 m lateral distances (196 cpm). However, in wide spacings (12x12 m) the lateral spread of active roots were more at greater depth (1 m); this helps pumping of soil nutrients from the deeper layers. The bulk density of soil increased with increasing depth of soil and spacings of bamboo. The N, P and K content of soil significantly decreased with increasing spacing of bamboo. Closest spacing (4x4 m) of bamboo recorded maximum amount (2109 kg/ha) of total N and 10x10 m spacing had lowest (1430 kg/ha). The available P at surface soil (0-20 cm) ranged from 12.86 kg/ha under bambooless control plot to 21 kg/ha at closest spacing. The available P up to 1 m soil depth was highest (42 kg/ha) in closest spacing and decreased with increasing spacing of bamboo. The total available K up to 1 m depth of soil in closest spacing was 35% higher compared to widest spacing. The amount of soil organic carbon (SOC) in the whole soil at 0-20 cm was highest (11.50 Mg/ha) due to 4x4 m spacing and lowest (6.61 Mg/ha) due to widest spacing (12x12 m). The total SOC up to 1 m depth in closest spacing declined by 143% compared to widest spacing. The SOC in silt and clay fraction (<53 µm) was highest (16 Mg/ha) in closest spacing (4x4 m) and lowest (5.20 Mg/ha) in bambooless control plot at 20-50 cm soil depth. The SOC in macro sized fraction (>250-2000 µm) in closest spacing was 9 Mg/ha at 0-20 cm depth; this decreased to 2.27 Mg/ha at 80-100 cm depth. Due to decrease of bamboo spacing from 12x12 to 4x4 m, the clump DBH decreased from 1.61 to 1.06 m. The crown spread, number of live culms and MAI of bamboo also increased due to increasing spacing. Due to closest spacing (4x4 m), culm wood biomass decreased by 54% compared to widest spacing (12x12 m) of bamboo. The twig biomass recorded maximum (28%) at 6x6 m and 8x8 m spacing of bamboo and minimum (19%) in closest spacing. The total aboveground biomass in closest spacing was 112 kg/clump which increased to 271 kg/clump due to 12x12 m spacing. At stand level, the culm wood biomass was maximum (49 Mg/ha) in densest stand (625 clumps/ha); this decreased to 11.49 Mg/ha due to least dense stand (69 clumps/ha). The twig and leaf biomass reduction in least dense stand was 206% and 114% compared to densest stand. The total aboveground biomass at densest stand was 274% more compared to least dense stand. Nutrient removal at harvest from the site depends on both nutrient concentration of different plant parts and biomass yield. Nutrient concentration (NPK) in aboveground biomass under all the spacings of bamboo decreased in the order of: leaf>twig>culm wood>dried wood. The total N accumulation in the aboveground biomass was highest (323 kg/ha) in densest stand and lowest (108 kg/ha) in least dense stand. Aboveground biomass P accumulation in densest stand increased by 161% than the least dense stand. The total amount of K accumulated in aboveground biomass ranged from 354 kg/ha in densest stand to 157 kg/ha in the least density of 69 clumps/ha. Higher amount of NPK was retained mainly in the culm wood followed by twig, leaf and dried wood mass. However, dense stands can store significantly higher amount of nutrients in its biomass. The carbon partitioning among the aboveground parts in bamboo show that almost 57-68% was in stem, whereas twigs, leaf and dried wood stored 20-30%, 4-8% and 3-6% in all the spacings of bamboo. The C storage in culm wood varied from 35 kg/clump at closest spacing to 79.12 kg/clump in widest spacing of bamboo. The consistent increase in aboveground C stock with increasing spacings of bamboo might be due to more number of culms per clump and in turn higher dry matter production. At stand level, the total C accumulation in the aboveground biomass was highest (32 Mg/ha) in densest bamboo stand compared to 8.85 Mg/ha in the least dense stand. The study clearly revealed that wider spacings (10x10 and 12x12 m) of bamboo are ideal for better growth and productivity of understorey crops. Even though chittaratha perform best in open condition, among the varying spacings of bamboo, the widest spacing (12x12 m) of bamboo is best. The dense stands of bamboo had the potential of higher aboveground biomass production, nutrient storage and carbon accumulation. However, the study recommends wider spacings (12x12 m) for clump-wise biomass production/C storage and nutrient uptake.

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