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Optimization of fertilizer regimes and understorey productivity in four-year-old Swietenia macrophylla King stands
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...
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| Format: | Ph.D Thesis |
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Vellanikkara
Department of Silviculture and Agroforestry, College of Forestry
2018
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| LEADER | 06912nam a2200169 4500 | ||
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| 082 | |a 634.9 |b VIK/OP | ||
| 100 | |a Vikas Kumar | ||
| 245 | |a Optimization of fertilizer regimes and understorey productivity in four-year-old Swietenia macrophylla King stands | ||
| 260 | |a Vellanikkara |b Department of Silviculture and Agroforestry, College of Forestry |c 2018 | ||
| 300 | |a 192p. | ||
| 502 | |a PhD | ||
| 520 | 3 | |a 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. | |
| 650 | |a Silviculture and Agroforestry | ||
| 700 | |a Kunhamu, T K (Guide) | ||
| 942 | |2 ddc |c TH | ||
| 999 | |c 161924 |d 161924 | ||
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