Browsing by Author "Asokan, P K"

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Dissolution rate of urea and muriate of potash packed in perforated polybags
(Kerala Agricultural University, 1985) Asokan, P K; Vikraman Nair, R; Sudhakara, K
Ecophysiological studies in disturbed forest ecosystem: a case study at Pattikkad
(College of Forestry, Vellanikkara, 1993) Nameer, P O; Asokan, P K
Moist deciduous forests of Kerala are prone to comparatively more biotic interference, as it occupies a buffer zone between human population and evergreen forests. An investigation was carried out at Pattikkad range of Peechi- Vazhani wildlife Sanctuary, in Trichur Forest Division, Kerala. The objectives of the present study were to understand the floristic, structural, functional, physiological, edaphic and micrometeorological changes accompanying degradation. Three experimental plots namely highly disturbed ( PATK – BT), partially disturbed (PATK – MD) and more less undisturbed (PATK – TP) were identified taking into consideration the proximity to human settlement. Each plot had a size of 10000 m2 and were subdivided into quadrats having 100 m2 each and observations on frequency, density, basal area, Importance Value Index (IVI), diversity indices, height – diameter relationships, regeneration pattern, litter quantification, litter decomposition, phenology, leaf area, leaf area index, light infiltration, physic-chemical properties of soil, soil moisture and soil temperature were recorded at periodic intervals for an year. The results indicate that the moist deciduous forest tend to become a semi – evergreen forest it left undisturbed for several years. The undisturbed (PATK – TP) plot recorded maximum density (882), in 143 species (48 families) whereas the density is only 154 in the highly disturbed (PATK – BT) plot. The number of species at PATK – BT is only 31 (19 families). The species diversity is also very high in the undisturbed plot (Simpson’s index = 0.97 ; Shanon –Weiner’s index = 5.97) whereas the Simpson’s index and Shannon – Weiner’s index are 0.92 and 4.16 respectively for PATK – BT. The height – diameter relationship clearly show that the set of the future is more or less absent in the disturbed plots. The regeneration survey reveals that the regenerating community is sparse in the disturbed plots. While the disturbed plots (PATK – BT and PATK – MD) had 3825 and 5045 seedlings per hectare the undisturbed (PATK – TP) plot had 26,500 seedlings per hectare. The litter production was found to be positively correlated with basal area. The rate of litterfall ranged from 6.14 t ha-1 to 8.66 t ha-1 in the moist deciduous forests. The decay rate was fastest in the disturbed (PATK – BT) plot (‘K’ value = 0.26) and slowest in the undisturbed (PATK – TP) plot (‘K’ value = 0.17). The light infiltration to the forest floor was maximum in the highly disturbed (PATK – TP) plot (44.42 mol m-2 s-1 ). The PATK – TP had a leaf area index of 4.04 and that of PATK BT was only 1.06 While most of the leaves in the undisturbed plot belonged to notophyllous (leaf size = 20.25 cm2 to 45.00 cm2 ) type of leaves, that of distributed plots were mesophyllous (leaf size = 45.00 cm2 to 182.25 cm2 ). The physic – chemical properties of the soil were better in the undisturbed plot when compared to the disturbed plots. The gravel content was 23 to 33 per cent at PATK – BT whereas it was 22 to 23 per cent at PATK – TP. Soil was more acidic (pH 5.51 to 5.57 ) at PATK – TP, whereas at PATK – BT the pH varied from 6.13 to 6.14. The organic carbon at undisturbed (PATK – TP) plot ranged between 1.4 to 3 per cent while in the highly disturbed (PATK – BT) plot ranged from 0.9 to 2 per cent. N, P and K also followed a similar pattern. The soil moisture was always maximum in the undisturbed (PATK –TP) plot. The soil moisture varied between 14 per cent (March) to 50 percent (July). The soil moisture at the highly disturbed (PATK – BT) plot was always the minimum. The values varied between 3 per cent (March) to 30 per cent (July). The undisturbed (PATK – TP) plot consistently recorded minimum soil temperature throughout the year when compared to the disturbed plots. The values varied between 220 C (July) to 280 C (April). Whereas in the highly disturbed (PATK – BT) plot the soil temperature was always high. The soil temperature recorded at PATK – BT ranged between 250 C (July) to 360 C (April).
Effect of levels and time of application of potash on growth and yield of tapioca
(Kerala Agricultural University, 1978) Asokan, P K; Sreedharan, C
A field experiment was conducted to study the effect of different levels and time of application of K in conjuction with farm yard manure in tapioca variety H—97. The results indicated that maximum tuber yield was obtained at 112.5 kg level of K. Three split application had given better response at lower levels of K. Farm yard manure application had given a better response at higher levels of K. Utilisation index showed a decrease after 75 kg level of K.
Evaluation of sequential and mixed row intercropping in cassava
(Kerala Agricultural University, 1987) Asokan, P K; Sreedharan, C
The prospectus of sequential intercropping of cassava, planted in paired row with groundnut/cowpea and mixed row intercropping with groundnut+redgram was studied in a field trial. Groundnut and cowpea was successful as a Kharif intercrop. The Rabi intercrops sown in sequence to Kharif intercrop failed to give economic yield. Mixed row intercropping of cassava with groundnut + redgram gave the highest benefit : cost ratio followed by cassava+groundnut. None of the intercrops affected the cassava yield.
Growth and nodulation characteristics of selected indigenous tree legumes
(Department of Tree Physiology and Breeding, College of Forestry, Vellanikkara, 1997) Harikrishnan Nair, G; Asokan, P K
An investigation was carried out to study the nodulation characteristics of seven Indigenous/ naturalized tree legumes in Trichur district of Kerala State. The homesteads of five selected panchayats viz. Pananchery, Madakkathara, Nadathara, Puthur and Ollukkara of the district were surveyed to assess the natural nodulation and to collect nodules for isolating Rhizobium.• The response of these tree legumes to inoculation with local isolates and commercial cultures of Rhizobium were done by seed inoculation and growing the seedlings in a glass house. In a separate experiment, the soil collected from the base of the nodulating tree were also evaluated as an inoculant. The inoculation studies were laid out in CRD with ten replications.
Influence of host plants and soil moisture stress on the water relations in sandal
(Department of Tree Physiology and Breeding, College of Forestry,Vell, 2006) Dhaniklal, G; Asokan, P K
The influence of host plants and soil moisture stress on water relations in sandal was investigated in a pot culture experiment at College of Forestry, Kerala Agricultural University, Vellanikkara. Five host plants, Divi divi (Caesalpinia coriaria Jacq.), Casurina (Casuarina equisetifolia J.R & H.G. Forst), Pongamia (Pongamia pinnata (L.) Pierre), Lantana (Lantana camara L.) and Erythrina (Erythrina indica Lamk.) were selected for this study. The results showed that Sandal seedlings with and without host showed similar height increment, except when erythrina was the host. The host plant had no influence on most of the growth parameters of sandal seedlings. The collar diameter of sandal seedlings with and without host was on par during the early seedling stage and by the end of the experimental period it showed a significant difference. There was no significant difference in the number of leaves, leaf area and root length of sandal with different hosts. Haustorial connections were not recorded even after the experimental period. Sandal seedlings with Erythrina indica as host decreased the pre dawn water potential. Water stress decreased the seedling height, collar diameter, number of leaves, leaf area, shoot dry weight and total dry weight of sandal seedlings. Fully irrigating the pots once in three days resulted in better growth of sandal seedlings as compared to irrigation once in six days. Water stress increased the root length and root dry weight. Root length was found to be more for sandal seedlings which were irrigated once in six days compared to that, irrigated once in three days. Water stress decreased leaf area of sandal seedlings. Transpiration rate at 14:00 hrs was found to be more than that of transpiration at 8:00 hrs. Transpiration rate decreased with increase in soil moisture stress. Pre dawn water potential was lower for sandal seedlings irrigated once in six days compared to that irrigated once in three days. As the haustorial connections were not observed even after 270 days after planting it can be concluded that the difference in the seedling growth parameters of sandal with some of the hosts is due to the above and below ground competition for sun light, water and nutrients.
Quality attributes of colocasia (Colocasia Esculentus)
(Kerala Agricultural University, 1980) Asokan, P K; Hassan, M A; Neelakantan Potti, N
Zonation,leaf phenology and litter dynamics of mangrove forest at Puduvyppu
(Department of Tree Physiology and Breeding, College of Forestry,Vellanikkara, 2003) Ajay Dattaram Rane; Asokan, P K
As species distribution along the sea-land interface to the land interior IS attributed to gradients in soil electro-chemical properties and tidal frequency and nutrient cycling in a system is dependent on litterfall and decay dynamics. Hence, the study for estimating zonation pattern and regeneration status of species along the ocean-land interior trans~cts, along with litter dynamics (literfall and litter decay) was carried out at Puduvyppu mangrove forest. Zonation pattern of species was revealed by carrying out phytosociological analysis along the land-ocean transect and correlating with gradients in electro-chernical properties of soil. Litterfall was studied by evaluating interzonal and monthly variations in litterfall between species for one year. Leaf fall and production was inturn correlated with weather parameters. Decay dynamics was studied by involving six predominant species of the forest namely, Avicennia officinalis, Bruguiera cylindrica, Rhizophora mucronata, Sonneratia caseolaris, Acanthus ilicifolius and Excoecaria agallocha and by estimating interzonal and monthly variations in mass loss and nutrient concentrations of decomposing leaf samples for 12 months. Results show that the area can be divided into three zones (zone I: 0-300 m, zone U: 301-800 m, zone Ill: 801-1200 m from the sea) based on species distribution pattern. Species diversity along the zones decreased from zone I to zone I I, whereas, phytosociological para~1eters of species increased. It was also observed that species like R. mucronata and S. caseolaris were restricted in zone I, whereas, A. officinalis and B. cylindrica were abundant towards the landward side, due to the tidal sorting of the species. Electrical conductivity and soil nutrient (N, K, Na) concentrations increased towards the landward side, whereas, pH decreased. Furthermore, soil P concentrations and in situ redox potential positively affected stand density and E. agallocha stand density respectively. Regeneration was profuse in the central zone of the forest (700-800 111 from the sea) and decreased towards the landward side and the seaward side, implying that monospecifity and tidal inundation affected regeneration. Among the species, A. officinalis seedlings were abundant in the lower height class «50 cm) and B. cvlindrica in upper height class (>50 cm), implying that shade tolerance of the species decided its establishment potential. Litterfall did not vary among the zones suggesting that the dominant A. officinalis determined litterfall of the forest. Leaf fall peaked during winter season (November-December), whereas, leaf production was initiated by rainfall, implying that rainfall and temperature controlled phenological cycles in species. Mass loss followed an exponential pattern in A. ilicifolius, A. officinalis. E. agallocha and S. caseolaris, whereas, it followed a linear pattern in B. cylindrica and R. mucronata. Similarly decay rates were inversely related with initial lignin and lignin: nitrogen ratio of the decomposing leaves. And also, interzonal variations in decay rates were observed, implying that site and species affected decay rates. Nutrient concentrations decreased with Nand K concentrations decreasing and P moderately increasing in the litter bags during the course of decomposition, implying that tidal frequency and mineralization-immobilization frequencies decided nutrient release patterns in these species. In general this is a low diversified, juvenile with an efficient nutrient input-out put mechanism.