Effect of free range poultry system on land use efficiency and floral diversity in Rubber plantations

Plantation crops like rubber were traditionally grown in monocultures to avoid any risk on their productivity. However, with the smallholder farmers being involved in rubber cultivation, the idea of farming system evolved with the maximizing the overall land productivity and diversifying the income sources in order to meet the need of the resource poor. At present, rubber based intercropping systems with other economically beneficial crops are recommended and being practised to some extent particularly in smallholdings. However, no successful attempts were taken on livestock integration to the rubber system. With the understanding of practical limitations in incorporating ruminants to the system, the present study was commenced as a preliminary investigation to assess the effectiveness of free range poultry with respect to productivity and its effects on floral diversity under rubber. Based on the experience in coconut based poultry systems in Sri Lanka, a strain developed as a backcross of the hybrid between CPRS (Central Poultry Research Station) Brown and indigenous with indigenous, was used in this study expecting desired characteristics of both types, i.e., high level of egg production and adaptability to the environment. The trial began with 30 birds in a mature rubber clearing of the Rubber Research Institute of Sri Lanka. Information on egg production, the effect poultry on weed growth and its diversity were recorded together with visual observations on birds’behavior.

Average egg production was 8 eggs per bird per month. This value has dropped to 3 when the majority of birds were in moulting, However, in some months, it has gone up to 14. Some birds were killed by predators and even unsuccessful attacks affected the egg production. Birds showed poor brooding characters with that attempts taken to hatch eggs were failed. Poultry feeds had to be supplied (50g layer ration per bird) to maintain the continuous egg production. Birds always used to feed on the area close human dwelling. Dominance of the floral species under rubber was changed with the incorporation of poultry. Although Adiantum latifolium was dominant throughout the study, Summed Dominance Ratio (SDR) of Paspalam conjugatum and Syngonium podophyllum declined with the poultry integration. Measures to be taken to improve the poultry system were also identified.

B M D C Balasooriya1, V H L Rodrigo1, S M M Iqbal1 and D V S de S Gamage2,

1Rubber Research Institute of Sri Lanka, 2 Veterinary Research Institute, Sri Lanka

Species diversity and forage value of herbage in a neglected coconut land proposed for livestock integration

The proposed coconut land is situated in the southern province, belongs to the land suitability class S4 which is moderately suitable for coconut. Therefore, managing coconut as monoculture is unprofitable and steps have been taken to optimize the land use through livestock integration. Therefore, objective of this study was to investigate the species diversity and forage value of understory vegetation in the coconut land before introducing cattle. Stratified quadrate sampling technique was adopted and 4 samples each from 6 paddocks (approx 0.4 ha) were randomly taken. Each stratum contained more than 80% of edible species while the non edible species found in all strata were common upland weeds. Axonopus affinus (carpet grass), Axonopus compressus (narrow carpet grass) and Desmodium trifolium were dominant prostate grass and legume species found in 0-5 cm strata above ground level. In addition to above species Pueraria phasioloides (Centro) was found to be dominant in 5-15 cm strata. Crysopogen ariculatus and Pueraria phasioloides were dominant in 15-25 cm strata while Seteria anceps (fox tail grass) found to be dominant above 25 cm height. The common non-edible species found in the lower two strata’s were Urena lobota, Hemidesmus indicum and Ocimum tenuiflorum while Lantana camara and Ocimum tenuiflorum were dominant in upper two strata’s. The dry matter (DM) and crude protein (CP) content of edible herbage increased from bottom to top layers ranged from 390 gkg-1 to 480 gkg-1 and 75 gkg-1 to 100 gkg-1 respectively.

The results of this study reveal that the species diversity and forage value are in an acceptable standard to initiate cattle grazing. However, crop and cattle management strategies are important in order to improve coconut and livestock performance.

L Kumanayaka, T Seresinhe, M de S Liyanage and I Pathirana

Faculty of Agriculture, University of Ruhuna, Mapalana, Kamburupitiya, Sri Lanka.

Evaluation of different cover crops on vacant areas (pottal) in mature tea plantation

I R Palihakkara, B G D Udesh, P W D Vithanage
Department of Crop Science, University of Ruhuna, Sri Lanka.
Didenipotha estate, Maturata plantations Ltd., Sri Lanka

An experiment was conducted at a low country tea plantation in Matara district to Evaluate different cover crops species for vacant areas. It was conducted during the period of January to June 2006; the selected site was 2nd year after pruning, T.R.I 2025 that was establishing in 1980 and the field with lot of vacant areas.

Six cover crop species (Desmodium triflorum, Arachis pintoy, Desmodium heterocarp, Vetiveria zizaniodes, Crotalaria ochroleuca, Cymbopogon nardus) were selected for the experiment. The experiment followed a Latin Square Design. Trees planted in vacant areas, with the space of 6 inches for 1,2,3, spp and 8 inches for 4,5,6 spp. Data were collected one month after the establishment.

Soil nitrogen content, pH, biomass production and soil organic matter content were measured. Weeds count was taken two weeks interval. Survey was conducted to evaluate workers preference level of the each cover crop.

There was no significant difference within the treatments in soil pH, organic matter % and soil N %, but Vetiver was found to be suitable for acid soil (p>0.05). Organic matter added by D. heterocarpon, D. triflorum was significantly higher than other species. D. heterocarpon and Crotalaria was highly effective in improving the soil N among the legumes. Before the experiment soil C: N was 7:1. D. triflorum improved the soil C: N (10.7:1) during research period.

In generally workers did not like cover crops. However they preferred legume rather than grasses. 60% of the workers selected D. triflorum as their first choice. 26% of the workers selected A.pintoy as their first choice. D. heterocarpon, C. ochroleuca, and C. nardus were selected by only 3%. Workers did not select vetiver as their first choice. Dry matter production of grasses was higher than that of legumes. V. zizanioides, D. triflorum had approximately similar shoot: root ratios.

Treatments effect for weeds population was not significant (p>0.05), but A. pintoy, D. heterocarp were fast growing and suppressed the weeds than other legumes. It was concluded that workers preferred four legume species rather than two grasses. A. pintoy, D. heterocarpon, C. nardus can aggressively suppress the weeds. D. heterocarpon, D. triflorum were highly improved soil nitrogen and organic matter than other legumes during the research period.

Assessment on timber and carbon in rubber plantations with special reference to the wet zone of Sri Lanka

E S Munasinghe, V H L Rodrigo P K W Karunathilaka and U A D P Gunawardena
Rubber Research Institute of Sri Lanka.
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka

Rubber (Hevea brasilensis) has traditionally been cultivated for the latex extraction; however, its importance in other uses, particularly producing quality timber and sequestering atmospheric carbon as a permanent sink, is also often highlighted. The amount of timber produced and carbon sequestered in rubber trees has been assessed in isolations. Those values would differ under different growth conditions and to date, no simple protocol is available to quantify the amount of timber and carbon in rubber plantations. Therefore, the study reported here was aimed to develop simple growth models to assess the timber production and carbon fixing capability of rubber plantations in Sri Lanka.

Initially, a growth function was developed to assess the girth development with respect to age and thereafter another three functions to quantify the amount of timber, biomass and carbon in the rubber tree based on girth diameter. Also, wood density variation with age of the tree was modeled to determine the biomass in timber under different age categories. The assessment on the available carbon was based on the carbon content in unit biomass and the total amount of biomass in the tree. Growth data required for the girth development function were gathered from secondary sources and girth measurements made on existing rubber clearings. Destructive sampling was conducted to assess the timber, biomass and wood density.
Based on above models, an average rubber tree at 30 years achieves a girth of 88.64 cm and produces 0.656 m3 of timber and 594.46 kg of biomass. The amount of atmospheric carbon fixed in timber at this age was estimated as 193.7 kg per tree and 45.86 MT per hectare. However, total amount of organic carbon fixed in above ground components was 220.8 kg per tree and 52.27 MT per hectare. The models of this study were developed under general conditions in the wet zone, hence should be validated for drier regions of the country before any wide scale adoption.

Rubber latex production in Hevea brasiliensis with high density planting

T U K Silva, V H L Rodrigo, S M C U P Subasinghe
Rubber Research Institute of Sri Lanka,
Department of Forestry and Environmental Science, University of Sri Jayewardenepura, Sri Lanka.

Despite short-term fluctuation of rubber prices, the demand of natural rubber has increased continuously with the increase in population and living standards of the human being. Nevertheless, urbanization results in the fast depletion of forests as well as the land area under rubber. Therefore, in order to meet the continuous demand on latex, the productivity of rubber plantations should be increased. While producing high yielding clones for improved yield per tree which is a long-term process in perennial crops, planting density could be adjusted to obtain high productivity in rubber plantations. The present level of planting density of rubber in Sri Lanka has been decided on the experiments conducted with the genotypes which are not in common use at the moment. Also, the optimum density should vary with different socio-economic conditions. Therefore, the present study was aimed to identify the suitable planting density for the recently developed and commonly used genotypes of rubber. Specifically, this paper is focused to assess the overall productivity of rubber with respect to latex yield.

The experiment was set up in Rathnapura district of Sri Lanka in 1992. Rubber was planted in three high densities, i.e., 600, 700, 800 trees per hectare, with the presently recommended level of 500 trees per hectare. Also, 3 genotypes (clones) i.e., RRIC 100, RRIC 110 and RRIC 121 were incorporated with the statistical design of split plot where the planting densities were laid as the main plots whilst clones were in the sub plots. Growth and yield parameters in terms of girth, bark thickness (BT), and the incidences of tapping panel dryness (TPD) were assessed yearly and the latex volume (LV), % dry rubber content (DRC), number of trees in tapping (TIT) were assessed on daily basis up to 2004.

Irrespective of the clone used, mean yield per tree per tapping decreased with increase in planting density. However, it was vice versa in the case of yield per hectare (YPH) due to the increase in TIT with increase in planting density. The percentage of trees with TPD was not significantly affected by the planting density. The clone RRIC 110 was infected with Corynespora leaf disease hence poor performance was shown in all densities. The trend of increasing YPH was similar in both other clones, i.e. RRIC 100 and RRIC 121. However, the rate of increase in TIT showed a decline of 700 trees per hectare resulting in a lower YPH at this level than expected. Although latex productivity could generally be increased with increase in planting density, overall economic profitability of the system will also depend on cost of production, amount and value of timber and carbon produced. Therefore, study warrants further investigations on above issues before making any changes to the presently recommended planting density.

A study on palmyrah (Borasus flabellifer) utilization pattern and socio- economic status of dependent livelihood in Mannar district of Sri Lanka

S Arulmageswaran, I M N Chandrasiri and J V Culas
Extension and Training Centre, Department of Agriculture, Peradeniya, Sri Lanka

Tha palmyrah palm (Borassus flabellifer L.) is a multipurpose tree of great utility, occurs extensively in Northern and Eastern part of Sri Lanka. This tree engages human labour in the industries around it irrespective of gender or age. This survey was carried out to study utilization pattern of palmyrah tree and assess the socioeconomic parameters of randomly selected 60 families registered in five co-operative societies of Mannar district.

This study revealed that 93 % of males and 7 % of females entirely engaged in this industry with the average of 1.2 persons from each family. The average monthly family income of study population was RS 11320 ± 318 rupees, comes under higher income group. When comparing the family income with the average household number of 5.8 ± 1.3 showed inadequacy to meet present expenditure. Further more, study showed that these families did not show much interest on children education and most of youngsters leave school before sitting General Certificate of Education Ordinary Level examination. 58 % of families were living in small or medium size cottage made up of timber and palmyrah leaves as roofing material.

Tapping of mature tree was main source of income. One male tapped 14 ± 2.7 trees per day with the average of 8 ± 1.2 liter of toddy per tree. They did not produce sweet toddy (unfermented sap) because of low demand. They normally market toddy (fermented sap) to their customers for drinking, co-operative society under palmyrah development board and for vinegar production. The price of toddy also varied from RS 6 to 20.00 rupees depending on quality. Apart from that, most of the tappers had to travel about 3 km out of co-operative boundary for tapping and selling their product. During off season and free time, they do timber carving, animal raring and palmyrah tuber production. Women did not actively engage in this industry except few workers in coir factory. Based on this study, it is concluded that this industry provides vast opportunity for further exploiting labour force in respect to production of beverage, sugar , alcohol, fibre, fuel wood, timber and row materials for handicrafts. As well as this study clearly stated that implementing innovative technologies with product diversification and opening new market channels are the necessary pre requisite of this industry in future.

Predicting the optimal rotation length of Teak plantations using a simulation model

L H P Gunaratne and T N Subramanium
Department of Agricultural Economics and Business Management,
University of Peradeniya, Sri Lanka.

The traditional problem in Forest Economics has been mainly dealt with the estimation of optimal rotation length for sustainable management. However, given the limitation of the availability of time series data on growth and management in forest plantations in Sri Lanka, such estimations are not feasible. Against this background, this study attempted to develop a simulation model and predict rotational interval of teak plantation under different management conditions.

A field survey was conducted to identify the plantation related parameters in the Kurunegala District. Meantime, a simulation model was developed with Microsoft Visual Basic and Microsoft Excel using the equations specified in the Teak Management Plan (1997) to supplement the field data. The past data obtained from the Forest Department was used to parameterize the model. Using the age and the height of a plantation at a particular time, the model was capable of predicting the plantation related parameters such as dbh and timber volume over the time.

According to the values predicted by the simulation model, four different categories were identified based on the site index, which represents the level of growth of a stand. Rotational interval was estimated using the Faustman rotational model at different discount rates. Thereby it was estimated that the rotational intervals for the four categories at discount rates 10%, 15% and 20% as 19, 17 and 15 years respectively. The internal rate of return obtained through the simulation was above the market rate of 12%. Though the model yielded shorter rotational intervals than the present field values, the approach could be used in future with more reliable field data.