ARS - 2005
Permanent URI for this collectionhttp://repository.kln.ac.lk/handle/123456789/162
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Item The effects of application of three different phosphate fertilizer sources on the short term availability of some phosphorus fractions in the lateritic soils of intermediate zone of Sri Lanka(Proceedings of the Annual Research Symposium 2005-Faculty of Graduate Studies, University of Kelaniya, 2005) Duminda, D.M.S.; Pathiratne, K.A.S.; Somasiri, L.L.W.The present study investigates, the application of three phosphorous (P) fertilizer sources; Imported Rock Phosphate (IRP), Eppawela Rock Phosphate (ERP) and Triple Super Phosphate (TSP) on the short term availability of different P fractions in the lateritic soils in the intermediate zone of Sri Lanka. The available different P fractions in pots with and without Ruzi grass (Brachiaria ruziziensis L.) as an indicator plant was determined after six months from the date of application of the fertilizers. Each P fertilizer, was treated in triplicate at three different levels, viz., 15, 30, 60 mg P2 O5 /100g soil, separately into pots with and without Ruzi grass. The control with and without Ruzi grass was also carried out in triplicate without fertilizers. The soil moisture content in all the pots was maintained at 60% of field capacity. Phosphorus concentration and total dry matter content of grass were determined bimonthly over six month period. The soils were analyzed for the concentrations of different P fractions, viz., saloid bound P (Sa–P), aluminium bound P (Al–P), iron bound P (Fe– P), occluded P (Occ–P) and calcium bound P (Ca–P). The results revealed that, (i) Ruzi grass utilize more Sa-P and Al-P fractions than Occ-P, Fe-P and Ca-P fractions. (ii) The P uptake by Ruzi grass was low for both IRP and ERP applications compared to TSP application. (iii) Both ERP and IRP fertilizers did not show any significant increase in P uptake with increasing level of their application. Unlike ERP and IRP, the TSP applications showed a linear increase of P uptake by Ruzi grass with increasing the level of P treatment. The overall results indicated that, for short term application TSP is superior to IRP and ERP, though IRP was found to be slightly better than ERP in providing available P.Item Effect of application of three phosphate fertilizer sources on long term availability of different phosphorus fractions in lateritic soils in the intermediate zone of sri lanka(Proceedings of the Annual Research Symposium 2005-Faculty of Graduate Studies, University of Kelaniya, 2005) Duminda, D.M.S.; Pathiratne, K.A.S.; Somasiri, L.L.W.The application of three different phosphorous (P) fertilizer sources, viz., Eppawela rock phosphate (ERP), Imported rock phosphate (IRP) and Triple super phosphate (TSP) on the long term availability of several different P fractions in Lateritic soils in the intermediate zone of Sri Lanka was investigated. Each P fertilizer was treated at three different levels: 25, 50 and 100 g / palm/ 6 months in triplicate over a period of 11 years to all 6 coconut trees grown in each of the 30 experimental plots. Three experimental plots with 6 coconut trees in each with no fertilizer application were used as controls. After 11 years of fertilizer applications, soils were sampled 90 cm away from the base of coconut palm at 2 depths; (0-25) cm and (25-50) cm from randomly selected three plants from each of the plot. Soils of each treatment, sampled in triplicate, for each of the two depths were composited separately. Different P fractions, viz., saloid bound P ( Sa-P), aluminum bound P (Al-P), iron bound P (Fe-P), occluded P (Occ-P) and calcium bound P (Ca-P) were determined in each composited soil. The results showed that, in the soil depth of (0-25) cm, the ability of different fertilizers in producing plant available P; Sa-P and Al-P vary in the order of TSP>> IRP>ERP. Further, it was found that, the availability of Sa-P and Al-P in the TSP treated soil increased with increasing level of TSP application to the soil. The concentration of different P fractions in the TSP treated were in the order of Sa-P>Al-P>Occ-P>Fe-P>Ca-P. The increasing level of IRP and ERP applications did not increase the Sa-P and Al-P concentrations in the soil. The trend of the availability of different P fractions in the soil depth of (25-50 cm) was the same for all three of fertilizer sources at all three levels applications. However, the concentrations of soil P fractions found in this depth was smaller than the amounts found in the (0-25) cm depth.