Journal of the Rubber Research Institute of Sri Lanka
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Item Diurnal variation in nitrogenase activity of common cover crops in rubber plantations of Sri Lanka(Rubber Research Institute. Agalawatta, 1989) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.Diurnal fluctuations in nitrogenase activity (acetylene reducing activity) have been observed in several nitrogen fixing systems. All experimental plants viz. P. phasides D. ovalifolium and M. invisa demonstrated diuanal rhythm withlight intensity. The lowest acetylene reduction activiteswere detected around midnight and they were activelyu fixing nitrogen by 8.00 am. M. invisa responded to high soil temperature in addition to light intensity. A marked drop in acetylene reduction activity was observed by about 4.00pm when the soil temperature was around 38ºCItem Seasonal variations in nodule activity of Pueraria phaseoloides (Roxb) Benth(Rubber Research Institute. Agalawatta, 1990) Jayasinghe, C.K.; Parker, C.A.; Kulasooriya, S.A.The age of Pueraria phaseoloides plants had a marked effect upon the rate of acetylene reduction in their nodules. Acetylene reduction activity increased with the age of the plant and maximum efficiency of nodule activity was detected 60 days after sowing, followed by a marked decline on the 120th day and continued at a low rate. Dry matter yield and total nitrogen in plants was more or less constant thrugh out the assay period.