The introduction of synthetic fertilizers has brought various types of detrimental impacts and people attempt to find out eco-friendly alternatives to chemical compounds for minimizing the dependency on synthetic chemicals. In this context, the exploitation of alternative growth substrates is of great interest like compost-like substrates. Therefore, the study was made to study the effect of compost and different levels of NPK fertilizer on growth and yield performance of three different recommended tomato varieties under different field conditions at Walimada, Sri Lanka. Treatment consisted of three tomato varieties (Roma, Thilina, and T 245) and five different fertilizer levels including compost & NPK fertilizers. Treatments were considered as control (without compost and NPK fertilizer), 100 % of compost, 100 % of recommended dosage of NPK fertilizers, 50% of compost with 50% of recommended dosage of NPK fertilizers, and 75 % of compost with 25 % of recommended dosage of NPK fertilizers. Field management practices were practiced according to the recommendations given by Department of Agriculture of Sri Lanka. Effect of different fertilizers on vegetative growth, reproductive growth and yield of three tomato varieties was evaluated. According to results, there was a significant different among control treatment and treatment consisted with 50% of compost with 50% of NPK fertilizer treated Roma and Thilina on days to attained 50% of flowering. There were no significant differences between treatments consisted with 100% of NPK fertilizer with 50% of compost and 50% of NPK fertilizer on days to attained 50% of flowering, number of fruit per plant and yield of varieties except the yield of Roma variety (P<0.05). Results showed that all treatments except chemical fertilizer application improved the soil organic C, total N, P and K status. Increase in microbial biomass C and N was observed in soils receiving organic manures only or with the combined application of organic and chemical fertilizers.

This study was conducted to investigate the allopathic effects of Cyperus rotundus and Cynodan dactylon (L.) extracts on seed germination and seedling growth characters of lettuce (Lactuca sativa). Four concentrations (5, 10, 15 and 20 %) of whole plant aqueous extracts of both weeds were tested for assessing their allelopathic effect on seed germination and seedling growth of Rapido 344 lettuce variety. This study was conducted at Biology Laboratory of Uva Wellassa University, Sri Lanka in 2014 and experimental units were petri dishes in depths and diameters of 2 and 5 cm, respectively. The shoot and root length, dry weight, germination percentage were measured. The experimental results revealed that all the concentrations of both the weed extracts had inhibition effect on germination percentage, shoot & root length and dry weight of lettuce. The inhibitory effect of the extracts was concentration dependent. However, at 5% of C. dactylon extract did not significantly affect on seed germination and growth of seedlings. The highest degree of growth inhibition was observed in 20 % of both weed extracts.