No abstract

This study examined the influence of biofilmed biofertilizers (BFBFs

Ammonia volatilization is one of the major nitrogen loosing pathways in agricultural fields. Particularly, Low-country tea growing areas of Sri Lanka having warm humid climate, often records low or poor responses to current fertilizer recommendations. Therefore, a glasshouse experiment was conducted to determine the gravity of ammonia volatilized from four major tea growing Soil Series of the Low-country wet zone. Air tightened closed chambers with soils containing acid traps were used to quantify ammonia volatilized from applied fertilizers. The experiment was conducted for 100 days while monitoring temperature and relative humidity in the glasshouse which were comparable with prevailing conditions in the low-country wet zone. Volatilized ammonia was quantified daily at the beginning and later with elapsed time. Curves defining the release of ammonia with time and the change of pH with time were plotted from the results.Significant differences were observed in soil pH changes among treatments. Sulphate of ammonia based T1130 mixture recorded the least change in soil pH while urea based VPLC 880 showed the highest variation. During the experimental period, highest pH was recorded at the fourth day after treatment application which confirms the peak hydrolysis of urea. No significant differences were recorded in soil pH changes with soil series. Ammonia volatilization was lowest in T 1130 treatment and it behaved similar to the control treatment without fertilization. Ammonia losses were highest in VPLC 880 fertilizer amounting to 29%. Other urea based mixtures also showed considerably higher losses as U 709 -27%, U834 -27%, UT 752 -26%. T 1130 showed minimum losses as 1% similar to the control. Among soil Series NH 3 losses sequenced as Dodangoda > Weddagala > Malaboda > Pallegoda. As these soils show lower pH buffering ability, split application of urea based fertilizers may effective to minimize said NH 3 losses.

This study was conducted to determine the variability of soil pH, macronutrients and Na contents in long term sugarcanegrowing Alfisols at Sevanagala, South-East of Sri Lanka. The study site included the entire sugarcane-growing area covering its contrasting cropping systems namely, irrigated and rain-fed cultivation on low humic gley (LHG) and reddish brown earth (RBE) soils, and adjacent undisturbed soils. The mean pH of the two soil types was significantly different and ranged from 4.5 to 9.3. Except some soils under rain-fed cultivation with a pH less than 5.5 in RBE soil and a pH greater than 7.5 in LHG soils, pH in all other soils favoured sugarcane growth. Plant available P content of soils were not significantly different among cropping conditions due to its wide variation. In both cropping systems and soil types there were areas with very low to nondetectable P levels. Exchangeable K content was significantly different between LHG and RBE soils with the latter having a mean concentration of 257 mg/ kg that is favourable for sugarcane cultivation. Though, the mean values are higher than the optimum range, there were K deficient patches in the studied area. Soil exchangeable Ca, Mg and Na contents were low in the study area but were significantly higher in LHG soils than in RBE soils contributing to alkalinity in the former soils especially under rain-fed conditions. The sugarcane-growing soils except LHG under rain-fed conditions showed chemical properties similar to undisturbed soils in the area highlighting their buffered nature despite long-term sugarcane cultivation. This study also emphasised the need for site-specific soil fertility management strategies for the Sevanagala sugarcane growing areas.

Large diameter open dug Agro-wells have become increasingly popular among farmers in the Dry and Intermediate Zones of Sri Lanka during the decades of 1980 and 1990. The numbers have expanded up to around 50,000 in an unprecedented manner as those were meant to serve as sources of water for irrigation of agricultural crops during the much drier Yala season as well as during the water stress times of the Maha season.However, the haphazard expansion of Agro-wells has created complications after some time of use pertaining to the quantity and quality of available water. As Agrowells were constructed frequently by neglecting the appropriate technical norms, drying up of those have been experienced very often along with a lowering of the groundwater level in the respective areas. Moreover, the water in Agro-wells started to show increasing salt concentrations over the period of usage, which has affected the soils and crops detrimentally. As a result, farmers by now have abandoned a considerable number of Agro-wells, which were constructed by spending a significant amount of money.As such, this paper describes the past and present scenarios of Agro-well farming in Sri Lanka considering the Agro-well net in the country as a national asset and attempts to suggest some possible trustworthy measures to be considered for efficient use and proper re-use of abandoned Agro-wells diverting away from the popularly accepted common paradigm "Agro-wells are only for irrigation of agricultural crops".