ABSTRACT The accurate prediction of N transformation is an important requisite for optimizing N use efficiency in cropping systems. An incubation study was conducted to verify the impacts of nitrification inhibitor (NI) with organic manure (OM) and urea on N dynamics and N2O emission in acid sulphate soil. The conducted experiment was two-level factorial with 4 N sources (N1 = 100% of N from urea, N2 = 75% of N from urea + 25% N from rice straw, N3 = 75% of N from urea + 25% of N from cow dung and N4 = 75% of N from urea + 25% of N from poultry dung) and two levels of NI (with and without DCD). The NI (Dicyandiamide - DCD) with OM + urea enhanced mineral N contents and it was the highest (255.07 µg∙g-1) for urea with DCD applications. The highest net N-mineralization (213.07 µg∙g-1) was recorded for the application of urea with DCD and net nitrification (16.26 µg∙g-1) was recorded for the application of urea alone, but the highest cumulative N2O emission (5.46 µg∙g-1) was in urea + poultry dung (PD). In addition, DCD most effectively inhibited net nitrification (28.78%) and N2O emission (32.40%) from cow dung (CD) and urea in the tested soils. The combination of DCD with CD and urea was more effective in reducing N2O emissions (43.69%). These results suggest that the DCD with CD and urea may be the most potential combination to reduce nitrification and N2O emission as well as N loss from acid sulphate soil.

Balanced nutrient elements in fertilizer play a critical role in oil palm seedling successful growth and development, and at the same time reduces of fertilizer losses in the environment. This study examines the effect of different levels of N, P2O5 and K2O for oil palm seedlings in solution culture on growth traits, nutrient uptake in plant tissues and biomass accumulation under nursery conditions. Five concentration levels of N (50, 100, 300, 600 and 900 mg L–1), P2O5 and K2O (15, 30, 60, 90 and 120 mg L–1) were used in a completely randomized design (CRD) with five replications for each. Parameters measured during the growing period include - plant height, leaf number/plant, stem diameter, SPAD chlorophyll value, and at harvest – total leaf area, root dry weight, shoot dry weight and total dry weight. Different levels of N, P2O5 and K2O showed significant effects on all the parameters studied. The highest values for diameter, plant height, leaf number/plant, total leaf area, root dry weight, shoot dry weight and total dry biomass were obtained using 100, 90 and 300 mg/L levels of N, P2O5 and K2O, respectively. Most of the growth parameters, declined with lower levels of N, P2O5 and K2O. The results of this study provide a new knowledge to produce oil palm plant with better nutrient management at the nursery under solution culture.

As análises de qualidade de Lençol de Água incluíram pH, EC, e os cations,(Ca2+, Mg2+, Na+, K+, Zn2+, Cu2+, Mn2+, Fe3+ e As3+), aníons ( CO32-, HCO3-, NO3-, SO42-, PO43- e Cl-e TDS do noroeste do Bangladesh. As amostras continham Ca2+, Mg2+ e Na+ e como o cations dominante HCO3- e Cl foram os aníons dominantes. Segundo o TDS e valores de SAR, todas as amostras foram classificadas como categorias 'de água doce' e 'excelentes'. O SSP de todas as águas foi nas classes 'excelentes' e 'boas'. Todas as amostras foram dentro da classe 'suave' quanto à dureza com RSC 'conveniente'. Baseado As3+, Zn2+, Mn2+, Fe3+, SO42-, NO3- e Cl- - todas as amostras de lençol de água foram dentro do limite 'seguro' como água de bebida mas impróprias para algumas indústrias que emprega íons específicos.

Groundwater quality analyses included pH, EC, cations (Ca2+, Mg2+, Na+, K+, Zn2+, Cu2+, Mn2+, Fe3+ and As3+), anions (CO32-, HCO3-, NO3-, SO42-, PO43- and Cl-) and TDS of northwestern Bangladesh. The samples contained Ca2+, Mg2+ and Na+ as the dominant cations and HCO3- and Cl- were the dominant anions. Ratios of major cations and anions of water samples suggest the predominance of Ca and Mg-containing minerals over Na-containing minerals. According to TDS and SAR values, all samples were classed as 'freshwater' and 'excellent' categories. The SSP of all waters was under 'excellent' and 'good' classes. All samples were within 'soft' class regarding hardness with 'suitable' RSC. Based on As3+, Zn2+, Mn2+, Fe3+, SO42-, NO3- and Cl- all groundwater samples were within the 'safe' limit for drinking but unsuitable for some industries for specific ions.