Arien Heryansyah

Trends in rainfall and rainfall-related extremes in the east coast of peninsular Malaysia

The coastlines have been identified as the most vulnerable regions with respect to hydrological hazards as a result of climate change and variability. The east of peninsular Malaysia is not an exception for this, considering the evidence of heavy rainfall resulting in floods as an annual phenomenon and also water scarcity due to long dry spells in the region. This study examines recent trends in rainfall and rainfall- related extremes such as, maximum daily rainfall, number of rainy days, average rainfall intensity, heavy rainfall days, extreme rainfall days, and precipitation concentration index in the east coast of peninsular Malaysia. Recent 40 years (1971–2010) rainfall records from 54 stations along the east coast of peninsular Malaysia have been analyzed using the non-parametric Mann–Kendall test and the Sen’s slope method. The Monte Carlo simulation technique has been used to determine the field significance of the regional trends. The results showed that there was a substantial increase in the annual rainfall as well as the rainfall during the monsoon period. Also, there was an increase in the number of heavy rainfall days during the past four decades.

Predicting terrestrial gamma dose rate based on geological and soil information: Case study of Perak state, Malaysia

An extensive terrestrial gamma radiation dose (TGRD) rate survey has been conducted in Perak State, Peninsular Malaysia. The survey has been carried out taking into account geological and soil information, involving 2930 in situ surveys. Based on geological and soil information collected during TGRD rate measurements, TGRD rates have been predicted in Perak State using a statistical regression analysis which would be helpful to focus surveys in areas that are difficult to access. An equation was formulated according to a linear relationship between TGRD rates, geological contexts and soil types. The comparison of in situ measurements and predicted TGRD dose rates was tabulated and showed good agreement with the linear regression equation. The TGRD rates in the study area ranged from 38 nGy h(-1) to 1039 nGy h(-1) with a mean value of 224  ±  138 nGy h(-1). This value is higher than the world average as reported in UNSCEAR 2000. The TGRD rates contribute an average dose rate of 1.37 mSv per year. An isodose map for the study area was developed using a Kriging method based on predicted and in situ TGRD rate values.

Partial Substitution of Inorganic with Organic Fertilizer for Enhancement Fresh Fruit Bunch (FFB) Productivity in Oil Palm Plantations

Partial Substitution of Inorganic with Organic Fertilizer for Enhancement Fresh Fruit Bunch (FFB) Productivity in Oil Palm Plantations This paper describes the alternative fertilizer application in oil palm plantations of Riau Province, Indonesia. Expensive Inorganic fertilizer is needed in a considerable amount that farmers seek for alternatives. One of the solutions is by using organic palm residue fertilizer, as it is cheap, much available, and rich in nutrition. Fertilizer application is differentiated based on the four age category: young (3-8 years), juvenile (9-13 years), mature (14-20 years), and old (21-25 years). Three types of fertilizer, which is Inorganic fertilizer, organic fertilizer, and Inorganic fertilizer with partial substitution, was applied to each category. For a one year, several data such as type of fertilizer, fertilizer dose, fertilizing rotation and FFB productivity was observed monthly. The result shows that partial substitution of Inorganic fertilizer with organic fertilizer significantly raise FFB productivity, especially for young (Yplus) and old (Oplus) age category. It yields continuous improvement of FFB productivity, beginning from age young until old. Thus, the productive period of oil palm can last more than 25 years. Besides, better FFB productivity is achieved in young age category compared to usual production.