Analysis of soil water balance to determine the available growing period in Nusalaut Island, Maluku Province

Climate information plays an important role in regional agricultural development. Climate information can be used to forecast planting and harvest times, the period of drought and flood events, pest and disease attacks, and to determine a suitable plant type. This study aimed to determine the available soil water and growing period in Nusalaut Island, Maluku, using 30 years of monthly rainfall (1992–2021) and 15 years of other climate data (2007-2021). The soil water balance was calculated using the Thornthwaite-Mather method, and the available growing period was determined based on optimum groundwater conditions, water deficit, and the ratio between rainfall and potential evapotranspiration. The results showed that water deficit is not found in the average rainfall conditions, and the soil water content is always at optimum conditions throughout the year. However, the water surplus is found for eight months (April to November), totaling 1870 mm/year. The growing period in Nusalaut Island is available throughout the year (12 months). When the probability of the occurrence of rainfall is greater than 75%, the water deficit will occur for five months (November to March); the total water deficit is 171 mm/year, and the water surplus will occur for six months (May to October) with a total of 713 mm/year. The available growing period (effective growing season) on Nusalaut Island lasts seven months (April to October).