Analysis of Water Balance to Determine Cropping Pattern of Food Crop In Sub-Watershed Tenggarong, Kutai Kertanegara Regency

Growing periods can be determined using water balance analysis to decrease harvest risk in certain area. Generally, there are two types of land use for crop, i.e. irrigated land and non-irrigated land. This research was aimed to determine water input, water use and water loss, consumptive use crop water balance and designing a cropping pattern on rainfed paddy field at Watershed Tenggarong. Determination of field capacity and permanent wilting point using soil texture data was input through Bouyoucos hydrometer methods. The calculation of land water balance according to Thornthwaite and Mather (1957) was employed to determine the agro-climate condition, particularly the dynamics of soil moisture content to plan a general cropping patterns was used based on monthly data. The planting time period is the water holding capacity > 50% from available water. Water balance monthly indicated that this area has potential growing season about 9 months, water surplus 8 months (439.6 mm year-1) and water deficits about 3 months (59.7 mm year-1). In these area, paddy could be planted twice a year without irrigation. Whereas when there are climate anomalies, paddy fields can be cultivated on certain land (swamps or suburbs of lake/river)