ANALISIS NERACA AIR UNTUK PENGEMBANGAN TANAMAN PANGAN PADA KONDISI IKLIM YANG BERBEDA Water Balance Analysis for the Development of Food Crops in a Different Climate Conditions

In order to develop food crops in upland in the tropics area, the potential water resources, such as the availability of soil moisture and surface water can be used as a source of water supply especially during the deficit. Therefore, to develop a sustainable food crop,  the water balance analysis is absolutely necessary. The data used were series of climate data (temperature, precipitation, evaporation) for 37-year period (1971-2007) at Japura station, Rengat, Riau, heat index data and soil data (soil moisture at field capacity and permanent wilting point) and the effective rooting depth. Exceeded rainfall probabilities and water balance were analyzed using statistical methods. The results showed that soil moisture conditions were always above the limit of water availability for crops although the water balance was deficit for normal, wet and dry conditions. This shows that food crops can be planted all for the whole year in the research area. ABSTRAK Dalam rangka pengembangan tanaman pangan di lahan tadah hujan/kering di daerah tropik basah, potensi sumberdaya air, baik berupa ketersediaan lengas tanah maupun air permukaan dapat dijadikan sebagai sumber pasokan air terutama pada saat defisit. Oleh sebab itu untuk pengembangan tanaman pangan yang berkelanjutan, maka analisis neraca air mutlak diperlukan. Data yang digunakan berupa data seri iklim (temperatur udara, curah hujan, evaporasi) periode 37 tahun (1971­2007) stasiun Japura, Rengat, Riau, data indeks panas serta data tanah (lengas tanah pada saat kapasitas lapang dan titik layu permanen) serta  kedalaman perakaran efektif. Peluang curah hujan terlampaui dan neraca air dianalisis meng­ gunakan metode statistik. Hasil penelitian menunjukkan bahwa keadaan lengas tanah selalu pada batas air tersedia bagi tanaman meskipun neraca air mengalami defisit baik pada kondisi normal, kering maupun basah. Hal ini menunjukkan bahwa di wilayah penelitian dapat dilakukan penanaman tanaman pangan sepanjang tahun.