Value potential of dry land for future agricultural development in Bali

The calculation of crop water requirement for dry lands is expected to assist in policymaking and planning in Bali on the effective use of limited water resources to support food security and environmental conservation. Farmers need information that can assist them to use rainfall effectively, such as planting in the fixed time of plant growth phase with rain season or groundwater availability. The present research aims to (1) evaluate the potential of dry land in the research area, (2) develop water balance on dry land, (3) estimate crop water requirements of dry land, (4) develop alternative cropping calendar for pattern rotation cropping in a year and (5) simulate alternative crop rotation pattern in the most profitable year. Research sites with water balance in the Bali area included Gilimanuk, Banyuwedang, Celukan Bawang, Seririt, Buleleleng, Kubut additions, Kubu, Banjar Bunutan, Padangbai and Sanur. The amounts of rainfall and evapotranspiration yearly were approximately 1723.9 and 1833.7 mm, respectively. The amount of rainfall in the last five months from December to April was 1394.5 mm, whereas that from May to November was substantially low at only 329.4 mm. Water supply from January to April was surplus only, whilst that from May to November was deficient. These findings indicated the following conclusions. (1) Bali has a particularly hilly land condition and clay soil. As dry land farm has low soil fertility and sources water only from rainfall, cultivated plants include maize, cassava, beans, turi, banana, papaya, coconut, mango, oranges, sugar apple and teak. (2) Thornthwaite and Mather indicated that water surplus occurs from January to April whilst deficit occurs from May to November based on the water balance for Bali. High rainfall (1394.5 mm) occurs from December to April, whereas low rainfall (329.4 mm) occurs from May to November. (3) Crop water requirement in the root zone of cassava monoculture (1087.34 mm) were lower compared with those of intercropping cassava + maize (1088.89 mm) and cassava + maize − groundnut (1109.99 mm). (4) The pattern of crop rotation intercropping cassava + maize − groundnut can be planted from October 22 until June 21. Fresh tuber yields of cassava intercropping with maize and groundnut are 22.54 t ha−1 . (5) Cassava can be planted from October 22 to 29, sweet potatoes can be planted from February 3 to 17 and groundnut and maize can be planted from February 3 to March 17. The revenue of intercropping cassava + maize − groundnut is 25.3% larger compared with that of cassava monoculture.