Wet-seeded rice for increasing land and water productivity in Jatiluhur irrigation system, West Java, Indonesia

Wet-seeded rice matured earlier (103-110 d in WSR [wet seeded rice] and 118-120 d in TPR [transplanted rice]) and had a shorter farm activity duration (117 d in WSR and 126 d in TPR) than TPR. Total irrigation water consumption was lower in WSR (784 mm) than in TPR (1,464 mm). Rice yields of TPR (6,182 kg/ha) and WSR (5,474 kg/ha) were statistically not different. Water productivity was higher in WSR than in the TPR in the following: a) per unit volume of irrigation water (0.71 kg/ cu m for WSR and 0.43 kg/cu m for TPR), b) per unit volume of gross water supply (irrigation + rainfall) (0.47 kg/cu m for WSR and 0.33 kg/cu m for TPR), and c) per unit volume of water depleted (irrigation + rainfall - surface drainage) (0.49 kg/cu m for WSR and 0.43 kg/cu m for TPR). Labor use in WSR (104 person-day/ha) was lower than in TPR (143 person-day/ha). One important constraint to crop establishment of WSR was the uneven level of the field. From the TPR system analysis and field study, there is a potential for planting of WSR on a large scale. The proposed design of the WSR system showed that WSR can reduce labor shortage. especially for souring seed. In Jatiluhur irrigation system, the total labor need for TPR was 553,859 person-day for transplanting, while in WSR only 11,684 person-day for sowing seed. The farm activities for WSR can save time and it becomes more possible to grow upland crops in each water schedule group. In water schedule groups 1 and 2, 3-3.5 mo upland crop such as soybean and corn, can be grown, while in groups 3 and 4 shorter duration upland crops (2-2.5 mo) such as mungbean and vegetables can be cultivated. The irrigation water requirement for WSR (4,075 mm/yr) was less than that for TPR (4,759 mm/yr). The land-based constraints associated with WSR in the Jatiluhur irrigation system were low elevation, low slope steepness, and high rainfall during planting time. It was estimated that a level to nearly level land form with 0-2 percent slope poses more risk than a higher one. There is a high risk of high rainfall of more than 150 mm for 15 d and flood occurrence during crop establishment. These areas cover about 26.3 percent of the land. From the whole Jatiluhur irrigation system, about 67.3 percent is suitable for WSR (highly suitable in the wet season and marginally suitable during the dry season, 10.5 percent; moderately suitable in the wet season and marginally suitable during the dry season, 32.4 percent; wet and dry season, 15.4 percent; marginally suitable in the wet season and moderately suitable in the dry season, 9.0 percent)