The number of presently operating small tanks in the Kurunegala district is 4,482 of which 2873 tanks have less than 6 ha of command area. Capacity of these tanks is low and the amount of water stored is not sufficient to fulfil the water requirement of the rice crop throughout the cropping season. Many farmers in Udakadawala area in the Kurunegala district adopts to start land preparation (LP) after filling tanks and start LP using tank water. This situation results in the delaying of the cultivation and limiting the use of rain water during the initial stages of the crop. On the other hand, due to high variability of rainfall, severe crop damages are frequently experienced. The objectives of this study were to identify the factors affecting low water productivity and to introduce and evaluate a new land and water management approach to increase rice yields. A trans-disciplinary esearch methodology was used employing participatory research tools. Seedling broadcasting (parachute) method with proper LP technology, time of cultivation, water management practices and use of good quality seed paddy were applied to five separate plots in the field while other fields were under their normal activities. Yield components data were collected and were analyzed. According to the results obtained, farmers delayed LP until water issue from the tank and cultivation is mainly done by rotavators mounted to two wheel tractors. In treatment, early LP with onset of rainfall using four wheel tractors save water up to 66% of the total water requirement. LP using tine tiller compared to rotavator reduces the amount of water required for the LP and increase the access to more water and nutrients by increasing the root depth. Tank water productivity was 1.93 and 0.28 kg/m3 in treatment and control, respectively. The effect is more useful in Yala than in the Maha season. “Parachute” method and other agronomic practices such as recommended seeds, using organic matter, proper weeding is important along with land and water management. Conjunctive use of rainfall and tank water in combination with other management techniques was successful in increasing water productivity in small tank irrigation system.
Tropical Agricultural Research Vol. 26 (4): 684 – 692 (2015)