Scheduling the cropping calendar in wet-seeded rice schemes in Malaysia

Abstract

The Besut Irrigation Scheme, Terengganu, Malaysia is one of the eight gazetted main rice-growing areas in Malaysia. These eight granaries are targeted to produce only 65% of the total rice requirements of the nation. This scheme faces water scarcity especially during the off-season with the present existing cropping schedule. This study discusses the ways and means to overcome the water scarcity problem by setting the calendar for cropping schedules taking into consideration rainfall, river flow available and irrigation water requirements. A water balance approach using 48 years of rainfall and weather data was pursued in this study. The present main season from land preparation to crop harvest lasts from 1st November to 6th April, with land preparation being carried out during the heaviest rains in early November. However, the heavier rains may result in the postponement of seeding. Delays in crop planting during this main season can result in the cancellation of the following off-season crop from May to October. Shifting the land preparation works from November 1 to an earlier date, September 15, would result in a better match of crop water needs with the prevailing rainfall season (normally most of the rainfall occurs between September and December). This proposed schedule (15th September?10th February) also increases the probability that land preparation and subsequent seeding can be done for a second crop in the revised off-season period, 15th March?10th August. The present off-season schedule is from 5th May to 7th October and water scarcity during the vegetative and reproductive phases of the crop growth can be a problem. With the shifting of the off-season to start on March 15, severe water shortage can be avoided. The proposed revised cropping schedules could reduce the irrigation water requirements for the main season and off-season by 30% (equivalent to 60 mm of water) and 19% (equivalent to 37 mm of water), respectively.