RICE RATOONING - IRRI books - International Rice Research Institute

132 RICE RATOONINGability, a ratoon crop is possible during this season. Average maximum andminimum temperatures throughout the year remain between 24.3 and29.3 °C.2. High plateau. This is a large area of about 300,000 ha. Some intermediatehill valleys can grow a ratoon crop of rice, especially in an area around the nationalcapital, where they grow a first crop called varyaloha (April-February). Anadditional ratoon crop could be possible with Taiwanese and japonica type varieties.The main problem is excessive water accumulation in low-lying areas and lowtemperatures. In some valleys in the high plateau, especially in the Manjakandrianaarea, farmers demand ratooning varieties for animal feed. Lowland fields are mostlymonocropped because of poor drainage. It seems that the demand for palatable riceratoon fodder is growing and this can be met to a certain extent by selecting vigorousratooning types. In this area temperature is not enough for panicle formationbecause the rice crop is harvested during April and temperature goes down fastbeginning in May.Animal population in Madagascar is around 10 million, mostly zebu (cattle).Only with the varyaloha crop which is harvested during February is a ratoon croppossible because the temperature is right for panicle maturity. Average maximumand minimum temperatures range between 14.9 and 21.1 °C and reasonablevegetative growth of ratoons can be maintained.3. East Coast. The East Coast is blessed with good temperature and heavyrainfall. Annual rainfall is about 3,500 mm in 241 d per year and it graduallydecreases toward the south; in Manankara it is about 2,700 mm. Average maximumand minimum monthly temperatures range between 21.6 and 26.3 °C. Farmers growexcellent crop of vary-tavy (slash-and-burn upland) where there is no moisturestress. The area under different systems of culture is about 250,000 ha. This includesa vatomandry or rainy-season crop grown between December and May and adry-season crop hosy grown between June and November in Manankara andMananjary region in the east-south coast. In Manankara, Soanierana-Ivongo,Sainte-Marie, Ivoloina, Brick-a-ville, and Mahanoro in the Tamatave region, twocrops of lowland rice are grown. They are the rainy-season crop called asarake,grown between October and April, and ririnina, grown between May andNovember. Often, the second-season crop or the dry-season crop of some varieties isleft for ratooning. The east coast region can indeed be a good crop growing area withappropriate varieties and management practices. The east coast is also dotted byslash-and-burn (vary-tavy) upland rice; generally small hillocks (shifting cultivation)are used where water does not accumulate. Conventional upland rice is also grownon level surfaces.POSSIBLE VARIETIESVarietal requirements for the high plateau, the west coast, and the east coast differbecause of different ecological conditions in the regions. Cold-tolerant, shortduration,blast-resistant varieties with good ratooning ability are needed for the high