RICE RATOONING - IRRI books - International Rice Research Institute

ALTERNATIVE TO DOUBLE CROPPING IN TROPICAL ASIA 7Table 3. Mean grain yield potential and growth duration of ratoon rice - estimatesfrom 126 published reports (1942-82). aYearMaturity (d)Grain yield (t/ha)MC RC % of MC MC RC % of MC1942-82RangeMean85-174 40-113122-52 67-1331 -7854-790.8-8.03.970.1-8.7 –1.54 38.8a MC = main crop, RC = ratoon crop. Source: Chauhan et al (3).Table 4. Main crop and ratoon crop grain yield and crop duration performance ofsix semidwarf rice cultivars.CultivarGrain yield (t/ha) aMain cropRatoon cropMain cropDuration (d)Ratoon cropC-38 10RatnaTNAU 13613CR 220-66OR 100-25CR 157-22-19004.13.93.52.63.94.0Mean 3.66 1.6S. Em ±0.13 0.092.1 (51.1)1.8 (46.5)1.6 (44.9)1.5 (56.5)1.3 (34.3)1.4 (34.9)124125121123122123123–54504948495250.33–a Figures in parentheses are percentages of main crop yield. Source: (6).Wide variation exists among rice cultivars in their genetic potential forratooning and yield levels. On an average, ratoon rice can give a yield roughlyequivalent to 40% that of the main crop, with 40% reduction in crop duration(Table 3). However, there could also be cultivars that can give ratoon grain yields ashigh as 140% of the main crop, as reported from Karnataka (21), with variety Intan.In Ethiopia, a ratoon crop of IR8 yielded an unusual 8.7 t/ ha. The highest yieldobtained by scientists at IRRI with cultivar IR2058-78-1-3-2-3 was 3.3 t/ha.In a set of 6 semidwarf rice varieties, Das and Ahmed (6) noted that the ratooncrop produced, on an average, a yield equivalent to 43% of the main crop, with 60%reduction in duration. In this study, cultivar C3810 was rated as having the highestpotential, with a ratoon yield of 2.1 t/ha (Table 4).These large variations in yield suggest genetic divergence among the cultivars,which could be exploited through breeding and management for ratooning ability.The donors specific to the location should be carefully earmarked for future use.AGRONOMIC PRACTICESSpacingThe effect of spacing on grain yield of the main and ratoon crops was studied inIR28 (2). Main crop yield was not altered significantly by different levels of spacing(Fig. 1). However, at 20 × 20 cm spacing, the number of missing hills wassignificantly lower than at 15 × 15 cm and equal to that at 25 × 25 cm spacing. In thisstudy, the optimum spacing for the best ratoon yield was 20 × 20 cm.