RICE RATOONING - IRRI books - International Rice Research Institute

88 RICE RATOONINGTable 1. Average monthly rainfall and temperature in the hilly region of Karnataka(Uttara Kannada, Belgaum, Shimoga, Chikkamagalur, Dharwad, Coorg, andHassan districts). Values represent average of 6 yr, 1978-83.MonthJanuaryFebruaryMarchAprilMayJuneJulyAugustSeptemberOctoberNovemberDecemberRainfall(mm)2.22.59.651.796.7438.5914.2509.6166.6155.250.822.1Max25.928.129.929.427.923.521.521.923.324.924.924.0Temperature (°C)Min14.515.517.118.518.918.117.817.917.517.516.314.3Ratoon crop management involves specialized practices from the time themain crop is cut until harvest. The adoption of this technology in the hilly region ofKarnataka started with the excellent ratooning ability of Intan observed at theUniversity experimental station Madikere, as well as on private farms. Thisprompted the University scientists in 1976 to initiate some agronomic investigationson the private farms of Chikkamagalur District. Since then, research on varietal andagronomic aspects has been carried out in a small way. An experiment was alsoconducted in collaboration with IRRI in the Philippines during 1981-82.This paper summarizes past studies on rice ratoon crop management in thehilly region of Karnataka and suggests future prospects for agronomic research toimprove and stabilize ratoon yields.RATOON CROP MANAGEMENT EXPERIMENTSCutting of main crop: time and stubble heightTwo replicated experiments were conducted during 1977 to determine the effect ofcutting time and height on ratoon crop yields. A third experiment continued theyield performance study conducted in 1978. All studies were conducted with thestubble of the 1978 wet-season harvest at Sringeri, Chikkamagalur District, which isrepresentative of the hilly region.In the first experiment, cutting time was fixed at 35, 40, and 45 d after 50%flowering (40 d is the normal harvest time). Plot size was 10 m 2 , with 3 replications ina randomized complete block design. The main crop, seeded on 30 Jun andcultivated with prevailing farmers’ practices, was cut to a 13-cm stubble height on13, 18, and 23 Dec. The entire experimental area was topdressed with 50 kg urea/ha(44.0%) 30 d after cutting the main crop (18 Jan 1979).In the second experiment, also a randomized complete block design with4 replications, cutting heights were 8, 13, and 18 cm above ground. Plot size was adirect seeded 2-m row. The main crop, seeded on 30 Jun and managed with farmers’practices, was cut on 23 Dec 1978 and topdressed with 50 kg urea/ ha 30 d later. Thethird experiment, at Balehonnur, repeated the 1977 experiment.