Effect of Different Methods and Timings of Stand Establishment on Performance of Rainfed Lowland Rice Under 0–50 cm Water Depth

About one-third of the total rice is grown under rainfed lowland conditions, mostly m south and south-east Asia. Crop productivity in this ecosystem can be improved by adopting suitable management practices as drainage of excess water is not feasible in the catchment and coastal areas. Field experiments were conducted using a long-duration (165 days), photosensitive, semi-tall (150 cm) rice cultivar Utkalprabha established through direct sowing or transplanting on different dates under 0–50 cm water depth at Cuttack, India, during 1989–91. Direct sowing was done in lines in dry soil from 10 May onward using 400 seeds/m² and continued at 10 day intervals until June. Transplanting was done after accumulation of water in the field from July until 15 August with seedlings raised in nursery seed-beds with or without fertilizer application (100 kg N and 8.7 kg P and 16.7 kg K/ha) and tillers removed from the direct-sown crop. Seedling emergence varied significantly from 127–212/m, irrespective of sowing date and was dependent on rains received after sowing. However, the early sown crops in spite of poor germination, performed well due to better establishment and tiller production before water rose to higher depths in the field. There was a decreasing trend in grain yield, particularly when the sowing was delayed beyond end of May. The loss in yield with delayed sowing in June was due to poor crop stand which could not be compensated for by applying 50 % more seed (600/m²) and N fertilizer (60 kg N/ha). Removal of some of the tillers (100–130/m²) from crops sown on 30 May with 600 seeds/m² for planting on an equivalent plot area did not cause any adverse effect on the performance of mother crop. The anticipated shortfall in yield due to lower panicles/m² with clonal tiller separation was compensated for by the resulting increase in panicle weight. The performance of transplanted crops depended greatly on the water depth at or soon after planting. In 1990, planting on 15 July in 30 cm water depth helped in relatively better establishment and grain yield at par with sowing on 10 May. However, in 1991, when there was a sudden and rapid increase in water level to higher depths (50 cm) immediately after planting, the early planted crops produced only a negligible yield (0–1.2 t/ha). Highest yield was obtained from the crop planted with clonal tillers followed by that raised with fertilized and unfertilized nursery seedlings. Clonal tillers were taller (90 cm) and had more dry weight (1.78 g) compared with nursery seedlings (50–80 cm and 0.25–0.91 g). Therefore, the clonally propagated crop established well and acclimatized faster in the similar flooded environment, resulting in significantly higher grain yield particularly under late planted conditions. The results suggested early sowing by the end of May and transplanting with clonal tillers uprooted from the direct-sown crops for higher productivity of rice under uncontrolled excess water conditions.