Effect of form, method and time of urea nitrogen application on growth, yield and nitrogen uptake of direct sown and transplanted rice under intermediate deep water (15–50 cm) conditions

SummaryUnder intermediate deepwater (15–50 cm) conditions, sulphur-coated urea (SOU) drilled behind the plough at sowing was superior to other coated (neem, lac, coaltar) urea materials and broadcast incorporation of prilled urea in increasing the yield of direct-sown rice. In transplanted rice, the grain yield was highest with urea super granules (USG) placed 30 days after transplanting (DAT) followed by SOU broadcast incorporation at planting. N-use efficiency increased considerably with SCU drilled behind the plough or USG placed 20 days after sowing in shallow standing water in direct-sown rice and SCU broadcast incorporation or USG placed 30 DAT in transplanted rice.

Effect of nitrogen fertilizer on yield and nitrogen concentration in grain and straw of rice under semi-deepwater conditions (51–100 cm)

SummaryUnder conditions of semi-deep water (51–100 cm) rice varieties with greater plant height produced more dry matter and grain yield as N fertilizer was increased from 0 to 20 and 40 kg/ha. The varieties which performed better in a situation of slow rise in water level to a depth of 120 cm could not survive a quick rise in water level owing to their lesser plant height and elongation ability. The loss of dry matter (dead and dried leaves) was also greater in varieties susceptible to deep water than varieties tolerant of deep water.With the increase in N fertilizer, there was increase in plant height, number of tillers, dry-matter production and grain yield. The loss of dry matter was less in crops given N fertilizer than in those not given N fertilizer. The varieties capable of producing higher grain yield in response to N fertilizer under semi-deep water did not improve their grain yield under intermediate deep water (15–50 cm). With increase in application of N fertilizer from 0 to 40 kg/ha the N concentration in grain increased. N concentration did not vary in straw under intermediate deep water, there was no definite trend in semi-deep water, and it was higher under conditions of semi-deep than intermediate deep water.

Effect of methods of stand establishment on grain yield of rice under intermediate deep water conditions (15–50 cm)

SummaryIn intermediate deepwater conditions (15–50 cm), direct seeding was superior to transplanting in 20 cm of water. Varieties with greater plant height performed better under transplanted conditions. Nitrogen fertilizer application at 40 kg/ha increased the grain yield under both direct-seeded and transplanted conditions. Though yield of the transplanted crop was less than that of the direct-seeded crop, the decrease was less in the crop given nitrogen fertilizer.

Effect of Transplanting Date and Seedling Age on Stand Establishment and Grain Yield of Rice in Rainfed Lowland (Intermediate Deep-Water) Conditions

SummaryWater depth at or shortly after planting is critical for the establishment and subsequent tolerance of excess water in rice. A crop transplanted early in the season produced twice as much grain as a later planted crop. A semi-dwarf variety (CR 1018) and a taller variety (CR 1030) performed similarly after early transplanting, but the tall variety performed better when planted late under excess water. Seedling age did not greatly alter the yields when crops were transplanted early, but after late planting 45-day-old seedlings were best.