Nitrogen uptake and yield of deepwater rice in the central plain of Thailand uri icon

abstract

  • Surveys to determine the relation of uptake of nitrogen to yield of deepwater rice (DWR) in farmers' fields were conducted in the Central Plain or Thailand in 1988 and 1989. Farmers sowed their fields at the beginning of the wet season and the crops grew under rainfed dry land conditions until the flood arrived. Fields were sampled for soil pH, soil total N and available P, plant production and N content close to the arrival of the flood (pre-flood) and again at maturity. Start of flooding ranged from 22 to 122 days after emergence, with a mean of 66 bays. Maximum water depths ranged from 0.30 to 2.10 m. Data from 32 fields in 1988 and 53 fields in 1989 were included in the analyses. Thirty seven DWR varieties were found. The mean farmer application of N for the 52 fields sampled in 1989 was 15.2 kg ha(-1). Above-ground plant dry mass at maturity ranged from 2.7 to 20.5 t ha(-1), with a mean of 10 t ha(-1). Nitrogen content at maturity ranged from 23 to 115 kg ha(-1), with a mean of 66 kg. Eighty percent of N was accumulated during the flood, but pre-flood plant production had a significant correlation with above-ground dry mass at maturity, indicating the importance of good early crop development for DWR. Yield ranged from 0.65 to 4.87 t ha(-1), with a mean of 2.13 t ha(-1). Factors closely correlated with yield were dry mass at maturity (r=0.69**), panicles m(-2) (r=0.59**) and rate of N uptake during flooding (r=0.33**). Nitrogen content was most closely related to grain yield through total dry mass, but as most N was accumulated during the flood, a question still not answered is what proportions of this N came from the soil and from other sources, and how can the natural supply of N be sustained. These observations are also relevant to other rainfed lowland rice crops in Asia.

publication date

  • 1994
  • 1994
  • 1994