Rice Plant Population Density Effect on Early-Season Nitrogen Requirement
1990
Counce, Paul A. | Wells, B. R.
Rice (Oryza sativa L.) growers sometimes have yield losses because of inadequate rice population densities. One way to partially alleviate the yield loss resulting from inadequate plant populations may be to increase early season N fertilization. The objective of this study was to determine whether the N response differed among significantly different plant populations of the two predominant cultivars grown in the South. Field experiments were conducted in 1987 and 1988 at Keiser, AR. The treatments were cultivar (‘Lemont’ and ‘Newbonnet’), preflood N rates (0, 40, 70, and 100 lb/acre), and seeding rates (5, 40, and 125 seeds/sq ft). Grain yield increased linearly with N increases at the inadequate population density (5 seeds/sq ft seeding rate with a mean population of 3.1 plants/sq ft). At near-optimum (40 seeds/sq ft, 21.8 plants/sq ft) and excessive populations (125 seeds/sq ft, 67.8 plants/sq ft) there was a large yield increase in response to the first N increment (0 to 40 lb N/acre) and smaller increases in response to the next two N increments (40 to 70, and 70 to 100 lb N/acre). Yield component responses to N varied with population: at the inadequate population, increases were the result of greater tillering; at the near-optimum population, yield increases were the result of a combination of increases in tillering and in the number of seeds per panicle; and at the excessive plant population, yield increases were primarily the result of increased numbers of seeds per panicle. It is recommended that inadequate rice populations should have substantially greater early season N rates.
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