Dicyandiamide Influence on Uptake of Preplant-Applied Fertilizer Nitrogen by Rice
- C. E. Wilson ,
- B. R. Wells and
- R. J. Norman
Dep. of Agronomy, Univ. of Arkansas, Fayetteville, AR 72701
Univ. of Arkansas Rice Research and Extension Center, Stuttgart, AR 72160
A field study was conducted to determine the influence of dicyandiamide (dcd) on fertilizer N recovery from soil and rice (Oryza sativa L.) when 15N-labeled urea was applied preplant (20 g N m−2). Microplots consisted of polyvinyl chloride pipes, 20.3 cm in diameter, driven into the soil. ‘Newbonnet’ rice was seeded, thinned to five plants per microplot, and flooded when the plants were at the four- to five-leaf stage of development. Soil and plant samples were analyzed for N every 7 d for 49 d following application (plant samples beginning at 35 d) and then every 14 d. Prior to flooding, urea with dcd reduced nitrification. With dcd, 51 and 8% of the applied N was recovered at flooding as NH4 and NO3, respectively, compared with 8 and 23%, respectively, without dcd. Dicyandiamide, by maintaining more fertilizer N in the NH4 form, appeared to cause greater immobilization of the fertilizer N than when dcd was not applied (19 and 15% of applied N, respectively). More fertilizer N was recovered in the shoots and roots (17.2 and 2.9% of applied N, respectively) when urea was applied with dcd than when used alone (9.7 and 1.9%, respectively). However, fertilizer N recovered in the panicles and grain yield were not significantly different between treatments. Fertilizer N recovered in the total plant increased significantly from 35 to 42 d, after which no further changes occurred. However, total plant N and native soil N uptake increased significantly throughout the growing season.
Contribution from the Dep. of Agronomy, Univ. of Arkansas and the Arkansas Agric. Exp. Stn. Partial support provided by the Tennessee Valley Authority's National Feritilizer Development Center, Muscle Shoals, AL, and the Arkansas Rice Research and Promotion Board.
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