HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Savant, N. K. Articles by Craswell, E. T. Search for Related Content PubMed Articles by Savant, N. K. Articles by Craswell, E. T. Agricola Articles by Savant, N. K. Articles by Craswell, E. T.

Distribution Patterns of Ammonium Nitrogen and ¹⁵N Uptake by Rice after Deep Placement of Urea Supergranules in Wetland Soil¹

ABSTRACT

In-situ distribution patterns of ammonium nitrogen (NH⁺₄-N) and ¹⁵N uptake by wetland rice (Oryza sativa L.) were studied on the farm of the International Rice Research Institute (IRRI) during the 1979 dry season. Individual 2-g urea supergranules were placed at 5-, 10-, and 15-cm soil depths in wetland rice plots transplanted at spacings of 20 by 20 cm and 10 by 40 cm. The ammonium (NH⁺₄) concentration gradients near placement sites showed that the NH⁺₄ movement was slow; in the transplanted plots, NH⁺₄ concentrations decreased with time largely due to plant uptake. Distribution patterns of NH⁺₄ were influenced by the depth of supergranule placement and the transplanting geometry. In general, the greater the distance from the point of placement of supergranule to the plant, the slower was the depletion of NH⁺₄-N at the placement site. During the dry season, the NH⁺₄ almost completely disappeared during the 40 days after transplanting, whereas during the wet season, NH⁺₄ persisted for up to 40 days after transplanting.

The ¹⁵N uptake patterns were s-shaped. During the first 20-day period after transplanting, deep-placed N was presumably physically or spatially unavailable, and negligible plant uptake occurred. After 20 days, the ¹⁵N uptake was retarded by placement of supergranules at lower depths and away from the rice hills. However, at final harvest more ¹⁵N was taken up from urea placed at the 15-cm depth than from the 5-cm depth. A marked lower recovery of split-applied urea-N (25 to 34%) than that of deep-placed urea-N (50 to 61%) was observed.

¹ Contribution from the Dep. of Agron., the International Rice Research Institute (IRRI), Los Banos, Laguna (Mailing Address: P.O. Box 933, Manila), Philippines, and the International Fertilizer Development Center (IFDC), Muscle Shoals, AL 35660.

² Postdoctoral Research Fellow, Head (Dep. of Agronomy, IRRI), and Soil Scientist (IFDC), respectively. The Senior Author is now Research Chemist (Soils) with IFDC.

Received for publication May 28, 1981. Accepted for publication January 20, 1982.