Uptake of 15N-Labeled Nitrate by Sugar Beets from Depths Greater than 180 CM
1979
Peterson, G. A. | Anderson, F. N. | Varvel, G. E. | Olson, R. A.
Previous investigations had shown that irrigated sugar beets (Beta vulgaris L.) extracted NO₃⁻ from depths of 135 cm. Since excessive N availability late in the growing season can adversely affect root sucrose content, it was necessary to determine if the plant could extract NO₃⁻ from even greater depths. Thus, a field experiment was conducted on a Typic Haplustoll with ¹⁵N labeled NO-N placed at depths of 180, 210, and 240 an below the soil surface in tracer amounts. Petiole ¹⁵N uptake was monitored on 2 July, 1 August, 1 September, and 12 October, representing points during the growing season of 86, 107, 138, and 165 days after emergence, respectively. At 86 days no ¹⁵N uptake had occurred from any placement depth. By 107 days slight uptake was occurring at all depths. Between the 107th and 138th days large increases in uptake occurred from the 180- and 210-cm depths. It was concluded that under growing season lengths such as those in western Nebraska sugar beet roots can effectively absorb nitrate from depths as great as 210 cm. Slight absorption may occur from depth as great as 240 cm.
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