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Tillage Effect on Seasonal Accumulation of Labeled Fertilizer Nitrogen in Sorghum

USDA-ARS, Southern Weed Sci. Lab., Stoneville, MS 38776
Soil and Crop Sci. Dep., Texas A&M Univ., College Station, TX 77843

^* Corresponding author.

Limited information is available regarding tillage effects on seasonal N accumulation in sorghum [Sorghum bicolor (L.) Moench], especially where labeled N was used. Tillage effects on fertilizer N accumulation in 1985 and 1986 were evaluated in a field study on a Weswood silt loam (Fine-silty, mixed, thermic Fluventic Ustochrept) near College Station, TX. Nitrogen-15 depleted NH₄NO₃ (150 kg N ha^–1) was surface broadcast or subsurface banded under no-tillage or conventional tillage management to monitor fertilizer N accumulation in sorghum at boot, anthesis, soft dough, and harvest. Both years, most tillage effects on fertilizer N accumulation were manifested early in the season. The tillage-by-placement interaction was not significant for N uptake parameters, indicating a similar N accumulation response to placement for both tillage systems. Most fertilizer N uptake occurred by anthesis (84% averaged across years). Fertilizer N accumulation in no-tillage sorghum was generally higher throughout the 1985 season, resulting in significantly greater fertilizer N recovery by harvest. This effect occurred even though yields and total N accumulations for both tillage systems were similar. No tillage difference in whole plant fertilizer N accumulation at harvest was observed in 1986. No-tillage delayed early development of sorghum approximately 2 wk in 1986. Fertilizer N accumulation in leaves was less with conventional tillage than no-tillage early in the 1986 season. Leaf fertilizer N did not differ between tillage treatments after anthesis when vegetative demand declined. Conventional tillage culms contained more fertilizer N thoughout the season. Tillage effects on panicle fertilizer N accumulation coincided with periods of high N requirement, such as at soft dough, when no-tillage was higher. The plant growth delay for no-tillage sorghum in 1986 may have subjected the crop to additional moisture or temperature stress resulting in a tillage by fertilizer placement interaction, whereby banded treatments produced more grain than broadcast in no-tillage plots. Yields for banded no-tillage sorghum did not differ from those for either placement treatment in conventional tillage plots.

Key Words: Sorghum bicolor L. Moench • Nitrogen-15 depleted NH₄NO₃ • N uptake • Growth stages • Leaves • Culms • Panicles • Stores

Received for publication August 21, 1987.

This article has been cited by other articles:

				D. W. Sweeney and J. L. Moyer In-Season Nitrogen Uptake by Grain Sorghum following Legume Green Manures in Conservation Tillage Systems Agron. J., March 1, 2004; 96(2): 510 - 515. [Abstract] [Full Text] [PDF]