Nitrogen Status of Cotton Following Winter Cover Crops

G. A. Breitenbeck, R. L. Hutchinson and D. J. Boquet


The beneficial effects of reduced tillage and winter legume crops on the yields of cotton may result from enhanced N availability as well as from improved soil tilth and other advantageous changes these practices cause in the soil environment. To assess the relative importance of these factors, N status of cotton was determined by collecting petioles and leaf blades between first bloom and end of the effective bloom period from cotton grown under different tillage and N fertilizer regimes after wheat, vetch and fallow cover crops. Analyses of these plant components indicated that while petiole nitrate (NO3-) and leaf blade N both tended to show the same effects of management practices on N status of cotton, leaf blade N was less variable than petiole NO3- and was generally a more sensitive and reliable indicator of N status. Using blade N to assess N nutrition showed that no-till management increased N status of cotton grown on Gigger silt loam after fallow or a wheat cover, but had no effect after winter vetch. Leaf N contents suggested that a vetch cover could supply most of N required to obtain maximum yields of cotton grown on this soil. In contrast, reduced tillage appeared to reduce N availability to cotton grown on a Sharkey clay regardless of cover crop, and the N contributions of vetch were less evident. The increased yields obtained on Sharkey clay by reduced tillage and a vetch cover appear to result primarily from an improved soil environment rather than from enhanced N availability.

Reprinted from Proceedings of the 1994 Beltwide Cotton Conferences pp. 1505 - 1507
©National Cotton Council, Memphis TN

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Document last modified Sunday, Dec 6 1998