Nitrogen Management in Sod-Based Cotton Cropping Systems.
T.W. Katsvairo1, D.L. Wright1, J.J. Marois1, D.L. Hartzog2, K.B. Balkcom2, J.R. Rich1, and P.J. Wiatrak1. (1) Univ. of Florida, 155 Research Rd., Quincy, FL 32303, (2) Auburn University, Wiregrass Reg. Res. & Ext. Cntr, P. O. Box 217, Headland, AL 36345
Concerns about N leaching into ground water have prompted the need to re-evaluate the current N use in intense peanut (Arachis hypogaea) and cotton (Gossypium hirsutum L.) rotation in favor of a less intense and more sustainable system. It has been proposed that 2 years of bahiagrass (Paspalum notatum) rotated with peanut and cotton vs. the traditional peanut/cotton rotation results in more N use efficiency. Studies were conducted at Quincy, FL between 2003-2006 to evaluate N rates, N uptake and residual soil N and soil water N in sod-based peanut/cotton production systems compared to traditional peanut/cotton cropping systems. In general, the cotton in the sod-rotation had greater N uptake compared to conventional cotton. The greater roots in the bahiagrass rotation enabled the cotton to develop a deep rooting system which extracted more nutrients from deeper soil profiles. Similarly, the sod rotation generally had reduced soil water nitrates during the 3 years. In 2005, sidedress N application rates of 34 kg ha-1 vs. 67 kg ha-1 did not affect yield in both the sod-based rotation and the conventional rotation. The sod-based rotation also had greater amount of residual N at the end of the season, presumably from the decomposition of the bigger rooting system. The sod rotation has the potential to reduce N need and simultaneously reduce N leaching losses.