Wednesday, November 15, 2006

Nitrogen Uptake and Utilization by Strip-Till Sugarbeet.

William Stevens1, Robert Evans1, Bill M. Iversen1, and Michael Baefsky2. (1) NPARL USDA-ARS, USDA-ARS N. Plains Agric. Res. Lab, 1500 N. Central Avenue, Sidney, MT 59270, (2) Self-employed, Baefsky & Associates, PO Box 311, Orinda, CA 94563

Strip tillage (ST) has been used successfully with large seeded crops like corn (Zea mays L.) and soybeans (Glycine max (L.) Merr.). Difficulties associated with seedbed preparation, fertilizer management, and weed control have inhibited its use for small seeded crops like sugarbeet (Beta vulgaris L.). A project was initiated near Sidney, MT (47.7255 N, 104.1514 W) to research the applicability of ST for sugarbeet rotated with small grains. Objectives were to (i) develop a prototype strip tiller and banded fertilizer application system suitable for small seeded crops, (ii) compare effect of tillage system (conventional tillage (CT) vs. ST) on sugarbeet yield and quality parameters, and (iii) compare N uptake and utilization efficiency in a ST sugarbeet production system to that in a CT system. Treatments were randomly assigned to 15 m × 25 m sprinkler-irrigated plots arranged in an unbalanced stripped block design. For ST, 30-cm strips were tilled into the small grain straw residue using a combination of straight and paired fluted coulters, a modified parabolic shank, and a crows-foot packer wheel. Dry urea was banded about 8 cm below and 2.5-5.0 cm to the side of the seed row location. Preliminary results suggest that root yield and sugar production are similar with the two tillage systems under typical conditions; however, root sucrose content has been consistently higher with ST than with CT. Midseason soil samples and petiole nitrate concentrations suggest that ST sugarbeet does not absorb N as effectively as does CT sugarbeet even though N is banded with ST and broadcast with CT. Research is ongoing to determine the reason for the difference in N uptake and to investigate options for corrective modifications.