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Fluid Journal : Fluid Journal 2002-2004
Figure 1. Profile distribution of bio-available P 43 days after dribble application of 15-30-10 (left) and 60-30-10 (right) two inches to side of corn row. Figure 2. Profile distribution of bio-available P 68 days after dribble application of 15-30-10 (left) and 60-30-10 (right) two inches to side of corn row. movement when increasing N relative to P2O5 is unclear. To characterize this effect, more intensive sampling is needed. Hybrid response. Although soil and plant data are still being analyzed, preliminary results suggest that two non- transgenic corn varieties took better advantage of growing conditions in Clarion silt loam soil than did two transgenic varieties. Dry matter accumulation 13 days after seedlings were planted was greater for both non- transgenic isolines, regardless of the N:P2O5 ratio of the starter. At this point, it is difficult to draw any conclusions because information is not yet available on root growth, plant uptake of N, P and other nutrients, and changes in soil nutrient supply. It may be that the non-transgenic isolines produce more above-ground biomass early or that transgenic isolines require higher nutrient levels, greater light intensity, or some other input to produce similar levels of plant dry matter after emergence. Moreover, these differences may disappear later in the season under field conditions. The results of this preliminary study under controlled conditions set the stage for further field trials. Specifics Location. Field plots were established at the Iowa State University Agricultural Engineering Research Farm west of Ames, Iowa. Soil at this site is a Canisteo silty clay loam. Plot size was 12.5 by 90 feet. Experimental design was a randomized complete block with 13 treatments and 4 replications. Fertilizer applied included: 6-20-0 (5 gal/A 10-34-0), 6-20-6 (8.7 gal/A 7-21- 7), 14-48-0 (12 gal/A 10-34-0), 15-30- 10, 30-30-10, 45-30-10, and 60-30-10. Accounting for N in the starters, a total of 150 lbs/A was applied to all plots. Placement included in-furrow, surface band over row, and dribble band over row and two inches to the side of the row. Dr. Kovar is a soil scientist at the USDA/ARS National Soil Tilth Laboratory, Ames, Iowa. Early Spring 2003
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