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Fluid Journal : Fluid Journal 2008-2009
WINTER 2008 Fluid Journal 13 Figure 2. Soil becomes dominant source of P for corn at about the V-2 growth stage. Table 1. Band starter placements continue to show equality. Starter application Starter formulation Method 25-20-5-28S-0.6Zn 25-20-5-28S-0.6Zn S as ammonium sulfate S as thiosulfate 2 x2 156 ---- 2 x0 155 146 N and K constant on all plots seedling effects. At lower rates of starter S, 5 to 7 lbs/A, differences between S sources are unlikely. Placement of a band 1 x 1 was not as effective as 2 x 2, possibly because of diffusion into the seed row of the urea-containing solution used to increase the N content of the starter. Population problems can result from such diffusion and the resulting free ammonia from urea hydrolysis. Coarse-textured soils are more susceptible to this kind of problem and thus N rates with 1 x 1 placement should be limited. Our studies have shown minimal problems when starter N in 1 x 1 placement was limited to around 24 lbs/A. Studies at other locations with finer-textured soils have shown that much higher N rates can be successfully banded 2 x 2 or 2 x 0 on soil surfaces beside the row. (Note results in article on page 17.) Timing. Our starter N rate comparisons support the importance of adequate N close to the emerging plant in the first crucial days after planting. Broadcast N is not the same and, like high P soil tests under high residue, cold soil conditions do not provide high enough N (or P) concentrations in the young plants' root zone to overcome soil environmental restrictions to nutrient uptake. Numerous studies have also emphasized the importance of readily available NPKS and Zn close to the developing root system to meet the demands of young plant roots. Nutrient adsorption per unit of root length is extremely high in early growth stages (Figure 2). Ron Mulford is agronomist, University of Maryland, Lower Eastern Shore Research and Education Center. 130 120 110 100 90 80 70 Application Method 12-20-5-15 24-20-5-15 48-20-5-15 bu/A Control Broadcast 2X2 1X1 Dribble 0 2 4 6 8 10 12 14 2030405060708090100110120 Days After Planting P Uptake per Unit Length of root Mengel and Barber, 1973 Figure 1. Effects of starter formulation on corn yields.
Fluid Journal 2005-2007