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Fluid Journal : Fluid Journal 2005-2007
Early Spring 2005 Fluid Journal 3 that the APP band 6 inches below the soil surface performed better than all other treatments for two of the three locations evaluated. P uptake critical The nutrient analysis shows substantial increases of N and P in the stems/leaves and roots when sampled early in the season (data not shown). These tissue concentration differences disappeared late in the season for the stems/leaves, but not so for the root P concentrations. The banded P treatments consistently exhibited higher root P concentrations than the broadcast or unfertilized check. The tissue nutrient concentration results from the 2002 study, combined with evidence from the results of the 2003 study, lead one to believe that all or much of the yield response observed with the deep-banded APP treatment is due to enhanced P uptake and use for both years of this study. No response was observed when N was added by itself, again indicating that the response was due to P or the synergistic effect of N and P applied together. Going where roots are During the early half of the season, sugarbeet roots are oriented dominantly downward as compared to a more diagonal orientation for most other plant species. The architecture of the sugarbeet root results in more exploration of the subsoil and less of the surface soil, especially in the first two months of growth. Subsurface P concentrations tend to be very low, especially in alkaline, calcareous soils common in the western states. This combination of sugarbeet roots not effectively exploring the surface soil and low subsoil P levels results in a potential problem for P availability early in the season, even in high P-testing soils. Deep banding APP seems to effectively correct this problem. Methodology Locations. Three trials were conducted in irrigated fields near Minidoka, Idaho, in 2002 and near Twin Falls and Blackfoot, Idaho, in 2003. Soils were alkaline (pH 8.0 to 8.4), calcareous (5 to 12% CaCO3), with medium-high soil test P (15 to 35 ppm bicarbonate P). Treatments included four placements of two fertilizer sources (APP and PA in 2002 and APP and UAN in 2003). Placement methods included: broadcast and banded fertilizer at 0, 3, and 6 inches below the surface (directly above/below the seed). Fertilizers were applied either as APP (both years) with 6 lbs/A of N + 20 lbs/A of P2O5, as UAN (2003) with 6 lbs/AofNand0lbs/AofP2O5,or asPA (2002) with 20 lbs/A of P2O5. No additional fertilizer was needed, based on soil and petiole analyses, with the exception of broadcast N, which was applied to all plots uniformly at planting. Plots were arranged in a randomized complete block design (RCBD) with six replications and were established as six 40-foot rows on 22-inch centers. Timing. Broadcast applications were applied and tilled into the soil at final ground preparation. Subsurface bands were applied after hilling and prior to planting. Surface banding occurred immediately after planting by spraying fertilizer over the seed zone in a two- inch band. Dr. Hopkins is a cropping systems soil scientist at Idaho Falls and Dr. Ellsworth is a soil fertility specialist at Twin Falls in the College of Agriculture and Life Sciences, University of Idaho.
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