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Fluid Journal : Fluid Journal 2005-2007
SPRING 2007 Fluid Journal 21 Starter-band N (lbs N/A) 01 02 03 04 05 06 07 08 0 Percent N in Tissue 2.0 2.2 2.4 2.6 2.8 3.0 3.2 3.4 3.6 Broadcast 60 lbs N/A plus Starter-band 10 lbs N/A Soil Series Mehlich I P Calibration* Yield Response Average Test Available P Yield (bu/A) (ppm) Pamunkey sil 7 Medium Plus No 87 Slagle sil 41 High No 149 Pamunkey fsl 22 High Minus No 142 Slagle sl 16 Medium Plus No 147 Turbeville sl 49 High Plus No 95 Cullen l 8 Medium Minus No 116 Eubanks sil 60 Very High No 110 Ross l 17 Medium Plus Yes ** Pamunkey sil 12 Medium No 143 *Mehlich I extractable P calibration used by Virginia Tech Soil Testing Laboratory. **12 bu/A yield increase with 60 lbs P2O5/A. Table 1 Corn grain yield response to starter band-applied phosphorus applied at 0,20,40,60 lbs P2O5/acre. shows the increased root growth associated with enriched levels of phosphate, nitrate, and ammonium. Response to K is limited. Although increased root growth normally has been associated with enhanced levels of P placed in starter fertilizer bands, these results illustrate that plant root growth is also increased with increased levels of ammonium and nitrate, as well as P. Cor n N response Early-season nutrient availability is influenced by fertilizer placement. Germination and emergence of the corn seedling usually occur in six to ten days with reasonable temperatures and moisture. The corn seedling can be expected to develop two fully expanded leaves and a primary root system that obtains needed nutrients from the soil within seven days after emergence. The supply of nutrients in the seed will be exhausted by this time (seven days after emergence). The corn plant roots generally do not reach the middle of the rows until the corn plant has eight fully emerged leaves, which is about the time corn is knee-high. Therefore, during approximately the first six weeks Figure 2. Percent N in whole corn plant (12- to 15-inch height) related to starter-band and broadcast N applications on a Slagle silt loam soil. Nitrate Ammonium Potassium Low High Low Low High Low Low High Low 10 cm
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