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Fluid Journal : Fluid Journal 1999-2001
2 Fluid Journal Winter 2001 of P2O5 in 12-inch band spacing) but not at high P rates (Figure 5). Governing factors It is apparent that liquid P distribution as commonly delivered from hose pumps is affected by several factors. Application rate at each delivery point, which changes in direct relation to band spacing, is a primary factor. For example, continuous bands occurred only at P application rates of 78 lbs/A of P2O5 with band spacing of <12 inches. This indicates that row crop starter applications using 10-34-0 must be in excess of 30 lbs/A of P2O5 if they are to be applied in a continuous band, unless row spacing is wider than 30 inches. Placement. Nebraska experiments on wheat and corn show the effect of different methods of P application on wheat grain yields as related to application rates (Figure 6). Both knifed bands and seed application had a spacing of 12 inches. Seed placement and knife methods of P application generally produced equal yields. However, a significant P rate by method interaction indicated knife applications became increasingly as effective as seed application and more effective than broadcasting as rate of application increased. Since knifed bands were applied prior to seeding, they varied in distance from the seed row, reducing the probability of root-P fertilizer contact, compared with seed applications. Therefore, one would expect seed application to be somewhat more effective than knifing at low P rates (as shown in Figure 6). The disadvantage of knifing at low P rates seems to be overcome at high rates where a continuous band is applied. Figure 7 shows that knifed liquid P for irrigated corn was more effective at high P rates than at low rates. The predicted distance between droplets for the knifed Pwas1.0and0.3inchforthe18and36 lbs/A rate of P2O5, respectively. Closer distances between droplets at high rates increased the probability of root contact with P, which is important in P uptake. Figure 8 shows results of two methods of P application on grain yield on winter wheat in Kansas. In this experiment, the same amount of solution was applied for all P rates (the fertilizer solution was diluted for rates <50 lbs/A of P2O5). Knifed P resulted in higher grain yield than seed applied. The predicted distances between droplets were 0 (continuous band) and 0.7 inch for knifed and seed applied P respectively (rates determined from regression equation used in this study). Root contact. The probability of root- P contact is known to be very important to P efficiency. The growth rate of roots is much greater in P-treated than untreated soil. It has been shown that Droplet Distance (inches) Figure 1. Traveling speed = 2.8 mph Band spacing = 12 in Tube size = 0.4 P O Rate lb/A 25 Effect of P application rate on distance between droplets in an applied band as determined from multiple regression. 3.0 2.0 1.0 010 22 35476072 mg P/droplet Figure 2. Traveling speed = 2.8 mph Band spacing = 12 in Tube size = 0.4 P O Rate lb/A 25 Amount of calculated P in each droplet as affected by P application rate using multiple regression 10 20 30 40 50 60 12 11 10 9 8 7 6 5 4 3 2 Droplet Distance (inches) Figure 3. Traveling speed = 2.8 mph Tube size = 0.4 15lbPO/A 30lb /A 45lb /A 60lb /A 25 PO PO PO 25 25 25 Band Spacing (in) Effect of band spacing on distance betwe en droplets at different rates of P application as determined by multiple regression 48121620242830 6 5 4 3 2 1 Figure 4. Effect of traveling speed on the distance between droplets in the applied P band as determined by multiple regression P=20lb /A Band spacing = 12 in Tube size = 0.4 in PO 25 Droplet Distance (inches) Travel Speed (mph) 1234567 3.0 2.0 1.0 0 15lbPO/A 30lb /A 45lb /A 60lb /A 25 PO PO PO 25 25 25 Traveling speed = 2.8 mph Band spacing = 12 in Droplet Distance (inches) Delivery Tube Size (inches) 0.3 0.4 0.6 3.0 2.0 1.0 0 Figure 5. Effect of delivery tube size on distance between fertilizer droplets at different P rates as determined by multiple regression
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