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Fluid Journal : Fluid Journal 1999-2001
1 Fluid Journal Winter 2001 by Drs. B. Eghball and D.H. Sander Does Variable Distribution Affect Liquid P-Use Efficiency? Florida scientist offers tips on how to use starters, plus describes the many benefits that accrue from their use. He focuses on corn. anding either dry or liquid P fertilizer has been shown to be more effective than broadcast. Experiments with different rates of P indicate that handing becomes increasingly superior to broadcasting as P rate increases up to the optimum rate. In Nebraska, results indicate that seed applied P versus broadcasting becomes increasingly effective as the rate of application increases. Additional winter wheat trials showed that although both knife and seed application were superior to broadcast P, knifed P tended to be less effective than seed application at low P rates, but were equal at higher rates of application. In a Kansas wheat trial, knifed P in a band spacing of 15 inches over four P B Summary: Experiments show that banding of liquid P is more effective than broadcast. The effectiveness of banded P has been shown to be increasingly superior compared to broadcasting P when P rate increases to the optimum level. The greater the speed of application, the smaller becomes the distance between droplets. Results of this study suggest that lower analysis P fertilizers could be more effective than widely used 10-34-0 for preplant banding and starter row applied fertilizers. Mixing of 10-34-0 with UAN may improve P-use efficiency both through improved P distribution and through ammonium-N effects on P uptake and P fixation. application rates resulted in greater grain yield than seed applied P in a 7- inch spacing. Speculation attributes the difference to P distribution in the applied band. Distribution of P in the knifed or seed band could influence the probability of root-P fertilizer contact and affect soil-fertilizer contact. Experiments have also shown that particle size of solid P, which affects the distribution of applied P in an applied band, is a factor that influences efficiency of P. Optimum P fertilizer particle size is affected by the relative severity of soil P fixation, plant root characteristics, band spacing, and proximity of seed row to the band. Objectives of this experiment were to 1) determine how application variables affect the distribution of liquid P in a band, and 2) observe how different methods of P application relate to performance in the field. Field observations P distribution. Figures 1 through 5 are derived from multiple regression. Multiple regression indicates that liquid P distribution, as delivered from a standard hose pump, was significantly affected by rate of application, band spacing, and speed of travel (speed of pump revolutions) during application. Delivery tube size appeared to be less important in P distribution than other factors, but did interact with the rate of application. Band spacing. Figure 1 shows that at a 12-inch band spacing (traveling speed of 2.8 mph with a tube size of 0.4 inch) P was delivered in unevenly spaced droplets. Droplet distances ranged from about 2 inches at a P2O5 rate of 15 lbs/A to zero distance or a continuous band at 75 lbs/A of P2O5. The amount of P in each droplet decreased (droplets became smaller) in direct proportion to the rate of P application (Figure 2). Increasing band spacing decreased the distance between droplets at the same application rate (Figure 3). The smaller the band spacing, the greater the distance between droplets. With a spacing of 12 inches, distance between droplets was 2, 0.75, 0.35, and 0.12 inches with P2O5 application rates of 15, 30, 45, and 60 lbs/A, respectively. Continuous bands were formed at band spacings of about 17, 22, and 31 inches with application rates of 60, 45, and 30 lbs/A of P2O5, respectively. No continuous band of P was formed at 15 lbs/A of P2O5, even at the highest band spacing. Effect of speed. Distance between droplets was affected by speed (Figure 4). As speed increased and pump speed increased, the distance between droplets decreased up to a speed of about 2.8 mph, where speed no longer seemed to affect droplet distances. Although delivery tube size did not significantly affect the distance between droplets, an interaction between rate and tube size indicated that tube size was affecting the solution distribution at low (<20 lbs/A
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