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Fluid Journal : Fluid Journal 1996-1998
3 Fluid Journal Summer 1997 Soil samples (0 to 6 inches) were collected at the initiation of the study and showed: pH 7.8, phosphorus (Bray/ Kurtz #1) 2.3 ppm, phosphorus (Olsen) 4.3 ppm, and potassium 166 ppm. Plot design. Four factors (tillage system, row spacing for soybeans, frequency of phosphate application, and phosphate rate) were combined in a complete factorial design with three replications. Tillage systems (fall chisel, no-till) were the main plots. Soybean row spacings (7, 30 inches) were the sub plots. Frequency, placement, and rate of phosphate applications were the sub-sub plots. Application rate. Biennial applications of phosphate were first applied in the fall of 1994 and repeated in the fall of 1996. For these applications, phosphate rates were 46, 92, 138, and 184 lbs/A of P2O5. Annual phosphate applications were made in late fall of 1994, 1995, and 1996. For these applications, phosphate rates were 23, 46, 69, and 92 lbs/A of P2O5. Appropriate zero phosphate controls were used for each frequency of application. Adequate N, supplied as 82-0-0, was applied on June 11 when the corn was in the two-leaf stage of development. Placement. A coulter and knife assembly was used to band phosphate at a depth of approximately 4 inches below the soil surface. The bands (both biennia and annual) were placed on 15- inch centers for the narrow row soybean treatments. Bands were on 30-inch centers for the 30-inch row spacings. Phosphate applications (both band and broadcast) were completed before the chisel plow tillage operation each fall. There was no incorporation of broadcast phosphate in the no-till planting system. Planting. Corn planting in 1996 was delayed by frequent rains. DeKalb (DK- 442) was planted at a density of 30,100 seeds/A on May 24. Row spacing was 30 inches. Weed control was achieved with a preemergence application of Dual, followed by a postemergence application of Permit and Accent. Rotation. Corn was grown in 1994 and 1996. Soybeans were grown in 1995. Dr. Rehm is extension soil scientist, Department of Soil, Water and Climate, University of Minnesota.
Fluid Journal 1993-1995
Fluid Journal 1999-2001