Phosphorus Application Frequency and Sources for Grain Sorghum
1985
Janssen, K. A. | Whitney, D. A. | Kissel, D. E.
A field study was conducted for 8 yr on an initially low soil test P, Woodson silt loam soil (fine, montmorillonitic, thermic Abruptic Argiaquolls) in east-central Kansas to determine the effectiveness of ortho-and polyphosphate fertilizers applied annually at 25 kg ha⁻¹, every 2 yr at 50 kg ha⁻¹, and every 4 yr at 100 kg ha⁻¹ for grain sorghum (Sorghum bicolor L.) production. The first year, yield was higher with the larger, less frequent P applications because of the low P status of the soil. Second-and third-year yields were not statistically different. The fourth year, when the time span was longest since the every 4-yr P application had been applied, yield was lower with the every 4-yr P application compared to annual P. The every 2-yr P treatment produced intermediate results. Total grain production for the first 4 yr did not differ significantly with the P application frequency treatments. During the second 4 yr, when soil P levels were higher, the P application frequency treatments produced no significant differences in yearly or total yield. The ortho-and poly-phosphate P sources, in general, produced similar response applied annually, or at infrequent intervals. These data suggest that there are Argiaquolls in east-central Kansas on which infrequent P fertilizer applications can perform similarly to annual P applications.
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