Correlation of the olsen phosphorus soil test: spring wheat response
1997
Jackson, G.D. | Kushnak, G.D. | Carlson, G.R. | Wichman, D.M.
Spring wheat producers in central and north central Montana are lacking information to interpret the Olsen phosphorus (P) soil test. This study was conducted to evaluate spring wheat P response and the Olsen P soil test. Field experiments were conducted at 29 cultivated fallow, 5 no-till fallow, 16 no-till recrop, and 2 cultivated recrop locations from 1986 to 1995. Phosphorus treatments ranging from O to 29 kg P/ha were applied on sites with Olsen P soil tests varying from 4 to 37 mg/kg. Grain yield, protein, and test weight responses were measured. Yields fluctuated from 1082 to 6270 kg/ha and P response from 0 to 1210 kg/ha. A Cate-Nelson plot of the response data confirmed the current critical level of 16 mg/kg, but P fertilizer recommendations were adjusted. Multiple regression was utilized to develop a highly significant P response equation Y = -11.18 + 67.672 P - 1.22 P2 - 0.98 (P x ST), R2 = 0.55 where Y = grain yield response (kg/ha), P = P rate (kg/ha), and ST = Olsen P soil test (mg/kg). Grain test weight and protein content were generally unaffected by P except protein was depressed at several environments with high yields and high P soil tests. Growers should use a P starter fertilizer regardless of soil test.
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