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1. Soybean Whole Plant, and Trifoliate Phosphorus Concentration Relationships to Yield and Phosphorus Removal RatesPlant tissue analysis is becoming a more popular tool to diagnosis nutrient deficiencies. Whole plant samples may be taken early ( corrections. Leaf samples taken just before grain fill may be used to diagnose problem spots in a field. Benton Jones Jr. et al. (1991) reports that the phosphorus (P) sufficiency range for upper most developed trifoliates is between 0.26 and 0.50 percent P. There is no published data on whole plant P sufficiency ranges from V4 to V6. Nutrient grain analysis is valuable... |
2. Correlation and Calibration of the Mehlich 3 P Soil Test for Soybeans in KansasKansas currently uses the Mehlich 3 soil test for P, with a general P soil test (STP) critical level for all crops of 20 ppm (colorimetric). This critical level was established based on field research primarily with wheat in 2003. A review of the limited research data available from Kansas suggests that soybeans may not require as high a STP level as wheat for optimum yield. Therefore the objective of this study is to determine what the appropriate critical STP level is for optimum soybean production... |
3. Soybean Response to Potassium Fertility and Fertilizer in ManitobaSoybean acres have increased greatly in Manitoba in recent years, now occupying more than 25% of the province’s annual crop land. Potassium removal by soybean is greater than any other crop grown in Manitoba (1.1 – 1.4 lb K2O/bu). This large removal, accompanied by the large and rapid expansion in soybean acres, has contributed to an increase in province-wide potassium removal rates and likely explains the increase in incidence of potassium deficiency symptoms reported in recent years.... M. Bourns, D. Flaten, J. Heard, G. Bartley |