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Abstract
Soil testing determines nutrient, lime, gypsum or S, leaching requirements for crops, and potential elemental toxicity to crops and/or their consumers. The majority of farmers do not use soil testing or use higher or lower than economic optimum nutrient rates. Shortcomings of the current soil testing methodology are inability to predict yields, large soil test spacial and temporal variability, inability to reflect dynamics of field parameters that affect nutrient availability, lack of accurate tests for nutrient mineralization, and lack of accurate nutrient response functions. In situ chlorophyll and quick sap tests; or remote sensing with variable rate technology (VRT) can overcome some of soil testing problems. Nutrient uptake efficiencies are low due to the lack of well-funded research efforts on breeding crops with better root systems and nutrient uptake efficiencies. Skogley's diffusion-dependent resin test, with a long equilibrium time, should be used as a standard to evaluate other soil tests, instead of the current resin test which requires shaking the soil and resin. The AB-DTPA test of Soltanpour and Schwab better reflected the effect of texture on P availability than Olsen NaHCO3 or Mehlich 3 tests due to its narrower solution to soil ratio. We give new field calibration P levels for AB-DTPA. Mulvaney's test for soil organic N availability index shows promise and should be evaluated. We will discuss the available best nutrient management strategies and our projection of future needs. Future nutrient management systems should be developed by regional cooperation between environmental soil scientists, geneticists, and economists.