Recalibration of Mehlich-I and Mehlich-III Methods for the Estimation of Extractable Phosphorus in Potato Crop

Monday, July 26, 2021
4:15 PM - 4:30 PM


There are several nutrient analysis methods used to estimate the nutrient concentration in soil. The Mehlich-I and Mehlich-III are the most commonly used to estimate the available nutrient in soils. Mehlich-I was designed to estimate extractable nutrients from acidic soils with low cation exchange capacity (CEC). Still, it is not effective in neutral and alkaline soils with high cation exchange capacity (CEC) and the soils having high aluminum (Al), iron (Fe) accumulation, and organic matter. To overcome the constraints of Mehlich-I, Mehlich-III was developed. This study aims to recalibrate Mehlich-I and Mehlich-III soil extractants. The experiment was established on two sites at the University of Florida research station in Hastings and four sites on the cooperator's farm using randomized complete block design with four replications for growing season 2021. Eight different P rates, i.e., 0, 25, 50, 75, 100, 125, 150, and 200 lbs. per acre as Triple Super Phosphate (TSP) (46% P2O5), were applied. Soil samples were taken from each treatment from the two depths 0-6 inches and 6-24 inches before potato planting and between the tuber initiation and tuber bulking stage. Mehlich-I extractant (a dilute double acid mixture of 0.0125 M H2SO4 + 0.05 M HCl) and Mehlich-III extractant (a solution containing 0.015 M NH4F + 0.25 M NH4NO3 + 0.001 M EDTA + 0.2 M CH3COOH + 0.13 M HNO3) with inductively coupled plasma atomic emission spectroscopy (ICP-AES) used to estimate available nutrients in soils. Preliminary results found some discrepancies in the already recalibrated Mehlich-I and Mehlich-III correlations line.

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