A SIMPLIFIED METHOD FOR THE EXTRACTION AND ANALYSIS OF AVAILABLE NITROGEN, PHOSPHORUS, AND POTASSIUM IN SOILS

Sodium bicarbonate (NaHCO3) and calcium chloride (CaCl2) are proposed as simultaneous extractants of available nitrate-nitrogen (NO3--N), ph osphorus (P), potassium (K) in soils. Flow Injection methods were used for the determination of NO3- and P, and atomic emission spectroscopy for K. Parameters, such as reproducibility, precision, and recovery o f the different extraction processes were studied. The usefulness of t he proposed extractants was tested by applying them to different sampl es from the Spanish Soil Collection. The results obtained were compare d with those provided after using the extractants recommended by the o fficial methods. Sodium bicarbonate turned out to be suitable for the simultaneous extraction of NO3-, P, and K in alkaline soils, whereas C aCl2 was only advisable for NO3-.