EFFECTS OF HUMIC SUBSTANCES FROM CHERNOZEMIC Ah HORIZONS ON NUTRIENT UPTAKE BY PHASEOLUS VULGARIS AND FESTUCA SCABRELLA

Abstract

Plants were grown in nutrient solution fortified with humic substance at five levels, 0, 1, 5, 10, or 50 mg/liter. The humic substances were extracted by three methods, with Chelex-100, with Na4P2O7 alone, or with NaOH after the Na4P2O7 extraction, from the top horizon of three soils, a Dark Brown Chernozem Ah, a Black Chernozem Ah, and a Dark Gray Luvisol Ahe. The plants were analyzed for N, P, Na, K, Ca, Mg, and Fe. There were some differences in terms of concentration but negligible differences in terms of total uptake in the effects of humic substances derived by different methods of extraction from soil on nutrient uptake by Phaseolus vulgaris L. and Festuca scabrella Torr. There was no difference between the effects of the humic substances from the Dark Brown and the Black Chernozem on total nutrient uptake by Festuca, but the humic substances from the Dark Gray Luvisol led to significantly greater uptake of all elements tested. While both source and rate of humic substance used did affect the growth of the shoots of Festuca, neither had any effect on the growth of roots and shoots of Phaseolus and roots of Festuca. Total nutrient uptake was suppressed by the 1- and 5-mg additions of humic substance, whereas it increased when humic substances were added at 10 or 50 mg/liter of nutrient solution.