APPLICATION OF NO3/AL INDEX FOR ASSESSING ALUMINUM PHYTOTOXICITY OF WINTER WHEAT (TRITICUM AESTIVUM L.) AND SUGAR BEET (BETA VULGARIS L.) IN ARABLE SOILS

Acid soils are still a constraint for agrochemists as well as crop plant breeders and growers. The emerging acidity activates aluminum, which becomes harmful for crop plants at relatively high levels. Under such conditions, plant growth and the consecutive formation of dry matter are strictly controlled by nitrogen and aluminum. The boosting properties of nitrogen versus the depressing effect of aluminum are considered as agrochemical driving forces potentially regulating cropping goals. The field study (agricultural farm in Western Poland) was scheduled on the basis of the concept illustrated on the graph 1. It was assumed that the index NO3/Al-ex (ratio of nitrate to exchangeable aluminum) should be a targeted parameter for evaluating their pH-mediated geochemical interactions and the resulting effects on crop plant growth. Next, two contrasting crop plants i.e., winter wheat (Triticum aestivum L.) and sugar beet (Beta vulgaris L) were used for calibrating the biomass and elaborating ranges of NO3/Al-ex indices. On the basis of the study, four operational NO3/Al-ex ranges were elaborated and implemented within the values < 0.50 to 2.00 (for winter wheat) and < 0.35 to 1.40 (for sugar beet). Experimental sites were characterized by less favorable growth conditions, specifically for sugar beet with 85% of root biomass formed at NO3/Al-ex< 0.35. The same applies for winter wheat with slightly improved growth medium (i.e., 75% of green biomass established at NO3/Al-ex< 0.50. The NO3/Al-ex phytotoxicity index was conceived as a simple, easily applicable, but critical tool for assessing crop plant response under acidification constraints, where the "curative" application of nitrogen seems to be the sole aluminum salutary "escapement".