ZINC DYNAMICS IN AN ARABLE SOIL AS AFFECTED BY PLANT RESIDUES INCORPORATION: AGROENVIRONMENTAL CONCERN

摘要

Laboratory experiments were carried out in order to examine the effects of plant residues (PR) incorporation into an arable soil and different zinc (Zn) rates on its dynamics in the soil and the agroenvironmental concern of these interactions. Soil (light loamy sand) for the experiment as well as sugar beet leaves (SB) and wheat straw (WS) were collected from an Experimental Station belonging to the University of Life Sciences (Poznan). Plant residues were added to soils at 1 % (dry weight basis) and three treatments (triplicated) were set: without plant residues (-PR), 1% SB and 1% WS preincubated at 20℃ for 180 days. After this date, zinc (as ZnSO_4) was applied at rates 0, 50, 150, and 250 mg kg~(-1). The incubation proceeded for next 107 days and soil samples for chemical assays were collected at 35 and 107 days. Zinc dynamics evaluated by batch studies showed that SB treatments exhibited high buffering capacities and consequently Zn was wholly sorbed, irrespective of its rates. In the case of the WS treatments, desorption processes took place and at 35 days of incubation, varied from -25.2 to -52.3 mg kg~(-1), respectively for the rates 150 and 250 mg kg~(-1). At 107 days, the range was from -19.6 to -58.8 mg kg~(-1) for the same Zn rates. Bioavailable Zn pools (0.10 mole NaNO_3) used for evaluating the agroenvironmental impact showed that aqueous-based microbial activity thresholds should be applied with restrictions. Therefore the use of bioavailable Zn forms for this purpose may be recommended, mainly for arable soils and other ecosystems.