Abstract
Little is known about the effect of nitrogen (N) application via biochar on the removal of trace elements by crops, and the effects with chemical fertilizers are inconsistent. We determined, from a previous study, the influence of increased N addition via biochars produced from switchgrass (SGB) and poultry litter (PLB) on cadmium (Cd) removal by ryegrass. The biochar rates of 0, 0.5, 1, 2, and 4% w/w were applied to a Cd-contaminated soil before seeding in a potting experiment with a complete randomized block design (CRBD). Ryegrass yield and N and Cd removed by harvest were strongly related (p < 0.05). The ryegrass yields increased up to 1% of PLB, and Cd removal was also the highest at 1% of PLB. The biomass of ryegrass roots increased with Cd accumulation (p < 0.05). Overall, the Cd transfer factor (TF) from ryegrass roots to shoots increased when up to 206 ± 38 kg N ha−1 was removed in ryegrass shoots (p < 0.0001). The application of PLB up to 1% might be a viable option since it is a practical rate for handling operations requiring less volume of material than SGB. Additionally, the Cd concentration in the aboveground forage remained acceptable for grazing cattle. Future studies are encouraged to evaluate different sources of N fertilizers affecting Cd uptake on cash crops.
Highlights
Human activities have gradually transferred many toxic metals from the earth’s crust to the environment, resulting in the spread and contamination of toxic metals in the ecosystem [1,2,3,4]
As highlighted in the previous work of Antonangelo and Zhang [11], the ryegrass shoots, roots, and whole plant yielded better when treated with poultry litter-derived biochars (PLB) presenting, on average, an increase of 64, 51, and 59% respectively when compared to those treated with SGB (Table 2)
The Cd accumulation in ryegrass plant parts decreased with biochar application rates regardless the feedstock from which the biochar was produced (Table 2)
Summary
Human activities have gradually transferred many toxic metals from the earth’s crust to the environment, resulting in the spread and contamination of toxic metals in the ecosystem [1,2,3,4]. The metals originate from many sources including mining activities, industrial waste disposals, paints, and gasoline additives that lead to physical and chemical processes such as leaching and oxidation causing the accumulation of metals in the soil. Toxic metal pollution has become a serious problem worldwide in the last decade. Cadmium (Cd) is considered the most toxic element among toxic metals for living organisms and has been detected in some agricultural lands [1]. It is important but challenging to remediate Cd-contaminated soils worldwide
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