The effectiveness of poly(isosorbide carbonate) (PIC)—a bio-based polycarbonate synthesized from isosorbide (ISB)—degradation products in complex soil environments remains unverified. In the present study, the agricultural potential of PIC ammonolysis products—comprising urea and ISB—as a nitrogen (N) fertilizer was evaluated in a soil system. A pot experiment was conducted using komatsuna (Brassica rapa var. perviridis) to compare PIC degradation products with commercial urea, a urea and ISB mixture, and a no-N control. Application of PIC degradation products significantly enhanced plant growth, yielding fresh weight and N uptake comparable to those associated with commercial urea. The calculated N recovery efficiency for the PIC degradation products was 50%, falling within the typical range (30–60%) for inorganic fertilizers. Contrary to previous in vitro study results, ISB exhibited no significant biostimulant effect in the soil environment, likely owing to rapid microbial degradation. These findings serve as a preliminary proof-of-concept that PIC degradation products are a highly effective and bioavailable N source. Overall, the results suggest that if scaled appropriately, PIC ammonolysis products could contribute to circular use pathways for this specific plastic. Nonetheless, further studies across a broader range of crops and soils are required to confirm the generalizability of these results.

Acidic subsoils can restrict root growth and nitrogen (N) uptake and increase the risk of N loss; however, the extent of genotypic variation remains unclear. We evaluated two bread wheat cultivars, Haruyokoi and Harukirari, and one spelt line, KU-1025, under limed and acidic subsoil treatments to clarify whether maintaining root growth in acidic subsoil contributes to greater N capture and lower N loss. After 78 days, we measured shoot dry weight, shoot N uptake, root dry weight, total root length, soil nitrate (NO₃-N) concentration, and cumulative N leaching. The acidic subsoil reduced shoot N uptake, root length in the subsoil, deep-root ratio, and NO₃-N depletion, indicating that it restricted root proliferation and N acquisition. KU-1025 showed the greatest shoot dry weight, shoot N uptake, root dry weight, and total root length under both treatments. It also maintained a high deep-root ratio under acidic subsoil conditions and showed lower soil NO₃-N concentrations and less N leaching than the two wheat cultivars. Across genotypes and treatments, shoot N uptake was positively correlated with root dry weight and total root length, whereas N leaching was negatively correlated with these traits. These results suggest that maintaining a large root system, rather than deep rooting alone, is important for improving N capture and reducing N loss under acidic subsoil conditions, and that KU-1025 may provide useful genetic variation for breeding wheat adapted to acidic subsoil environments.

Currently, for land-based agriculture, such as rice propagation in paddy fields in Japan, there is rapid expansion in field area at the scale of a single farmer (or farming organization) and at the...

Plastics have long been designed as durable materials with limited consideration of their fate after use. In contrast, a polymer system that enables end-of-life plastics to no longer to be discarded but instead to be transformed into fertilizers that actively benefit ecosystems, would be very desirable indeed. Such a concept may offer a new direction for polymer design and expand the potential roles of plastic materials. In our previous studies, we demonstrated that isosorbide-based polycarbonates (PIC) can be converted into fertilizer-compatible components through ammonolysis after use. Building on this concept, the present study introduces dual-functional isosorbide-based plasticizers that simultaneously reduce the brittleness of PIC while also being convertible into fertilizer-compatible components through ammonolysis after use. The effectiveness of the degradation products obtained from this plastic system, composed of PIC and isosorbide-based plasticizers, as fertilizers was validated through the growth of both a model plant and an edible vegetable.