Abstract:
The increasing population has led to a rise in global food demand, which has put
immense pressure on the agricultural soils to boost crop yield. This has urged farmers
to resort to the utilization of excessive amounts of urea fertilizer to match the demand.
However, highly volatile and soluble nature of urea has resulted in various forms of
environmental pollution, leading to low Nitrogen use Efficiency (NUE). Moreover, Zn
deficiency in soil has also emerged as a growing concern, causing low crop productivity
and nutritional value which eventually translates to Zn malnutrition in humans. This
study aimed to address both the issues by developing a Zn fortified, controlled release
urea fertilizer. A dual-coated urea was formulated featuring an inner coat of bio-based
polyurethane and an outer coat of ZnO loaded mesoporous nanosilica particles
(MSN@ZnO) embedded in a hydrogel matrix. FTIR, XRD, BET and SEM-EDX were
employed to ensure successful synthesis of MSN and MSN@ZnO. Then to assess and
optimize the N release of the bio-polyurethane coated urea (BPCU) and dual-coated
urea (DCU), water and sand column release tests were performed. The results of Total
Kjeldahl Nitrogen (TKN) revealed that coating urea, with both the layers decreased its
nitrogen release. In water release tests, BPCU and DCU gave a cumulative N release of
71% and 68% respectively on day 28 and in sand column release tests BPCU and DCU
gave a release of 73% and 68% respectively on day 28. This indicated viability of the
coatings. Then to test for Zn release from DCU, Atomic Absorption Spectroscopy
(AAS) was performed, the results of which demonstrated a burst release of Zn in water,
whereas, in sand a prolonged micronutrient release profile was observed, extending up
to 7 days. Hence, this study demonstrated a viable solution to combat two of the most
concerning issues related to agriculture. For prospects, it is recommended to study the
biodegradability of the coatings done and to assess the release of N and Zn from coated
urea fertilizer in real-world environment.
