Effects of Zinc-Layered Hydroxide on Controlled Release of Plant Nutrients and Growth Performance of Kelempayan (Neolamarckia cadamba) Seedlings

Abstract

The loss of nutrients from conventional fertilisers is often encountered by the agricultural industry. Slow-
release fertilisers by nanotechnology application can maintain nutrient availability for effective plant
growth. Zinc-layered hydroxide nanohybrids have been little explored as controlled release systems of
functional anions, unlike the Layered Double Hydroxides (LDH) that belong to the same family of
anionic clays. The objective of the study was to investigate the effectiveness of zinc-layered hydroxide
nanohybrid containing plant nutrient anions as a controlled-release formulation. Two nano-delivery
materials namely zinc-layered hydroxide nitrate (ZLN) and zinc-layered hydroxide phosphate (ZLP) were
successfully synthesised through the co-precipitation and anion exchange methods. The PXRD patterns of
the resulting nanohybrids, ZLN and ZLP recorded basal spacing of 9.57 and 6.78Å, respectively, at a
lower 2 angles range of 0-60 o . FTIR analyses confirmed the formation of host-guest nanohybrid which
comprised the characteristic bands of nitrate and phosphate. Thermogravimetric analyses showed the
thermal stability of the nanohybrid obtained where the capability of the host material to function as a
controlled release agent was determined through a controlled release study. Controlled release of plant
nutrient sources, nitrate and phosphate from their respective nanohybrids were evaluated using various
release medium solutions. The accumulated release of guest anion from interlayer zinc layered hydroxide
(ZLH) nanohybrid into pH 4 solution was observed to be faster than pH 6.5. A higher concentration of
sodium carbonate solution showed an increase in the percentage release for both nitrate and phosphate
anions into the release medium. A plant growth trial using Kelempayan (Neolamarckia cadamba)
seedlings showed that treatment with ZLN and ZLP recorded the highest biomass weight compared to
application with commercial fertiliser and raw chemicals. The content of N, P and Zn in Kelempayan
leaves showed the highest readings for similar treatment. The study found that ZLH has acted as a good
host for inorganic plant nutrients with slow-release properties and thus has improved the growth
performance of Kelempayan seedlings with better nutrient uptake.