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

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 plantgrowth. Zinc-layered hydroxide nanohybrids have been little explored as controlled release systems offunctional anions, unlike the Layered Double Hydroxides (LDH) that belong to the same family ofanionic clays. The objective of the study was to investigate the effectiveness of zinc-layered hydroxidenanohybrid containing plant nutrient anions as a controlled-release formulation. Two nano-deliverymaterials namely zinc-layered hydroxide nitrate (ZLN) and zinc-layered hydroxide phosphate (ZLP) weresuccessfully synthesised through the co-precipitation and anion exchange methods. The PXRD patterns ofthe resulting nanohybrids, ZLN and ZLP recorded basal spacing of 9.57 and 6.78Å, respectively, at alower 2 angles range of 0-60 o . FTIR analyses confirmed the formation of host-guest nanohybrid whichcomprised the characteristic bands of nitrate and phosphate. Thermogravimetric analyses showed thethermal stability of the nanohybrid obtained where the capability of the host material to function as acontrolled release agent was determined through a controlled release study. Controlled release of plantnutrient sources, nitrate and phosphate from their respective nanohybrids were evaluated using variousrelease 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 ofsodium carbonate solution showed an increase in the percentage release for both nitrate and phosphateanions 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 toapplication with commercial fertiliser and raw chemicals. The content of N, P and Zn in Kelempayanleaves showed the highest readings for similar treatment. The study found that ZLH has acted as a goodhost for inorganic plant nutrients with slow-release properties and thus has improved the growthperformance of Kelempayan seedlings with better nutrient uptake.