Synthesis and Characterisation of Novel ι-Carrageenan Hydrogel Blends for Agricultural Seed Coating Application

Abstract

Radical science and innovation in farming is vital to produce the food that the world will need by 2050. To feed an estimated world population of nine billion people in 2050, 70 % to 100 % increase in food production will be required if it continues rising at the current rate. The aim of this project is to develop novel revolutionary super absorbent hydrogel coatings for agricultural use. Hydrogel seed coatings improve the rate of seed germination and emergence and enhance seed survival during critical development periods, especially under less than optimal conditions. Preliminary work withι-carrageenan hydrogel showed a promising results including higher seed germination rates, faster plant emergence, lower water requirement, enhanced root development and potential carrier of nutrients. Two hydrogel blends – agar/ι-carrageenan and xanthan/κ-carrageenan/ι-carrageenan – were synthesised and characterised in this project as potential seed coating materials based on their biodegradable, non-toxic sugar based natural polymers and their excellent water absorbing/holding capability. The newly formulated hydrogels were characterised by swelling studies, rheological measurements and infrared spectroscopy. It was found that the addition of xanthan/κ-carrageenan intoι-carrageenan hydrogel improved the water absorbing capacity from 117.90 % to 139.05 %, the life-span of the hydrogel from 6 hr to 24 hr in excess water and the gel strength from 108.4 Pa to 267.98 Pa. The addition of agar intoι-carrageenan showed an increase in gel strength and a greater improvement in water holding capacity giving 67.33 % water content whileι-carrageenan on its own had only 39.64 % after 72 hr of incubation at 30 °C, which showed higher potential to be used in drought conditions. The ATR-FTIR results proved that the hydrogels were physically cross-linked. A further evaluation such as the germination profile test is required to test the effectiveness of the hydrogel coatings on seeds. It is anticipated that this work will be extended to coating different seed varieties in the future with these newly developed hydrogels.