Effect of polyvinyl alcohol to starch ratio on the nutrient release and water absorption behaviour of slow release fertiliser

Abstract

In the present study, polyvinyl alcohol (PVA) has been blended with starch to confine the fertiliser particles in the polymer matrix. NPK fertiliser particles have been embedded in polymer matrix by a solution casting method. Different weight ratios of PVA to starch, that are 7:3, 5:5 and 3:7 have been investigated. Morphologies of the samples have been studied using optical microscopy. Higher content of PVA in composition leads to a smooth surface of film. The prepared samples have been characterised by ionic conductivity measurements and water absorption tests to estimate the fertiliser release rate and water retention capacity, respectively. Sample containing higher content of PVA shows lower change in ionic conductivity and hence, lower release of nutrients in 24 h of soaking in distilled water. Among the three samples, composition having PVA to starch ratio of 5:5 shows uniform surface, higher water retention characteristics and thereby, better slow release capabilities.