Agro-process intensification using nano-structured micro-porous polymers as soil additives to enhance crop production

Abstract

Polymerised High Internal Phase Emulsion Polymer (PHP) is a nano-structured microporous polymeric material with a variety of applications. PHPs may have a role to play in sustaining or enhancing crop yields in increasingly alien environments. An elastic hydrophilic version has been developed that has been shown to increase crop yields when used as a soil additive. Soil is a natural carrier of water and nutrients as well as bacteria all of which are widely distributed in the soil and inefficiently maintained and utilised by plants. When polymer is added to the soil, water is attracted to the polymer because of its hydrophilic nature, then roots are attracted to the water and nutrients (if present) in the polymer and they become intimately associated with PHP which therefore brings the plant into close proximity with any fertiliser and bacteria loaded into the polymer. Hence the polymer promotes the interactions between water/nutrients/bacteria/plant roots as well as root exudates within microscopic scale acting as a synthetic rhizosphere which benefits the plant in three ways: (1) Efficient water utilisation and conservation by the plant thus allowing plants to grow in drier environments than would otherwise be possible. The dry weight of soybean shoots with PHP added was increased over 100% compared to plants with no PHP. (2) By adding a fertiliser component to the polymer it can act as a slow release fertiliser, releasing the fertiliser in close proximity to the plant roots, so a larger proportion is utilised by the plant rather than being leached away as normally happens when fertiliser is added direct to the soil. By modifying the production method of PHP so that it contained ammonium sulphate, a major component of many fertilisers, the dry weights of soybean shoots and pea shoots were increased by 66% and 48% respectively after 6 weeks growth. (3) By loading the polymer with beneficial bacteria and fungi, in particular nitrogen fixing bacteria and mycorrhizal fungi, it then offers a protective environment for the organisms which then have a competitive advantage over other soil organisms so their numbers can increase enabling them to make a significant contribution to the nutrient requirements of the plants, in particular nitrogen. The addition of PHP soaked with Azospirillum brasilense broth produced a dry weight increase in grass shoots of 9.6%, 9.5%, 40% and 145% after 3, 6, 9 and 12 weeks growth respectively compared to plants with no PHP or bacteria