Chitin-enriched compost to increase soil moisture retention and resilience against drought

Abstract

Intensified droughts under future climate are threatening agricultural production in Western Europe. As a consequence, there is a growing interest in soil amendments that have the capability to enhance the water storage capacity of soils, increasing their resilience against drought. Chitin is a natural biopolymer known to hold potential to improve soil moisture retention. Considering the variable success of compost on soil hydrological properties documented in literature, enriching compost with a soil amendment such as chitin could potentially improve the functioning of the compost. An eight-week pot experiment with lettuce as test crop was set up under greenhouse conditions where multiple treatments consisting of a sandy loam soil mixed with 1 g kg⁻¹ or 2 g kg⁻¹ of crude chitin in its pure form, mixed with compost as chitin-enriched compost, and three types of pure compost were tested under two water regimes. The addition of crude chitin without compost, after this referred to as pure chitin significantly increased the readily available water defined as the macro-mesoporosity (30 µm – 3 µm) and the plant available water after this referred to as the mesoporosity (30 µm – 0.2 µm) under water regime 1, which comprised a sudden, dry period halfway the growing period of the crop. Under this water regime, the treatment with chitin-enriched compost resulted in a significant improvement in macro-mesoporosity and mesoporosity, when compared to the unamended compost. A different trend was obtained under the second water regime, featuring a cyclic pattern of dry periods, which points to the importance of the environmental conditions with regard to the functioning of chitin. These results highlight the potential of chitin-based amendments to enhance soil water retention properties, with their effectiveness strongly influenced by the prevailing water regime.