Coating of nonwovens with potassium nitrate containing carboxymethyl cellulose for efficient water and fertilizer management

This paper presents the generation of an innovative agrotextile material possessing a controlled fertilizer release with an improved water absorption/retention property. To this end, nonwoven fabrics were coated with carboxymethyl cellulose/potassium nitrate solutions. Coatings were carried out on polyvinyl alcohol pre-coated and non-pre-coated structures. Citric acid was used as the cross-linker for carboxymethyl cellulose. Fertilizer release from the coated nonwoven structures was calculated as cumulative percentages from nitrate nitrogen amounts measured by a UV/Vis spectrophotometer. In addition to morphological and structural analyses, the gel fraction (degree of cross-linking), water absorbency and water retention capacity of the generated materials were investigated. Usage of citric acid cross-linked the carboxymethyl cellulose polymer chains. The best results were obtained with the pre-coated structure together with 10 wt% citric acid. Pre-coating with polyvinyl alcohol acted as a supporting layer for carboxymethyl cellulose to form a quite compact layer on the nonwoven fabric and thus enabling increased water absorption (up to 4000%) and water retention capacity (up to 46 h). Also, the fertilizer release profile was improved markedly (starting with a release value of 28% and reaching a value of 75% after the 19th irrigation). These property enhancements would result in decreased amount of water and fertilizer and thus contribute to sustainable agriculture.