Macro- and Micronutrient Simultaneous Slow Release from Highly Swellable Nanocomposite Hydrogels

Abstract

Clay-loaded hydrogels have been arousing great interest from researchers and academics due to their unique properties and broad applicability range. Here we developed hydrogel-based nanocomposites intended for slow/controlled release of macro- and micronutrients into independent or concurrent systems. The produced nanocomposites underwent a hydrolysis treatment that improved their physicochemical properties. We obtained materials capable of absorbing water contents 5000 times greater than their weights, an outcome that makes them promising, particularly if compared with commercially available materials. Though swelling degree was affected by the presence of calcium montmorillonite (MMt), MMt has increased nutrient (urea and boron) loading capacity and, as a consequence of its interaction with the studied nutrients, has led to a slower release behavior. By evaluating the simultaneous release behavior, we observed that both the ionic (sodium octaborate) and the nonionic (urea) sources competed for the same active sites within the nanocomposites as suggested by the decreased loading and release values of both nutrients when administrated simultaneously. Because of its great swelling degree, higher than 2000 times in water, the nanocomposites formulated with high MMt contents (approximately 50.0% wt) as well as featuring high loading capacity and individual (approximately 74.2 g of urea g(-1) of nanocomposite and 7.29 g of boron g(-1) of nanocomposite) and simultaneous release denote interesting materials for agricultural applications (e.g., carriers for nutrient release).

Growth of tomato seedlings in substrates containing a nanocomposite hydrogel with calcium montmorillonite (NC-MMt)

“…These amounts of hydrogel NC-MMt employed in the present study followed the recommendations derived from previous assays (Bortolin et al, 2016) and are in agreement with the quantities reported in literature for other vegetable crops such as cauliflower (Castoldi et al, 2016).…”

“…Nc-MMt hydrogel was synthesized utilizing PAAm (polyacrylamide compression) and biodegradable polysaccharide CMC (carboxymethyl cellulose) with molecular weight = 90,000 g mol −1 , 0.7 carboxymethyl groups per anhydroglucose unit (data provided by Sigma-Aldrich). In this sense, the hydrogel (1:1) contains ≈ 50% MMt (Bortolin et al, 2016). Three rates of hydrogel NC-MMt (on w w -1 basis) were employed; they corresponded to the second factor, being: 0% (control), 1.5% and 2.0%.…”

“…A n i n n o v a t i v e t e c h n i q u e for NC production using calcium montmorillonite (MMt) allowed the development of a new class of hydrogels with great swelling degree (higher than 2,000 times in water) (Bortolin et al, 2016). This new NC is formulated with a high content of MMt (≈ 50% wt) and it has high loading capacity and displays slow release of macro-as well as micronutrients when they are incorporated in the hydrogel synthesis or through fertigation (Bortolin et al, 2016). Therefore, this NC-MMt hydrogel may represent an interesting crop management tool, which could be suitable for a wide array of agricultural applications (Bortolin et al, 2016).…”

“…This new NC is formulated with a high content of MMt (≈ 50% wt) and it has high loading capacity and displays slow release of macro-as well as micronutrients when they are incorporated in the hydrogel synthesis or through fertigation (Bortolin et al, 2016). Therefore, this NC-MMt hydrogel may represent an interesting crop management tool, which could be suitable for a wide array of agricultural applications (Bortolin et al, 2016).…”

Why nonconventional materials are answers for sustainable agriculture

“…Even with that reduction, it is noteworthy that these systems keep a relative nutrient:adjuvant (the nanocomposite) relationship higher than 2, which is still possible for practical applications. 120 Increasing the solubility: the particle size effect…”