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Developing efficient crop fertilization practices has become more and more important due to the ever-increasing global demand for food production. One approach to improving the efficiency of phosphate and urea fertilization is to improve their interaction through nanocomposites that are able to control the release of urea and P in the soil. Nanocomposites were produced from urea (Ur) or extruded thermoplastic starch/urea (TPSUr) blends as a matrix in which hydroxyapatite particles (Hap) were dispersed at ratios 50% and 20% Hap. Release tests and two incubation experiments were conducted in order to evaluate the role played by nanocomposites in controlling the availability of nitrogen and phosphate in the soil. Tests revealed an interaction between the fertilizer components and the morphological changes in the nanocomposites. TPSUr nanocomposites provided a controlled release of urea and increased the release of phosphorus from Hap in citric acid solution. The TPSUr nanocomposites also had lower NH3 volatilization compared to a control. The interaction resulting from dispersion of Hap within a urea matrix reduced the phosphorus adsorption and provided higher sustained P availability after 4 weeks of incubation in the soil.

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We report in this paper a strategy to prepare nanocomposite fertilizers based on the dispersion of Hap into urea and thermoplastic starch at nanoscale, where Hap was assumed as a model for poorly soluble phosphate phases, such as phosphate rocks.

The development of smart and eco-friendly fertilizers is pivotal to guarantee food security sustainably. Phosphate rock and struvite are promising alternatives for P fertilization; nevertheless, the solubility of these sources is a challenge for consistent use efficiency. Here, we propose using a polysulfide obtained via inverse vulcanization as a novel controlled-release fertilizer matrix in a system containing either Bayóvar rock (Bay) or struvite (Str). The polysulfide provides S for plants after being biologically oxidized to sulfate in soil, generating local acidity for P solubilization. After 15 days of soil incubation, the composites with 75 wt % Str and 75 wt % Bay achieved, respectively, 3 and 2 times the S oxidation from the elemental sulfur reference. Results indicated that P content stimulates the soil microorganismsʼ activity for S oxidation. The matrix had a physical role in improving Bay dissolution and regulating the rapid release from Str. Moreover, the available P in soil was 25–30 mg/dm3 for Bay composites, while for pure Bay, it was 9 mg/dm3.

In this article a nanocomposite based on starch gel, a renewable polymer, and montmorillonite clay (MMT) is proposed as a host system for the slow‐delivery of a hydrophobic herbicide loaded in very high contents (50% in total weight), where the nanocomposite structure controls the release by imposing diffusional barriers to the active compound. The herbicide release rate in water showed that nanocomposites presented higher retentions than the neat samples (herbicide‐loaded starch or MMT), revealing a cooperative or synergic effect between the constituents. Biodegradation essays also revealed this cooperative behavior, showing longer biodegradation periods for the nanocomposite than the pristine materials. Also, a two‐step release was noticed, where the first step was controlled by starch (short periods) and the second was played by MMT (longer times). The nanocomposite structural analysis gave evidence that the release behavior is governed by the interaction between the constituents, even at very high herbicide contents. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 41188.

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