Livestock keratin waste is a rich source of protein. However, the unique structure of livestock keratin waste makes its valorization a great challenge. This paper reviews the main methods for the valorization of livestock keratin waste, which include chemical, biological, and other novel methods, and summarizes the main agricultural applications of keratin-based material. Livestock keratin waste is mainly used as animal feed and fertilizer. However, it has promising potential for biosorbents and in other fields. In the future, researchers should focus on the biological extraction and carbonization methods of processing and keratin-based biosorbents for the soil remediation of farmland.

The co-transport of contaminants by soil colloids can generate substantial environmental risk, and this behavior is greatly affected by environmental conditions. In this study, AF4-ICP-MS was used to investigate the size distribution and composition of Cd/Pb-bearing colloids; saturated sand column experiments were used to investigate the impact of soil colloids on the transport of Cd/Pb under different pH and ionic strength conditions. AF4-ICP-MS characterization showed that natural colloids were primarily associated with two sizes ranges: 0.3–35 KDa (F1, fine nanoparticles) and 280 KDa–450 nm (F2, larger nanoparticles), which mainly consisted of organic matter (OM), iron (Fe), and manganese (Mn) (oxy)hydroxides and clay minerals. Fine nanoparticles could strongly adsorb Cd and Pb under all environmental conditions. Mn and Fe (oxy)hydroxides generally formed under neutral to alkaline conditions and exhibited adsorption capabilities for Cd and Pb, respectively. Transport experiments were conducted under different pH and ionic strength conditions. At pH 3.0, soil colloids had little effect on the transport of Cd²⁺ and Pb²⁺. At pH 5.0, soil colloids inhibited the transport of Cd²⁺ by 16.1%, and Pb²⁺ recovery was still 0.0%. At pH 7.0 and 9.0, soil colloids facilitated the transport of Cd²⁺ by 15.6% and 29.6%, facilitated Pb²⁺ by 1.3% and 6.4%. At an ionic strength of 0, 0.005, and 0.01 mol L⁻¹ NaNO₃, soil colloids facilitated the transport of Cd²⁺ by 77.7%, 45.8%, and 15.6%, only facilitated the transport of Pb²⁺ by 46.2% at an ionic strength of 0 mol L⁻¹ NaNO₃. At an ionic strength of 0.05 mol L⁻¹ NaNO₃, soil colloids inhibited the transport of Cd²⁺ and Pb²⁺ by 33.1% and 21.0%, respectively. The transport of Cd²⁺ and Pb²⁺ facilitated by soil colloids was clearly observed under low ionic strength and non-acidic conditions, which can generate a potential environmental risk.

Yangchun City, a typical polymetallic ore distribution area in Guangdong Province (China), was selected as the research region to study the content, distribution, source, and possible impacts of heavy metals (HMs) (Arsenic: As; Cadmium: Cd; Chromium: Cr; Copper: Cu; Mercury: Hg; Nickel: Ni; Lead: Pb; and Zinc: Zn) on the farmland soil of this City. According to our findings, the spatial distribution of HMs in Yangchun City shows higher concentrations in the north and southeast and lower in the west and other regions. Metal content in some sampled sites of the agricultural land exceeded the soil pollution risk screening values, particularly As (7.5%), Cd (12%), Cu (4%), Hg (14.5%), and Pb (3%). Additionally, the average content of As, Cu, Cd, Pb, Hg, and Zn from the studied areas surpassed the soil background value of Guangdong Province for all metals. The absolute principal component score-multiple linear regression (APCS-MLR) was used to identify potential sources of HMs in the soil samples. There are three potential sources identified by the model: traffic emissions, natural sources, and agricultural activities, accounting for 28.16%, 16.68%, and 14.42%, respectively. Based on the ecological risk assessment, the potential ecological risk ($E_r^i$ = 310.77), Nemero pollution index (PN = 2.27), and multiple possible effect concentration quality (mPECQs = 0.23) indicated that the extent of heavy metal pollution in the soil samples was moderate. Three sources were identified: traffic emissions, natural sources, and agricultural activities. We suggest that by combining the above results, a monitoring and early warning system focused on Cd and Hg can be established. The system could utilize geographic information systems and remote sensing technologies to achieve dynamic monitoring and prediction of pollution. Regular testing of soils and sustainable management practices are also recommended to control and remediate contamination.

Soil fertility in Ghana continues to decline due to the overdependency on farm machinery to till the land coupled with the continuous application of mineral fertilizer, which has a resultant effect on agricultural non-point source (AgNPS) pollution. A two-year field experiment was conducted to evaluate the effects of different tillage methods on soil properties, nitrogen loss reduction and rice productivity of a gleysol, developed over granite. Five tillage methods—namely, zero tillage direct seeding (ZTDS), zero tillage transplanting (ZTTS), reduced tillage direct seeding (RTDS), reduced tillage transplanting (RTTS), and conventional tillage (CT)—were studied in a Randomized Complete Block Design (RCBD) with three replicates. After two cropping seasons, soil bulk density was in the order of (ZTTS = ZTDS) ˃ RTDS ˃ RTTS ˃ CT. ZTDS and ZTTS were associated with significantly higher levels of nutrients in the top soil (0–20 cm) as compared with the rest of the treatments. Plant height was in the order of CT > RTTS = ZTTS > RTDS > ZTDS. The highest grain yield was recorded by both CT and ZTTS significantly different from the rest of the treatments. ZTDS recorded the highest stover yield for both years. Subsequently, CT was associated with high release of potential pollutant loads which could lead to AgNPS pollution, as is evident from the high nutrient loss. Considering the high nutrient concentration at 0–20 cm, the reduced nutrient movement and the corresponding yield improvement, ZTDS and ZTTS are recommended for farmers in Ghana to ensure sustainable rice production, reduce AgNPS pollutant movement and ultimately provide an eco-protective and friendly environment for sustainable rice production.

The application of nanotechnology offers a promising solution to improve fertilizer utilization efficiency by mitigating the losses and volatilization of conventional fertilizers, contributing to sustainable agriculture. In this study, a core–shell nanocarbon-based slow-release foliar fertilizer (CN@mSiO2-NH2@Urea@PDA) was synthesized using nanocarbon (CN) as the core, amino-functionalized mesoporous silica (mSiO2-NH2) as the shell, and polydopamine (PDA) as the coating layer. BET analysis revealed a 3.5-fold and 1.9-fold reduction in material porosity after PDA encapsulation, confirming successful synthesis. The controlled-release performance was enhanced, with a 24% decrease in the release rate and a prolonged nutrient delivery duration. Hydrophobicity tests demonstrated a 20° increase in the contact angle, indicating improved adhesion. Seed germination assays validated biosafety, while field trials showed a 69.94% increase in the choy sum (Brassica rapa) yield, 21.64% higher nitrogen utilization efficiency, and 22.21% reduced nitrogen loss. The foliar application increased the plant nitrogen use efficiency by 18.37%. These findings highlight the potential of CN@mSiO2-NH2@Urea@PDA as an advanced foliar fertilizer, providing a strategic approach to promote nanomaterial applications in agriculture and enhance the acceptance of functional fertilizers among farmers.