Barley Seeds Encapsulated in Calcium‐Alginate Gels with Phosphatase and Humate‐Phosphatase Complexes for Improving Phosphorus Bioavailability

A large portion of the soluble P fertilizers introduced into soil reacts with soil components forming insoluble P products, which are not efficiently taken up by plants. Barley seed (Hordeum vulgare L. 'Volley') encapsulation in Ca-alginate gels containing phosphatase free or immobilized with soil humates (humate-phosphatase complexes, HPC) was investigated as a tool to enhance the utilization by plants of accumulated soil P. The effect of the enzyme/carboxymethylcellulose solution ratio on the coating phosphatase activity and on seed germination was studied. A pot experiment with encapsulated seeds was conducted. Dry weight, length and shoot P content were estimated at different days after planting (DAP). Under optimal conditions (0.20 mL mL-1 free phosphatase and 0.13 g mL-1 HPC), the seed encapsulation with free phosphatase and HPC resulted in a coating phosphatase activity of 20 and 17% and in germination percentages of 92 and 85%, respectively. Increased phosphatase activity was observed in the rhizosphere of encapsulated seeds in comparison with non-treated ones. Under pot culture conditions, at 35 DAP, the inorganic P in soil planted with encapsulated seeds was higher (14-16%) than in control soil. In contrast, soil planted with treated seeds showed lower content of organic P (20-29%) than the control soil. Furthermore, the seed encapsulation significantly increased the shoot P content and the P uptake between 24 and 28% and 15 to 20%, respectively, at 35 DAP. In conclusion, seeds treated with phosphatase could substantially contribute to enhance the plant P nutrition in the early stages of seedling establishment. © 2013 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved.