Sustainable crop fertilization by combining biogenic nano-hydroxyapatite and P solubilizing bacteria: Observations on barley
Laura Pilotto, Mônica Yorlady Alzate Zuluaga, Francesca Scalera, Clara Piccirillo, Luca Marchiol, Marcello Civilini, Youry Pii, Stefano Cesco, Guido Fellet
Abstract
Nano-enabled agriculture involves researching smart nano-agrochemicals for sustainable farming. Nano-hydroxyapatite (nHAP), a phosphorus-rich compound, has the potential to be used as a fertilizer with reduced environmental impact. This study tests the effectiveness of nHAP produced from waste materials (animal bones) on barley plants ( Hordeum vulgare ). Two different nHAPs were prepared by thermal treatment of chicken bones at 300 °C and 700 °C (nHAP 300 and nHAP 700 , respectively). The nanopowders were then tested in a seed toxicity trial and in a greenhouse pot experiment with barley, using Pseudomonas alloputida , a P-solubilizing bacterium (PSB). The treatments were unfertilized soil, conventional triple superphosphate (TSP), and the nHAP treatments alone. The results indicated that: (i) the nHAP materials had particle sizes of 1 micrometer (nHAP 300 , due to aggregation) and 50–70 nm (nHAP 700 ), with P contents of 12.8 % and 19.6 %, respectively; (ii) no toxicity was observed on barley seeds, and nHAP 300 at maximum dose stimulated root length by 45.6 % compared to the control; (iii) compared to conventional P fertilizer TSP, nHAP 300 and nHAP 700 stimulated root growth by 7 % and 18 %, respectively; (iv) the fraction of available P produced through nHAP 300 -PSB (40.6 mg kg −1 ) was higher than that from TSP (39.2 mg kg −1 ); (v) ions associated with the nHAP structure supplied supplementary nutrients, predominantly allocated in root tissues. This study provides valuable insights for future investigations to assess the implications of P nano-fertilizations in achieving sustainability in agriculture.