Prof. Moshe Shenker, Prof. Yona Chen, and Prof. Daniel Mandler; The Hebrew University of Jerusalem
| Category | Agriculture and fertilizers industry. |
| Keywords | Fertilizer; Phosphorus; Soil chemistry. |
| Current development stage | General list: TRL3 Experimental proof of concept |
| Collaboration Opportunity | Sponsored Research with an option to License Research Results |
Abstract
In many agro-ecosystems, all the existing fertilizers fail to increase P availability in the root-zone depth. We propose here “new-generation” P-fertilizers to solve this problem.
Background
Phosphorus (P) fertilizers are among the most commonly used fertilizers needed for crop production. Phosphorus is consumed by plants as phosphate, which is the form released by P fertilizers, however, phosphate mobility in soils is very low. As such, in orchards and no-till agro-ecosystems where ploughing is not applicable P from all the existing fertilizers is retained in the soil upper layer, largely reducing P efficiency, increasing P loss, and promoting eutrophication in downstream surface waters. In many parts of the world, regulations largely restrict P fertilization in sensitive zones. Further, P natural resources are limited and extinction of global nonrenewable reserves is expected to occur within a few decades.
We postulate that increasing P mobility in soils will: (1) increase its availability to the plants roots, thus increase P use efficiency for the farmers and reduce mining of the limited global P reserves; (2) decrease P enrichment of surface soil, thus decreasing P loss from fertilized land and reduce the risk of downstream surface water eutrophication; (3) allow P fertilization in agricultural land in sensitive regions where otherwise P fertilization is banned, thus allowing intensive crop production in these regions. All in all, the suggested approach will increase sustainable P fertilization, will increase yields, and will protect the environment and preserve the limited natural resources of this nutrient.
Our Innovation
- We propose P-bearing nanoparticles with chemically modified particle surface to allow mobility in soils. Selecting proper characteristics will keep particle stability in the bulk soil, and enable reaching the rhizosphere in the plant’s roots. P nanoparticles were prepared with different size, shape, stability, and surface charge.
- Modified particles were shown to have increased mobility in high-pH clayey soil (Terra-Rossa) and in acidic soil (Oxisol from Brazil).
- The nanoparticles were shown to act as available P source for plants grown in hydroponics.
Technology
The basic idea is presented in Fig. 1 showing the limitation of the available P fertilizer (left) and the expected improved function of the mobile “New generation” nano-P-fertilizer (right).
Nanoparticles should retain their shape and integrity to penetrate into the dry soil depths via air-filled pores in the soil. Once in the depth of the effective root-zone, the nanoparticles need to solubilize to make the nutrients available to the plants.
The particles mobility was tested in water-saturated and unsaturated states of a few soil types. While the saturated state represents transport downwards with percolating irrigation water, the unsaturated state represents transport from the bulk soil to the rhizosphere. This test was performed in a few soil types, of different clay content and soil pH, to represent different soil types and different regions of the globe (the potential market for the product). Sample results are shown in Fig. 3 for transport in high-pH Terra Rossa and in Low-pH Oxic soil from Brazil. In each soil hydroxyapatite particles (190 nm, slightly above the nano scale) stabilized by polyacrylic acid (PAA) were compared to soluble P (phosphate), each with two replicates. For both soils, P transport was much improved by our approach of the “New-generation” P fertilizer. For the acidic soil this effect was much more pronounced.
In fig. 2, the solubilities of a selection of a few P minerals are shown at two pH values, representing acid and alkali soils in which P deficiency is common. It is evident that the selection may differ according to the target soil (i.e., the target market, regions of acid soils or region of alkali soils).
So far, we synthesized and tested nanoparticles of hydroxyapatite and b-Ca-P with varied characteristics of size, ranging from about 30 nm to 500 nm, in spheric rod-like shapes, and with modified surface charge (z-potential), ranging from +50 mV to -50mV. Struvite was tested as well, but at larger particle size.
Opportunity
If successful, the proposed approach is expected to be a breakthrough in optimization of P fertilizer use, increasing its use efficiency while decreasing its negative foot prints on the environment. The global market for such a product might be huge. A successful study and understanding will further allow adjustment of the “new generation” fertilizer to meet characteristics of different soils and agrosystems.
Patents and Publications
Zhang, Z., Y. Chen, D. Mandler, M. Shenker. 2023. Transport of hydroxyapatite nanoparticles coated with polyacrylic acid under unsaturated water flow in soil columns. Soil Sci. Plant Nutr. doi.org/10.1080/00380768.2022.2163457.
