Phosphorus in agriculture is an essential, limited, and strategic resource, and its sustainable management is a global challenge. Phosphorus (P) recovery as struvite (NH ₄ MgPO ₄ .6H ₂ O) from manures and municipal and agro-industrial wastewaters has been considered one of the most sustainable technologies, based on the circular economy, to face challenges regarding P reserves and its use for conventional fertilizer production. Struvite is a slow-release P-fertilizer (5 % N, 12 % P, 10 % Mg), which could significantly reduce the Brazilian dependency on fertilizer imports. We found a large number of recent studies that show its predominant application for temperate and Mediterranean regions. However, its potential as a fertilizer and better use for subtropical and tropical regions, such as Brazilian agriculture, is still unknown. We highlight that: (i) crop responses reported were quite variable with few field studies carried out; (ii) the crop yield expected may be on average 10 % below those in soluble P sources; (iii) a potentially high residual effect should be effectively measured; (iv) promising use of struvite mixed with soluble P-fertilizers to produce high yields; (v) higher efficiency than manure, composts or phosphate powder rocks. In fact, there is a lack of studies carried out on subtropical and tropical soils and climates; none were found in Brazil. Therefore, the lack of studies on Brazilian soils is a barrier to a precise evaluation of struvite as a fertilizer for Brazil’s agricultural systems, especially for acidic Oxisols and no-till systems. Finally, struvite production from swine wastewater can expand in specific states in the South, Southeast, and Midwest of Brazil, where the swine production is concentrated. S truvite production technology might be easily adopted and affordable for medium- to large-scale confined swine operations, which could yield some 300,000 Mg of struvite per year.

The effect of this plant study was determined by the application of different nutrient solutions and increasing doses of dry mass and pots potential on aerial production of corn plants grown in a sample content of a Red-Yellow Latosol in pots under greenhouse conditions. The treatments consist of three nutrient solutions, the treatments of additional doses (K) and a solution that received neither nutrient nor K application. The root quadratic model is the most suitable among the results to describe a dry mass production of corn plants as a function of the K dose.

Widespread use of soluble mineral fertilizers derived from non-renewable sources has raised concerns about environmental impacts, energy expenditures, and sustainability. Combining biosolid and mineral sources of phosphorus and potassium to produce organomineral fertilizers (OMF) can be used as an alternative nutrient source while reducing the environmental impact of sewage residues. As this approach simultaneously provides nutrients and incorporates organic matter, we hypothesized the presence of an organic source (biosolid) granulated with mineral sources of potassium (K) and phosphorus (P) would reduce leaching due to the benefits of the organic source and the slower release caused by granulation. Our goal was to evaluate the effect of different OMFs on the leaching losses of nutrients. Two forms of isolated N, P, and K sources (granulated and non-granulated), five OMFs with different NPK proportions (1-2-0, 1-4-0, 1-0-2, 1-2-2, 1-2-4), and a control (unfertilized) were evaluated over ten weeks in a leaching column experiment. Non-granulated potassium sulfate exhibited the highest K leaching and did not differ from OMFs with K in their formulation (granulated PS, 1-0-2, 1-2-2, and 1-4-2). Planned contrasts showed that granulation was particularly effective at reducing K leaching, resulting in a 70 % reduction compared to non-granulated PS. While formulation and granulation showed a trend of potential benefits in reducing N-(NO ₃ ^- + NO ₂ ^- ) leaching, the effect was not statistically significant. Interaction between fertilizer treatments and leaching events was marginally significant for NH ₄ ⁺ leaching, indicating temporal variations of OMFs in nutrient dynamics may be influenced by mineralization. As granulation modulated how OMFs affected nutrient leaching dynamics, this highlights the importance of the physical characteristics of fertilizers for effective nutrient management.

Purpose: This study aimed to evaluate the agronomic efficiency of nanoparticle suspension fertilizers containing Ca, B, Mg, and Zn when applied by foliar fertilization to maize in contrast to commercial product and reagent grade salts. Methods: We conducted two greenhouse experiments, with and without soil fertilization with B and Zn, to evaluate the effects of four foliar treatments: a test suspension, a commercial product, a reagent grade salt, and control. We evaluated the plant height, leaf number, stem diameter, SPAD index, and dry mass of the aerial parts and roots. Additionally, we determined the contents and accumulation of K, Ca, Mg, B, Fe, Mn, and Zn in the aerial parts. Results: The commercial and test suspension products increased the stalk diameter. Under conditions with soil-applied boron, the commercial product and the Ca/B suspension were most effective, promoting greater accumulation of K, Ca, Mg, and B in the aerial part. Overall, the suspensions containing Ca, B, Mg and Zn presented agronomic efficiencies comparable to those of the other products evaluated. Conclusion: Foliar application of Ca, B, Mg or Zn alone was not enough to meet the nutritional requirements of maize in soils with low availability of B and Zn. The commercial product outperformed the suspensions, especially when integrated with soil B and Zn fertilization. The best agronomic responses were associated with this combined soil and foliar approach. The tested suspensions require optimization to match the efficiency of established commercial formulations. This study reinforces the strategic importance of integrated nutrient management.