Fertilizer-use efficiency is one of the most critical concerns in rice cultivation to reduce N losses, increase yields, and improve crop management. The effects of a new polymeric-coated controlled-release fertilizer (CRF) were compared to those of other slow-release and traditional fertilizers in a microscale experiment, which was carried out in cuvettes under partly controlled ambient conditions, and a large-scale field experiment. To evaluate the fertilizer’s efficiency, nitrogen and water-use efficiency were calculated using the measurement of different photosynthetic and crop yield parameters. Improved responses regarding some of the analyzed physiological and growth parameters were observed for those plants fertilized with the new CRF. In the microscale experiment, significantly increased yields (ca. 35%) were produced in the plants treated with CRF as compared to traditional fertilizer. These results were in accordance with ca. 24% significant increased levels of N in leaves of CRF-treated plants, besides increased P, Fe, Mn, and cytokinin contents. At the field scale, similar yields were obtained with the slow-release or traditional fertilizers and CRF at a 20% reduced N dose. The new controlled-release fertilizer is a urea-based fertilizer coated with lignosulfonates, which is cheaply produced from the waste of pulp and wood industries, containing humic acids as biostimulants. In conclusion, CRF is recommended to facilitate rice crop management and to reduce contamination, as it can be formulated with lower N doses and because it is ecological manufacturing.

Presently, there is a growing interest in developing new controlled-release fertilizers based on ecological raw materials. The present study aims to compare the efficacy of two new ureic-based controlled-release fertilizers formulated with water-soluble polymeric coatings enriched with humic acids or seaweed extracts. To this end, an experimental approach was designed under controlled greenhouse conditions by carrying out its subsequent field scaling. Different physiological parameters and crop yield were measured by comparing the new fertilizers with another non polymeric-coated fertilizer, ammonium nitrate, and an untreated ‘Control’. As a result, on the microscale the fertilizer enriched with humic acids favored a better global response in the photosynthetic parameters and nutritional status of wheat plants. A significant 1.2-fold increase in grain weight yield and grain number was obtained with the humic acid polymeric fertilizer versus that enriched with seaweed extracts; and also, in average, higher in respect to the uncoated one. At the field level, similar results were confirmed by lowering N doses by 20% when applying the humic acid polymeric-coated produce compared to ammonium nitrate. Our results showed that the new humic acid polymeric fertilizer facilitated crop management and reduced the environmental impact generated by N losses, which are usually produced by traditional fertilizers.

The control and development of plant growth promoters is a key factor for the agro-nomy industry in its economic performance. Different genera of bacteria are widely used as natural biostimulants with the aim of enhancing nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of their nutrients content. However, the complete exo-metabolome of the bacteria responsible for the biostimulant effect is still unknown and needs to be investigated. Three bacteria with different biostimulant effects were studied by untargeted metabolomics in order to describe the metabolites responsible for this effect. The pentose phosphate pathway, tryptophan metabolism, zeatin biosynthesis, vitamin B6 metabolism and amino acid metabolism were the highlighted pathways related to bacteria biostimulant activity. These results are related to the plant hormones biosynthesis pathway for auxins and zeatins biosynthesis. Fourteen metabolites were identified as biomarkers of the biostimulant activity. The results suggest a greater relevance of auxins than cytokinin pathways due the importance of the precursors identified. The results show a clear trend of using indole-3-pyruvate and 3-Indoleglycolaldehyde pathways to produce auxins by bacteria. The results demonstrate for the first time that 4-Pyridoxic acid, the fructosamines N-(1-Deoxy-1-fructosyl)phenylalanine and N-(1-Deoxy-1-fructosyl)isoleucine and the tripeptides diprotin A and B are metabolites related to biostimulant capabilities. This study shows how untargeted metabolomic approaches can be useful tools to investigate the bacteria exo-metabolomes related to biostimulant effects.

Increasing nutrient use efficiency of fertilizers is one of the major challenges to improve crop yields and minimize environmental impacts. This work compared the efficacy of a new ecological polymer-coated urea fertilizer and a slow release urea-based traditional fertilizer. Reductions in the N doses of the polymer-coated fertilizer were tested. A comparative study was first carried out by measuring the different physiological and yield parameters at the micro-scale level, and later-on field experiments were performed. Grain yield in the field was significantly higher (20%) when applying the new controlled-release fertilizer than when using the traditional one at the same dose. A 20% reduction in N content in the new fertilizer gave similar physiological and yield responses compared to the traditional fertilizer. We conclude that this new fertilizer can be used in extensive cropping of maize, guaranteeing at least the same yields than traditional fertilizers, with a reduction on the impact on soil properties and nitrogen losses.