Development and Agronomical Validation of New Fertilizer Compositions of High Bioavailability and Reduced Potential Nutrient Losses

Abstract

To optimize the economical cost of each unit of fertilizer applied and to reduce the environmental contamination caused by nutrient losses, the development of highly efficient granulated fertilizers is of great importance. This study proposes a strategy that consists of developing specific fertilizers having nutrient release patterns that are dependent on plant activity in the rhizosphere. This type of fertilizer is named "rhizosphere-controlled fertilizer" (RCF fertilizer). This fertilizer is based on the introduction of an organomineral matrix composed of metal [Mg (Ca is also possible), Zn (Fe and other metals are also possible)]-humic phosphates. The presence of this matrix modifies the nutrient release pattern of the fertilizer. In this way there are two main nutrient fractions: (i) a water-soluble fraction or "starter" fraction and (ii) a "rhizosphere-controlled" fraction insoluble in water but soluble by the action of the rhizospheric acids released by plants and microorganisms. This study shows the chemical and structural characterization of the organomineral matrix, as well as its efficiency in slowing the nutrient release rate of the RCF fertilizer, principally with respect to P and N. It is demonstrated how these properties of the matrix were also reflected in the significant reduction in both ammonia volatilization and N leaching in a pot system consisting of wheat plants cultivated in a calcareous soil and fertilized with a RCF fertilizer.

Incorporation of humic-derived active molecules into compound NPK granulated fertilizers: main technical difficulties and potential solutions

“…Obtained humic-metalphosphate complexes were only partially soluble in water but totally soluble in rhizospheric root exudates and neutral ammonium citrate (an indicator of potential P availability for plants) [47,49]. The main interest of compound fertilizers based on these types of complexes is that their potential soil fixation (P retrogradation) and leaching are very low due to their low water solubility, while they are able to provide available P for plants [46,47].…”

“…A number of studies have shown that the simultaneous reaction of phosphoric acid with alkaline compounds containing Mg (MgO products), and metals (for instance, Zn or Fe oxides or carbonates) in the presence of specific amounts of potassium or sodium salts of humic acids produced humic-double metal-phosphate complexes [47]. These complexes were identified in solid matrices using 31 P-NMR as described in Riggle and von Wandruska [42] and Erro et al [48].…”

“…The main interest of compound fertilizers based on these types of complexes is that their potential soil fixation (P retrogradation) and leaching are very low due to their low water solubility, while they are able to provide available P for plants [46,47]. However, plant roots need to interact in some way with fertilizer granule to solubilize phosphate by the action of root exudates [46,47] (Fig. 9).…”

FERTILIZANTES DE LIBERACIÓN CONTROLADA APLICADOS AL ESTABLECIMIENTO DE Pinus radiata D. DON EN CHILE

“…Por ello, la aplicación de estos fertilizantes se realiza normalmente con dosis inferiores a aquellas de los fertilizantes hidrosolubles tradicionales. Por otra parte, los FLC pueden disminuir el impacto ambiental por lixiviación o volatilización de elementos nutritivos y, dada su relación costo-eficiencia, también son econó-micamente rentables en muchos cultivos (Erro, Urrutia, San Francisco, & García-Mina, 2007;Iyer, Dobrahner, Lowery, & Vandettey, 2002).…”

“…Therefore, the application of these fertilizers is normally at lower doses than those for traditional water-soluble fertilizers. Furthermore, the CRF can reduce leaching or volatilization of nutrients of environmental impact, and given their cost-effectiveness, they are also cost-effective in many crops (Erro, Urrutia, San Francisco & García-Mina, 2007;Lyer, Dobrahner, Lowery, & Vandettey, 2002). The CRF's use in Chile has been limited because the cost per unit item exceeds that of traditional soluble fertilizers.…”