Dynamic of P Flux in Tropical Acid Soils Fertilized with Humic Acid–Complexed Phosphate

Abstract

Soils are characterized by high phosphorus (P) immobilization, considering the major limiting factor for agricultural production in Brazil. Phosphate fertilizers complexed with humic acids (HA) have been presented as an alternative to inhibit P immobilization in soils; however, little is known regarding its efficiency or its effect on soil P dynamics when associated with liming. The objective was to investigate labile moderately and non-labile P changes in sandy and clayey soils under application of distinct P sources and liming. Tropical soils were incubated using 200 mg kg −1 of P (simple superphosphate-SSP and SSP + HA), associated or not with calcium oxide. Check-plots were run in both soils without any P addition and/or no liming. After 60, 90, and 180 days of incubation, P contents were fractionated into P inorganic (Pi) and organic (Po), in the following pools: labile (P AER and P BIC), moderately labile (P HCl and P HID-0.1), and non-labile fractions (P HID-0.5 and P residual). There was a P flux between non-labile and labile fractions, controlled by the use of P fertilizer and liming. In sandy soil, the P addition promoted a clear P flux from non-labile to labile fractions; however, in clayey soil, there was a reverse P flux. The lack of P addition promotes a negative balance in soil with a decrease of labile fractions, mainly when associated with liming. Therefore, inputs are necessary to avoid soil P depletion.

Soil P Diffusion and Availability Modified by Controlled-Release P Fertilizers

“…However, this was not the only driver for P diffusion, since RH0 and RH13 showed similar MPAC and higher P diffusion. This may be a result of P fluxes between the soil P pools as shown by Zavaschi et al (2020). As it was observed for available P, the results depended not only on the fertilizer coating but also on the base fertilizer, since the results with TSP (Table 2) were different from those observed for SSP.…”

“…In products that release P slowly as plants grow, there is less opportunity for stronger P bond formation. It has been concluded that the use of P fertilizer with humic acid appears to be an alternative to increase labile P in the soil, by reducing P adsorption (Zavaschi et al 2020). A simpler alternative would be to cover the phosphate with humic acid.…”

Impact of Humic Acids on Phosphorus Retention and Transport

“…1 XPS analysis of pure silica sand, GS1 (goethite/silica sand w/w = 1/10), GS2 (goethite/silica sand w/w = 1/5), and GS3 (goethite/silica sand w/w = 1/3) previous researches. Studies confirmed that the ability of soil constituents to bind PO 4 3− is dominantly contributed to Fe/Al oxide and clay mineral (Gérard 2016;Zavaschi et al 2020). In Bortoluzzi et al's study, Fe/Al sesquioxide distribution controls soil P sorption capacities regardless of the environmental gradient conditions (Bortoluzzi et al 2015).…”

“…The impacts of HA on P were various in previous studies, because of different soil properties, forms of nutrient, and even the extraction methods (Mumbach et al 2020;Zavaschi et al 2020). For example, Fu et al verified higher P adsorption onto goethite was achieved with a lower pH either with the presence or absence of HA (Fu et al 2013).…”

Inoculation with Plant Growth-Promoting Bacteria to Reduce Phosphate Fertilization Requirement and Enhance Technological Quality and Yield of Sugarcane

“…Sugarcane can export approximately 30 kg P 2 O 5 to produce 100 Mg ha −1 of stalks [14]. The high adsorption of P on Fe and Al oxides/hydroxides, which normally adsorb most of the P applied in the soil [15], explains the high rate of P applied at sugarcane fields in Brazil. Withers et al [16] showed that in acid tropical soil, a rate of 80 kg ha −1 P 2 O 5 is required to overcome soil P adsorption.…”