Soil phosphorus mobilization as affected by long-term organic fertilization in a tropical Regosol

Authors

• Kalline De Almeida Alves Carneiro ¹
• Tancredo Augusto Feitosa De Souza * ¹
• Gislaine Dos Santos Nascimento ¹
• Vânia Da Silva Fraga ¹
• Bruno de Oliveira Dias ¹

• Postgraduate Program in Soil Science, Centre of Agrarian Sciences, Federal University of Paraiba, Areia, 58397-000, Paraiba, Brazil

Abstract

Purpose: Phosphorus mobilization (PM) in tropical Regosols may be harmful to the environment and water quality. It is expected that high contents of soluble phosphorus in sandy soils may promote the P leaching through the transport of the available phosphorus from the soil surface to deeper layers. This study aimed to evaluate the PM in a tropical Regosol by using soil columns (10 cm depth) during steady saturated water flow and PM was correlated with Fe and Al oxides.
Method: Soil samples were collected in four sites characterized as smallholder farming systems that shared the same land uses and soil type with each other. P content was estimated by using water, Melich-1, and resin extraction protocols. We estimated the contents of Fe and Al oxides with high and low crystallinity. The miscible displacement technique was used to simulate P leaching in soil columns, and the leached P was quantified by colorimetry.
Results: Soil P loss showed a significant coefficient of determination (r2 > 0.80) with P content. We found the highest values of Fe oxalate (0.30 mg/g), and Al oxalate (0.53 mg/g) in the long-term organic fertilization, while the highest values of Fe dithionite and Al dithionite were found with the non-fertilization system.
Conclusion: The highest soil pH (8.01), soil P content by different extractors (P mehlich-1, P water, and P resin were 54.45, 14.36, and, 38.70 mg/kg, respectively), and soil P loss (128.83 mg/kg) were observed with the long-term non-fertilization system.

Highlights:

• The continuous use of higher rates of farmyard manure influences the soil chemical properties and P loss in a Regosol.
• Areas with long-term use of farmyard manure show a high rate of P mobilization.
• Areas with the addition of high rates of farmyard manure in a short-term schedule may increase P mobilization.
• The use of farmyard manure improves the organic matter accumulation, and available phosphorous, which leads to high vertical P loss.

Graphical Abstract

Keywords

• Organic fertilization
• Farmyard manure
• Phosphorus leaching
• Smallholder farming system
• Tropical Regosol