Influence of filter cake associated with mineral phosphate sources on soil phosphorus dynamics in sugarcane

• Autor(a) principal: Soares, Thaís de Marchi
• Data de Publicação: 2022
• Tipo de documento: Tese
• Idioma: eng
• Título da fonte: Biblioteca Digital de Teses e Dissertações da USP
• Texto Completo: https://www.teses.usp.br/teses/disponiveis/11/11140/tde-13022023-122539/
• topic: Saccharum spp; Saccharum spp; Byproduct; Fosfato reativo; Reactive phosphate; Subproduto; Superfosfato triplo; Triple superphosphate

Increasing the phosphorus (P) use efficiency is a challenge in tropical soils because of its high P adsorption capacity, leading to excessive P inputs via water-soluble fertilizers to achieve acceptable yields. The use of filter cake (FC), a byproduct of the sugarcane industry, has shown good results in increasing the P use efficiency in the short term. We aimed to evaluate the long-term effect of FC associated with mineral P sources - triple superphosphate (TSP) and rock phosphate (RP) - on the P availability and dynamics in the soil. To track the uptake of P released in the soil solution, in Chapter 2 a method was developed to quantify P in sugarcane leaves in vivo using portable X-ray fluorescence (pXRF) spectroscopy. In Chapter 3, the release and dynamics of P from the association of FC with TSP, and RP, were evaluated in a greenhouse experiment. The treatments were: FC, TSP, RP, TSP+FC (35:65), and RP+FC (35:65). The P content in the leaves (measured by pXRF), the P concentration in the solution, and the P pools in the soil showed that the use of FC positively affected the labile and moderately labile P, and increased the RP solubility and the P content in the leaves, enabling reductions in the amount of TSP applied. In Chapter 4 the kinetics of P release by these treatments was accessed for 10 days using a column perfusion system, and the mobility, and lability of P in acidic (limed and non-limed) and alkaline soils, were evaluated in a 5-week soil incubation experiment. The FC showed a rapid P release rate and its mineralization/dissolution was facilitated in the acidic soil. In the acidic-limed soil, the reduction in the amount of P applied as TSP in TSP+FC did not negatively affect the P diffusion and availability. In this soil condition, the FC positively affects the P diffusion from RP+FC. Overall, the FC effect was not observed in the alkaline soil. In Chapters 5 and 6, was evaluated the long-term effect of FC (10 ton ha-1) associated with TSP and RP (rates of 90 and 180 kg ha-1 P2O5) on the P dynamics in the soil and on the agronomic performance of sugarcane, at Agudos (sandy soil) and Macatuba (clayey soil). In both soils, FC associated with mineral P sources reduced the P conversion into low available P forms in the soil and increased the P uptake by plants. In Agudos, RP+FC (180 kg ha-1 of P2O5) was as efficient as TSP (+ and - FC), in increasing the labile pool of P and the yield, showing that RP can replace TSP. However, in Macatuba, only TSP+FC (180 kg ha-1 of P2O5) increased the available P, and in the last harvest only TSP, both doses tested, performed better than the control. Thus, the association of FC with TSP and RP had different effects on the P release and dynamics in the soil and on the sugarcane performance, depending on the soil condition.