Abstract
We investigated labile P and roots distribution in the soil profile and their effect on phosphorus uptake and soybean and corn yield under different tillage systems and phosphate fertilization managements. In a long-term experiment fertilized with triple superphosphate (TSP) or reactive phosphate rock (RPR), where the fertilizer was band-applied in the crop row or broadcasted under conventional tillage (CT) or no-tillage (NT), we evaluated labile P (Bray-1) and root density distribution in depth, and crop yield, biomass production and P uptake by soybean (16th crop) and corn (17th crop). The soil disturbance in CT promoted more homogeneous soil P distribution while in NT there was a strong gradient in depth, with nutrient accumulation in the fertilizer application zone. In general, the average content of P in the 0–20 cm layer was similar for the two soil management systems and for the two application methods, but higher for TSP in relation to RPR. Root distribution of soybeans in NT and corn in both tillage systems showed a strong relationship with soil P distribution. The production of biomass, P uptake and grain yield of soybean in CT was influenced by phosphate fertilization management and generally presented lower performance than in NT, what did not occur for corn possibly due to a better P uptake efficiency compared to that of soybean. Greater stratification on the distribution of soil P and soybean and corn roots in NT did not represent any limitation on the nutrient uptake and yield of these crops, not even in the extreme case where the fertilizer was continuously broadcast on the soil surface. The influence of soil tillage management and phosphate fertilization was more evident in soybeans than corn.
Highlights
When triple superphosphate (TSP) was used, increased P contents in NT compared to conventional tillage (CT) generally occurred at 0–5 cm for broadcast application and at 5–10 cm for row application
In general the average P content in the 0–20 cm profile was similar for the two soil management systems and for the two application modes, while the TSP provided greater Bray-1 P contents in relation to reactive phosphate rock (RPR)
P availability and root density of soybeans and corn were influenced to a greater extent by the soil management system, followed by the source and mode of application of phosphate fertilizer
Summary
Despite the adoption of no-tillage (NT) in Brazilian grain production mainly due to cost reduction and tillage erosion minimization (Bolliger et al, 2006), several benefits have been attributed to this management system as compared to conventional tillage (CT), such as the accumulation of organic matter (Nunes et al, 2011a; Figueiredo et al, 2013), lower soil temperatures and moistureCrops’ Yield and Roots Response retention in surface layers (Costa et al, 2003; Martorano et al, 2009), better soil structure (Bertol et al, 2004), increased microbial activity (Mendes et al, 2003; Lopes et al, 2018) and diversity (Souza et al, 2012) and better nutrient dynamics (Santos and Tomm, 2003), resulting in a new soil fertility dynamics (Nicolodi et al, 2008). The maintenance of fertilizers and lime in the surface layers associated with cycling of nutrients by crops provides a concentration gradient of nutrients in the soil profile under NT (De Maria et al, 1999; Santos and Tomm, 2003; Calegari et al, 2013) This is especially true for P, a nutrient that presents low mobility in soil (Barber, 1995) and very low natural availability in the oxidic soils of the Brazilian Cerrado bioma (Sousa and Lobato, 2004). The intensity of this effect depends on the management of phosphorus fertilization. The use of high solubility phosphate fertilizer sources in acidic tropical soils with high P adsorption capacity allows for rapid conversion of P to less available forms to plants and possibly could have its efficiency decreased over time (Prochnow et al, 2004), in contrary to what would occur with the use of reactive natural sources, which promote gradual solubilization of phosphorus, limiting specific adsorption by clays (Novais et al, 2007) and could allow for greater fertilizer efficiency (Sousa et al, 2010; Oliveira et al, 2019)
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