Abstract
ABSTRACT The overloading of soil with manure or mineral fertilizers enhances phosphorus (P) availability, promoting its loss to water bodies and increasing the risk of eutrophication. In this sense, the establishment of an environmental P threshold is a simple and useful tool to classify soils regards its risk of P losses. Here we propose a P-threshold for soils from the state of Rio Grande do Sul (RS) in Brazil, with the soil clay content as the principal variable of the [...]
Highlights
The soils in the Southern region of Brazil are naturally acid and have low natural fertility (Ernani and Almeira, 1986; Bortoluzzi et al, 2015), being necessary to add correctives and fertilizers to obtain an adequate response of plants
We propose a P-threshold for soils from the state of Rio Grande do Sul (RS) in Brazil, with the soil clay content as the principal variable of the model
Will be “P-threshold = 21.787 + 0.968 × clay” and “P-threshold = 20.371 + 0.918 × clay” to define the clay through the pipette and hydrometer methods, respectively. Based on these equations and aiming at benefitting the usage of the model in agricultural properties, we suggest the adoption of the equation “P-threshold = 20 + clay” for RS soils, which is statistically equivalent to the equations obtained by both methods for the determination of clay (Figure 5a)
Summary
The soils in the Southern region of Brazil are naturally acid and have low natural fertility (Ernani and Almeira, 1986; Bortoluzzi et al, 2015), being necessary to add correctives and fertilizers to obtain an adequate response of plants. In RS, the system of swine production is defined as intensive confined, in which many animals are stocked in a reduced space (Guerini Filho et al, 2015). In such a system, the generation of a high quantity of pig slurry is a problem that must be taken into account. The legislation of Rio Grande do Sul defines that the amount of pig slurry to be applied must be based on the nutrients content and the crop needs, taking into account the resistance of the soil type regarding the environmental impact (Fepam, 2014). There are no current numeric parameters that set the superior limit of P in soil, that once crossed, would represent a high potential for environmental contamination
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