Soil Phosphorus Thresholds in Evaluating Risk of Environmental Transfer to Surface Waters in Santa Catarina, Brazil

Abstract

The State of Santa Catarina, Brazil, has agricultural and livestock activities, such as pig farming, that are responsible for adding large amounts of phosphorus (P) to soils. however, a method is required to evaluate the environmental risk of these high soil P levels. one possible method for evaluating the environmental risk of P fertilization, whether organic or mineral, is to establish threshold levels of soil available P, measured by mehlich-1 extractions, below which there is not a high risk of P transfer from the soil to surface waters. however, the mehlich-1 extractant is sensitive to soil clay content, and that factor should be considered when establishing such P-thresholds. The objective of this study was to determine P-thresholds using the mehlich-1 extractant for soils with different clay contents in the State of Santa Catarina, Brazil. Soil from the B-horizon of an oxisol with 800 g kg -1 clay was mixed with different amounts of sand to prepare artificial soils with 200, 400, 600, and 800 g kg -1 clay. The artificial soils were incubated for 30 days with moisture content at 80 % of field capacity to stabilize their physicochemical properties, followed by additional incubation for 30 days after liming to raise the ph(h 2 O) to 6.0. Soil P sorption curves were produced, and the maximum sorption (Pmax) was determined using the langmuir model for each soil texture evaluated. Based on the Pmax values, seven rates of P were added to four replicates of each soil, and incubated for 20 days more. following incubation, available P contents (P-mehlich-1) and P dissolved in the soil solution (P-water) were determined. a change-point value (the P-mehlich-1 value above which P-water starts increasing sharply) was calculated through the use of

Phosphorus fractions in soil with a long history of organic waste and mineral fertilizer addition

“…Therefore, it is estimated that there was a surplus of 2; 184; 693; 796 and 865 Mg P 2 O 5 •ha −1 with the addition of SDB, PSM, LCM, and NPK, respectively. Despite P having little mobility in the soil, doses higher than those supported by the system may increase P transfer risks by runoff (Gatiboni et al 2015), and it may also migrate to deeper soil layers (Guardini et al 2012). the surface allowed the P content of the runoff to exceed the maximum permissible concentration for water class 3 (0.15 mg of P•L −1 in lotic environments), i.e.…”

“…However, when the addition of P is excessive, higher than the absorption capacity of plants and the soil adsorption, there may be losses of P by runoff or percolation in the soil profile (Rubaek et al 2013;Schoumans et al 2014;Gatiboni et al 2015).…”

Poultry Litter and Pig slurry Applications in an Integrated Crop-Livestock System

“…Specific recommendations include the development of critical P limits (Gatiboni et al, 2015) to obtain the expected benefits from the chemical, physical, and biological properties of the soil and subsequent crop yield (Mafra et al, 2014;Grave et al, 2015). The concept has been adopted that organic fertilizers help promote system sustainability and should not be regarded as a potential source of environmental pollutants (Lourenzi et al, 2013).…”

Phosphorus Fractions in Soil with Organic and Mineral Fertilization in Integrated Crop-Livestock System

“…In regions of high swine and poultry concentration, as in southern Brazil, rational use of animal waste as fertilizer mainly considers the phosphorus (P) level, and this level guides the agronomic recommendations (Gatiboni et al, 2015;CQFS-RS/SC, 2016). In addition, in the state of Santa Catarina, the nutrient limits foreseen in environmental legislation must be observed.…”