Phosphorus downward movement in soil highly charged with cattle manure

In the rolling pampa region, the intensification of beef cattle feeding operations generates large volumes of solid organic manure which has high concentrations of phosphorus (P). This residue can be reused like organic fertilizer in agricultural practices, increasing crop production and closing the nutrients cycle. However, this practice can cause water pollution if not well managed. The aim was to study the vertical and temporal migration of P and its relations with edaphic properties in agricultural soil that has received a single heavy application of cattle manure. Three treatments were analyzed: (1) Zone 4 (Z4)—plot manured with 1600 tn ha⁻¹ in 2004; (2) Zone 10 (Z10)—plot manured with 500 tn ha⁻¹ in 2010 and (3) Zone control (ZC)—plot free of cattle manure. Water extractable phosphorus—WEP, soil test Bray and Kurtz P—Bray P, total phosphorus—TP, organic carbon—OC, pH and electrical conductivity were quantified. Results indicate high concentration of TP, Bray P and WEP in deeper horizons of impacted plots, showing the mobility of this nutrient. Correlation between TP and OC% were established for Z4 y Z10 in 88 and 84 %, demonstrating that the organic matter that moved in the profile presented high P content. An increase of salinity of 257 and 345 % for Z4 and Z10, respectively, was found in the deepest samples. The quantification of an empirical rate (EARP) showed the downward movement of P reaching 150 cm in Z4 and 90 cm in Z10. The results have shown that application of large volumes of solid manure saturated P retention capacity favoring its movement towards underlying water.