Soil nitrate, phosphorus and potassium concentration after four years of liquid swine manure application on Tifton 85

Abstract

One major problem of swine production is the huge volume of manure generated; this involve
difficulties in proper handling of the residue when applied to the soil, given that such elements can be
toxic to the environment. This study examined the vertical movement of the P, K and mineral N in the
soil profile cultivated with Cynodon dactylon cv. Tifton 85 which was submitted consecutively to rates
of Liquid Swine Manure (LSM) application (four years). The experiment was done using a randomized
block design with four replications in a split-plot arrangement, where the whole plots were semiannual
applications (November, 2002 to September, 2006) of increasing levels of LSM (0, 30, 60, 90, 120 and 180
m
3
ha-1
); while the sub-plots were the soil samples at different depths (0-10, 10-20, 20-40, and 40-60 cm).
The N-NO3
-
leaching was observed when application of LSM exceeded 90 m3
ha-1
twice annually or
during the year, suggesting a limit level for fertilizer on Tifton 85 pastures. Phosphorous and potassium
accumulation was observed at higher LSM rate, mainly at the 0-10 cm soil layer since the soil P levels
increased up to the highest evaluated depth at the 180 m3
ha-1
LSM level. LSM meets the Tifton 85
nutritional requirement regarding N, P and K when applied semi-annually at the rate of 90 m³ ha-1
without causing pollution effects; although the grass production responds up to 180 m3
ha-1
levels