Soil Profile Phosphorus and Arsenic Changes in a Captina Silt Loam as Affected by Broiler Litter Application Rate.

The broiler (Gallus gallus domesticus) industry generates large quantities of nutrient- and metal-enriched litter, particularly where production is highly concentrated, such as in areas like northwest Arkansas.  Broiler litter is typically land applied as a means of disposal and as a nutrient source for forages.  Continual annual broiler litter applications can increase nutrient and metal concentrations in soils over time creating the potential for negative environmental impacts if soil properties are altered to increase elemental mobility.  The objective was to determine the effects of broiler litter application rate (0, 5.6, and 11.2 Mg ha^-1) on phosphorus (P) and arsenic (As) contents in a Captina silt loam (Fine-silty, siliceous, active, mesic Typic Fragiudult) over a five-year period.  It was hypothesized that soil P and As contents will increase with annual broiler litter application and will be most concentrated in the top 30 cm.  Soil samples were collected at 10-cm increments to 90 cm prior to annual broiler litter applications.  Acid-recoverable soil P increased as broiler litter application rate increased and was most concentrated in the top 30 cm.  Soil acid-recoverable As did not change for the 0 Mg ha^-1 rate, increased for the 11.2 Mg ha^-1 rate, but decreased for the 5.6 Mg ha^-1 rate and was most concentrated in the 60- to 90-cm depth.  The decrease in soil As in the 5.6 Mg ha^-1 litter rate is likely partially due to P and As competition for soil adsorption sites.  Phosphorus may be out-competing As to increase As mobility and leaching from the soil profile, which could ultimately negatively affect groundwater quality.