Submitted to: Soil Science
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/25/2009
Publication Date: 12/15/2009
Citation: He, Z., Endale, D.M., Schomberg, H.H., Jenkins, M. 2009. Total phosphorus, zinc, copper, and manganese concentrations in cecil soil through ten years of poultry litter application. Soil Science. 174:687-695. Interpretive Summary: Poultry litter (PL) is an inexpensive and effective organic fertilizer. However, over application may result in accumulation of phosphorus (P) and heavy metals in soil. A long-term field experiment in Georgia was used to evaluate such effects. Following five years of cotton production and a relatively low rate of PL application, levels of P and heavy metals in the soil were unaffected. However, when PL application was increased by 2-4 times, much higher levels of P and heavy metals were observed in the soil. This research showed that soils receiving poultry litter should be carefully monitored to reduce the risk of over application.
Technical Abstract: Poultry litter (PL) is an inexpensive and effective source of plant nutrients. However, over application could result in phosphorus and heavy metal accumulation in soils. A field experiment evaluating PL application to a Cecil soil used for cotton and corn production has been maintained for 10 years. At the end of the cotton phase (i.e., the first 5 yr) PL annually applied at 4.5 Mg ha-1 did not increase concentrations of total soil P, Zn, Cu or Mn. During the corn phase (i.e. the second 5 yr), PL application rates were increased from 2 to 4 times that used for cotton, partly because of corn’s greater N demand. With this change, the average total P in the surface 15 cm soil nearly doubled to about 560 mg kg-1 of dry soil in both conventional till and no-till fields at the end of the corn phase. In the same time, Cu increased from 7 to 22 mg kg-1 and Zn increased from 17 to 32 mg kg-1 of dry soil. Levels of Mn were basically unchanged. Total P and Cu also increased in the 15- to 30-cm depth with concentration in the 0-15 cm being 1.8 to 2 times that in the 15-30 cm for P and approximately 2 times for Cu. Relationships between extractable versus total P and Zn changed at a threshold point beyond which extractable P and Zn increased at more than double the initial rate. It appears that once accumulation of P and Zn exceeded the soil buffer capacity, nutrient availability was significantly altered. Therefore close monitoring of soil nutrients is essential to avoid over application of PL that may potentially pose environmental risks.