|PAGLIARI, PAULO - University Of Minnesota|
|ZHANG, MINGCHU - University Of Alaska|
Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/16/2015
Publication Date: 12/11/2015
Citation: Waldrip, H., Pagliari, P.H., He, Z., Harmel, R.D., Cole, N.A., Zhang, M. 2015. Legacy phosphorus in calcareous soils: effects of long-term poultry litter application. Soil Science Society of America Journal. 79(2015):1601-1614.
Interpretive Summary: Phosphorus from manure can build up to high levels in soil and may runoff into lakes and other bodies of water. Soil phosphorus exists in many forms that differ in availability for plant use and risk for runoff. However, how these forms of phosphorus are affected by manure applications is poorly understood. ARS scientists from Bushland, TX., New Orleans, LA., and Temple, TX., and cooperating scientists from University of Minnesota and University of Alaska used various methods to evaluate how 10 years of poultry litter application at rates of 4.5 to 13.4 tons of litter per acre changed forms of soil phosphorus. Major findings were that litter increased total extractable phosphorus when compared to plots that did not receive litter. Some of the changes were due to higher levels (7 to 34% more) of soluble phoshorus, which increased runoff risks. Most (68%) of the extractable phosphorus from these plots was associated with calcium. Thus, we concluded that repeated litter application increased levels of both soluble and stable phosphorus.
Technical Abstract: Sequential fractionation techniques, coupled with phosphatase hydrolysis, have allowed for greater understanding of manure/litter effects on soil P distribution. We evaluated the effect of long-term (greater than 10 years) poultry litter (broiler and turkey litter) application at annual rates of 4.5, 6.7, 9.0, 11.2, and 13.4 Mg manure/ha on P in watershed-scale plots (cultivated and grazed/ungrazed pasture) on calcareous Texas Blackland vertisol. Soil total extractable P (Pt) and inorganic P (Pi) were quantified following sequential extraction with H2O, NaHCO3, NaOH, and HCl. Hydrolyzable organic P (Pe) and non hydrolyzable organic P (Pne) were determined in the extracted fractions following enymatic hydrolysis. Litter application increased Pt regardless of land-use type; compared with the control. Compared with the control, H2O Pi from litter amended plots increased by 9 to 34% (cultivated) and 7 to 30% (pasture), indicating substantial risk of soluble P runoff. Labile organic P (Po) extracted with H2O and NaHCO3 decreased in the order: monoester greater than nucleic acid greater than phytate greater than Pne. Litter application did not affect NaOH Pi or NaOH Pe (P greater than 0.05), but increased NaOH Pne. An average of 68% of Pt was extractable with HCl. The HCl Pt composition was predominantly (95%) Po. Only trace levels of HCl Pe were found; however, litter application increased HCl Pne up to 217%. Thus, we concluded that repeated litter application increased levels of both soluble Pi and stable Pne, but specific response varied with application rate and land management. This study increased understanding of P distribution over time in soil with high clay and calcium carbonate contents under differing land use scenarios.