Submitted to: Soil Science Society of America Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2001
Publication Date: 1/1/2002
Citation: Franzluebbers, A.J., Stuedemann, J.A., Wilkinson, S.R. 2002. Bermudagrass management in the southern piedmomt usa. ii. soil phosphorus. Soil Science Society of America Journal.
Interpretive Summary: Plant production can be limited by low levels of available phosphorus (P) due to high P fixation capacity in soils of the southeastern USA. On the other hand, there is increasing concern about the excessive application of P to soil, especially when the manure application rate is based upon nitrogen content. Extractable soil P increased to the higher levels of agronomically acceptable levels within five years of broiler litter fertilization aimed at supplying 200 kg nitrogen/ha/year. Most of the change in extractable soil P occurred within the surface 6 cm of soil. Haying of bermudagrass, even with broiler litter fertilization, kept extractable soil P levels constant with time due to continual removal of P with harvested biomass. Enrichment of the surface soil with P could put surface water systems at risk of contamination if significant runoff were to occur. Fortunately, the permanent vegetation associated with pastures increases the probability of greater retention of low to moderate rainfall intensities. More information on surface runoff characteristics under these management systems is needed to quantify the threats to water quality.
Technical Abstract: We evaluated the changes in extractable soil P during the first five years of bermudagrass management varying in fertilization [inorganic and broiler litter and harvest strategies (unharvested, low and high cattle (Bos taurus) grazing pressure, and haying). At a depth of 0 to 6 cm, extractable soil P increased at a rate of 0.8 mg/kg/yr(4% of total P added) )with inorganic only fertilization, 2.4 mg/kg/yr (9% of total P added) with clover cover crop plus inorganic fertilization, and 8.7 mg/kg/yr (6% of total P added) with broiler litter. Haying tended to keep extractable soil P constant with time due to removal of P with harvest of biomass. At the end of five years of broiler litter application to grazed land, extractable soil P was 135, 50, 22, and 4 mg/kg higher than with inorganic fertilization at depths of 0 to 3, 3 to 6, 6 to 12, and 12 to 20 cm, respectively. Broiler litter fertilization was effective at increasing extractable soil P to an agronomically acceptable level (50 to 60 mg/kg/15 cm), but continued application could lead to excessive P accumulation that could threaten water quality from surface runoff unless appreciable soil fixation or removal of forage biomass were to occur.