Bermudagrass Management in the Southern Piedmont USA. II. Soil Phosphorus
2002
Franzluebbers, Alan J. (Alan Joseph) | Stuedemann, J. A. | Wilkinson, S. R.
Plant production can be limited by low levels of available P due to high P-fixation capacity in soils of the southeastern USA. On the other hand, there is increasing concern about excessive application of P to soil, especially when manure application is based upon N content. We evaluated changes in Mehlich-I extractable soil P during 5 yr of bermudagrass [Cynodon dactylon (L.) Pers.] management varying in fertilization [inorganic and broiler chicken (Gallus gallus) litter] and harvest strategy (unharvested, low and high cattle (Bos taurus) grazing pressure, and haying). Broiler litter supplied eight times more P than inorganic fertilization to meet the N requirement. At a depth of 0 to 6 cm, Mehlich-I extractable soil P increased 0.8 ± 1.6 mg kg⁻¹ yr⁻¹ (4 ± 8% of total P added) with inorganic-only fertilization, 2.4 ± 3.0 mg kg⁻¹ yr⁻¹ (9 ± 11% of total P added) with clover (Trifolium incarnatum L.) cover crop plus inorganic fertilization, and 8.7 ± 9.8 mg kg⁻¹ yr⁻¹ (6 ± 7% of total P added) with broiler litter. Haying kept Mehlich-I extractable soil P constant with time due to removal of P with harvest of biomass. At the end of 5 yr of broiler litter application to grazed land, Mehlich-I extractable soil P was 135, 50, 22, and 4 mg kg⁻¹ 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 Mehlich-I extractable soil P to an agronomically productive level (50 to 60 mg kg⁻¹ 15 cm⁻¹), 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.
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