Fertilization and pine straw raking in slash pine plantations: P removals and effects on total and mobile soil, foliage and litter P pools

Pine straw raking and fertilization effects on phosphorus (P) removals, total and mobile P in foliage and straw, and soil extractable P pools, were examined in 15 and 17-year-old slash pine (Pinus elliottii Engelm.) stands on soils (an Ultisol and an Entisol) with contrasting nutrient sorption potentials and internal drainage. A factorial study of P fertilization (0, 29, 87 kg P ha−1 for two years) and commercial straw raking (no raking vs. annual raking) was used to investigate P removals and changes in total and mobile P pools in foliage, pine needle litter and surface mineral soil. After three years of raking at the Ultisol site, litter in the non-raked plots had approximately 15% more Pi (TCA extractable) than did litter in the raked plots. Raking removed mobile P and broke the P cycle in these stands. Also, pine straw raking depleted extractable soil P, as evidenced by the change in soil P in the surface 10 cm. After five or four raking events, the difference between non-raked and raked treatments ranged from 4 to 11 kg P ha−1 at the two sites. An estimate of the number of rakings that would move the sites' surface soil into P deficiency, was linked to the soil's ability to sorb P. These results indicate that Best Management Practices for pine straw raking should include specific P fertilization recommendations to replace depleted soil extractable P, based on raking frequency and the soil sorption capacity.