Soil Science

Skip Navigation LinksHome > February 2000 - Volume 165 - Issue 2 > PHOSPHORUS AVAILABILITY AND SPECIATION IN LONG-TERM NO-TILL...
Soil Science:
Articles

PHOSPHORUS AVAILABILITY AND SPECIATION IN LONG-TERM NO-TILL AND DISK-TILL SOIL

Essington, Michael E.; Howard, Donald D.

Collapse Box

Abstract

Conservation tillage results in the concentration of plant-available P near the soil surface. We studied the effects of conservation tillage on P speciation by examining the distribution of P in inorganic and organic chemical pools. Depth-incremented soil samples were collected from long-term (9- and 10-yr) no-till (NT) and disk tillage (DT) systems cropped in corn (Zea mays L.) with a wheat (Triticum aestivum L.) cover crop. Rates of P were 0, 20, and 60 kg P ha−1 yr−1. Total P (PT), organic P (PO), and available P (Mehlich-3, M3-P; Olsen NaHCO3-pH 8.5, Olsen-P) were determined. P was also extracted from the following chemical pools: non-occluded Al-bound (Al-P), non-occluded Febound (Fe-P), occluded-reductant-soluble (CBD-P), and Ca-bound (Ca-P). Total P did not vary with depth, but was greater in NT than in DT and increased with P rate. Organic P increased with P rate in the 0- to 8-cm depth. Organic P was greater in NT plots in the 8- to 60-cm depths, averaging 75 mg kg−1 for NT and 48 mg kg−1 for DT plots. Mehlich 3-P and Olsen-P were greatest in the surface 4 cm and in the 60-kg P ha−1 plots, with higher levels observed in NT plots. On average, the forms of P (as a % of total P) in NT soil was 6.2% Al-P, 33.9% Fe-P, 33.9% CBD-P, and 4.7% Ca-P. Average P distribution in DT soils was 5.4% Al-P, 35.6% Fe-P, 31.3% CBD-P, and 5.1% Ca-P. The influence of tillage on P distribution was primarily limited to the soil surface, with the exception of Al-P, which was greater in the 8- to 30-cm depths of the NT plots. Because the impact of tillage was limited to a thin, soil surface layer (<4 cm), soil P-test rating would not be affected by tillage practice. However, the improper collection of soil samples from NT (i.e., too shallow) for P-testing may provide erroneous P-test results and fertilizer recommendations.

© 2000 Lippincott Williams & Wilkins, Inc.

Login

Article Tools

Share

Article Level Metrics

Search for Similar Articles
You may search for similar articles that contain these same keywords or you may modify the keyword list to augment your search.