Ca. Campbell et al., INFLUENCE OF LEGUMES AND FERTILIZATION ON DEEP DISTRIBUTION OF AVAILABLE PHOSPHORUS (OLSEN-P) IN A THIN BLACK CHERNOZEMIC SOIL, Canadian Journal of Soil Science, 73(4), 1993, pp. 555-565
Inorganic phosphorus (P) is generally believed to be relatively immobi
le in Chernozemic soils. However, available P (e.g., Olsen-P) has been
found at depth in some soils and this has been postulated to be eithe
r the result of leaching or of transportation by plant roots. Lagumes,
in particular, are believed to be involved in the latter mechanism. A
long-term (34-yr) crop rotation study conducted on a heavy clay, thin
Black Chernozemic soil at Indian Head, Saskatchewan, was sampled to a
depth of 4.5 m in May and September 199 1, to determine the influence
of fertilization, cropping frequency, legume green manure and legume-
grass hay crops on Olsen-P distribution in the soil profile. The resul
ts indicated that Olsen-P may indeed leach in Chernozemic soils, espec
ially when fallow-containing cropping systems are fertilized. It also
appeared that deep-rooted legumes, such as sweetclover Melilotus offic
inalis L.) green manure and alfalfa-bromegrass (Medicago sativa L. - B
romus intermis Leyss) hay crops do increase Olsen-P in the subsoil, po
ssibly through root decomposition in situ.