TITLE:
Phosphate and Nitrate Release from Mucky Mineral Soils
AUTHORS:
Michaël A. Leblanc, Léon E. Parent, Gilles Gagné
KEYWORDS:
Degree of Phosphate Saturation; Gleysol; Humisol; Organic Nitrogen Mineralization; Zero-Order Kinetics
JOURNAL NAME:
Open Journal of Soil Science,
Vol.3 No.2,
June
4,
2013
ABSTRACT: High-organic (mucky) mineral soils
make a small proportion of the Canadian agricultural land but are highly
productive, especially for organic farming. Although these high-quality soils
may release large amounts of nitrate and phosphate to the environment,
there is yet no reliable agro-environmental indicator for managing N and P
compared to the adjacent mineral and organic soils. Our objective was to
quantify the N mineralization and P environmental risks of mucky mineral soils.
Nine Canadian soil series (eight Orthic Humic Gleysols and one Terric Humisol
with three variants) were analyzed for texture, pH(CaCl2), total C
and N, oxalate and Mehlich-III (M-III) extractable P, Al and Fe, and water extractable P (Pw).
Soil texture varied from loamy sand to heavy clay, organic carbon (OC) content
ranged from 14 to 392 g·OC·kg-1, total N from 1.21 to
16.38 g·N·kg-1, and
degree of P saturation (DPSM-III) as molar (P/[Al + γFe])M-III percentage between 0.3% and 11.3%. After 100 d of incubation, soils released 31
to 340 mg·N·kg-1. The N mineralization rate was closely correlated
to organic matter content (r = 0.91, p Sandy to loamy soils released 1.2 - 1.8 kg·N·ha-1·d-1 compared to 1.6 - 2.4 kg·N·ha-1·d-1 for
clayey soils, 2.0 - 2.8 kg·N·ha-1·d-1 for
mucky clayey soils and 2.6 - 2.7 kg·N·ha-1·d-1 for Humisol.
For (P/[Al + 3Fe])M-III ratios of mucky
clayey soils below 4.5%, water-extractable P did not exceed threshold of 9.7 mg
Pw L-1. Mucky clayey soils could be managed for N
similarly to Humisol and for P with (P/[Al + 3Fe])M-III percentage not
exceeding 4.5%.