Long-term crop rotation effects on organic carbon, nitrogen and phosphorus in Haplustoll soil fractions
Soil
organic matter (SOM) or carbon (SOC) consists of a number of fractions (which can
be separated by granulometric wet sieving) having different properties among them.
Information on fraction nutrient distribution and long-term crop rotations is lacking
for semiarid environments. The objective of this research was to study the agronomic
effects on soil OC, N, and P factions. The humified OC was the largest and
least variable fraction of the SOC. Soil under continuous mixed pasture had higher
OC contents than under annually tilled treatments. Similarly, soil total
nitrogen under the cropped treatments decreased from 1.7 g N kg-1 in
noncultivated soils (reference plots) to 1.0, 0.7 and 0.7 g N kg-1
under mixed pasture, pasture-crop, and wheat-crop respectively, in the fine
soil fraction. The reference plots also showed significantly lower levels of
organic phosphorus (Po) in comparison to the other treatment (from 67.1 µg Po g-1
to greater than 100 µg Po g-1 in the fine fraction of the treatments
and years). The noncultivated soil showed larger values of Po and inorganic P
in the large-size granulometric fraction (0.1-2 mm) than in the soil fine
fraction (0-01 mm). However, the rotation treatments had greater concentrations
of P in the fine fraction. The Po from the coarse fraction appears to be the most
labile and sensitive fraction to tillage and environmental conditions, and may be
closely related to P availability.
Keywords semiarid soil fractionation, organic
P, inorganic P, tillage systems
Rosell R.A., J.A. Galantini, L.G. Suñer. 2000. Long-term crop rotation effects on organic carbon, nitrogen and phosphorus in Haplustoll soil fractions. Arid Soil Research and Rehabilitation 14 (4) 309-316.