Effects of Crop Rotation and Management System on Water‐Extractable Organic Matter Concentration, Structure, and Bioavailability in a Chernozemic Agricultural Soil

Abstract

Water-extractable organic matter (WEOM) in soil affects contaminant mobility and toxicity, heterotrophic production, and nutrient cycling in terrestrial and aquatic ecosystems. This study focuses on the influences of land use history and agricultural management practices on the water extractability of organic matter and nutrients from soils. Water-extractable organic matter was extracted from soils under different crop rotations (an annual rotation of wheat-pea/bean-wheat-flax or a perennial-based rotation of wheat-alfalfa-alfalfa-flax) and management systems (organic or conventional) and examined for its concentration, composition, and biodegradability. The results show that crop rotations including perennial legumes increased the concentration of water-extractable organic carbon (WEOC) and water-extractable organic nitrogen (WEON) and the biodegradability of WEOC in soil but depleted the quantity of water-extractable organic phosphorus (WEOP) and water-extractable reactive phosphorus. The 30-d incubation experiments showed that bioavailable WEOC varied from 12.5% in annual systems to 22% for perennial systems. The value of bioavailable WEOC was found to positively correlate with WEON concentrations and to negatively correlate with C:N ratio and the specific ultraviolet absorbance of WEOM. No significant treatment effect was present with the conventional and organic management practices, which suggested that WEOM, as the relatively labile pool in soil organic matter, is more responsive to the change in crop rotation than to mineral fertilizer application. Our results indicated that agricultural landscapes with contrasting crop rotations are likely to differentially affect rates of microbial cycling of organic matter leached to soil waters.

Effects of human land use on the terrestrial and aquatic sources of fluvial organic matter in a temperate river basin (The Meuse River, Belgium)

“…For example, our results contrasts with a field study conducted in headwater catchments in Germany where agricultural practices led to the mobilization of more humified and aromatic DOM in streams compared to forest and wetland catchments (Graeber et al 2012). Similarly, waterextractable DOM from agricultural soils in Canada was found to be more chemically complex compared to forest and grassland soils (Xu et al 2013). In Australia, the reconversion of coastal wetlands for agricultural and urban purposes was without effects on stream DOM, the latter being characterized by a chemical composition typical of former wetland ecosystems (Petrone et al 2011).…”

Water-extractable organic matter and its fluorescence fractions in response to minimum tillage and organic farming in a Cambisol

“…Our result suggested that complex crop rotations release WEOM with higher aromaticity and humification. This is opposite to that of Xu et al [18] who reported the inclusion of a perennial crop alfalfa in a crop rotation, which releases WEOM with lower aromaticity and lower extent of humification. This may be attributed to simpler crop rotations in their study and different crop species they planted compared with our study.…”

“…Reduced tillage and organic farming as alternative practices of conventional tillage and farming were reported to increase WEOC content by reducing soil disturbance and the addition of organic matter [11][12][13][14], while negative or neutral effect also existed [15][16][17][18]. However, most of the previous studies focused less on the quality of WEOM.…”

Soil phosphorus spatial variability due to landform, tillage, and input management: A case study of small watersheds in southwestern Manitoba

“…For these samples gravimetric soil moisture was quantified and this value was utilized to determine amount of water to add to field moist soils samples to ensure a 1:5 dry soil mass/ultrapure water volume for WERP extraction. Resulting soil water mixtures were shaken for 3 h, centrifuged at 4000 rpm to improve filtration, and then filtered with a 0.2 μm polycarbonate membrane filter prior to utilizing the ascorbic acid colourimetric method for determination of PO 4 -P in filtrates (Xu et al, 2013).…”