No abstract

Larney, F.J., Janzen, H.H. and Olson, A.F. 2011. Residual effectsof one-time manure, crop residue and fertilizer amendments on a desurfaced soil. Can. J. Soil Sci. 91: 1029–1043. Organic amendments are often used to mitigate the effects of soil degradation caused by erosion. In spring 1992, a desurfaced soil (∼15 cm depth mechanically removed to simulate erosion) received one-time applications of amendments (20 Mg ha−1dry wt), and was subsequently seeded annually to spring wheat (Triticum aestivum L.). By 2009, six treatments (fresh and old cattle manure, hog and poultry manure, alfalfa (Medicago sativa L.) hay and straw+200 kg P ha−1) had cumulative yields which were not significantly different (−6.5 to −19.5%) from the topsoil check treatment (no topsoil removed, no amendment). Most (8 of 13) amendment treatments showed significant power function relationships between cumulative grain yield (expressed as a percent of topsoil check) and time while two (hog and poultry manure) were quadratic. Soil organic carbon (SOC) accrued on all treatments over time, increasing significantly from an average of 12.2 g kg−1in 1992 to 13.2 g kg−1(0–15 cm depth) in 2003. Residual amendment effects on total nitrogen (N) and phosphorus (P) were apparent 11.5 yr after application. Results demonstrated that while drastically disturbed soils may recover productivity in the absence of organic amendments (e.g., eroded check treatment), organic amendments play a residual role in their ongoing maintenance.

Pageni, B. B., Lupwayi, N. Z., Akter, Z., Larney, F. J., Kawchuk, L. M. and Gan, Y. 2014. Plant growth-promoting and phytopathogen-antagonistic properties of bacterial endophytes from potato (Solanum tuberosum L.) cropping systems. Can. J. Plant Sci. 94: 835–844. Endophytes are microorganisms that live within a plant without harming it. Bacterial endophytes were isolated from roots of potatoes (Solanum tuberosum L.) grown under different rotations (3 to 6 yr in length) and soil management (CONV, conventional; CONS, conservation) in irrigated cropping systems with dry bean (Phaseolus vulgaris L.), sugar beet (Beta vulgaris L.) spring wheat (Triticum aestivum L.) and timothy (Phleum pratense L.). The endophytes were characterized for nitrogen fixation potential, phytohormone production and phytopathogen-antagonistic properties. The nitrogen-fixing nitrogenase (nifH) gene was detected in potato grown in all rotations, presumably partly because the soil in all rotations contained Rhizobium leguminosarum bv. phaseoli from the dry bean phase. Sequence analysis revealed that it was homologous to the genes found in Burkholderia, Azospirillum, Ideonella, Pseudacidovorax and Bradyrhizobium species. Indole acetic acid (IAA) hormone production by endophytes isolated from potato grown under CONS management was 66% greater than that those isolated from potato grown under CONV management, and tended to be greater in longer than shorter rotations. When 12 endophytes were inoculated to dry bean, four increased shoot biomass by 27–34%, and six increased total (shoot+root) biomass by 25% on average. Endophytes from the longer CONS rotations (4–6 yr) resulted in significantly higher (by 9%) shoot biomass than the shortest CONS (3 yr) rotation. Six of 108 endophyte isolates exhibited antagonistic properties (reduced pathogen biomass by 12 to 58% in dual culture assays in liquid media) against potato pathogens Pectobacterium atrosepticum, Fusarium sambucinum and Clavibacter michiganensis subsp. epedonicus. All the six isolates were from CONS soil management. Therefore, the benefits of long rotations, with their associated CONS soil management, to crop productivity in these irrigated cropping systems probably include nutritional (biological nitrogen fixation and IAA hormone production) and disease-control benefits imparted by endophytic bacteria.

Smith, E. G., Janzen, H. H. and Larney, F. J. 2015. Long-term cropping system impact on quality and productivity of a Dark Brown Chernozem in southern Alberta. Can. J. Soil Sci. 95: 177–186. Long-term cropping system studies offer insights into soil management effects on agricultural sustainability. In 1995, a 6-yr bioassay study was superimposed on a long-term crop rotation study established in 1951 at Lethbridge, Alberta, to determine the impact of past cropping systems on soil quality, crop productivity, grain quality, and the relationship of yield productivity to soil quality. All plots from 13 long-term crop rotations were seeded to wheat (Triticum aestivum L.) in a strip plot design [control, nitrogen (N) fertilizer]. Prior to seeding, soils were sampled to determine soil chemical properties. Total wheat production for the last 4 yr of the study was used as the measure of productivity. The 1995 soil analysis indicated crop rotations with less frequent fallow and with N input had higher soil quality, as indicated by soil organic carbon (SOC) and light fraction carbon (LF-C) and N (LF-N). SOC had a positive relationship to total wheat yield, but was largely masked by the application of N in this bioassay study. Frequent fallow in the previous crop rotation lowered productivity. The concentration of LF-C had a negative relationship, whereas LF-N had a positive relationship to total wheat yield, with and without N fertilization in this bioassay study. Grain N concentration was higher with applied N and when the long-term rotation included the addition of N by fertilizer, livestock manure, annual legume green manure or legume hay. This study determined that long-term imposition of management practices have lasting effects on soil quality and crop productivity.

Larney, F. J., Olson, A. F., Miller, J. J. and Tovell, B. C. 2014. Soluble salts, copper, zinc, and solids constituents in surface runoff from cattle manure compost windrows. Can. J. Soil Sci. 94: 515–527. Composting has become widely adopted by the beef cattle feedlot industry in southern Alberta. Compost windrows subjected to heavy rainfall can lead to runoff whose properties may vary with compost maturity. A rainfall simulator generated runoff on days 18, 26, 40, 54, 81, 109 and 224 of manure composting. Runoff was collected in timed 5-L increments to 30 L, creating the variable “time during runoff event” (TDRE). Calcium, K and S showed significant maturity×TDRE interactions, especially earlier in the composting process, e.g., on day 18, Ca values increased from 34 mg L−1 for the initial 0- to 5-L runoff increment to 43 mg L−1 for the final 25- to 30-L increment. Most significant changes in runoff concentrations occurred between days 26 and 40, e.g., Cu levels fell by 67% and Zn levels by 78%. Even though compost Cu and Zn concentrations were higher during the latter stages of composting, their transport potential in runoff was curtailed due to binding with stable organic matter (OM). The C:N ratio of runoff solids decreased from 10.5 on day 18 to only 4.9 on day 224, suggesting the transport of very stable OM after compost curing. The study showed that runoff quality was influenced by compost maturity, which has implications for the timing of rainfall events relative to the maturity spectrum and the potential risk to surface water quality if runoff is not contained.