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Articles by Y.K. Soon
Total Records ( 2 ) for Y.K. Soon
  N.Z. Lupwayi , M.A. Arshad , R.H. Azooz and Y.K. Soon
  More than 90% of acid soils in western Canada are in Alberta, yet the use of agricultural lime is limited because it is expensive. Wood ash, a by-product of pulp and lumber mills, can be used for liming acid soils. We investigated the effects of amending an acid Luvisol with wood ash or lime on soil microbiological properties at Beaverlodge, Alberta. Both soil amendments were applied at a calcium carbonate rate of 6.72 t ha-1, which was 8.40 t ha-1 for wood ash and 7.47 t ha-1 for lime, in 2002. Soil microbial biomass C (MBC) and the functional diversity and community structures of soil bacteria (indicated by substrate utilization patterns) were measured from 2002 to 2005 under barley (Hordeum vulgare L.), canola (Brassica napus L.), field pea (Pisum sativum L.), and timothy grass (Phleum pratense L.). In the rhizosphere, wood ash increased soil MBC between 2.4-fold in 2002 and 1.3-fold in 2005, and lime increased MBC from 3.2-fold in 2002 to 1.3-fold in 2005. In bulk soil, the increases in MBC ranged from 3.0-fold in 2003 to 1.8-fold in 2005 for wood ash, and from 4.9-fold in 2002 to 2.0-fold in 2005 for lime. Crop effects on MBC were not consistent. Because annual crops were grown in rotation, it is possible that the results obtained in one crop were confounded by effects of the preceding crop. In 2003 and 2004, both amendments increased Shannon index (H’) of bacterial functional diversity in the rhizosphere, and similar results were observed in 2005 in bulk soil. Shifts in the functional structure of bacterial communities due to soil amendment were observed in bulk soil, and shifts due to crop effects were observed in the rhizosphere. In 2003, the average soil pH(CaCl2) increased from 4.91 in control treatments of different crops to 6.60 in lime-amended plots and 6.70 in wood ash-amended plots. In 2004, both wood ash and lime significantly increased soil C mineralization (up to 10 d incubation), but basal respiration (11-24 d incubation) was not affected. The large effect (up to about fivefold) of soil amendments on MBC implies that soil acidity is a major limiting factor for biological processes and the productivity of some Luvisolic soils in Alberta. Wood ash could be used to alleviate these limitations.
  S.S. Malhi , Y.K. Soon , C.A. Grant , R. Lemke and N. Lupwayi
  Field experiments were conducted on Dark Gray Luvisolic soils (Typic Cryoboralf) from 2004 to 2006 (wheat-canola-barley rotation) near Star City, Saskatchewan, and from 2004 to 2007 (barley-canola-wheat-barley rotation) near Beaverlodge, Alberta. The aim was to compare the effects of controlled-release urea (CRU) vs. conventional urea (hereafter called urea) on seed yield and N (i.e., protein) concentration, and N use efficiency (NUE). The treatments were combinations of tillage system [conventional tillage (CT) and no tillage (NT)], and N source (urea, CRU and a blended mixture), placement method (spring-banded, fall-banded and split application) and application rate (0-90 kg N ha-1). There was no tillage × fertilizer treatment interaction on the measured crop variables. Seed yield and crop N uptake and, to a lesser degree, seed N concentration generally increased with N application to 90 kg N ha-1. Fall-banded CRU or urea generally produced lower crop yield and N uptake than spring-banded CRU or urea. Split application of urea (half each at seeding and tillering) resulted in higher seed yield and N concentration in at least 3 of 7 site-years than did CRU and urea applied at a similar rate. A blend of urea and CRU was as effective as spring-banded CRU (at Star City only). Seed yield, N recovery and NUE were higher with spring-banded CRU than urea in 2 site-years, and similar to urea in other site-years. We conclude that for boreal soils of the Canadian prairies, spring-banded CRU is as effective as urea, and in some years more effective, in increasing crop yield and N recovery; however, urea split application can be even more effective in addition to having an advantage in managing risk.
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