• Authors:
    • Mustafa, A.
    • Ellis, B.
    • Whalen, J.
    • Gul, S.
  • Source: Pedobiologia
  • Volume: 55
  • Issue: 6
  • Year: 2012
  • Summary: Alteration of plant lignin concentration is expected to affect the C mineralization of crop residues. Mutations of single genes involved in biosynthesis of secondary cell walls such as KNOTTED ARABIDOPSIS THALIANA 7 (KNAT7), PRODUCTION OF ANTHOCYANIN PIGMENT 1 (PAP1) also known as MYB75, and cinnamoyl CoA reductase 1 (CCR1) coding genes could change lignin concentration in specific plant tissues. This study assessed the CO2-C production of soil amended with stem and root tissues of down-regulated (k/o) and over expression (o/x) KNAT7 and MYB75 and the CCR1 k/o mutant lines of A. thaliana. KNAT7 k/o and MYB75 k/o were grown in two different environmental conditions (two cohorts) in the greenhouse. Oven dried, finely ground (<0.5 mm) stem and root residues underwent biochemical analysis, then were mixed separately with sandy loam or clay loam soil to assess CO2-C production under controlled laboratory conditions for 63 days. Compared to wild ecotypes, C:N ratio and acid unhydrolyzable fraction (AUF) concentration tended to be higher in stem residues of KNAT7 k/o and MYB75 k/o mutant lines. The C:N ratio was lower in stem and roots of CCR1 k/o line, and the AUF concentration was lower in CCR1 k/o stem residues than in the wild ecotypes. Hemicelluloses were lower in stem residues of KNAT7 k/o and MYB75 k/o (first cohort) than their wild ecotypes. Cumulative CO2-C production was lower in soil amended with stem residues of KNAT7 k/o (first cohort) and MYB75 k/o (first and second cohorts). CCR1 k/o stem tissues caused higher CO2-C production from soil. After 63 days incubation, the acid/aldehyde ratio (Ad/Al) of vanillin (V) and syringyl (S) lignin monomers of soil was higher for stem amended CCR1 k/o and lower for stem amended MYB75 k/o soils as compared to their wild ecotypes. Generally root residues caused lower CO2-C production from soil than stem residues. There was no difference in CO2-C production for root residues between mutant lines and their wild ecotypes. In conclusion, KNAT7 k/o, MYB75 k/o and CCR1 k/o mutations resulted in altered C:N ratio and resistant compounds (i.e., AUF) especially in stems, and these alterations in residue chemistry influenced CO2-C production and also lignin degradation in soil. (c) 2012 Elsevier GmbH. All rights reserved.
  • Authors:
    • Swartz, H.
    • Proctor, J.
    • Sullivan, J.
    • Harbut, R.
  • Source: Journal of the American Society of Horticultural Science
  • Volume: 137
  • Issue: 3
  • Year: 2012
  • Summary: The net carbon exchange rate (NCER) of Fragaria species, synthetic octoploids [SO (interspecific hybrids)], F-1 (SO X cultivar), and first outcross [OC1 (F-1 X cultivar)] hybrids were evaluated in both field and greenhouse conditions. Plants were grown in a field trial at the Elora Research Station in Ontario, Canada, for one season and then plants were dug and moved into a greenhouse where the trial was repeated during the next season. Single leaf photosynthesis measurements and light response curves were generated at different stages of plant development. Photosynthetic capacity of the species was related to the ecological background of the species with sun-adapted species having higher rates compared with the shade-adapted species. The Fragaria species and introgressed hybrids (F-1 and OC1) had significantly higher NCERs compared with the cultivars with rates 28% and 23% higher, respectively. Species and hybrids also appear to have increased adaptability to both high and low light conditions. These increases in NCER may be a heterotic effect because NCER of the hybrids were consistently higher compared with the midparent values and in some cases, they were higher than the high parent. These results suggest that the introgression of lower-ploidy Fragaria species into the cultivated strawberry (Fragaria Xananassa) may lead to increased NCER and light adaptability.
  • Authors:
    • Morrison, M. J.
    • Biswas, D. K.
    • Liang, B. C.
    • Ma, B. L.
    • McLaughlin, N. B.
  • Source: Nutrient Cycling in Agroecosystems
  • Volume: 94
  • Issue: 1
  • Year: 2012
  • Summary: Studies on the sustainability of crop production systems should consider both the carbon (C) footprint and the crop yield. Knowledge is urgently needed to estimate the C cost of maize (Zea mays L.) production in a continuous monoculture or in rotation with a leguminous crop, the popular rotation system in North America. In this study, we used a 19-year field experiment with maize under different levels of synthetic N treatments in a continuous culture or rotation with forage legume (Alfalfa or red clover; Medicago sativa L./Trifolium pratense L.) or soybean (Glycine max L. Merr) to assess the sustainability of maize production systems by estimating total greenhouse gas (GHG) emissions (kg CO2 eq ha(-1)) and the equivalent C cost of yield or C footprint (kg CO2 eq kg(-1) grain). High N application increased both total GHG emissions and the C footprint across all the rotation systems. Compared to continuous maize monoculture (MM), maize following forage (alfalfa or red clover; FM) or grain (soybean; SM) legumes was estimated to generate greater total GHG emissions, however both FM and SM had a lower C footprint across all N levels due to increased productivity. When compared to MM treated with 100 kg N ha(-1), maize treated with 100 kg N ha(-1), following a forage legume resulted in a 5 % increase in total GHG emissions while reducing the C footprint by 17 %. Similarly, in 18 out of the 19-year period, maize treated with 100 kg N ha(-1), following soybean (SM) had a minimal effect on total GHG emissions (1 %), but reduced the C footprint by 8 %. Compared to the conventional MM with the 200 kg N ha(-1) treatment, FM with the 100 kg N ha(-1) treatment had 40 % lower total GHG emissions and 46 % lower C footprint. Maize with 100 kg N ha(-1) following soybean had a 42 % lower total GHG emissions and 41 % lower C footprint than MM treated with 200 kg N ha(-1). Clearly, there was a trade-off among total GHG emissions, C footprint and yield, and yield and GHG emissions or C footprint not linearly related. Our data indicate that maize production with 100 kg N ha(-1) in rotation with forage or grain legumes can maintain high productivity while reducing GHG emissions and the C footprint when compared to a continuous maize cropping system with 200 kg N ha(-1).
  • Authors:
    • Kutcher, H. R.
    • Johnston, A. M.
    • Bailey, K. L.
    • Malhi, S. S.
  • Source: Field Crops Research
  • Volume: 124
  • Issue: 2
  • Year: 2011
  • Summary: The impact of tillage system, rotation sequence and foliar fungicides on diseases and seed yield and quality of wheat, barley, pea, canola and flax was determined in the second cycle of three, 4-year rotations from 1998 to 2001 on a Black Chernozem (Udic Boroll) at Melfort, Saskatchewan, Canada. The objective of the study was to evaluate the impact of reduced-tillage production systems, broadleaf cropping intensity and fungicide use on cereal, oilseed and pulse crops in northeastern Saskatchewan, a sub-humid region of the northern Great Plains. A split-split plot design was used with three tillage systems (conventional, minimum and no-till) as main plots, three rotations of increasing broadleaf crop intensity (1. canola-wheat-barley-barley; 2. canola-barley-pea-wheat; and 3. canola-pea-flax-barley) as sub-plots, and fungicide treatments (treated or untreated) as sub-sub-plots. Fungicides appropriate for the diseases of concern were applied at recommended crop development stages and application rates, followed by assessment of diseases. Tillage system had little impact on diseases of any crop, although seed yield was usually greater under no-till for most crops under dry conditions. Rotation was not a major factor in disease severity of most of the crops, except barley in the rotation where it was grown for two consecutive years. Under dry conditions, barley yield was reduced when it followed flax compared with other crops, most likely due to less available soil moisture after flax. Fungicide application had the greatest impact on disease control and seed yield increase, although results varied among crops and years. In conclusion, the findings indicate that tillage system had little effect on disease severity, rotation contributed to greater disease severity only when a crop was grown intensively, such as on its own stubble, and fungicide application had variable effects on both disease control and seed yield.
  • Authors:
    • Walley, F.
    • May, W. E.
    • Holzapfel, C. B.
    • Lafond, G. P.
  • Source: Soil & Tillage Research
  • Volume: 117
  • Year: 2011
  • Summary: Meeting the needs of an increasing population requires protection of our arable land base and improvements in productivity. The study compared soil quality characteristics and crop yield to nitrogen (N) fertilizer in two adjacent fields; one field managed with no-till for 31 years while the other for 9 years. In 2003, the two fields along with native prairie were sampled for soil quality parameters across two landscape positions. A small plot study involving five rates of urea N (0, 30, 60 90 and 120 kg N ha -1) and two phosphorus fertilizer placement methods (seed-placed vs side-banded) was conducted on the two adjacent fields for the period 2002-2009. The rates of N were superimposed on the same plots each year whereas wheat and canola were normally grown in alternate years. An N balance was conducted after 8 years to account for inputs and outputs of N. Soil bulk density values were 0.98 g cm -3 for native prairie and 1.46 for LTNT and STNT in the 0-15 cm soil layer. The native prairie had 48.2 t ha -1of SOC vs 44.4 and 36.7 for LTNT and STNT, respectively, in the 0-15 cm soil layer and no detectable differences for the 15-30 cm soil layer in 2003. Potentially mineralizable N using the Hot KCl digestion in the 0-15 cm soil layer was 60 kg ha -1 of ammonium nitrogen for native prairie and 30 and 22 kg ha -1 for LTNT and STNT, respectively. For amino sugar-N, native prairie had 558 kg ha -1 vs 462 and 370 kg ha -1 for the LTNT and STNT, respectively. This indicates a positive relationship between SOC levels measured and potentially mineralizable N reflecting differences in land management. Phosphorus fertilizer placed in the side-band with N yielded 3.5% more than seed-placed phosphorus in spring wheat and no difference in canola. Grain yields were 14% and 16% more for LTNT than STNT in spring wheat and canola, respectively. Maximum grain N removal averaged in wheat was 87 kg ha -1 for LTNT and 74 kg ha -1 for STNT and 71 and 65.4 kg ha -1 in canola, respectively. A positive N balance was obtained provided that 60 kg ha -1 of N was applied every year and no accumulation of nitrate-N was noted even with rates that exceeded N removal in the grain. This supports the view that no-till combined with continuous cropping and proper fertility represents a path to sustaining the global soil resource.
  • Authors:
    • Malhi, S. S.
    • Nyborg, M.
    • Solberg, E.
    • Wang, Z.-H.
    • Henriquez, B.
  • Source: Journal of Plant Nutrition
  • Volume: 34
  • Issue: 10
  • Year: 2011
  • Summary: Most soils in the Prairie Provinces of Canada are deficient in plant-available nitrogen (N), and many soils in the Parkland region also contain insufficient amounts of plant-available sulfur (S) for high crop production. A field experiment with perennial grass stand was conducted to determine the effects of long-term annual N (112 kg N ha -1), S (11 kg S ha -1) and potassium (K) (40 kg K ha -1) fertilization, and one-time lime application on forage dry matter yield (DMY) and soil properties [pH, total organic carbon (TOC) and N (TON), and light fraction organic C (LFOC) and N (LFON)] on a Dark Gray Chernozem (Boralfic Boroll) loam at Canwood in north-central Saskatchewan, Canada. The experiment had surface-broadcast annual treatments of no fertilizer (Nil), N, S, NS, and NSK fertilizers from 1980 to 2002, and one-time lime application in 1992 to bring soil pH to about 7. Application of N or S alone had only a little effect on DMY compared to unfertilized Nil treatment, while application of both NS together substantially increased DMY, and forage yield was further increased when K was also applied (NSK). The DMY following one-time liming was greater in limed plots than in unlimed plots for at least 10 years. Decline of soil pH by fertilization mainly happened in the 0-10 cm depth with N only, and in the 0-5 cm layer with NS treatment, whereas these treatments tended to increase soil pH in layers below 10 cm. One-time surface application of granular lime increased soil pH, mainly in the 0-5 cm layer, and the effect was maintained for at least 9 years. Mass of TOC, TON, LFOC, and LFON in different soil layers increased with combined applications of N and S fertilizers (NS), but the effect was much more pronounced in the 0-7.5 cm soil layer, and also varied with organic fraction. Light organic fractions were more responsive to applied NS than total organic fractions. The findings suggest that application of N and S together was effective in sustaining high forage yield and increasing C and N sequestration in a soil deficient in both N and S.
  • Authors:
    • Ziadi, N.
    • Angers, D. A.
    • Morel, C.
    • Parent, L. E.
    • Messiga, A. J.
  • Source: Geoderma
  • Volume: 164
  • Issue: 3-4
  • Year: 2011
  • Summary: Under long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0-5 cm layer from plots under NT and MP receiving 35 kg P ha -1 and 160 kg N ha -1. Samples were separated into three water-stable aggregate-sized classes (macro, 2000-250 m; meso, 250-180 m; micro, 180-53 m) and (silt+clay)-sized particles (<53 m) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt+clay)-sized particles < micro- < meso- < macro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt+clay)-sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes under NT in relation to Pw concentration was also observed for carbon content, indicating that Pw is influenced by soil aggregation as driven by SOM accumulation. The lower Pw concentration in (silt+clay)-sized particles could be explained by a greater retention of P by reactive oxides and highly disordered alumino-silicates present on (silt+clay)-sized particles, thereby reducing the soluble P released from these particles. One important aspect of this study is the contrasting P sorption characteristics of solid particles under NT and MP. The P sorption maxima (S max value) of the (silt+clay)-sized particles was twice that of the water-stable aggregates. Sorption characteristics reflect the hierarchy observed under NT for organic C and Pw, indicating a closer link between SOM and P dynamics within soil aggregates in contrast with MP.
  • Authors:
    • Flaten, D. N.
    • Entz, M. H.
    • Vaisman, I.
    • Gulden, R. H.
  • Source: Agronomy Journal
  • Volume: 103
  • Issue: 3
  • Year: 2011
  • Summary: The blade roller offers new opportunities to reduce tillage, especially in organic farming. The objective of the study was to reduce tillage in the green manure phase of a green manure-wheat ( Triticum aestivum L.) rotation by substituting tillage with blade rolling. A pea ( Pisum sativum L.) and oat ( Avena sativa L.) green manure was used for two site-years at Carman, MB, while a pea monocrop was used for one site-year at Oxbow, SK. At pea flowering, the green manure was terminated by rolling, tilling, or a combination of the two. Ammonia emissions were greater in the no-till compared with the tilled green manure system, though total ammonia losses were low (<13 kg ha -1). Replacing tillage with rolling reduced soil nitrate N in autumn after green manure by 56 to 88 kg ha -1 in the 0- to 60-cm soil depth. Reduced green manure tillage did not affect wheat establishment but delayed plant development in some instances. Fewer weeds were often observed in wheat in the no-till compared with tilled plots. Total N supply in the green manure-wheat system was reduced in the no-till system compared to the tilled only system at two out of three site-years by an average of 44%. While reduced N supply in the reduced tillage system coincided with reduced wheat yield and protein, it was concluded that factors other than N also were involved. Using the blade roller instead of tillage in the green manure year provides soil conservation benefits and facilitates wheat production the following year.
  • Authors:
    • Drury, C. F.
    • Carter, M. R.
    • Angers, D. A.
    • Janzen, H. H.
    • Ellert, B. H.
    • McConkey, B. G.
    • Bremer, E.
    • VandenBygaart, A. J.
    • Lafond, G. P.
    • McKenzie, R. H.
  • Source: Soil Science Society of America Journal
  • Volume: 75
  • Issue: 1
  • Year: 2011
  • Summary: The depth of sampling has recently been highlighted as critical to making accurate measurements of changes in SOC stocks. This paper aimed to determine the effects of land management changes (LMC) on soil organic carbon (SOC) by re-sampling long-term agoecosystem experiments (LTAEs) across Canada using identical sampling and laboratory protocols. The impact of sampling depth on the monitoring of LMC-induced differences in SOC stock in LTAEs in Canada, and the implications on statistical power and sampling design, were assessed. In most cases, four cores would be suitable for detecting a significant difference in SOC stock of 5 Mg ha -1 at 95% confidence for LMCs in western Canada. The impact of eliminating fallow on SOC stocks was typically restricted to the surface 15 cm. The impact of perennial forages on the average cumulative SOC was sufficiently large to be detectable at all sampling depths (to 60 cm). In three of the six LTAEs sampled in western Canada comparing conventional tillage to no-till, there was a significantly greater SOC storage in the 0- to 30-depth than the 0- to 15-cm depth, suggesting that sampling below 15 cm could be necessary. The same comparisons in eastern Canada suggested that sampling often must exceed the 30-cm depth to account for any changes in SOC due to moldboard plow tillage. Nonetheless, there was little evidence to suggest that increasing sampling intensity or sampling deeper would improve the ability to detect a difference in SOC stocks for this LMC.
  • Authors:
    • Lemke, R.
    • Frick, B.
    • Nagy, C. N.
    • Campbell, C. A.
    • Ulrich, D.
    • Thomas, A. G.
    • Brandt, S. A.
    • Basnyat, P.
    • Zentner, R. P.
    • Malhi, S. S.
    • Olfert, O. O.
    • Fernandez, M. R.
  • Source: Renewable Agriculture and Food Systems
  • Volume: 26
  • Issue: 3
  • Year: 2011
  • Summary: Producers in the semi-arid Dark Brown Chernozemic (Typic Boroll) soil zone of the Canadian Prairie are contemplating changes to land-use practices, moving away from conventional high-input production systems that specialize in one or two annual grain crops to more diversified and extended cropping systems that use reduced-input and organic management practices. This study examined the economic merits of nine cropping systems, consisting of a factorial combination of three input management methods and three levels of cropping diversity. It was conducted over the 1996-2007 period on a loam soil at Scott, Saskatchewan. The input treatments were: (1) high input (HIGH), which used conventional tillage and full recommended rates of fertilizers and pesticides 'as required'; (2) reduced input (RED), which used conservation tillage and integrated weed and nutrient management practices in an effort to lower requirements for fuel, fertilizers and pesticides; and (3) organic input (ORG), which used tillage, non-chemical pest control, higher seeding rates, delayed seeding and legume crops to replenish soil nutrients. The crop diversity treatments included: (1) a fallow-based rotation with low crop diversity (LOW); (2) a diversified annual rotation of cereal, oilseed and pulse grains (DAG); and (3) a diversified rotation using annual grains and perennial forages (DAP). All crop rotations were 6 years in length. At the 2007 input costs and prices, average net returns and 12-year net present values were higher for organic than for non-organic treatments, with the ORG input/LOW crop diversity system being the most profitable (net returns=$234 ha -1 yr -1 and net present value=$1953 ha -1). Net returns averaged about 10% less for ORG/DAG compared to the most profitable system, and about 22% less for HIGH/DAG and RED/DAG (the best non-organic systems). The DAP treatments that included forage were not economically competitive with the other treatments, often producing economic losses. The relative profitability of the organic treatments was highly dependent on the existence of organic price premiums. When price premiums for organic crops were reduced to less than 70% of the 2007 levels, the organic treatments were less profitable than the comparable non-organic treatments. The organic treatments also experienced significantly lower (and often negative) net returns compared to the non-organic treatments during completion of the 3-year organic certification period. We estimated that it required 5-7 years after completion of certification for the organic treatments to break even with the comparable non-organic treatments. Thereafter the organic treatments produced consistently higher net earnings. Production costs averaged 16% lower with ORG management compared to the HIGH-input treatments, but we found little difference in total costs between the respective HIGH- and RED-input treatments. The organic treatments also displayed lower income variability than the non-organic treatments, with the ORG/LOW system being preferred by risk-averse producers, who do not subscribe to all-risk crop insurance, and with the ORG/LOW and ORG/DAG systems preferred by low and medium risk-averse producers when having the added financial protection from the Canada/Saskatchewan all-risk crop insurance program.