C. F. Drury

Impact of tillage practices on organic carbon and nitrogen storage in cool, humid soils of eastern Canada

Abstract Soil organic matter storage capacity in agroecosystems varies with soil type, climate and agricultural management practices. The effects of different tillage systems on organic C and N storage were determined for a range of soils of eastern Canada mainly under continuous corn and small grain cereal production. Soil profiles from eight sites on which comparative tillage experiments had been performed for up to 11 years were sampled to a 60 cm depth in four increments (0–10, 10–20, 20–40 and 40–60cm). Organic C and N contents and dry bulk density were determined for each sampling depth. Bulk density measurements showed that the total soil mass in the soil profiles was not influenced by the tillage systems. No significant differences were found between tillage treatments in the total organic C and N storage down to 60 cm depth; the soil profiles under no-till (NT) and chisel plowing (CP) generally did not contain more C and N than those under conventional moldboard plowing (MP). However, the depth distribution of soil C and N varied with tillage. In the surface 0–10cm, C and N contents were higher under NT than under MP, whereas at deeper levels (20–40cm) the reverse trend was observed. It is concluded than under eastern Canadian conditions, where crop production and residue inputs are not affected by tillage, reduced tillage systems would not result in the storage of more soil organic matter in the entire soil profile at least in a 5–10 year period. Placement of the residues would be a major factor influencing the C and N distribution at specific depths.

Elucidation of the source and turnover of water soluble and microbial biomass carbon in agricultural soils

Understanding the dynamics of soil C is key to managing soil organic matter to enhance soil quality and ecosystem functioning, and reduce trace gas emissions from soils. Our objective was to determine the source and turnover of C pools in some agricultural soils in eastern Canada. Soils from five field experiments under continuous maize cropping for 4–37 yr were sampled, and the organic C content and stable C isotope (13C) composition of whole soil and water soluble and microbial biomass fractions determined. The 13C results showed a clear distinction between the water soluble organic C and microbial biomass C, with the water soluble organic C more like the whole soil and the microbial biomass more like the maize residues. A simple linear model was used to explore the relationship among the soil organic constituents and evaluate the turnover of these carbon pools. Even though the water soluble organic C had a higher turnover rate than the microbial biomass C, the proportion of C4-derived C in the biomass was about 2.5 times greater than that in water soluble organic C. Apparently the large amount of native soil C, the small amount of water soluble organic C, and its equilibrium with the native soil C, cause humus to dominate the isotopic composition of water soluble organic C even though the water soluble C is very active. Our results suggest that the quantity, as well as the turnover rate, of soil organic matter constituents that are in equilibrium influence the isotopic composition of such constituents.

Opportunities for improved fertilizer nitrogen management in production of arable crops in eastern Canada: a review.

There is increasing public pressure to reduce the environmental impacts of agricultural production. Therefore, one key challenge to producers is to manage their crop production systems in order to minimize losses of nitrogen to air or water, while achieving crop yield and quality goals. Many strategies have been developed in recent years to meet this challenge. These include: development of new tools to measure crop N status in order to refine in-season fertilizer N management, development of new soil N tests to improve prediction of soil N supply, development of new fertilizer N products with release patterns more closely matched to crop N uptake patterns, and development of site-specific N management strategies. We review the opportunities and limitations to these new strategies within different arable crop production systems under the humid and sub-humid soil moisture regimes present in eastern Canada. Future research opportunities to improve the efficiency of fertilizer N utilization include developme...

Toward Improved Coefficients for Predicting Direct N2O Emissions from Soil in Canadian Agroecosystems

Agricultural soils emit nitrous oxide (N2O), a potent greenhouse gas. Predicting and mitigating N2O emissions is not easy. To derive national coefficients for N2O emissions from soil, we collated over 400 treatment evaluations (measurements) of N2O fluxes from farming systems in various ecoregions across Canada. A simple linear coefficient for fertilizer-induced emission of N2O in non-manured soils (1.18% of N applied) was comparable to that used by the Intergovernmental Panel on Climate Change (IPCC) (1.25% of N applied). Emissions were correlated to soil and crop management practices (manure addition, N fertilizer addition and inclusion of legumes in the rotation) as well as to annual precipitation. The effect of tillage on emissions was inconsistent, varying among experiments and even within experiments from year to year. In humid regions (e.g., Eastern Canada) no-tillage tended to enhance N2O emissions; in arid regions (e.g., Western Prairies) no-tillage sometimes reduced emissions. The variability of N2O fluxes shows that we cannot yet always distinguish between potential mitigation practices with small (e.g., <10%) differences in emission. Our analysis also emphasizes the need for developing consistent experimental approaches (e.g., ‘control’ treatments) and methodologies (i.e. measurement period lengths) for estimating N2O emissions.

Managing tile drainage, subirrigation, and nitrogen fertilization to enhance crop yields and reduce nitrate loss.

Improving field-crop use of fertilizer nitrogen is essential for protecting water quality and increasing crop yields. The objective of this study was to determine the effectiveness of controlled tile drainage (CD) and controlled tile drainage with subsurface irrigation (CDS) for mitigating off-field nitrate losses and enhancing crop yields. The CD and CDS systems were compared on a clay loam soil to traditional unrestricted tile drainage (UTD) under a corn (Zea Mays L.)-soybean (Glycine Max. (L.) Merr.) rotation at two nitrogen (N) fertilization rates (N1: 150 kg N ha(-1) applied to corn, no N applied to soybean; N2: 200 kg N ha(-1) applied to corn, 50 kg N ha(-1) applied to soybean). The N concentrations in tile flow events with the UTD treatment exceeded the provisional long-term aquatic life limit (LT-ALL) for freshwater (4.7 mg N L(-1)) 72% of the time at the N1 rate and 78% at the N2 rate, whereas only 24% of tile flow events at N1 and 40% at N2 exceeded the LT-ALL for the CDS treatment. Exceedances in N concentration for surface runoff and tile drainage were greater during the growing season than the non-growing season. At the N1 rate, CD and CDS reduced average annual N losses via tile drainage by 44 and 66%, respectively, relative to UTD. At the N2 rate, the average annual decreases in N loss were 31 and 68%, respectively. Crop yields from CDS were increased by an average of 2.8% relative to UTD at the N2 rate but were reduced by an average of 6.5% at the N1 rate. Hence, CD and CDS were effective for reducing average nitrate losses in tile drainage, but CDS increased average crop yields only when additional N fertilizer was applied.

Evaluation of two process-based models to estimate soil N2O emissions in Eastern Canada

Process-based models play an important role in the estimation of soil N2O emissions from regions with contrasting soil and climatic conditions. A study was performed to evaluate the ability of two process-based models, DAYCENT and DNDC, to estimate N2O emissions, soil nitrate- and ammonium-N levels, as well as soil temperature and water content. The measurement sites included a maize crop fertilized with pig slurry (Quebec) and a wheat-maize-soybean rotation as part of a tillage-fertilizer experiment (Ontario). At the Quebec site, both models accurately simulated soil temperature with an average relative error (ARE) ranging from 0 to 2%. The models underpredicted soil temperature at the Ontario site with ARE from −5 to −7% for DNDC and from −5 to −13% for DAYCENT. Both models underestimated soil water content particularly during the growing season. The DNDC model accurately predicted average seasonal N2O emissions across treatments at both sites whereas the DAYCENT model underpredicted N2O emissions by 32...

Short-term Effects of Tillage Practices on Organic Carbon in Clay Loam Soil of Northeast China

A tillage experiment, consisting of moldboard plow (MP), ridge tillage (RT), and no-tillage (NT), was performed in a randomized complete block design with four replicates to study the effect of 3-year tillage management on SOC content and its distribution in surface layer (30 cm) of a clay loam soil in northeast China. NT did not lead to significant increase of SOC in topsoil (0–5 cm) compared with MP and RT; however, the SOC content in NT soil was remarkably reduced at a depth of 5–20 cm. Accordingly, short-term (3-year) NT management tended to stratify SOC concentration, but not necessarily increase its storage in the plow layer for the soil.

Nitrous oxide and carbon dioxide emissions from monoculture and rotational cropping of corn, soybean and winter wheat

It is well established that nitrous oxide (N2O) and carbon dioxide (CO2) emissions from agricultural land are influenced by the type of crop grown, the form and amount of nitrogen (N) applied, and the soil and climatic conditions under which the crop is grown. Crop rotation adds another dimension that is often overlooked, however, as the crop residue being decomposed and supplying soluble carbon to soil biota is usually from a different crop than the crop that is currently growing. Hence, the objective of this study was to compare the influence of both the crop grown and the residues from the preceding crop on N2O and CO2 emissions from soil. In particular, N2O and CO2 emissions from monoculture cropping of corn, soybean and winter wheat were compared with 2 -yr and 3-yr crop rotations (corn-soybean or corn-soybean-winter wheat). Each phase of the rotation was measured each year. Averaged over three growing seasons (from April to October), annual N2O emissions were about 3.1 to 5.1 times greater in monocu...

Impacts of Zone Tillage and Red Clover on Corn Performance and Soil Physical Quality

benefits of conservation tillage with the yield benefits of conventional moldboard plow tillage (e.g., Pierce et Despite extensive research, reduced corn (Zea mays L.) performance is still encountered using conservation tillage on fine-textured al., 1992) for cool humid climatic zones. Here, a narrow soils in cool humid temperate climates. These problems are intensified zone 10 to 20 cm wide by 10 to 30 cm deep is conventionwhen corn is planted into residue from a previous crop such as winter ally tilled in the crop row while the rest of the soil surface wheat (Triticum aestivum L.). The objective of this 4-yr study was is left in an untouched no-till state. This supposedly to determine the influence of fall zone tillage (ZT), no tillage (NT), encourages the more favorable soil temperature, moisand conventional moldboard plow tillage (CT) (fall plowing) on corn ture, aeration, density, and strength conditions associperformance and soil physical quality under a winter wheat–corn– ated with conventional tillage in the narrow seedbed soybean (Glycine max L. Merr.) rotation with and without red clover (Trifolium pratense L.) (RC) underseeded in the wheat phase of the zones, while retaining the increased erosion resistance, rotation. A randomized complete block design (3 2 factorial, 4 organic matter protection and reduced energy inputs of replicates) was established on three adjacent fields in the fall of 1996 no tillage between the zones. Although there is much on a Brookston clay loam soil (fine loamy, mixed, mesic, Typic Argiainterest in the zone-till system, it has not yet been tested quoll) at Woodslee, ON Canada, and measurements were collected extensively in cool humid temperate climates, nor on during 1997 to 2000. Over both wet and dry growing seasons from the agriculturally important clay and clay loam soils of 1998-2000, zone tillage following underseeded RC produced average southern Ontario. In nearby Michigan, ZT on sandy corn grain yields (7.23 Mg ha 1) that were within 1% of those obtained using conventional tillage (7.33 Mg ha 1), and 36% higher than those loam soils did indeed improve potato (Solanum tuberoobtained using no tillage and RC (5.33 Mg ha 1). Zone tillage also sum L.) yields and soil physical conditions relative to improved soil quality as evidenced by generally lower soil strength conventional tillage in most years of a 4-yr study (Pierce than no tillage, and near-surface soil physical quality parameters that and Burpee, 1995); however, corn yields were not inwere equivalent to, or more favorable than, those of the other treatcreased by zone tillage in a similar 3-yr study, despite ments. It was concluded that corn production using zone tillage and substantially reduced soil strength (penetration resisRC underseeding is a viable option in Brookston clay loam soil, as it retains much of the soil quality benefit of conventional tillage but tance) within the 0to 30-cm depth range (Pierce et still achieves most of the yield benefit of conventional moldboard al., 1992). plow tillage. Red clover underseeded in cereals can produce large quantities of plant biomass and it fixes N in the nodules, which can in turn provide the equivalent of 90 to 125 C systems, such as no-till, have kg N ha 1 to the following crop (Bruulsema and Christie, been demonstrated to have several advantages 1987). In addition, RC can be effective in cool-temperover conventional moldboard plow systems, including ate climates for increasing microbial biomass, improving reduced soil erosion and surface runoff, slower loss of the structure of fine-textured soils (Drury et al., 1991), soil organic matter, and lower production costs. Howand for accelerating the decomposition of surface crop ever, there are many reports of reduced corn emergence residues (Drury et al., 1999). It was consequently hyand yields under no-till relative to conventional till on pothesized that including RC underseeding in a crop fine-textured soils in humid and cool temperate clirotation might further improve the potential yield and mates. This appears to be primarily a result of spring soil quality benefits of zone tillage on fine-textured soils. soil conditions that are cooler (Graven and Carter, 1991; The objective of this study was to determine, for a Fortin and Pierce, 1990; Fortin and Pierce, 1991) and clay loam soil in southern Ontario, if zone tillage and wetter (Fortin, 1993) relative to conventional tillage, RC underseeding could achieve corn yields comparable plus other factors such as increased soil bulk density with conventional moldboard plow tillage, but still reand strength (e.g., Hill, 1990; Pierce et al., 1992), detain most of the soil quality, environmental, and reduced creased soil air-filled porosity and saturated hydraulic energy inputs of no tillage. To accomplish this, convenconductivity (e.g., Pierce et al., 1992), and desiccation of seeds or seedlings through reopening of the planting tional moldboard plow tillage, no tillage, and zone-tillage slot produced by the no-till planter (Drury et al., 1999). systems were applied to a winter wheat–corn–soybean Zone tillage has been proposed as a possible alternarotation, with and without RC underseeded in the wintive tillage system that may combine the soil quality ter wheat. Evaluations were made on the basis of corn emergence, corn yield, and near-surface soil physical C.F. Drury, C.S. Tan, W.D. Reynolds, T.W. Welacky, S.E. Weaver, quality. and A.S. Hamill, Greenhouse & Processing Crops Research Centre, Agriculture and Agri-Food Canada, Harrow, ON, Canada N0R 1G0. T.J. Vyn, Dep. of Agronomy, Purdue Univ., West Lafayette, IN 47907Abbreviations: CHU, corn heat unit; CT, conventional moldboard 1150. Received 22 Jan. 2002. *Corresponding author (druryc@agr. plow tillage; FC, field capacity; NT, no tillage; PR, penetration resisgc.ca). tance; PWP, permanent wilting point; RC, red clover; WAS, wet aggregate stability; ZT, zone tillage. Published in Soil Sci. Soc. Am. J. 67:867–877 (2003).

Evaluating the Effect of Tillage on Carbon Sequestration Using the Minimum Detectable Difference Concept

Three long-term field trials in humid regions of Canada and the USA were used to evaluate the influence of soil depth and sample numbers on soil organic carbon (SOC) sequestration in no-tillage (NT) and moldboard plow (MP) corn (Zea mays L.) and soybean (Glycine max L.) production systems. The first trial was conducted on a Maryhill silt loam (Typic Hapludalf) at Elora, Ontario, Canada, the second on a Brookston clay loam (Typic Argiaquoll) at Woodslee, Ontario, Canada, and the third on a Thorp silt loam (Argiaquic Argialboll) at Urbana, Illinois, USA. No-tillage led to significantly higher SOC concentrations in the top 5 cm compared to MP at all 3 sites. However, NT resulted in significantly lower SOC in sub-surface soils as compared to MP at Woodslee (10-20 cm, P=0.01) and Urbana (20-30 cm, P＜0.10). No-tillage had significantly more SOC storage than MP at the Elora site (3.3 Mg C ha^(-1)) and at the Woodslee site (6.2 Mg C ha^(-1)) on an equivalent mass basis (1350 Mg ha^(-1) soil equivalent mass). Similarly, NT had greater SOC storage than MP at the Urbana site (2.7 Mg C ha^(-1)) on an equivalent mass basis of 675 Mg ha^(-1) soil. However, these differences disappeared when the entire plow layer was evaluated for both the Woodslee and Urbana sites as a result of the higher SOC concentrations in MP than in NT at depth. Using the minimum detectable difference technique, we observed that up to 1500 soil sample per tillage treatment comparison will have to be collected and analyzed for the Elora and Woodslee sites and over 40 soil samples per tillage treatment comparison for the Urbana to statistically separate significant differences in the SOC contents of sub-plow depth soils. Therefore, it is impracticable, and at the least prohibitively expensive, to detect tillage-induced differences in soil C beyond the plow layer in various soils.