Soil bulk density and crop yield under eleven consecutive years of corn with different tillage and residue practices in a sandy loam soil in central Canada
Introduction
Agricultural tillage practices have changed in Canada over the decades. The 2001 Canadian Agricultural Census showed an increasing trend in farms using conservation tillage practices (Statistics Canada, 2002). In 1991, for example, 31% of Canadian farms used conservation tillage practices. This rose to 60% in 2001. Conservation tillage is intended to leave residue on the soil surface, and may include reduced till (using disks or chisel plough, for example) or no-till. Meanwhile, conventional tillage typically involves moldboard plowing after harvest and disking in the spring before seeding.
Conventional tillage helps to control weeds, enhance porosity, and incorporate organic matter into the soil. However, conventional tillage also tends to increase soil erosion and degrade natural soil structure (Hillel, 1982). In contrast, conservation tillage minimizes erosion, conserves water within the root zone, and improves soil productivity (Dürr et al., 2001).
Conservation tillage practices can also impact soil physical properties, such as bulk density, total porosity, hydraulic conductivity and aggregate stability, both positively and negatively. For example, Ausilio et al. (2001) found that after 5 years of conventional tillage corn (Zea mays L.), the clay loam soil had a higher aggregate instability than no-till. Also, Kushwaha et al. (2001) found that no-till had a 10% higher bulk density than conventional tillage in a sandy loam soil study cropped to corn over 2 years.
Bulk density is considered to be a measure of soil quality due to its relationships with other properties (eg., porosity, soil moisture, hydraulic conductivity, etc.). Blevins et al. (1994) found that no-till and conventional tillage had no significant bulk density differences. Fausey et al. (1994) found that on continuous corn, corn-soybean (Glycine max. L. Merrill) and corn-oat (Avena sativa L.)-meadow rotations that no-till had a 7% lower bulk density in all rotations compared to conventional tillage. Fausey et al. (1994) concluded that, after 28 years, bulk density was lowest in no-till likely due to crop residues maintained on the soil surface.
Corn yields are undoubtably affected by such field characteristics and operations as soil strength, compaction, soil water, tillage and residue practices, time of field operations and soil fertility, which together influence emergence, root development and nutrient availability (Curnoe et al., 2001). Residues from the previous year left on the soil surface can influence subsequent yields, which Denton and Wagger (1992) attributed to the presence of residue cover, which increased soil water availability and grain yield in their no-till plots. Kapusta et al. (1996) found that no-till had a lower corn population and greater barrenness (where no corn grew) compared to conventional, reduced and alternating tillage practices over 20 years on a silt loam. They concluded that no-till was not beneficial on imperfectly drained soils (Kapusta et al., 1996). Poorly drained soils are of concern in parts of Quebec where corn production on heavy clay soils is common.
Considering that to obtain good yields, the early stages of growth are critical, especially optimal soil and air temperatures and soil moisture conditions for healthy emergence, no-till is generally perceived to produce lower yields than conventional tillage. Drury et al. (1999) found that no-till plots had delayed corn emergence on a clay loam site in Ontario, Canada due to cooler soil temperatures and wetter seed beds. Some of these poor seed bed conditions in no-till systems could be attributed to residue cover remaining on the soil surface. Residue cover in the spring can trap melting snow and also reduce evaporation from the soil surface in the spring, thus keeping the soil cooler which can be detrimental to early crop growth (Drury et al., 1999, Jamieson et al., 1999). Delayed corn emergence rates are a concern within minimally tilled sites. Early season growth might be delayed in conservation tillage systems due to higher water contents and lower soil temperatures. However, no-till systems could be beneficial to crop growth in seasons that are drier than normal, as Kapusta et al. (1996) found on a silt loam in Illinois.
Crop yield studies are difficult to compare due to variations in length of the study, soil type and climatic region between studies. Kapusta et al. (1996) found after 20 years of corn on no-till, reduced tillage and conventional tillage on a silt loam in southern Illinois, there were no significant differences in pooled corn yields between treatments. Clapp et al. (2000) working on a silt loam soil in east central Minnesota, found that in 9 out of 13 years of corn under no-till, chisel plow and moldboard plow, there were no tillage effects on grain yield, but there were differences due to residue management in 8 of the 13 years. In Atlantic Canada, Carter et al. (2002) found that after 6 years of corn on no-till, conventional and rotational tillage, the mean yield was 7.2–7.7 Mg ha−1 and it was not consistently influenced by tillage. Also, dry matter yield had a yearly variation of 5.1–10.6 Mg ha−1, which Carter et al. (2002) attributed to plant population and corn heat units rather than tillage or rotation.
Since the establishment in1991of the research site described in this paper, Burgess et al. (1996), Mehdi (1998), Mehdi et al. (1999), Callum (2001) and Dam (2003) have conducted research in different years each with different objectives related to tillage and residue differences. The common parameters taken during each study was bulk density, corn emergence rates (in some years) and crop yield. In order to investigate the trends or differences due to tillage practices or residue treatment, data was complied from those studies. Therefore, the objective of this study was to determine how 11 years of continuous and differing tillage and residue treatments affected soil bulk density, corn emergence rates, and yields on loamy sand–sandy loam soil cropped to corn in southwestern Quebec, Canada.
Section snippets
Site description
The site was located on a 2.4-ha area on the Macdonald Campus Research Farm of McGill University in Ste-Anne-de-Bellevue, Québec, Canada (latitude 45°30′N, longitude 73°35′W). The soil is St. Amable loamy sand and shallow loamy sand with pockets of Courval sandy loam, overlying clay at a mean depth of 0.46 m. It is classified as a Dystric Gleysol in the FAO soil classification system. The mean sand, silt and clay contents over the 0–0.20 m depth were 815, 89, 96 g kg−1, respectively. The average
Bulk density
Average bulk density was generally significantly lower at 0–0.10 m than in the underlying layer (1.29 and 1.35 Mg m−3, respectively). There was no depth × residue interaction in any of the 11 years and only one instance of depth × tillage × residue interaction was confined to 1996 (Table 2). The depth × tillage × residue interaction in 1996 could be attributed to significantly greater soil strength measured in the NTR and NTNR compared to the other treatments in early spring 1996 (Mehdi et al., 1999).
Conclusions
The following conclusions were drawn from this study:
- i.
Bulk density was affected by tillage practices, but only within the first 0.10 m. Both CT and RT reduced bulk density relative to NT. Residues did not affect bulk density nor was there any temporal trend in bulk density over the 11 years.
- ii.
Tillage × residue interactions affected corn emergence in most years. Poorer emergence found with NTR was attributed to cooler soil temperatures and higher soil moisture associated with the residues remaining on
Acknowledgements
This study was funded by the Fonds québecois de recherche sur la nature et les technologies du Québec (FQRNT). The authors would like to thank Peter Kirby, Department of Natural Resource Sciences, McGill University, for his assistance with the field work.
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