Effect of Long-Term Minimum Tillage Practices on Some Physical Properties of a Chernozemic Clay Loam

217

147

. Estimation of N 2 O emissions from agricultural soils in Canada. I. Development of a country-specific methodology. Can. J. Soil. Sci. 88: 641Á654. International initiatives such as the United Nations Framework Convention on Climate Change and the Kyoto Protocol require that countries calculate national inventories of their greenhouse gas emissions. The objective of the present study was to develop a country-specific (Tier II) methodology to calculate the inventory of N 2 O emissions from agricultural soils in Canada. Regional fertilizer-induced emission factors (EFreg) were first determined using available field experimental data. Values for EFreg were 0.0016 kg N 2 O-N kg(1 N in the semi-arid Brown and 0.008 kg N 2 O-N kg N(1 in the sub-humid Black soil zones of the Prairie region, and 0.017 kg N 2 O-N kg (1 N in the humid provinces of Quebec and Ontario. A function relating EFreg to the ''precipitation to potential evapotranspiration'' ratio was determined to estimate annual emission factors (EFeco) at the ecodistrict scale (:150 000 ha) in all agricultural regions of Canada. Country-specific coefficients were also developed to account for the effect of several additional factors on soil N 2 O emissions. Emissions from fine-textured soils were estimated as being 50% greater than from coarse-and medium-textured soils in eastern Canada; emissions during winter and spring thaw corresponded to 40% of emissions during the snow-free season in eastern Canada; increased emissions from lower (wetter) sections of the landscape and irrigated areas were accounted for; emissions from no-till soils were 10% greater in eastern, but 20% lower in western Canada than from those under conventional tillage practices; emissions under summerfallow were estimated as being equal to those from soils under annual cropping. This country-specific methodology therefore accounts for regional climatic and land use impacts on N 2 O emission factors, and includes several sources/offsets that are not included in the Intergovernmental Panel on Climate Change (IPCC) default approach. For personal use only.

Section: Determination Of Efecomentioning

confidence: 99%

Estimation of N₂O emissions from agricultural soils in Canada. I. Development of a country-specific methodology

Rochette¹,

Worth²,

Lemke³

et al. 2008

217

147

“…Tillage mixes the surface soil, thereby generally reducing its bulk densitl' compared to NT (Ellis et al 1977;Francis et al 1987;Chang and Lindwall 1989;Maule and Reed 1993), rhus we need to examine changes in organic matter on a mass basis.…”

Section: Canadian Journal Of So'l Sciencementioning

confidence: 99%

Carbon sequestration in a Brown Chernozem as affected by tillage and rotation

Campbell¹,

McConkey²,

Zentner³

et al. 1995

122

ence, l'effet des techniques de conservation de la neige sur la matiEre organique du sol mais cet 6l6ment s'est r6v6l6 non significatif. Les changemenm affectant la matidre organique 6taient observ6s principalement dans la couche de 0 d 7,5 cm de profondeur.Les corrcentrations et les quantit6s de C et de N 6taient plus 6lev6es en rdgime de bl6 en continu qu'en celui d'alternance jachdreb16, systdme qui est utilis6 dans cette rdgion depuis prds de 80 ans. Dans la tranche de 0-75, cm la quantit6 de m.o. n'6tait que mod6r6ment plus grande dans les parcelles conduites en semis direct que dans celles conduites selon les m6thodes de travail classique. En revanche, dans la rotationjachdre-b16, le r6gime de travail du sol ne produisait pas de diffdrences significatives (P > 0,10). Durant la p6riode de 12 ans, le b16 en continu, r6gimes de travail confondus, emmagasinait environ 2 tha-r plus de C dans les 15 premiers cm du sol que I'assolementjachdre-b16, le plus gros du gain survenant dans les cinq premidres anndes. En outre, lebl6encontinuenr6gimeSDacqu6raitquelquel,5tha-1 plusdeC qu'enr6gimeTCetl'assolementjachdre-bld0.5tha-ren r6gime SD qu'en rdgime TC. Aprds 9 ans de conduite en semis direct, le passage pendant 3 ans au r6gime TC de I'assolement b16 en continu a provoqud une baisse signiircative (P<0,05) de la m.o. Nos observations confortes par des calculs bas6s sur la production dei restei de culture montrint qu'un accroissement du C organique de I'ordre d'environ 0,4 it 4,5 t ha-l par ann6e s'est produit dans les 15 premiers cm du sol sous assolement bl6 en continu entre 1992 et 1993. Toutefois, vu I'incertitude des niveaux de C estim6s au d6but de 1'exp6rience, la nature du taux d'accroissement de C, lin6aire ou curvilin6aire, n'a pu Otre 6tablie.

“…Conventional tillage is commonly performed with a heavyduty cultivator, which reduces the original surface cover by average values of 30 to 50% during primary tillage, and by 5 to 20% during the second operation (Anderson 1961). The effect of CT and NT on selected soil physical properties in the Canadian Prairies (Chang and Lindwall 1989, 1990Grant and Lafond 1993;Lafond et al 1992;Maulé and Reed 1993;Larney and Lindwall 1995) has been examined, but few studies have compared the soil water characteristic, unsaturated hydraulic conductivity and pore-size distribution of soils under CT and NT (Azooz et al 1996).Overall, tillage effects on soil physical properties are uncertain and variable. For example, some researchers have found no tillage effect (Hill et al 1985;Benjamin 1993) on the soil water characteristic, while others found that NT retained more soil water than CT ( Reynolds et al 1995;Miller et al 1998).…”

mentioning

confidence: 99%

mentioning

confidence: 99%

Physical properties of a Chernozemic clay loam soil under long-term conventional tillage and no-till

Miller¹,

Larney²,

Lindwall³

1999

Self Cite

a Chernozemic clay loam soil under long-term conventional tillage and no-till. Can. J. Soil Sci. 79: 325-331. Conservation tillage practices such as no-till (NT) and conventional tillage (CT) with a heavy-duty cultivator can influence the physical properties of soils. This study was conducted to determine the effect of 24 yr of NT versus CT on the physical properties of a clay loam soil in southern Alberta. Physical properties quantified were bulk density (BD), mean weight diameter (MWD), plant-available water-holding capacity (PAWHC), saturated hydraulic conductivity (K sat ), soil water characteristic [θ θ(ψ ψ)] and unsaturated hydraulic conductivity [K(ψ ψ)] relationships, and pore-size distribution (PSD). Bulk soil samples and small soil cores (5-cm depth increments to 20 cm) were taken from CT and NT fields in 1992, and tension infiltrometer measurements were made in 1994. The results from this study are reported as general trends for the tillage fields. Statistical probability levels are not reported because of the unreplicated nature of the experiment, the limited number of sampling locations within each tillage field, and to a lesser extent, the different sampling times for CT and NT in 1992. Plant-available water-holding capacity was higher for the CT field (14.3%) than the NT field (10.8%), and a greater amount of water was held at a given water potential (-1500 to -1.5 kPa) for the former, indicating a higher potential for soil water conservation under conventional tillage. Geometric mean K sat values (small soil cores) were higher for the NT field (18.20 × 10 -6 m s -1 ) than the CT field (1.74 × 10 -6 m s -1 ). The K(ψ) values (small soil cores) between -10 and -2 kPa were higher for the CT field than the NT field at the 0-to 5-cm, 10-to 15-cm and 15-to 20-cm depths, but values were higher for the NT field at the 5-to 10-cm depth. Near-saturated K(ψ) values (-1.5 to -0.3 kPa) of the surface soil, as derived from tension infiltration measurements in 1994, were higher for the CT field (2.43 × 10 -7 m s -1 ) than for the NT field (6.09 × 10 -8 m s -1 ). There was a greater percentage volume of larger pores (30-40, 40-67, 67-200, >200 µm) for the NT field than for the CT field, and there was a lower percentage volume of smaller pores (0.2-0.6, 0.6-4 µm) for the CT field than for the NT field. Differences in certain soil physical properties between CT and NT fields may be related to the lag time between the most recent tillage event and sampling for the CT field.Key words: Conservation tillage, heavy-duty cultivator, physical attributes, soil water, hydraulic conductivity, porosity Miller, J. J., Larney, F. J. et Lindwall, C. W. 1999. Propriétés physiques d'un loam argileux tchernozémique exposé à long terme à des régimes de travail classique ou de semis direct. Can. J. Soil Sci. 79: 325-331. Les pratiques de travail de conservation du sol, tel le semis direct (SD), et les méthodes de travail classique (TC) utilisant le cultivateur lourd peuvent influer sur les propriétés physiques du sol. L'objet de nos...