Short-term impact of fallow frequency and perennial grass on soil organic carbon in a Brown Chernozem in southern Alberta

Abstract

. Short-term impact of fallow frequency and perennial grass on soil organic carbon in a Brown Chernozem in southern Alberta. Can. J. Soil Sci. 82: [481][482][483][484][485][486][487][488]. Maximum sequestration of atmospheric C in agricultural soils of the Canadian prairies can be achieved by the replacement of crop rotations that include summer fallow with continuous cropping or perennial forages. However, few studies have documented potential gains of soil organic C (SOC) in the region with the greatest use of fallow, the Brown soil zone. A dryland crop rotation study was initiated in 1992 on a Chin clay loam (Orthic Brown Chernozem) in southeastern Alberta on a site that had previously been under conventional irrigated cereal production. The study included fertilized and unfertilized treatments of the following crop rotations: fallow-wheat (FW), fallow-wheat-wheat (FWW), continuous wheat (W) and grass (G). The grass rotation consisted of pubescent wheatgrass (Agropyron trichophorum) harvested for hay. Total organic-, light fraction-and 10-wk mineralized-C and -N were determined in fall 1997, 6 yr after study initiation. Growing season precipitation (April through August) was 43% above long-term normals in the first 2 yr of this study, supporting excellent grass establishment and high crop yields, but was below normal thereafter. Fertilization with N and P increased average rotation yields by 21 to 56%, with the greatest yield increases in the G and W rotations. Total SOC to 15 cm (equivalent mass basis) was 1.5 Mg ha -1 higher (P = 0.03) in the W rotation and 3.0 Mg ha -1 higher (P = 0.0001) in the G rotation than in the FW rotation, but was not affected by fertilizer treatment or the interaction of fertilizer and crop rotation treatments. Low variability in measured SOC allowed us to detect differences as low as 1.3 Mg ha -1 among crop rotations, demonstrating that small effects of crop management on SOC can be detected using appropriate methods at uniform sites. Much of the gain in SOC in the G treatment was in mineralizable and light fraction material, indicating that this gain in SOC would be readily lost upon reversion to annual cropping. A simple calculation of residue C inputs and conversion to SOC showed that most of the gain in SOC in the W treatment was due to increased crop residue inputs, but that both increased inputs and reduced decomposition rates likely affected SOC gains in the G treatment. The average gain in SOC during the 6-yr period of this study was 0.25 Mg ha -1 yr -1 due to the elimination of fallow and 0.5 Mg ha -1 yr -1 due to establishment of a perennial forage.Key words: Soil organic matter, carbon sequestration, summer fallow, light fraction Bremer, E., Janzen, H. H. et McKenzie, R. H. 202. Incidence à court terme de la fréquence des jachères et de la culture de graminées vivaces sur la concentration en carbone organique d'un tchernoziom brun dans le sud de l'Alberta. Can. J. Soil Sci. 82: 481-488. Pour séquestrer un maximum de C atmosphérique dans les sols agricoles des Prairies ...

Greenhouse gas contributions and mitigation potential of agricultural practices in northwestern USA and western Canada

“…Table 2 grouped within 15-yr time steps. Campbell et al (1996a), Campbell et al (1996b), Campbell et al (1995), Larney et al (1997), Nyborg et al (1995), Campbell et al (2001), Grant andLaFond, 1994, McConkey et al (2003), Hao et al (2001a), Elliott and Efetha (1999); Dormaar and Carefoot (1998), Franzluebbers and Arshad (1996), Miller et al (1999), Angers et al (1997), Campbell et al (1991), Bremer et al (1994), Campbell et al (1998), Biederbeck et al (1998), Campbell et al (2000a, Campbell et al (2000b), Campbell and Zentner (1993), Bremer et al (2002), Nyborg et al (1998), Nyborg et al (1999), Malhi et al (1997), Solberg et al (1997), Liang and Mackenzie (1992), Gregorich et al (1996), Malhi et al (2002), and Izaurralde et al (2001).…”

Quantifying carbon sequestration in a conventionally tilled crop rotation study in southwestern Saskatchewan

“…Inadequate fertilization in the F-W-W system depressed C gain by about 50-60 kg ha -1 yr -1 , while withholding N in a Cont W system reduced C gain by about 130 kg ha -1 yr -1 . In a similar but shorter (6-yr) study conducted on a Dark Brown Chernozem at Lethbridge, Alberta (Bremer et al 2002), Cont W gained SOC in the 0-to 15-cm depth at a rate of 250 kg ha -1 yr -1 greater than F-W and 130 kg ha -1 yr -1 greater than F-W-W, while F-W-W gained SOC at a rate of 110 kg ha -1 yr -1 more than F-W. These rates of increase are much greater than those we observed in our study, which was not only much longer but was perhaps more representative of the semiarid conditions usually experienced in this region.…”

Influence of agricultural management on soil organic carbon: A compendium and assessment of Canadian studies

“…For example, if a cash-crop farmer, located in the Brown Chernozemic Soil Zone of Saskatchewan (native SOC in adjacent prairie is 50 Mg ha -1 to 30 cm) is currently using a fallow-wheat rotation in conventional tillage, and removes straw for off-farm sale, the SOC stock can be estimated. Soil Carbon native is 50 Mg ha -1 , the Base factor from Table 1 is 1 -(0.24 ± 0.06) = 0.76 ± 0.06, and the Input fac- Campbell et al (1991bCampbell et al ( , 1992Campbell et al ( , 1995Campbell et al ( , 1996aCampbell et al ( , b, 1998Campbell et al ( , 2000aCampbell et al ( , 2001, Larney et al (1997), Bremer et al (1994Bremer et al ( , 2002, Biederbeck et al (1998) …”

“…Solid line is regression; dashed line is 1:1. Data from Campbell, et al (1991bCampbell, et al ( , 1995Campbell, et al ( , 1996aCampbell, et al ( , b, 1998Campbell, et al ( , 2000a, Campbell and Zentner (1993), Bremer et al (1994Bremer et al ( , 2002, Larney et al (1997) and Biederbeck et al (1998). Biederbeck et al (1984), Campbell et al (1991bCampbell et al ( , 1998 and Bremer et al (1994).…”