Long‐Term Cropping System Effects on Carbon Sequestration in Eastern Oregon

Abstract

Soil organic carbon (SOC) has beneficial effects on soil quality and productivity. Cropping systems that maintain and/or improve levels of SOC may lead to sustainable crop production. This study evaluated the effects of long-term cropping systems on C sequestration. Soil samples were taken at 0- to 10-, 10- to 20-, 20- to 30-, and 30- to 40-cm soil depth profiles from grass pasture (GP), conventional tillage (CT) winter wheat (Triticum aestivum L.)-fallow (CTWF), and fertilized and unfertilized plots of continuous winter wheat (WW), spring wheat (SW), and spring barley (Hordeum vulgare L.) (SB) monocultures under CT and no-till (NT). The samples were analyzed for soil organic matter (SOM) and SOC was derived. Ages of experiments ranged from 6 to 73 yr. Compared to 1931 SOC levels (initial year), CTWF reduced SOC by 9 to 12 Mg ha(-1) in the 0- to 30-cm zone. Grass pasture increased SOC by 6 Mg ha(-1) in the 0- to 10-cm zone but decreased SOC by 3 Mg ha(-1) in the 20- to 30-cm zone. Continuous CT monocultures depleted SOC in the top 0- to 10-cm zone and the bottom 20- to 40-cm zone but maintained SOC levels close to 1931 SOC levels in the 10- to 20-cm layer. Continuous NT monocultures accumulated more SOC in the 0- to 10-cm zone than in deeper zones. Total SOC (0- to 40-cm zone) was highest under GP and continuous cropping and lowest under CTWF. Fertilizer increased total SOC only under CTWW and CTSB by 13 and 7 Mg ha(-1) in 13 yr, respectively. Practicing NT for only 6 yr had started to reverse the effect of 73 yr of CTWF. Compared to CTWF, NTWW and NTSW sequestered C at rates of 2.6 and 1.7 Mg ha(-1) yr(-1), respectively, in the 0- to 40-cm zone. This study showed that the potential to sequester C can be enhanced by increasing cropping frequency and eliminating tillage.

Soil Organic Carbon Pools as Early Indicators for Soil Organic Matter Stock Changes under Different Tillage Practices in Inland Pacific Northwest

“…As a consequence of higher SOM levels, GP soil had lower bulk density and higher soil water retention . Nevertheless, most studies claim that losses of SOM under arable systems can be minimized, at least within 0-15 cm top soil, by adopting reduced or conservation tillage systems (Machado et al, 2006;Dou et al, 2008;Chen et al, 2009;Awale et al, 2013). Such assertion was corroborated by our finding that DT/CT, a reduced tillage practice, tended to increase SOC content over FP.…”

“…Over the long-term, the magnitude of SOM storage depends on land-use and management practices (West and Post, 2002). Usually, SOM tends to decline when native ecosystems are converted to cropping systems (Machado et al, 2006), but the effect of different management practices on SOM dynamics in dryland cropping systems varies and is site-specific (Ghimire et al, 2017;Wang et al, 2017).…”

“…Storage of SOM in cropping systems depends on the balance between C-additions primarily from crop residues and Closses through SOM decomposition (Machado et al, 2006;Awale et al, 2013). Therefore, the degree to which a tillage technique influences SOM turnover is generally determined by the frequency and timing of soil disturbance, depth of soil disturbance, and degree of soil-residue mixing (Cookson et al, 2008;Dou et al, 2008;Machado, 2011).…”

“…Furthermore, tillage induced alterations on soil edaphic properties can significantly influence crop productivity and ultimately the quantity of residue input in soils (Payne et al, 2000). On the contrary, delaying residue incorporation or leaving it on soil surface may provide a steady substrate for microbial community (Balota et al, 2003;Machado et al, 2006).…”

Soils and food sufficiency. A review

“…These conclusions of improvements in soil quality are also supported by the data from Europe and Australia. Positive impacts of improving cropping intensity and eliminating tillage on increasing the SOM pool were also observed in Brazilian Cerrado by Machado et al (2006). In addition to cropping intensity, the impact of the climate gradient (temperature and moisture regimes) is also important to SOM and N dynamics (Ortega et al, 2005).…”