Browsing by Author "Graham, Michael W."
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- Modest capacity of no-till farming to offset emissions over 21st centuryGraham, Michael W.; Thomas, R. Quinn; Lombardozzi, Danica L.; O'Rourke, Megan E. (IOP, 2021-05-01)'No-till' (NT) agriculture, which eliminates nearly all physical disturbance of the soil surface on croplands, has been widely promoted as a means of soil organic carbon (SOC) sequestration with the potential to mitigate climate change. Here we provide the first global estimates of the SOC sequestration potential of NT adoption using a global land surface model (LSM). We use an LSM to simulate losses of SOC due to intensive tillage (IT) over the historical time period (1850-2014), followed by future simulations (2015-2100) assessing the SOC sequestration potential of adopting NT globally. Historical losses due to simulated IT practices ranged from 6.8 to 16.8 Gt C, or roughly 5%-13% of the 133 Gt C of global cumulative SOC losses attributable to agriculture reported elsewhere. Cumulative SOC sequestration in NT simulations over the entire 21st century was equivalent to approximately one year of current fossil fuel emissions and ranged between 6.6 and 14.4 Gt C (0.08-0.17 Gt C yr-1). Modeled increases in SOC sequestration under NT were concentrated in cool, humid temperate regions, with minimal SOC gains in the tropics. These results indicate that the global potential for SOC sequestration from NT adoption may be more limited than reported in some studies and promoted by policymakers. Our incorporation of tillage practices into an LSM is a major step toward integration of soil tillage as a management practice into LSMs and associated Earth system models. Future work should focus on improving process-understanding of tillage practices and their integration into LSMs, as well as resolving modeled versus observed estimates of SOC sequestration from NT adoption, particularly in the tropics.
- Organic Grain Amaranth Production in Kamuli District, UgandaGraham, Michael W.; Delate, Kathleen; Burras, C. Lee; Mazur, Robert E.; Brenner, David M.; Tenywa, Moses M.; Nakimbugwe, Dorothy N.; Kabahuma, M.; Abili, A. (2011)Grain amaranths (Amaranthus spp.) are high protein content and protein quality pseudo-cereal crops whose favorable nutritional profile belies their potential to alleviate nutrition and food insecurity in developing countries. Grain amaranth was introduced as a nutrient dense food into the Kamuli District, eastern Uganda, in 2006. However, initial analysis of protein content of amaranth grain pooled from farms in the Kamuli District indicated that protein levels ranged from 11.7% to 12.5%, lower than the average value of 15% found in the literature. Based on previous surveys of amaranth production practices in the area, this study was designed to determine: 1) variability of amaranth grain yields and protein content between farms; 2) variability of amaranth grain yields and protein content between varieties; and 3) the effects of soil physical and chemical properties, and the use of organic soil amendments, on amaranth grain yields and protein content. On-station and on-farm trials were conducted to determine the effects of organic soil amendments on amaranth grain yield and protein content. The on-station trials were conducted during 2009 in Wakiso District in south-central Uganda, to test effects of poultry manure and composted manure, while on-farm trials took place on ten farms during the short rainy season of 2009 in Kamuli District to determine the effects of cattle manure on the aforementioned parameters. On-station grain amaranth trials were conducted twice, during both the dry and short rainy seasons, and tested the effect of poultry manure and composted manure applied at 0, 1, 1.5, and 3 ton ha-1 on amaranth varieties “cream”, “golden” and ‘Plainsman’. There were no significant differences between amendment treatments for either trial, however, mean grain yields for the rainy season were higher at 1886 kg ha-1 compared to 1110 kg ha-1 for the dry season. Concerning varietal differences, yields for “cream” and “golden” varieties were significantly greater than those for ‘Plainsman’ during the dry season, whereas in the rainy season “cream” yields were significantly greater than those for “golden” and ‘Plainsman’. Amaranth grain was pooled across all treatments and varieties to determine a protein content of 14.5% and 15.1% for the dry and rainy seasons, respectively. For the on-farm trials, yields were lower than in the on-station trials and were significantly different between farms. Application of cattle manure provided a significant yield increase. While there were no significant differences between varieties, amaranth grain protein content was significantly different between farms. Average protein content of 14% across treatments and varieties revealed a greater amaranth protein content than previously reported for Kamuli District.