Informatics Publishing Limited

Ahmed Hasson ¹, Tim Wiley ¹, George Woolston ¹

Affiliations
1 Department of Agriculture and Food, Western Australia, Geraldton, AU

Abstract

Changing from annual to perennial pastures may be a key strategy for farmers to both adapt to, and help mitigate, climate. In this study organic carbon determined by Walkley and Black analysis of 'whole soil' samples (i.e., including ischolar_mains) from annual and perennial pastures was used to determine the carbon stocks in the top 30 cm of soil. Samples were collected from old perennial pasture trial sites, and also from adjoining paired paddocks of annual and perennial pastures. Sequestration rates were calculated as the increase in carbon stocks of the perennials above the traditional annuals, averaged over the number of years since the perennials were sown. The results indicate that denser perennial pastures can sequester in the range of 5 to 10 t CO₂e/ha/year. We hypothesise that the flux rates from particulate organic matter to the humus pool currently used for annuals in RothC may be too low for perennial pastures. These results are particularly encouraging as (a) all but one of the sites was on coarse sandy soils, and (b) all of the years since the perennials were sown were below average rainfall.

Keywords

Carbon Sequestration, Whole Soil Sampling, Pasture Land, Soil Organic Matter.

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Ahmed Hasson ¹, Muhsin Jweeg ¹

Affiliations
1 Desertification, Climate Change Section, Mechanical Engineering Department, College of Engineering, Nahrain University, Jaderia, Baghdad, IQ

Abstract

Two sites in Iraq were chosen to study the affect of annual pasture and perennial grasses (C4). The perennial grass pastures had SOC stocks, 1.6 (Baghdad) and 1.4 (Babylon) times that of the annual pastures. Soil Organic Carbon (SOC) pools were 1.90, 2.97 and 2.88% for annuals, perennials and tagasaste at Baghdad site. At Babylon the SOC pools were 2.7, 4.70, and 3.71% under annuals, perennials and tagasaste respectively. Estimated total C sequestration contribution to the resident soil organic C pool was 2.8 times greater for perennials and 2.7 times for tagasaste than annual pasture at the Baghdad deep sandy duplex site and 1.2 times greater for perennial pasture and 1.2 times greater for tagasaste than annual pasture at the Babylon deep-sand site. Both the sites were sampled to a depth of 1.6m. Perennial grasses in this region generally produced more above ground biomass than annual pastures. However, the differences in biomass input are unlikely to be large enough to explain the high rate of sequestration of these perennials. We hypothesise that the perennial grasses promote fungi such as mycorrhiza that convert a greater proportion of labile carbon to stable humic forms than under annual pastures.

Keywords

Soil Organic Carbon, Pastures, Arid Region, Carbon Sequestration.

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Ahmed Hasson ¹

Affiliations
1 Desertification Section, Department of Mechanical Engineering, College of Engineering, Nahrain University Jaderia, Baghdad, IQ

Abstract

Nitrification processes can play a key role in the functioning of Western Australia natural ecosystems. It is directly involved in plant nitrogen losses through leaching and denitrification. Suppression of this process by pastures is poorly understood. The research was conducted on the deep-sand at Mingenew in the Northern Agricultural Region, WA. Nitrification rate was determined under annual, perennial pastures and tagasaste fodders grown in situ. Nitrification and inhibition rates were calculated based-on measurements of NH₄-N, NO₃-N over a period of 6 months. Under natural conditions (control) the nitrification rates of ammonium-N (NH₄-N) were rapid from 80 to 97% during the season. Nitrification rates under annuals, perennial pastures and tagasaste plants were 35 to 80%, 58 to 58%, and 30 to 75% respectively. It was found that there is a high negative correlation (R²=-0.84) between biomass and nitrification rate, and a high positive correlation between biomass and inhibition rate (0.74). Such results suggest that pastures species can have important consequences for nitrogen cycling at the permanent growth and population density.

Keywords

Nitrification Rate, Nitrification Inhibition, Perennial Pastures, Leaching.

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