Carbon dioxide flux in a soil treated with biosolids under semiarid conditions

The restoration of degraded land using biosolids provides a well known means of recycling these organic residues. In semiarid ecosystems they can enhance the chemical and physical properties of the soil and stimulate soil microbe growth and activity, leading to increases in soil fertility and quality. However, the respiratory activity in biosolids-treated soil may contribute to an increase in atmospheric CO2. Few studies examining CO2 emissions from biosolids-amended soils in semiarid climates have been conducted under field conditions. The aims of the present study were to determine the effect of applying different amounts of biosolids on the soil organic matter content and respiratory activity of a semiarid, abandoned agricultural soil. The CO2 fluxed from the soil surface (kg CO2 ha−1 d−1) was measured using a portable analyser. Soil temperature and soil water content were measured in the first 5 cm of soil. The results show that a large proportion of the organic matter incorporated into the soil via the biosolids was easily biodegradable in the first three years following its application. In addition, biosolids application generally increased soil CO2 emissions, although in a manner not proportional to the quantity applied. Differences in soil humidity were associated with differences in soil CO2 flux over the year. The soil water content was the major factor affecting soil respiration; a strong correlation was found between these variables. Soil respiration activity could serve as a useful index of soil biological activity, allowing the decomposition of biosolids under field conditions to be monitored. © 2012 by The JG Press, Inc. All rights reserved

Restoration of abandoned, degraded agricultural soil using composted biosolid Influence on selected soil properties

One practice for reclaiming degraded agricultural soils under semiarid climate is to use organic amendment to improve the physical, chemical, and biological properties of the soil, therefore enhancing its fertility. A short-term field experiment was carried out to study the effects of different biosolid rates on selected soil properties and assess these as potential indicators of soil restoration. The organic waste was surface-applied once at three rates (30, 60, and 90 Mg ha-1) to an abandoned agricultural soil. Three years after the biosolid was applied several chemical and biological soil properties such as organic C (SOC), humified C fractions (THS-C), water soluble C (DOC), total nitrogen (Nk), basal respiration (CO2-E), and potential nitrogen mineralization (PMN) increased significantly in 60 Mg ha-1 and in 90 Mg ha-1 biosolid rates. The physical soil properties studied did not change with the biosolid treatments at least in this short-term experiment. The available heavy metals showed a slight increase in the biosolid treatments but the values obtained were below those considered phytotoxic. In spite of that the canopy cover was higher in the biosolid treatment plots than in the unamended soil which will contribute to soil restoration; the analysis of the biological properties did not show such a clear trend that they could be used as soil quality indicator under the condition of this study. © 2012 Copyright Taylor and Francis Group, LLC

LONG term management systems under semiarid conditions Influence on labile organic matter, β-glucosidase activity and microbial efficiency

Conservation agriculture (CA) practices have been widely applied on a variety of agro-ecosystems in order to prevent soil degradation and to improve fertility. We studied the long term influence of different management systems on soil properties in an experimental field located in semiarid central Spain. Soil organic carbon (SOC), dissolved organic carbon (DOC), soil basal respiration (CO2-C), microbial biomass carbon (MBC) and β-glucosidase activity have been measured during three cropping seasons. Results showed a high influence of date of sampling on the evaluated parameters and on the microbial status and activity, most likely due to variations in soil water content (SWC). Microbial efficiency and β-glucosidase activity were improved under CA, as SOC, DOC and MBC were accumulated in the surface. Microbial efficiency ratios, e.g.;qR (qR=MBC/SOC), qCO2 (qCO2=CO2-C /MBC) and qCO2/SOC, were useful to explain the influence of sampling date and the management practices on the microbial status. A stepwise procedure reduced considerably our data set, allowing the selection of MBC, DOC and qCO2/SOC as reliable indicators to evaluate soil quality in semiarid areas. © 2015 Elsevier B.V