Yasemin Kavdir

Earthworms and Soil Structure

Soil structure refers to the size, shape, arrangement of particles and pores in the soil. It effects many soil properties and plant growth including aeration, water holding capacity and hydraulic conductivity, drainage, resistance to erosion, root development, and water and nutrients uptake by plants. Earthworms play an important role in soils and they influence soil structure by mainly feeding, casting, and burrowing. These activities can either improve or reduce the stability of soil aggregates. In this chapter, effects of earthworms on soil structure will be discussed.

The impact of an open waste disposal site on soil and groundwater pollution

A study has been carried out of a waste disposal site, located in the valley of a small creek, 3 km south of Canakkale city centre. The surface area of the site was around 101000 square metres, and the total amount of waste deposited at the site since 1990 was approximately 1001000 tons. The major risks of the dump are its closeness to the university campus area to the south, the airport to the north, and residential areas encroaching towards the dump site. The nuisance caused by odour is high. The waste pile emplaced at the head of the tributary stream has caused channelling of the leachate to the creek, which is eventually washed towards the agricultural fields. The field investigation included surface geological, hydrogeochemical and geochemical studies. Water samples were collected at 11 points. Three observation wells were dug in front of the open waste disposal site. Soil samples from these observation wells were collected at 30, 70 and 150 cm depths, and some heavy metals were analysed. The concentrations of lead, copper and zinc in soil at the depth of 150 cm decreased with distance from the waste disposal site. Hydrogeochemical data analysis gave similar results.

Simulation of Leaching Losses in the Nitrogen Cycle

Abstract The CERES (Crop Estimation through Resource and Environment Synthesis) family of crop models predicts cereal growth, development, and yield. CERES simulates nitrogen (N) as a yield‐limiting macronutrient. Because N leaching is an economic and environmental concern, this study evaluated if CERES can be used to predict N leaching under different N management scenarios: background leaching in unfertilized corn (Zea mays L.), alfalfa (Medicago sativa L.) residue mineralization, and till versus no‐till management. Data were collected during a 7‐yr field experiment on tillage practices in a maize–alfalfa–maize succession. Sensitivity analyses were performed for decomposition rates of the different residue pools and the relative proportions of carbohydrate, cellulose, and lignin in the residues. During the last 5 yr, under corn, CERES accurately simulated nitrate leaching from the no‐till lysimeters. Nitrate leaching was underestimated in the tillage treatments, possibly because CERES does not simulate tillage. The model is not very sensitive to the decomposition rates and to the composition of the residues.

Development of a new long-term drought resilient soil water retention technology

Increasing frequencies of drought coupled with increasing populations are requiring more water for irrigated agriculture. As global populations approach 9 billion by 2050, even more water will be required to produce an estimated 60% to 70% more food (McKenna 2012). Production of these greater quantities of food require, at current water use efficiency rates, 50% more water (Clay 2004). Consequently, the growing demand for food and fiber combined with dwindling water supplies (in terms of both quantity and quality) available for agricultural irrigation require new soil technologies that conserve water. In the United States, the Ogallala Aquifer supplies 30% of groundwater for irrigated agriculture, and water supplies are being rapidly exhausted, especially in the southern regions (Steward et al. 2013). In other regions, reduced snow cover and surface water supplies are unable to sustain traditional irrigated agriculture, and severe drought is experienced more often (Clay 2004). Construction of large reservoirs along international and continental rivers is threatening natural water flow to communities and nations downstream. More frequent droughts with longer-term severity cause uncertainty in commodity prices and global food supplies. During this last century, global freshwater withdrawal increased more than six-fold, from 579 to 3,750 km3 y−1 (900 mi3 yr−1),…

Nitrogen leaching in an aquatic terrestrial transition zone

Large parts of East Germany are characterised by sandy soils with a high hydraulic conductivity. The risk of nitrogen leaching and groundwater pollution may be minimised by organic farming, which has been spread out in Germany during the last years. The study was conducted on an organically farmed rye field next to a lake in the state of Brandenburg between 2002 and 2004. In order to show how far organic farming may affect lake water quality, soil inorganic nitrogen (CaCl2 extraction) and denitrification (acetylene inhibition method) were studied along an aquatic terrestrial transition zone (A = field site: 5 m above water level, B = field site: 1 m above water level, C = riparian zone with macrophytes: 0.5 m above water level). Although the field did not receive any organic and mineral fertiliser there was a short-term shifting of nitrogen by leaching from the field to the groundwater and the lake. Nitrogen loss during the winter was 29 kg N ha -1 y -1 and 12 kg N ha -1 y -1 in 2002/03 and 2003/04, respectively. Deviation between the two years seemed to be caused by great differences in precipitation. No nitrogen loss was observed from a control site. High denitrification was measured at sites B and C indicating an efficient nitrogen removal capacity within the riparian buffer zone.

Impact of land cover types on soil aggregate stability and erodibility

Gökçeada is the biggest island, and it is also known as the organic island of Turkey. Approximately 65% of the Gökçeada lands have slope > 12%. Climate, topography, land cover, and soil characteristics are considered to be the main natural factors affecting soil erosion severity in the Gökçeada. Prevention of soil degradation, hence the preservation or improvement of the overall quality of the soil, is directly related to the presence of stable soil aggregates. In addition, the resistance to weathering and replacement of soil particles are also relevant aspects in terms of sustainability. Aggregate stability (AS) and erodibility of land (Kfac) are related to soil properties. However, this relationship can vary under different circumstances. In this study, 248 surface soil samples have been taken from forest and semi-natural areas (FSNA) and agricultural areas (AGRA) according to CORINE 2006. Eleven selected soil properties were measured, and their impacts on AS and Kfac (RUSLE-K) were determined by using the CRT (classification and regression tree) in Gökçeada. Results showed that the relations among soil characteristics changed according to the land cover classes. Total organic carbon is much more associated with AS in AGRA, while total carbon is associated with AS in FSNA. The effect of calcium carbonate on Kfac was higher than other soil properties when the land cover type was ignored. On the other hand, in AGRA, the effect of between clay content on Kfac was greater than those of FSNA.