Audit report on the City of Carlisle, Iowa for the year ended June 30, 2011

Audit report on the City of Carlisle, Iowa for the year ended June 30, 2011

Audit report on O’Brien County, Iowa for the year ended June 30, 2011

Audit report on O’Brien County, Iowa for the year ended June 30, 2011

Audit report on the City of Nevada, Iowa for the year ended June 30, 2011

Audit report on the City of Nevada, Iowa for the year ended June 30, 2011

N2O emissions from a cultivated mollisol: optimal time of day for sampling and the role of soil temperature

The correct use of closed field chambers to determine N2O emissions requires defining the time of day that best represents the daily mean N2O flux. A short-term field experiment was carried out on a Mollisol soil, on which annual crops were grown under no-till management in the Pampa Ondulada of Argentina. The N2O emission rates were measured every 3 h for three consecutive days. Fluxes ranged from 62.58 to 145.99 ∝g N-N2O m-2 h-1 (average of five field chambers) and were negatively related (R² = 0.34, p < 0.01) to topsoil temperature (14 - 20 ºC). N2O emission rates measured between 9:00 and 12:00 am presented a high relationship to daily mean N2O flux (R² = 0.87, p < 0.01), showing that, in the study region, sampling in the mornings is preferable for GHG.

Audit report on Union County, Iowa for the year ended June 30, 2011

Audit report on Union County, Iowa for the year ended June 30, 2011

Audit report on the Page County Landfill Association for the year ended June 30, 2011

Audit report on the Page County Landfill Association for the year ended June 30, 2011

Audit report on Pottawattamie County, Iowa for the year ended June 30, 2011

Audit report on Pottawattamie County, Iowa for the year ended June 30, 2011

Audit report on Taylor County, Iowa for the year ended June 30, 2011

Audit report on Taylor County, Iowa for the year ended June 30, 2011

Audit report on the City of Keota, Iowa for the year ended June 30, 2011

Audit report on the City of Keota, Iowa for the year ended June 30, 2011

Audit report on Clinton County, Iowa for the year ended June 30, 2011

Audit report on Clinton County, Iowa for the year ended June 30, 2011

Audit report on Poweshiek County, Iowa for the year ended June 30, 2011

Audit report on Poweshiek County, Iowa for the year ended June 30, 2011

Audit report on the Pocahontas County Solid Waste Commission for the year ended June 30, 2011

Audit report on the Pocahontas County Solid Waste Commission for the year ended June 30, 2011

Optimization of the sampling scheme for maps of physical and chemical properties estimated by kriging

The sampling scheme is essential in the investigation of the spatial variability of soil properties in Soil Science studies. The high costs of sampling schemes optimized with additional sampling points for each physical and chemical soil property, prevent their use in precision agriculture. The purpose of this study was to obtain an optimal sampling scheme for physical and chemical property sets and investigate its effect on the quality of soil sampling. Soil was sampled on a 42-ha area, with 206 geo-referenced points arranged in a regular grid spaced 50 m from each other, in a depth range of 0.00-0.20 m. In order to obtain an optimal sampling scheme for every physical and chemical property, a sample grid, a medium-scale variogram and the extended Spatial Simulated Annealing (SSA) method were used to minimize kriging variance. The optimization procedure was validated by constructing maps of relative improvement comparing the sample configuration before and after the process. A greater concentration of recommended points in specific areas (NW-SE direction) was observed, which also reflects a greater estimate variance at these locations. The addition of optimal samples, for specific regions, increased the accuracy up to 2 % for chemical and 1 % for physical properties. The use of a sample grid and medium-scale variogram, as previous information for the conception of additional sampling schemes, was very promising to determine the locations of these additional points for all physical and chemical soil properties, enhancing the accuracy of kriging estimates of the physical-chemical properties.

Cut-off importance sampling of bole volume

Summary