Soil Bulk Density

Soil saturated hydraulic conductivity (Ks) is an important soil physical property. Some laboratory and field methods are expensive, time consuming and labour intensive. Indirect methods such as pedo-transfer functions (PTF) are available. Effective porosity or macroporosity (Øe) is approximately equals to porosity minus volumetric soil water content at the field capacity. According to Kozeny–Carman equation, Ks could be evaluated using Øe. Franzmeier estimated the Ks from Øe based on Ahuja et al. He found a strong relationship between Øe and Ks. This paper presents results of a study to characterize the effective porosity in lowland paddy fields and to show the possibility of using the effective porosity (Øe) in estimating the saturated hydraulic conductivity (Ks). Soil in lowland paddy fields forms its horizon as topsoil, hardpan and subsoil. Soil samples were collected randomly within a 2300-ha rice cultivation area where there are five dominant soil series. A total of 408 soil samples were taken from 136 sampling points and at three depths, namely, the topsoil, hardpan and subsoil. Ks values were measured in the laboratory using the falling head method. Soil bulk density and moisture content at −66 kPa were determined. The Øe was then calculated using the difference of the total porosity (Ø) minus the volumetric moisture content at −66 kPa. The Ks values ranged from 5.35×10−4 to 8.77×10−2 m day−1. The Db varied from 0.62 to 1.91 Mg m−3, and the values of the Dp ranged from 1.10 to 2.89 Mg m−3. The Ø ranged from 0.17 to 0.68 m3 m−3. The results of the Øe of the samples in this study were obtained by calculating the difference of the total porosity and volumetric moisture content at field capacity. For clayey soils, field capacity is taken at the suction of −66 kPa. The Øe varied from 0.05 to 0.55 m3 m−3, with the mean value of 0.24 m3 m−3. The regression equation of a power function shows a highly significant regression coefficient, r2 of 0.50 (n=400). This indicates that there is a strong relationship between Ks and Øe for the lowland paddy soils in the study area.

Soil physical properties play an important role in vegetation growth on rangelands as a result of the effects they have on the development of root systems. The goal of this research was to investigate the trampling effect of livestock grazing on soil physical properties (moisture, bulk density, infiltration rate and mechanical resistance) and vegetation cover. The experiment was conducted on three rangeland condition areas - the reference area, a moderately grazed area and a heavily grazed area - in the Lar rangelands (84 km northeast of Tehran) during the grazing season of 2000 and 2001. Soil moisture was reduced from both the reference area and the heavily grazed area throughout the grazing season to depths of 0-15 and 15-30 cm. Soil bulk density increased during the grazing season, being lowest in the reference area and highest in the heavily grazed area. Throughout the grazing season, bulk density was higher in the top soil layer (0-15 cm) compared to underlying layer (15-30 cm)...

Despite the widespread recognition that silvicultural treatments (prescribed harvest residue burning, site preparation and replanting) applied following clearcutting may cause soil erosion and nutrient loss in Chinese fir (Cunninghamia Lanceolata (Lamb.) Hook) plantations, it is unclear which specific treatment leads to nutrient loss and whether an appropriate implementation of the treatments during the dry season could avert nutrient loss altogether. To address these two questions, nutrient changes in Alliti-Udic Ferrosols soils within a Chinese fir plantation located in Huitong County, Hunan Province, were investigated through the analysis of soil samples sequentially collected at depths of 0–15 cm and 15–30 cm before and after harvest with the residue material kept in place, a prescribed residue burning operation, site preparation and tree replanting initiative took place. Individual treatments significantly affected the soil pH value, organic matter and C and available N at depths of 0–15 cm, but did not significantly influence soil bulk density, total N and P contents and available P contents. The soil pH value decreased with successive application of the treatments. Soil organic C increased by way of the remaining residue after clearcutting, but declined after prescribed residue burning and ultimately returned to pre-harvest values after site preparation as a result of soil displacement and burning ash. Available N contents decreased significantly after clearcutting and residue burning, but the reduction was more or less offset after site preparation took place. Results after all silvicultural treatments were applied showed that no significant reduction in soil organic matter, C and N and P occurred to date in the Chinese fir plantation studied, suggesting that nutrient loss could be averted if the treatments were implemented during the dry season.

... arid rangelands is into a two-phase mosaic comprising shrub patches and intershrub areas, with the former acting as sinks for water and other water-conveyed resources, of which the latter act as sources ([Bergkamp, 1998], [Lavee et al., 1998], [Eddy et al., 1999] and [Galle et al ...

... Author Contact Information , E-mail The Corresponding Author , M. Ahmad a , E-mail The Corresponding Author , N. Ahmad a and M. Kaleem Abbasi b. ... soil consisted of 18.8% sand, 69.2% silt, 12.0% clay, 2.60% lime and 1.31% organic matter with pH of 5.9 (Ghani and Ali, 2003 ...

Inoculants are of great importance in sustainable and/or organic agriculture. In the present study, plant growth of barley (Hordeum vulgare) has been studied in sterile soil inoculated with four plant growth-promoting bacteria and mineral fertilizers at three different soil bulk densities and in three harvests of plants. Three bacterial species were isolated from the rhizosphere of barley and wheat. These bacteria fixed N2, dissolved P and significantly increased growth of barley seedlings. Available phosphate in soil was significantly increased by seed inoculation of Bacillus M-13 and Bacillus RC01. Total culturable bacteria, fungi and P-solubilizing bacteria count increased with time. Data suggest that seed inoculation of barley with Bacillus RC01, Bacillus RC02, Bacillus RC03 and Bacillus M-13 increased root weight by 16.7, 12.5, 8.9 and 12.5% as compared to the control (without bacteria inoculation and mineral fertilizers) and shoot weight by 34.7, 34.7, 28.6 and 32.7%, respectively. Bacterial inoculation gave increases of 20.3–25.7% over the control as compared with 18.9 and 35.1% total biomass weight increases by P and NP application. The concentration of N and P in soil was decreased by increasing soil compaction. In contrast to macronutrients, the concentration of Fe, Cu and Mn was lower in plants grown in the loosest soil. Soil compaction induced a limitation in root and shoot growth that was reflected by a decrease in the microbial population and activity. Our results show that bacterial population was stimulated by the decrease in soil bulk density. The results suggest that the N2-fixing and P-solubilizing bacterial strains tested have a potential on plant growth activity of barley.

Soil compaction is an environmental problem and has been recognized as the main form of soil degradation in Europe. Soil compaction may increase soil strength and compacted soil layers can affect root and shoot growth. The aim of this work was to investigate the effect of soil compaction on soil properties and on the growth of narrow-leafed lupine (Lupinus angustifolius L.), spring oilseed rape (Brassica napus ssp. oleifera Hertzg.), and spring barley (Hordeum vulgare L.). The experiment was carried out on the research field of the Estonian University of Life Sciences in the summers of 2004 and 2005 on the sandy loam Stagnic Luvisol. The field was compacted by tractor MTZ-82 (total weight 4.84 Mg) characterized by multiple tire-to-tire passing. Parameters such as plants biomass (roots and shoots) and the changes in physical properties, bulk density and penetration resistance of soil were measured. The results of the present study revealed that the highest increase of penetration res...

This study provides a profile comparison of several tree growth, phenology, and site characteristics. The comparisons are between sugar maple trees in a forest stand and those in tree lawns on urban streets, both sites within 2 km on the Michigan State University campus in East Lansing. Sampled trees are from a stratified random group of healthy sugar maples. The