Effects of rice husk application on mechanical properties and cultivation of a clay soil with and without planting

In this study, effects of rice husk (RH) application on mechanical properties and cultivation of a clay textured soil were investigated with and without barley planting. A rate of 5% (w/w) rice husk as a dry weight basis was added to a clay textured soil by alone (RH) and with 5 kg N/da of ammonium sulphate (RHN) in order to increase the biological activity and the decomposition rate of rice husk in soil. Rice husk applied soils including control treatment were incubated at field capacity under greenhouse conditions for 2 months. After this period, barley was sown in a half number of the pots. All pots having barley planted and without planted were incubated together for 6 more months. Study was carried out in a factorial experimental design on barley planting and without planting pots in 3 treatments (control, RH and RHN) with 3 replications. At the end of the study, liquid limit (LL), plastic limit (PL), plasticity index (PI), consistency index (Ic), field capacity (FC), permanently wilting point (PWP) and organic matter (OM) contents of soils were determined. The highest values were determined for LL in RH+nitrogen+barley planting (RHNP), for PL in RH application without planting and for PI in control application with barley planting (CP). Barley planting increased LL and PI values of soil significantly. LL values of soils significantly correlated with PL (0.664**), PI (0.880**) and PWP (0.948**). PL values of soils significantly correlated with OM (0.699**) and PWP (0.821**). PI values of soils significantly correlated with FC (0.654**) and PWP (0.713**). Ic values gave the significant correlations with PL (0.908**), OM (0.787**), FC (-0.611**) and PWP (0.615**). Ic values in all RH treatments were higher than that in control treatments. It was concluded that clay textured soil in control treatment can have deformation when it is cultivated at the field capacity without RH application; however clay soils can be cultivated without deformation after application of RH

Changes in penetration resistance of a clay field with organic waste applications

Effects of manure (M), hazelnut husk (HH), tobacco (TW) and tea (TEW) wastes on penetration resistance (PR) values in a clay field were determined after 8 months of organic wastes were incorporated into soil at four different rates (0, 2, 4 and 6 %) in a randomized plot design with three replicates. While bulk density (BD), relative saturation (RS) and PR values decreased, mean weight diameter (MWD), total porosity (F), gravimetric water (W) and organic matter (OM) contents of the clay soil increased with increasing the application rates of organic wastes. While the lowest PR (0.72 MPa) was determined in the highest application rate of HH which had the highest C:N ratio, the highest PR (1.72 MPa) was in the control. According to the control treatment, decreases in mean values of PR by the organic waste applications were in the following order; HH (52.10%) > TEW (42.07%) > TOW (30.73%) > M (25.17 %). PR values gave significant negative correlations with F (-0.551**), W (-0.439**) and MWD (-0.509**), and significant positive correlations with BD (0.550**) and RS (0.374*). Total porosity showed the highest direct effect (62.39%) on PR. The higher indirect effects of the other properties on PR were also obtained via F. Applications of the same doses of different organic wastes had different effects on the PR values with changing the structure of clay soil due to their C:N ratios

Using soil moisture constants and physical properties to predict saturated hydraulic conductivity

Saturated hydraulic conductivity (Ks) is an important variable in hydrological cycle processes. Determination of Ks in soils is a difficult and time consuming process. The objective of this study was to determine Ks in soils by pedotransfer (PTF) models derived using soil moisture constants and physical properties. Ks values were determined in 30 different soil samples using constant head permeability method. According to path analyses results, direct effects of some soil properties on Ks in soils were in the following order; permanent wilting point (PWP) > bulk density (BD) > clay (C) > silt (Si) > field capacity (FC). Soil physical properties generally had the highest indirect effects on Ks through PWP. Prediction of Ks by the second order PTF models was significant using only C, Si and DB (r=0.868**) and using only FC and PWP (r=0.796**) in the models. Using moisture constants with the other soil physical properties in the second order PTF model increased significance level of the relation between predicted and measured values of Ks (r=0.955**). Besides soil physical properties, having moisture constants in PTF models showed that saturated Ks values can be predicted more accurately in soils having similar physical boundary conditions such as texture, bulk density etc

Effect of manure on organic carbon content and fractal dimensions of aggregates

Effects of farmyard manure treatments on some soil structural parameters such as, aggregate stability (AS), geometric mean weight (GMWD) and mean weight (MWD) diameters, fragmentation (D) and mass (Dm) fractal dimensions, bulk density (BD) and organic C (OC) contents of aggregates were determined in a clay soil. Application of 67 Mg ha-1 farmyard manure to Vertic Haplustoll soil decreased AS 12.14% compared with the control. Manure treatment increased the proportion of microaggregates in the fractions 1.00 mm in size. While OC contents of aggregates increased between 22.8% and 123.4%, BD values decreased between 0.8% and 16.6% with the manure treatment. Fragmentation (D) and mass (Dm) fractal dimensions were increased with decreasing numbers of macroaggregates of the clay soil. GMWD (1.16 mm) and MWD (1.86 mm) obtained in the manure treatment were lower than that in the control treatment (1.20 mm and 1.95 mm, respectively). Although OC content of the aggregates increased with the manure treatment, the number of macroaggregates of clay soil decreased with decreasing AS

Spatial variability of soil physical properties in a cultivated field

Spatial variability of soil physical properties in a cultivated field such as; bulk density (BD), penetration resistance (PNT), saturated hydraulic conductivity (Ks), field capacity (FC) and permanent wilting point (PWP), were determined by geostatistical method. While BD values varied between 1.12 and 1.41 g cm-3, PNT resistance (0.66 to 1.88 MPa), clay content (31.48 to 43.97%), Ks (1.46 to 3.37 mm h-1), FC (30.40 to 39.66%) and PWP (19.22 to 24.42%) values showed variations with soil cultivation. In kriging interpolation for the spatial variability of soil properties, the biggest r2 and cross validation r2 values were determined with spherical model for PNT, Ks, FC values, and exponential model for clay, BD and PWP. Spatial dependences of the properties, except BD, were found to be strong in the field. Ks values significantly increased with increasing BD (0.340*), and decreasing clay content (-0.905**) and PNT (-0.288*) values in the field. Spatial variations of soil physical properties in the field are generally controlled by the particle size distribution as a fundamental factor. Heterogeneity and variation of soil physical parameters in a field due to soil plowing should be taken into consideration for a successful agricultural management