JWSS - Journal of Water and Soil Science

---

Tillage system effect, Conventional (CT) vs. No-Till (NT), on soil physical properties and Br transport was studied at two locations in North Carolina. The soil types were a Typic Paleudults at Coastal Plain (site 1) and a Typic Kanhapludults at Piedmont (site 2). Bulk density (BD), total porosity (TP), macroporosity (MP), and saturated hydraulic conductivity (K_s) .were measured in plant row (R), and trafficked (T) and untrafficked (N) interrows. A rainfall simulator was used to apply two early season rainfalls to 1 m² plots where KBr suspension was surface applied for Br leaching study. The first simulated rainfall event (30 min) consisted of a low (1.27 cm h^-1) or a high (5.08 cm h^-1) rate applied, 24 h after Br application. One week later, the high rainfall rate was repeated on all plots.

 Soil samples were taken two days after applying first and second simulated rainfall (a week between them) and the end of season from different depths for measuring Br concentrations. Soil physical properties were affected by both tillage system and position.

Bulk density was higher in NT versus CT and in T position versus Rand N positions. Total porosity was lower in NT versus CT but MP was significantly higher in NT. Saturated hydraulic conductivity was about 90% lower at T position versus N and R positions. Coefficient of variation was quite large, making it difficult to obtain statistical differences between tillage systems. The surface l0-cm of soil contained the highest Br concentration for depth treatments with treatment differences occurring primarily in 0 to 25 cm depth. In first and second sampling dates, more Br leached under NT versus CT system. However, there was no significant difference between the two tillage systems in Br leaching at the end of the growing Season. In site 1, Br leached more due to the coarse texture and high Ks of the soil.

---

The increased potential for soil erosion and compaction due to continuous row crop production and intensive tillage is causing some concern and has led to the consideration of reduced tillage techniques as part of the solution. The objective of this study was to investigate the short-term (one-year) influences of different management practices on the physical properties of a sandy loam soil under corn crop. Treatments were the combinations of three tillage systems (no-till, NT chisel plow, CP and moldboard plow, MP) and three composted cattle manure rates [0, 30 and 60 ton (dry weight) ha^-1]. The experiment was carried out in a split-plot design. Three replicates of the treatments were applied in a randomized block design. Saturated hydraulic conductivity (K_s), total porosity (TP), macro-porosity (Macro-P), micro-porosity (Micro-P) of soil and mean weight diameter (MWD) of aggregates, were measured to a depth of 22.5 cm when 100 percent of the tassels appeared. Tillage and manure combination had significant effects on Log[ K_s], TP, Macro-P and Micro-P. The MP system increased pore space and continuity due to complete inversion and loosening, and as a result K_s, TP, Macro-P and Micro-P were higher than NT system. Higher Macro-P observed for CP might have caused higher K_s versus MP. Reduced tillage systems increased MWD and the increment of manure caused an increase in MWD over all tillage treatments. The results indicate short-term positive effects of manure application on soil pore size characteristics and aggregate stability under moldboard and chisel plowings in the region.

---

This study was conducted to investigate the effect of water salinity and sodicity on pore size distribution and plant-available water of two clay and sandy clay loam calcareous soils. All combinations of water EC values of 0.5, 2, 4 and 8 dS m-1 and SAR values of 1, 5, 13 and 18 (in total 16 solutions) were used to wet and dry the soil samples for five cycles. Then, water retention of the soil cores was measured at matric suctions of 0 (θs), 10 (θ10) 100 or 300 cm (θFC) and 15000 cm (θPWP). The following quantities were calculated: the difference between θ100 or θ300 and θ15000 considered as available water contrent, the θs and θ10 as macrorosity, the θ10 and θ100 as mesoporosity, and the θ100 as microrosity. The initial porosity of both soils was similar, but the greater values of pore indices and θFC, θPWP and AWC were measured in the clay soil due to clay swelling. As water EC increased, mesopores were destructed and altered to macropores and micropores. Salinity altered the mesopores into macropores due to contraction of diffuse double layer and particle’s flocculation and consequently decreased the θFC, and created new micropores which were responsible for the higher value of θPWP. These trends ultimately diminished the AWC. As water SAR increased, mesopores were destructed and altered to micropores but it did not significantly affect the macropores. With increment of SAR, both θFC and θPWP increased due to structural distruption clay swelling and dispersion resulting in increased adsorptive and interlayer surfaces. The increasing effect of SAR on θPWP was greater and more distinct so that AWC was reduced. As a result, high values of SAR of irrigation water decreased the soil available water to plants besides its toxicity and hazardous effect on plants. With increment of irrigation water salinity, the destructive impacts of SAR diminished. The influence of water quality on water retention was pronounced for the clay soil.‎

---

Studies on the soils of western Golestan province show that regardless of increased rain and presence of clay minerals with high cation exchange capacity, potassium extractable with ammonium acetate is low. In order to find the reason for this low amount of available K, clay minerals and micromorphology of the soil porosity were studied. Twenty disturbed and undisturbed samples from each horizon were taken for physicochemical properties, mineralogy and micromorphological studies. Four selected profiles included Gypsic Aquisalids, Typic Endoaquepts, Typic Calcixerolls and Typic Hapludalfs. The results showed that in addition to the clay content and type of clay minerals in soils that can affect soil available K (Kava.), it seems soil porosity can also affect Kava. mainly through their effects on extension of roots, water and nutrients transmission. Favorable content of clay and dominance of smectites in Mollisols and also higher porosity and dominance of channel porosities caused the presence of higher Kava, in these soils. presence of HIS. poor soil drainage, reduction of Fe3+ in smectite crystal lattice in Inceptisols, and also less amount of porosities caused the presence of higher potassium fixation and reduction of Kava. in these soils.

---

Increase in soil bulk density and reduces in porosity and infiltration rate are the most common disturbances during timber harvesting and ground-base skidding. The present study was conducted to study soil physical properties e.g., soil bulk density, moisture, porosity and soil hydrological properties e.g., soil infiltration from ground-base skidding in twenty years since logging. After initial survey, four abandonment skid trails were selected with similar pedologic, climatic conditions and physiographic and different age in Necka-Zalemrod catchment in east of Mazandaran province. Results indicated that impacts of machinery traffices in high traffic intensity have remained yet 20 years since logging. Means soil bulk density, porosity and void ratio were 42.4 greater, 24.6 and 46.7 percent, respectively, lower than the undisturbed areas. The least infiltration rate was recorded in 1-5 years old skid trail, so the reduction of water was not considerable within 18 minutes after experiment into soil in inner ring in this skid trail. Results in each skid trail firmed that in low traffic intensity soil physical and hydrologic properties was tent to “normal” recover in compare to the undisturbed areas.

---

Effects of five various tillage systems on soil porosity, volumetric water content, diurnal and nocturnal soil temperatures, plant water uptake and dry matter yield was investigated using a completely randomized design with five treatments and four replications in Gorgan University of Agricultural Sciences and Natural Resources research farm located in Seyed-Miran during 2009-2010 growing season. Tillage systems were: moldboard plough followed by one discing (20-25 cm) rototiller (12-17 cm) double disc (8-10 cm) Chisel plow (25-30 cm) No-tillage. Results show that during all stages of wheat growth, the highest and the lowest soil porosities at 0-8 cm depth were obtained by moldboard plough and No-tillage treatments respectively. For all stages except before tillering and harvest, the highest soil porosity obtained by moldboard treatment at 8-16 cm depth. Increasing tillage intensity increased those porosity that keep water in potentials greater than -5 and those in potentials less than -15 bar. No-tillage and moldboard induced the highest and the lowest soil temperatures respectively before earring stage. Tillage intensification, increased soil porosity and root density. More roots reduced soil water content in response to increased water uptake by wheat, resulting greater dry matter accumulation.

---

Treated wastewater may influence soil structure, porosity and as a consequence, soil saturated hydraulic conductivity. This study aims to assess the effect of wastewater on saturated hydraulic conductivity; and to determine the suitable soil solids fractal dimension to incorporate into the pedotransfer function by Rawls et al (1993) for estimation of saturated hydraulic conductivity (Ks). Soil saturated hydraulic conductivity was measured by disc permeameter. Soil particle fractal dimension was calculated from linearized forms of mass- time, mass- diameter and mass- diameter as modified by Kravchenko- Zhang (1998) relations. Wastewater irrigation for 13 years increased the saturated hydraulic conductivity three times, from 7 mm/hour to 21 mm/hour, but longer application of wastewater did not further increase it. Rawls et al (1993) pedotransfer produced acceptable and relatively close saturated hydraulic conductivity values to that of disc permeameter when fractal dimension obtained from the linearized forms of mass- diameter and Kravchenko- Zhang relations were used. Therefore, Rawls et al (1993) pedotransfer was capable of reflecting the effect of wastewater application on soil saturated hydraulic conductivity.