نشریه مهندسی زراعی
سال سی و پنجم شماره 2 (زمستان 1391)

The erosion in dryland causes decrease in yield and soil quality، especially in slope lands with conventional tillage. To investigate the effects of tillage and planting methods in slope lands on erosion and yield of rain fed wheat، an experiment was conducted in 2007-2008 at Kermanshah Province. The statistical design for this research was strip split plots in randomized complete blocks (RCB) with three replications. The dimension of each plot was 4×14 meters. Two slope levels (6-8 and 10-12 percent) were arranged in main plots، using three tillage systems (conventional، reduced and no tillage)، and three planting methods (hand spreading، seeding by a grain drill parallel and perpendicular to slope) were arranged in sub-plots. Run off was shown 14020/19 L/hafor 6-8 percent slope while on 10 -12%، was measured to be about 15251/02 L/ha. Sediment was 10854 Kg/hafor 6-8% slope، and 12103 Kg/ha was found for 10 -12 percent slope. A significant (P<0. 01) amount of grain yield was produced (1010 kg/ha) compared to moldboard plow and sweeps where chisel and sweep ploughs were applied. No tillage system produced 960 kg/ha grain yield، but it was not significantly different compared to other tillage treatments.

Rose water residues are by-products of rose water industries. These residues do not have any industrial usage and they are returned to soil as crop fertilizer. In this research, the effects of adding rose water distillation residues to soil in different particle sizes and weight proportion were investigated and changes in mechanical strength, and water holding capacity of soil and the growth of barley were determined. The experiments were performed using a 3 × 3 factorial design in which the weight proportions of the residues were in three levels of 4%, 8% and 12%. The second factor was the size of the residues in three sieves meshes of 6, 16 and 20. The results indicated that with increase in the weight level of residue more moisture was retained by the soil, and the size of the soil particles had lower effect on water holding capacity of the soils. The mechanical strength of the soil decreased with increase in both weight proportion and the particle size of the residues. The length of the stems and roots did not show any definite trend with the variations in factors. In this research, the change in moisture content of the soil was expressed as a linear function of time and residues weight proportionas well as the particle size. The resulting model was well fitted to the experimental data (R2>0.98).

In Iran, most mountainous watersheds do not have enough hydrometery stations and defective stations have sparse data. Because of limited availability of hydrologic data, watershed modeling plays a crucial role in development of local resources. In this study, SWAT was applied to simulate runoff in Marun dam (Idanak) watershed, a sub-basin of Marun catchment. Calibration and sensivity analyses were performed with SUFI-2 program. The model was run for period of 1994-2006and data of one hydrometery station at Idanak watershed were used for calibration and validation. For calibration of monthly runoff, the Nash-Sutcliffe, R2, p-factor and d-factor were 0.63, 0.73, 0.59 and 1.23 and for validation, these values were 0.70, 0.75, 0.67 and 1.05 respectively. The results showed that SWAT could be a proper tool for simulating the flow rate values of the river.

The rate of soil erosion and sediment yield estimation in the catchment areas is considered as an important factor for soil and water conservation practices. Due to difficulties and restrictions in common soil erosion methods, applying a high accuracy method with lowest cost and time consuming would be necessary. Assessment of soil loss in hilly areas with capacity of rang land that has changed to cultivation areas because of high population and evaluation of Cesium 137 method to estimate soil loss constitutes two main purposes of this research. So, the Cesium 137 method was performed to measure soil loss in Raymaleh watershed where land use alteration is common. To do so, soil sampling and measuring soil surface features were done in seventeen transects composed of eleven transects on hilly area (complex slopes with 5-50 percent) and six transects on downhill areas (simple slopes with 2-8 percent) were performed by association with aerial photographs (1:20000) and topography map (1:50000). In addition, for complex slopes (including upper, shoulder, back, foot and top parts) and simple slopes (including upper, middle and lower parts) according to slope length between 2 to 7 soil samples (0-27 cm) the taken and Cesium-137 measured by Spectrometer device. Results showed that the average soil loss in different parts of complex slope including summit, shoulder and back slope respectively was 31.74, 66.28 and 48.77 ton/ha/yr, whereas for simple slopes the losses 78.60, 54.47, 79.54 ton ha-1 yr-1. The rate of sedimentation in non erosion parts such as top slope was 64.27 ton ha-1 yr-1 and for foot slope soil deposition was more dominant than soil loss. Generally, we may conclude that Cesium 137 could be considered as a high accuracy and fast method to estimate soil loss and sedimentation.

Soil salinity induces a stressful environment for soil micro-organisms and reduces their number and activity. The objective of this research is investigating the effect of different levels of salinity on some of soil biological indicators and also assessing the effect of two types of halotolerant rhizospheric bacteria on the value of these indexes in soil. 35 strains were isolated from saline rhizospheric soils and their ability to grow in concentrations of 0 to 600 mM salt was evaluated. Among them, two isolates were identified as salt tolerant bacteria that were recognized as genera of Bacillus subtilis and Corynebacterium glutamicum. The factorial experiment, as the completely randomized design, was performed with two factors including salinity in four levels (2, 4, 8 and 12 dS/m) and bacteria in three levels (none inoculated, inoculated with Bacillus subtilis and inoculated with Corynebacterium glutamicum) in the greenhouse. The cultivated plant was barley. Different levels of salinity in soil were created by adding the mixture of salts including NaCl, CaCl2 and MgCl2. After 8 weeks, the amount of soil respiration, microbial biomass carbon and qCO2 were measured in the soil. The results of the statistical analysis showed that the effect of salinity levels on these indicators were significant (P<0.001). Bacterial inoculation in different levels of salinity, significantly, increased the soil respiration (P<0.05) and microbial biomass carbon (P<0.001) and reduced qCO2 (P<0.001) in soil. The results of this research showed that the halotolerant rhizospheric bacteria reduced the negative effects of salinity on soil microbial indicators.

Increasing the concentrations and emissions of greenhouse gases makes the weather warmer and affects land uses. Carbon dioxide emission is recognized as one of the most important factors in global warming. The objectives of this research were to investigate the amount of CO2 emission from soil to atmosphere during the wheat growth under two different tillage and irrigation methods. In this study, an experiment with a combination of tillage practices (conventional and conservation tillage) and two irrigation practices (flooding and furrow irrigation), using 45% surface residue, with 6 times of sampling from soil gases and 3 replications was done. The Statistical design of split plot in time with covariance analysis was used. A closed chamber method and gas chromatography were applied at Ramin Agricultural University research station. In order to measure the amount of water used, the submerged siphon method was used. The results showed that, the overall carbon gas emissions were influenced by soil moisture and tillage systems. Conventional tillage systems caused more fluxes because of mixing soils, the increase for CO2, was 67%. The amount CO2 gas emission for the flooding system was 33% more than of that furrow irrigation. Conservation tillage with furrow irrigation produced the lowest (p≤0.05) carbon dioxide emission. This value was 1143 mg/ m3 whereas the conventional tillage-flood irrigation, with an average of 2592 mg/m3 showed the maximum (p≤0.05) emission.

Iran, with more than 90% of world production, is known as the main saffron producer. This plant is sterile and the saffron proliferation is possible only via cultivation of corms. One of the most problems in saffron cultivation is the yield reduction due to planting of small corms. In this research, a new saffron corm-grading machine is introduced. The machine includes a rotating drum, which is made of adjustable longitudinal rods. The small and unusable corms are separated via passing them between gaps of the rods. The physical properties of corms were determined and used to calculate gaps dimensions. The effective parameters in machine performance were: rotating drum speed (n), gradient of drum (α), and feeding rate (q). The response surface methodology (RSM) was used to optimize the parameters. An acceptable sizing accuracy of 79% were obtained at n= 33.85 rpm, α=4º, and q=340.1 kg/h as optimum conditions.

In order to investigate the effects of applying three and five continuous periods of municipal solid waste (MSW) with and without NPK chemical fertilizer on the amount of micronutrient uptake by different parts of wheat, a pot experiment was conducted in split plot based on randomized complete block design with four replications in 2009. The main plot was a six-fertilizers level including control (without MSW and chemical fertilizer), chemical fertilizers according to soil test (200 kg urea, 150 kg triple superphosphate, and 100 kg K2SO4 per ha) and 4 levels of MSW (20 and 40 ton.ha-1 without fertilizer and with half of fertilizer) and the sub plot was applying 3 and 5 continuous periods of MSW. The results showed that, by increasing the amount and periods of applying MSW, the concentration of Zn and Mn in flag leaf and straw of wheat increased, with the maximum amount of obtained with the application of five consecutive periods 40 ton MSW enriched with half of NPK fertilizer. Also, by increasing the amount of applying MSW, concentration of Fe increased in flag leaf. Dmoreoven, in wheat seed, the most amount of Zn, Fe and Mn was observed by applying 5 consecutive periods 40 ton MSW enriched with 1/2 fertilizer in soil. Meanwhile, by increasing the amount of applying MSW in soil, the concentration of Cu increased in flag leaf, straw and kernel wheat flag leaf, shoot and seeds, and the effects of periods of application of MSW was just showed in wheat seeds.