نشریه مهندسی زراعی
سال سی و ششم شماره 2 (زمستان 1392)

In order to evaluate the effects of seed bed preparation, fertilization and weed control (after planting) methods on growth and corn yield in northern part of Khuzestan a field experiment was conducted as split blocks in a randomized complete block design with four replications during 2009 and 2010. Three seed bed preparations consisting of Makhar condition (wet seeding) + conventional tillage (plough + disk + leveler), makhar condition + reduced tillage (disk) and without makhar + reduced tillage were performed in horizontal plots. Two methods of fertilizing (Broadcast and Drill) as main factors and weed controlling methods (once using of field cultivator in four-leaf stage (20 cm height of plants), two times using rolling cultivator in four and seven-leaf stage (20, 40 cm height of plant), using two liters Nicosolforon herbicides when the plant produced 3 - 4 leaves, and checking treatments (weed free and weed infect) as the sub-factors were conducted in vertical plots. The results indicated that population and biomass dry weight of weeds were significantly (p< %5) affected by Makhar. Planting in without makhar soil, caused reduction in the population and weed weight (30% and 40%) in the 5th week. In all tillage methods, the effect of two times using rolling cultivator and chemical control on grain yield and biological yield was statistically similar. In fertilizer drill method, grain yield and biological yields, kernel in rows and rows in ear were significantly (P<%1) higher than broadcast method. The most grain and biological yield were obtained in combination of makhar condition and fertilizer drill (in treatment of makhar condition + reduced tillage, grain yield was 9003.25 kg/ha.). Two times using rolling cultivator reduced the population and weight of weeds significantly more than chemical control in farm with plenty of Bind weed. In all of the Broadcast fertilizer methods, chemical control treatment had more yield (16%), but in fertilizer drill method there was no significant difference between chemical and two times using of rolling cultivator treatments. It seems that in corn farms when broadcasting fertilizer method is used, the chemical control of weed due to higher yield (15%) is more effective; two cultivator weed control method is recommended if the distribution of fertilizer is used with drilling method. The highest grain yield (9183 kg/ha) was obtained from the combination of makhar, reduced tillage, fertilizer drilling method and two times using rolling cultivator.

Penetration Resistance and Micromorphology of Biological Crusts Resulted by Simultaneous Application of Two Cyanobacteria Genes چکیده [English] Cyanobacteria play an important role in providing biological soil crusts in sandy soil of desert areas. The aims of the present research are to investigate the possibility of crust formation under three cyanobacteria (Nostoc. sp (N), Phormidium. sp (Ph) and combination of two genus (Ph + N), two polymer treatments [blank (S0) and 0. 3 g per 250 g soil (S1)] and two moisture levels [FC (M1) and 80% FC (M2)] in three separated parts. Crust thickness, increase in soil organic carbon and resistance to penetration of crusts after complete coating (60 days) were measured in the first part of the experiment. Then the effects of time (15, 30, 45 and 60 days) on crust thickness and micromorphological investigations of crusts were performed in the second and third parts of the experiment respectively. Results of the study showed that simultaneous application of two genus at FC level with polymer creates the thickest (6. 83 mm) and the most resistant crusts (0. 27 MPa) to penetration. Both cyanobacteria genus with polymer and FC level caused the highest organic carbon contents (1. 89% and 1. 66% respectively). Also the thickest crust (6. 8 mm) was formed by simultaneous application of two genus during 60 days. Micromorphological observation showed decrease in macro pores in treated samples compared to control and this decrease of pore space size with application of both cyanobacteria genus was higher than each of them alone.

Thyme is one of important medicinal plants that have been used since the past. This plant has many properties in the treatment of diseases، especially infectious diseases، thyme and its components are used in various industries such as pharmaceutical، food، cosmetics and health. In order to maintain the quality and quantity of essential oil extraction of plant drying process has a great role in the processing of medicinal plants. An important aspect of the drying technology with the aim of selecting the most appropriate drying method is mathematical modeling of the process. Therefore in this study، thin layer drying behavior of thyme (Thymus vulgaris L.) was experimentally investigated in a convective type dryer and the mathematical modeling performed by using adaptive neuro-fuzzy inference system (ANFIS). The drying experiments were conducted at inlet drying air temperatures of the 40، 50 and 60⁰C، at three drying air velocities of 1، 1. 5 and 2 m/s. For kinetic model simulation of thin-layer drying of thyme، four ANFIS models were used، and to generate the fuzzy inference system model، the two partitioning techniques، grid partitioning and subtractive clustering، were used. Results indicated that ANFIS model could satisfactorily describe the drying curve of thyme. Also، comparison of the results of the two partitioning techniques showed that subtractive clustering technique was found to be the most suitable for fuzzy inference system generation for predicting moisture ratio of the thin layer drying of thyme.

Effective operation of a system is related to acceptable programming of repair and service activities. Efficient managerial programming is associated with accurate estimation of maintenance system parameters. In this study، four tractors failure rate was investigated by completing 300 questionnaires from tractor operators in Khuzestan Province. The operators were interviewed in four regions of the province. Under study variables included driver experience، level of education، driving license، skill training course، work location (region and city)، type of service and maintenance، storage conditions، distance to first workshop، distance from shelter to farm، machine age، annual use hours and number of failure. Regression analysis by estimating an exponential function showed that the variables such as age of tractor، annual hours used and type of service and maintenance affected the failure rate of each four type tractors. For one percent increase in age of tractor and annual use hours، failure rate increased about 0. 6% and 0. 24%، respectively. Also، failure rate in MF285، MF399 and U650 tractors was about 0. 383، 0. 453 and 0. 143 percent more than JD3140 tractor، respectively. The preventive maintenance causes 0. 252 percent decrease in failure rate.

Replacement of tractors is a very difficult task. Farm managers often need to make such economic decisions about their machines. Repair and maintenance expenditures can have significant impacts on these economic decisions and forecasts. The purpose of this research was to identify a regression model that can determine economic life of two-wheel drive tractors. The study was conducted using empirical data on 60 two-wheel drive tractors from Astan Ghodse Razavi agro-industry during the years 1988 to 2005. A power model was selected as the best model for prediction of repair and maintenance costs. Based on the power model، the cumulative cost model (CCM) was used to predict the tractors economic life. 29025 hours was predicted as the economic life of the tractor by the CCM model، while according to cost minimization model (CMM) this parameter was equal to 27773 hours.

One of the basic principles for sustainable production is improving the quality of soil with regard to soil fertility and soil nutrients status. This study was conducted to investigate spatial variation of copper and manganese elements in soil farms in the northern part of Khuzestan region (100،000 ha). Therefore، 95 soil samples were collected from studied regions according to their wheat cultivation area. The data were analyzed to determine spatial variation and interpolation using Kirging technique. The results revealed that the average soil manganese concentration was 6. 75 mg/kg in the study regions. Also، more than 75% of studied soils had manganese concentrations less than 8 mg/kg (threshold value)، the average of copper concentration was 1. 35 mg/kg، and about 90% of soils had desirable copper concentration. According to the results، there were significant correlations between the soil''s copper and phosphorus (r= 0. 79*)، clay (r= 0. 78*) and salinity (r= 0. 77*) and also between soil''s manganese and pH (r=0. 83*). The best model for study characteristics was the spherical model. The highest soil manganese concentration was on the northeast، and the highest soil copper was on the west of the study regions. Finally، in some parts of the study area in which manganese and copper levels were less than the threshold value، application of copper and manganese fertilizers can be recommended. It increases the yield and improves the soils and agricultural products quality.

This study was investigated the effective parameters on the banana slices shrinkage during drying، using the response surface technique. In this study، the banana slices were dried using a thin-layer dryer made based on a computer vision system. Therefore، the shrinkage of the slices was determined using an image processing technique in the MATLAB environment. The response surface technique، central composite diagram (CCD) with four parameters، was used to investigate the effect of drying time، drying temperature، slice thickness and air velocity during the drying process (as the process parameters) on the shrinkage (as the process response). The second-order model was selected to describe the shrinkage as a function of the independent parameters (time، temperature، slice thickness and air velocity) due to RMSE=0. 033 and R2=0. 951. The results showed that the drying time، drying temperature، slice thickness and air velocity had the most effect on the banana slices shrinkage، respectively.

Knowing physical and mechanical properties of the flowers is one of the important factors in designing، harvesting and post harvesting machines. A completely randomized design with factorial test was used in this research. Effect of shear speed، flower diameter، blade mode and shear angle on shear strength and shear energy per stem area unit and effect of picking speed and petal diameter on petal and sepal on the tensile strength and energy consumed per unit of area were determined for Rosa damascena Mill. Shear strength was decreased by increasing shear angle from zero to 25 and 45 degree but it was not significant. Energy per unit of stem area and elastic modulus were decreased by increasing shear angle and it was significant at 5% probability level. Increasing shear speed from 150 to 250 mm/min was not significant on decreasing shear strength and elastic modulus but was significant at 5% probability level for 350 mm/min. Energy per unit of stem area was decreased by increasing shear speed. Shear strength، elastic modulus and shear energy per stem area unit were decreased by increasing flower diameter. Two treatments (Picking speed and flower diameter) were not significant on the tensile strength and picking energy per unit for both picking petal and sepal.