فصلنامه تحقیقات مهندسی کشاورزی
سال یازدهم شماره 3 (پاییز 1389)

Agricultural drought has resulted in great damage to Iran in recent years and it is crucial to cope with this adversity through logical management. One attempt in this regard is to compare affected sites and prioritize them for action plans. This paper develops a methodology for agricultural drought risk analysis based on rain-fed wheat data from Kermanshah province and employs it to compare affected cities in the province. Two models were developed using regression and ANFIS methods to estimate crop yield using drought indices as inputs. The results showed better performance for the ANFIS model using SPI and Z-index as inputs. A Monte Carlo simulation was applied to obtain the yield probability distribution for drought risk analysis within the cities. It was shown that the cities of Hersin and Songhor have the highest and lowest risk, respectively, when combating drought.

Crops and agricultural products are subject to natural loading during growth. Different mechanical forces are also exerted on them during harvest. One product, sugar cane, experiences large shear forces are during harvest. An examination of the crop properties and machine parameters of sugar cane are necessary to develop appropriate cutting tools and the optimization and design of harvesting machines. The determination of such physical properties as diameter, moisture content, bulk density and mass per unit length is indispensable to this process. Mechanical properties related to cutting, such as maximum cutting force and strength, required energy and specific energy required for cutting are important. For this research, two experimental samples of sugar cane stalk (CP57, CP69) were collected from Amirkabir Research Farm in southern Khuzestan province. The samples were transported to the laboratory while maintaining the moisture content as constant as possible. The stalks were tested under quasi-static conditions using twotypes of blades (serrated and smooth) at three speeds (0.2, 0.5 and 1.35 m/min). The resulting data were analyzed using MSTATC and SPSS software. The effect of the variety on maximum cutting force was not significant, but cutting strength was observed to be significant at the 1% level. The effect of speed change on maximum cutting force was also significant at the 1% level. The effect of blade type on both maximum cutting force and cutting strength was significant at the 1% level. Increasing the speed from 0.2 to 0.5 and then to 1.35 m/min, especially using the smooth blade, increased the efficiency of cutting. However, increasing the speed from 0.5 to 1.35 m/min using the serrated blade increased cutting strength and energy. The serrated blade, at low speeds, was observed to require lower energy. Serration reduced energy consumption and lowered the required cutting strength because of adequate primary penetration of the blade into shell of the stalk, and the reduction of compression time.

The conjunctive use of surface and groundwater in irrigation networks influences the performance of canals. One condition of conjunctive use is to add the groundwater to the surface water via a canal to satisfy demand. Management and operation of the canal is a complex task that must consider demand variation and groundwater entering the canal. The variety of decision variables in conjunctive use requires the use of optimization techniques to determine optimal operation. Simulation models should be combinedwith optimization models for this purpose. In this research, an irrigation conveyance system simulation (ICSS) hydrodynamic model was used to simulate the flow in an irrigation canal. A combined optimization technique was used that considered the complex and implicit relations between the objective function anddecision variables. A model based on the shuffled complex evolution (SCE) optimization technique, a heuristic intelligent search technique, was used to develop an ICSS-SCE model. The proposed model was applied to the L8 canal of the Qazvin irrigation network, consisting of five conjunctive wells. Two options (25 and 40%) for demand increase provided by groundwater was considered. For each option, regular and optimum operations (four options in total) were taken into account. Optimal control settings (for water flow) were determined and canal performance for each option was calculated using the ICSS-SCE model.The results showed that setting controls according to optimal recommendations influenced by conjunctive use led to considerable performance improvement of the canal and intakes. The objective function of the canal was improved in two cases by 40-48%. In general, it was concluded that the proposed model was capable of determining optimal operation of the irrigation canals under conjunctive surface and groundwater use.

The shear strength and shear energy per unit area, as well as the force and energy required for picking flowers, are important parameters in the design and development of harvesting mechanisms. In this study, shear strength and shear energy per unit area of saffron (Crocus sativus L.) stems were determined at different bevel angles and shear velocities. The force and energy required for picking of saffron flowers were determined as a function of picking velocity and age of plant. The experiments were conducted usinga universal testing machine on samples selected from the farms of Kashmar in eastern Iran. The data was statistically analyzed using a completely randomized design. The results showed that the bevel angle of the cutting blade and shear velocity had a significant effect on shear strength and shear energy per unit stem area, but their interaction was not significant. With an increase in bevel angle from 17° to 24°, the shear strength increased from 0.130 to 0.190 MPa and shear energy per stem area increased from 0.305 to 0.443 mJ/mm2. Increasing shear velocity from 20 to 200 mm/min decreased the average shear strength significantly from 0.179 to 0.158 MPa and shear energy per stem area significantly from 0.467 to 0.340 mJ/mm2. Further increase in shear velocity (from 200 to 500 mm/min) did not decrease shear strength andshear energy significantly. Thus, the cutting blade at a bevel angle of 17° and shear velocity of 200 mm/min is recommended for cutting saffron stems. The results showed that increasing picking velocity from 50 to 500 mm/min increased the average picking force, tensile strength and energy per unit area from 0.339 to 0.459 N, 0.169 to 0.229 MPa and 0.473 to 1.914 mJ/mm2, respectively. The age of the plants had no significant effect on picking force and energy and tensile strength. The data gathered can be useful for the design and development of saffron harvesting mechanisms.

In this project, the quantitative and qualitative characteristics of malt obtained from barley, (var. Sahra), wheat (var Tajan) and Triticale, and their admixtured malts were investigated in a completely randomized design with eight treatments to determine the optimal treatment using diastatic power, hot water extract and production of suitable raw materials for the malt beverage and bakery industries. The characteristics werehot water extract, cold water extract, diastatic power, total and soluble protein, nitrogen modification index, color and β-glucanase activity. Triticale and barley malts had the maximum and minimum Kolbach indices (p<0.05), respectively. Malt obtained from Triticale and the admixture of barley-Triticale (90:10) malts, and barley-wheat (90:10) malt had maximum and minimum (p<0.05) hot water extract, respectively. Malt obtained from an admixture of barley-wheat-Triticale (80:10:10) malt and a mix of barley-wheat (90:10) malt had the maximum and minimum (p<0.05) diastatic powers, respectively. The results showed that the addition of Triticale malt (10%) led to the production of suitable raw materials for the malts beverage industry and the addition of both Triticale and wheat (each 10%) malt for the bakery industry.

Applied and precise methods of evapotranspiration partitioning provide useful data for farm irrigation management and water use efficiency improvement. This knowledge is particularly important for modern irrigation systems that require high cost for implementation. Therefore, research was conducted in the summer of 1388 in the field at the Agricultural Engineering Research Institute in Karaj in which maize evapotranspiration and soil surface evaporation components were measured simultaneously using the Bowen ratio energy balance (BREB) method. Crop transpiration was then calculated by calculating the difference between these values. Soil type in the experimental field was loam texture irrigated with subsurface drip irrigation installed 15 cm below the soil surface. Irrigation was scheduled to reduce water stress in the maize crop. Data for the BREB method were collected from above canopy level, at canopy level and at the soil surface. Results for a sample day of a mid-season crop growth period (day 60) showedthat, of the total available energy for evapotranspiration, only 15% was used as sensible heat while the rest was used as evapotranspiration. Soil heat flux was less than 10% of net radiation, of which 93% of available energy was used as soil evaporation. At canopy level, about 19% of the available energy was used as sensible heat. A comparison between hourly values of evapotranspiration measured by the BREB and Penman-Monteith methods showed good correlation (R2 = 0/95) where BREB evapotranspiration showed 10% variation as compared to the Penman-Montieth method.

The management of machine replacement (specifically tractors) is one of the most critical factors for performing field operations on time. Therefore, tractor repair and maintenance costs must be accurately predicted. This research was carried out to evaluate the use of the regression technique in predicting tractor repair and maintenance costs. The study was conducted using empirical data on 60 two-wheel drive tractors from Astan Ghods-e Razavi agro-industry. Regression analyses were carried out. The response variable was repair and maintenance cost value and the independent variable was cumulative hours of use. Different second and third-order polynomial models and exponential and power models of age were examined. The results showed that the cubic regression model was the best model for predicting repair, oil and fuel costs based on the coefficient of determination and significance of regression coefficients. The performanc cubic regression model performed much better in the test phase for the prediction of repair costs with a mean absolute percentage error of 3.72 in comparison to oil and fuel costs with a mean absolute percentage errors of 5.21 and 9.51, respectively.