فصلنامه تحقیقات مهندسی کشاورزی
سال نهم شماره 3 (پاییز 1387)

The agriculture sector has been affected by severe drought in recent years, making development of a drought warning system for agriculture crucial. Such a system can be a useful tool for policy makers and investors. This research develops a model for agricultural drought risk assessment using statistical and intelligent methods. Kermanshah province, a major rain-fed region of Iran, was selected as the study area. The model is specific to rain-fed wheat and was updated during the different phonological stages of the growing season. The inputs are a combination of the PDSI, Z-index, CMI, SPI and EDI drought indices which were selected using genetic algorithm and artificial neural networking techniques. The results show that the Z-index better predicts possible losses. The general performance of the model increased toward the end of the growing season, especially after the third stage, when the significance level of the relation reaches 1% and the results become more reliable. Furthermore, linkage of the model to the geographical information system makes it more capable of spatial analysis and more suitable for presentation of the final results.

The mechanical strength of cumin seed and the effects of moisture content, seed size, speed and direction of loading on the force and energy required to fracture cumin seed were investigated. The results showed that moisture and loading direction were significant at the 1% level on the force and energy required to fracture cumin seed. The effects of seed size on force and loading speed on energy were also significant at the 1% level. Increasing moisture content decreased mechanical strength and increased elasticity under loading. The energy absorption capacity of wet seed was higher than that of dry seed and led to increased seed strength under loading. The highest energy absorption (15.31mJ) was found for small seeds at 15% moisture content under horizontal loading and the lowest energy absorption (1.72mJ) was found for largeseeds at 5.7% moisture content under vertical loading. Small seeds with 5.7% moisture content under horizontal loading had the highest mechanical strength and large seeds at 15% moisture content under vertical loading had the lowest mechanical strength.

In recognition of the value and limitations of available water resources in agriculture and the occurrence of periodic drought in Iran, water conservation and optimal usage of available water is essential. The main objective of this study was to optimize field water management and cropping patterns using deficit irrigation. The effect of reducing water consumption on different growth stages using different irrigation strategies for major crops (wheat, barley, corn, sugar beet, rice) in Doroodzan, Fars province was studied.Then, using these strategies, an objective function was defined and then optimized based on maximum net benefit using linear programming. The results of the study show that the optimal cropping pattern for the first season was mainly wheat and in the second season was corn. This study highlights the effect of water restriction in different growth stages on area cropping patterns for wheat and corn in the first and second seasons. The results show that the best time to perform deficit irrigation is in late vegetation, yield formation, and ripening stages for wheat and establishment and ripening stages for corn.

An understanding of the strength of rice grains as affected by moisture content and temperature is important for analysis and prediction of cracking and/or breakage behavior during handling and processing. Further, the magnitude of these properties at various moisture contents and temperatures is needed for the accurate design of milling machinery so that grain damage is minimized. To determine the compressive mechanical properties of grains, two types of quasi-static compressive tests, whole kernel and uniaxialcompressive tests, of core specimens were performed at three moisture contents, 10.2%, 12.2% and 13.25% (w.b.), at grain temperatures of 35, 45, 55 and 64°C. Failure force, deformation and energy at the breaking point and apparent elasticity modulus were determined for whole grain tests, and compressive strength, failure strain, toughness modulus and compression modulus of elasticity were determined for uniaxialcompressive tests. Statistical analysis of the mechanical tests results indicated that moisture content and temperature have a strong influence on the properties examined. There was no significant effect on rice compressive failure properties. Moisture content had the greatest effect on the mechanical properties of rice. In general, all strength values except compressive strain increased as moisture content and/or temperature of grains decreased. For the different rice grain conditions studied, failure force varied from between 37.01 to 89.96N, while compressive strength varied from between 16.43 and 44.42MPa.

Many factors affect yield loss in wheat harvesting with a grain combine harvester and there is no mathematical model to describe the behavior of this complex system. Thus in this study, a fuzzy logic controller (FLC) was designed, implemented and tested for the automatic settings of cylinder speed, concave clearance, fan speed and forward speed of a model 955 John Deere combine. First, the mechanical systems of these units were converted into hydraulic systems to implement the FLC. Then, seven sensors were installed to measure combine parameters (four sensors) and yield losses (three sensors). The yield loss sensors were very accurate and reliable. A fuzzy logic algorithm was proposed to control these units, with two inputs (straw walker and sieve loss) and four outputs (cylinder speed, concave clearance, fan speed and forward speed). Trapezoidal membership functions were selected as fuzzy linguistic input variables and fuzzy singletons were selected as output variables. Six rules having logical AND operators and Mamdaniimplications were employed. The fuzzy algorithm was implemented using a CJ1M model PLC. Laboratory and field experiments were carried out in the summer of 2006 to evaluate the performance of the proposed fuzzy inference system. Statistical analysis (t-tests) of the present investigation indicated a significant difference (p<1%) between loss mean in the combine with FLC installed and the combine without a controller.

Multistage and semi-mechanized harvesting of rice in Khouzestan province, Iran, causes much loss. Depending on available facilities and conditions, either spike-tooth or rasp-bar cylinders are employed with either direct or indirect combine harvesting methods. The present research studied the effect of these different harvesting methods on the amount of losses in two rice varieties in 2001-2002 at Shavour Agricultural Research Station in Khouzestan province. The experiment was devised as a strip-plot with a randomized complete block design with two variables (harvesting method, variety) and three replications. The vertical axis variable harvesting methods were: indirect harvesting (manual) plus threshing by rasp-bar cylinder combine; indirect harvesting plus with threshing by spike-tooth cylinder combine; direct harvesting with threshing by rasp-bar cylinder combine, direct harvesting with threshing by spike-tooth cylinder combine. The horizontal axis variables were: high yield LD183 rice variety; qualitative local RedAnboury rice variety. Analysis of the losses for the two years showed a significant difference between years for harvesting methods and their interactions but no significant difference between varieties. A comparison of averages showed that losses for the first year were greater at 3.34% than for the second year at 2.08%. However, average losses for the Red Anboury variety were 2.71% and 2.74% for the LD183 variety. For both direct and indirect harvesting methods, average losses for harvesting by spike-toothcylinder combine were 1.73%, which was less than the 3.68% for the rasp-bar cylinder combine. The spiketooth cylinder combine produced the least amount of loss over the two varieties. Indirect harvesting of LD183 with threshing by rasp-bar cylinder combined in the first year produced the greatest average loss at 5.42%. Indirect harvesting of Red Anboury with threshing by spike-tooth cylinder combine in second year produced the lowest average loss at 1.48%. There was no significant difference between harvestingmethods for quality of loss (broken rice rate) but there was a large significant difference by year with 45.6% for the second year and only 18.9% for the first year. This loss was also significant by variety with LD183 averaging 34.2% broken rice and Red Anboury averaging 27.6%. Over all harvesting methods,LD183 had greater broken rice rates.

This study evaluated the use of the solar dryer at Esfahan Agricultural Research Center for drying prunes. A factorial experiment was carried using a randomized complete block design with four replications. The four methods used to accelerate prune drying were: control group (no treatment), mechanical perforation at one week of drying, blanching, submersion in Australian cold dip method. The drying rate of the prunes was measured at: beginning of drying time (time zero), after 72 h, after 144 h, after 288 h, after 336 h.Weight variation, acidity percentage, humidity percentage and TSS of fruit were measured at each time interval. Measurement of color loss, as well as subjective evaluations of color, taste, appearance and overall acceptability of the dried prunes was carried out at the end of drying process. The dried fruit was then stored for two months and one year and were subjected to color and subjective appearance evaluations. Temperature measurement of the drying chamber indicated that the maximum temperature of the inlet air was 70°C, outlet air was 60°C and in the fruit was 51°C. The control and mechanical perforation pretreatments produced similar drying rates, while the Australian cold dip method pretreatment augmented it. The blanching pretreatment produced an inferior quality of fruit. The average comparison of quantitative color indices (L*, a*, b*) showed that dried fruit produced by the control and mechanical perforation were darkest, blanching produced the most redness and Australian cold dip method pretreatments produced the greatest yellowness. Judges preferred dried prunes subjected to Australian cold dip method for their taste and general acceptability. Also they gave the highest rating to the color of dried prunes subjected to mechanical perforation pretreatment and stored for two months.

Pistachio nuts are the major non-oil export agricultural commodity in Iran. The existence of empty shells among the shells with kernels reduces the quality of the nuts and, consequently, their market value. In pistachio processing plants, empty shells are generally separated from shells with kernels by the flotation method. But this method is not precise and may encourage the growth of fungi in the nuts. This research investigated an identification method based on sound reflection analysis. A sample of pistachio nuts was divided according to size into large, medium and small groups. Each group was further divided into empty and full shells. A sound box and PC computer were prepared to detect and analyze the echoes of the impacts of each of the nuts as it drops onto a steel plate. The impact echoes were recorded and the echo signals analyzed in both time and frequency domains using a nearest distance classification approach. The best results were obtained for the large sized nuts with 98.75% accuracy for detecting empty shells and 82.8% for detecting full shells. The classification results were also good for other classes, with the lowest accuracy rating being 62.75% for medium-sized full shells.

This study was conducted to evaluate the current management of furrow and border irrigation systems in the Dez irrigation network. Of the eight farms studied, three grew wheat and one each grew corn, sugar beets, lettuce, sesame and mung beans. The study found water application efficiency in the five farms with furrow irrigation systems to be 25.8% and for the three farms with border irrigation systems to be 32.7%. The main reason for water loss was found to be runoff and deep percolation. SCS infiltration equation parameters were calculated using the obtained data. For each farm, conditions were simulated using the SCS equation. Methods for optimum irrigation were developed based on variables such as discharge inflow, furrow/ border length and cut-off time and cut-back methods.

This study examined sourdough LAB containing specific starter cultures used to produce barbari-style bread and evaluated their microbiological shelf life and sensory properties. The effects of sourdough fermentation time (8, 16, 24h), fermentation temperature (28, 32, 36°C) and type of starter culture (Lactobacillus sanfransicencis, ATCC 14917; Lactobacillus plantarum, ATCC 43332; a mixture of both LABs) were analyzed in a completely randomized design factorial experiment with four replications. The microbiological shelf life of samples was determined by placing serial dilutions on plate count agar for one to seven days. The sensory properties of the bread were determined 1, 24, 48 and 72h after baking using AOAC standards. The results showed that sourdough had a significant effect (p≤0.05) on improving the microbiological shelf life and sensory properties of barbari bread in comparison with the control sample. Moreover, the sample produced with Lactobacillus plantarum (24h fermentation time and 32ºC fermentation temperature) had the maximum microbiological shelf life and the sample produced with a mixture of both LABs (16h fermentation time and 28ºC fermentation temperature) had the best sensory evaluation 72 h after baking.