فصلنامه تحقیقات مهندسی کشاورزی
سال دهم شماره 4 (زمستان 1388)

Research on the performance of conventional sprayers in on-farm conditions is essential to the development of effective usage techniques. In this study, conventional sprayers were surveyed and evaluated for the removal of pests, weeds and crop diseases in wheat crops in the Karaj, Urumieh, Khuzestan and Khorasan provinces of Iran. The sprayers used were tractor boom, tractor lance, Turboliner, Micronair and atomizer sprayers. The experimental design was a randomized completed design and data was collected using 179 surveys from farmers during spraying. Additional data wascollected on the farms. Results show that 39.7% of the sprayers were lance, 29.6% were boom, 14% were Turboliner and 8.4% were Micronair. There was a significant difference between sprayers in poison solution consumption per hectare at the 5% and 1% levels. The maximum and minimum solution consumption was for the lance (854.2lit/ha) and Micronair (35.4 lit/ha) sprayers, respectively. The Turboliner sprayer had the most theoretical and effective capacities (11.4 and 7.1ha/h); atomizer and Micronair sprayers had the lowest capacities (1.02 and 1.3 ha/h, respectively). Spraying homogeneity for lance, boom and atomizer sprayers were not evaluated because the surface of the sensitive papers were completely soaked. VMD for Micronair and Turboliner sprayers was 398 and 441 micrometers; NMD was 189 and 123.2 micrometers; spraying quality was 2.1and 3.57, respectively. It was found that Micronair sprayers performed better than Turboliner sprayers and these two sprayers performed better than the remaining types with respect to spraying homogeneity. The greatest percentage of crop loss was recorded for the boom sprayer (10.3%).

The consolidation test method proposed by Terzaghi and used in most soil mechanic laboratories has limitations and weaknesses. To get correct results, improvement and modification of the test method is essential. Several experimental methods, such as constant loading rate, gradient and constant rate of strain (CRS) have been used over the past 40 years. Of these methods, CRS is more advantageous and is more popular, but there is no unique criterion for when to use the test, although many researchers have proposed different methods. Considerable differences exist between standards in the literature. The present study investigates the causes of differences between standards by investigating basic assumptions about flow regime caused by pore water loading during consolidation. CRS consolidation tests were carried out using an MIT consolidometer under different strain rates. The results indicate that a Darcy flow regime is not valid throughout the CRS test, thus, a consolidation equation based on the Darcy flow regime cannot model the test correctly. Also the present research showed three different flow regimes during the test for strain rate, including prelinear (non-Darcy), linear (Darcy low) and postlinear (non-Darcy).

A field investigation was conducted to evaluate the effect of N and K fertilizers on qualitative and quantitative changes of potato tubers during five months of storage. This study was carried out in three replications at five levels (0, 60, 120, 180 and 240 Kg/ha) of nitrogen and three levels (0, 75 and 150 Kg/ha) of potassium fertilizer during 2004-2006. Measurements were recorded monthly. The results showed that the effect of different treatments of N and K fertilizers and storage period, and their interaction, significantly affects the quantitative changes in tubers (p<0.05). The greater the application of N fertilizer, the greater the loss of water, vitamin C, starch and reduced sugar content of the tubers during storage and an increase in K fertilizer decreased these changes. According to the results, it is better to use 180 Kg/ha N with 150 Kg/ha K when planning to store potatoes for three months or less. If the storage period is more than three months, it is highly recommended to use 120 Kg/ha nitrogen and 150 Kg/hapotassium fertilizer.

Cumin is an annual plant suitable for dry and semi-dry regions. It is harvested at two stages to prevent seed shedding. First, the cumin bushes are harvested by hand or using a scythe. After drying, the cumin bushes are beaten with a stick or trampled using animals or a small tractor. This harvesting method is time consuming, requires intensive labor and is an incomplete threshing process resulting in crop loss and poor quality. Prior to developing a cumin thresher, the efficiency factors of cumin threshing were investigated. This research studied the effect of moisture content, drum type and speed, feed rate and space between the drum and concave on weight percentage of separated seeds, shattered stems and damaged seeds. The results showed that the percentage (by weight) of the separated seeds decreased from 92.85% to 90.39% when moisture content increased from 7% to 13%. The percentage of damaged seeds (by weight) decreased as moisture content increased. However, by increasing drum speed from 700 to 900 RPM, the amount of separated seeds, shattered stems and damaged seeds increased. There was no significant effect of drum type on the percentage of separated seeds (by weight), but there was a significant effect on shattered stems and damaged seeds. It can be concluded that the rub-bar drum was better than the rasp-bar drum. The rub-bar drum, 900-RPM drum speed and 7% moisture content were the most suitable conditions for threshing cumin.

Effect of calcium chloride on tomato quality and shelf life of Petoearly CH, Koral and Rio Grand tomato cultivars were studied at the Agricultural and Natural Resources Research Center of West Azerbaijan, Iran over 2002-2003. A calcium chloride solution in 0, 0.5% and 1% concentrations was sprayed on the tomatoes three times. The fruit was harvested at the mature green stage and stored in cold storage at 14°C and 20±2°C (room temperature). The experiment was carried out as a factorial experiment based on acompletely randomized design. Before storage in two storage areas and during storage, tomato samples were obtained and their quality indicators of brix (TSS), pH, titrable acidity (TA), weight loss and percent of decay were measured at five intervals. The results showed that calcium chloride had a significant effect on the traits, increased shelf life, TSS, acidity and decreased weight loss and percent decay. The Rio Grand cultivar had the longest shelf life and least decay. The tomatoes stored at 14°C had less weight loss and decay and more acidity and shelf life compared to tomatoes stored at room temperature. The shelf life for Rio Grand sprayed with 1% calcium chloride and stored at 14°C and 20±2°C were 43 and 19.5 days, respectively.

Monitoring the effective parameters of drying crops is necessary to evaluate and determine system performance under real conditions. Hence, a monitoring system was constructed to determine the performance of a vegetation forced-convection solar dryer. Digital temperature sensors were set up in the air inlet and outlet of the collector and the air outlet of the drying chamber. A program was written using visual Basic 6 software to register sensor data and make calculations. To evaluate the dryer, experiments were carried out over eight hours between 10 am and 6 pm during the summer. Mint was used for drying in all experiments on 5Cm high trays of the dryer chamber. The results showed that the radiation energy, the heat energy absorbed by the collector and the energy required for product evaporation had linear relationships with temperature. Radiation energy increased at first and decreased later during the drying time. The results showed that the average temperature in the collector air inlet, outlet and drying chamber air outlet were 38.1°C, 54.7°C and 45.5°C, respectively. The average maximum and minimum energy efficiency were 49% and 14.7%, respectively. The average radiation energy and required energy for product evaporation were 4572.4 and 2772.2 KJ, respectively. The drying curve was Mwb = 1.827e-0.4857t with R2 = 0.945.