Iran Agricultural Research
Volume:32 Issue: 2, Winter and Spring 2014

Bruising degrades the quality of fresh apple fruits. Reducing bruise damage is of utmost importance in designing and developing processing equipments. The main objective of the present study was to introduce an analytical method to predict the allowable static load applicable to apple fruits. To predict the strain energy absorbed by the fruit، a point load was applied on the solid spherical object. The strain energy of the spherical element was extended to the whole body using a triple integral in the spherical domain. In order to verify the results، a series of compression tests were carried out using a universal testing machine on an apple kept at two different storage and initial fruit temperatures (zero and 25oC). The results showed a strong polynomial relation with a coefficient of determination of 0. 990 between the value of the theoretical stored strain energy and the experimental one. Also، it was found that the size of the bruised area can be determined by its corresponding theoretical stored strain energy with an error less than 3. 6 percent.

Mechanical damage degrades fruit quality in the chain from production to the consumption. Damage is due to static، impact and vibration loads during processes such as harvesting، transportation، sorting and bulk storage. In the present study finite element (FE) models were used to simulate the process of static bruising for apple fruits by contact of the fruit with a hard surface. Three dimensional finite element models with three different layer material models were developed. The force relation between the cortex and elastic core was simulated using a gluing mechanism. An external point load simulating the wall pressure was applied on the fruit skin. The elastic، plastic and total strain energies in apple fruits were calculated to estimate mechanical bruising. In order to validate the simulated data، compression tests were carried out using a universal testing machine. Force-deformation graphs were plotted and the area of the region restricted by the curve and deformation axis between zero and 1. 5، 3 and 4. 5 mm deformations were obtained at five replications to assess the stored strain energy in the fruit. Results revealed that any increase in applied external displacement increased the bruised area. A high correlation (r=0. 994) was observed between bruised area and amount of stored strain energy. Other results indicated that the bruised area highly depended on skin elasticity. Increasing in skin modulus of elasticity decreased the bruised surface.

The high production of orange fruit in Iran calls for quality sorting of this product as a requirement for entering global markets. This study was devoted to the development of an automatic fruit sorter based on size. The hardware consisted of two units. An image acquisition apparatus equipped with a camera، a robotic arm and controller circuits. The second unit consisted of a robotic actuator with required electronic circuits. For sorting purposes، an appropriate image processing technique was applied and two models of size thresholds were developed and incorporated in a number of image processing algorithms، which were، in turn، combined with Artificial Neural Network (ANN) techniques for classifying purposes. Multi Layer Perceptron models with various training functions and diverse numbers of neurons were also applied. Each algorithm was used to sort oranges into desired size groups (Small، Medium and Large). The sorter test rig was able to classify the product into three categories with considerably low errors. Although all twelve algorithms had acceptable results، those based on Red and Green segmentation were more satisfactory. For real time evaluation purposes، four algorithms، segmenting based on R color band، and two size threshold models were combined to form 8 comprehensive algorithms، which were used along with the ANN model at the evaluation stage. Results showed that algorithms based on Area، Perimeter and the ANN model، exhibited lower errors. Sorting records of each algorithm were compared to the relevant sorting data brought about by experts. Results show that sorting error can be as low as 1. 1%. Although the average capacity of the single sorter was limited to 1 t. h-1، the capacity can be markedly increased by adapting a bank of sorters in parallel mode. The study revealed that orange fruits can be sorted using the introduced techniques at high speed، high accuracy and low costs.

A real-time، site-specific، machine-vision based، inter-row patch herbicide application system was developed and evaluated. The image resolution was 640 × 480 pixels covering a total area of 350 mm x 240 mm of a field composed of four quadrants of 350 mm x 60 mm each. The image frames were processed by LabView® and MatLab®. The developed algorithm، based on weed coverage ratio and segmentation method for separating soil from plants، was chosen to be 2G-R-B. The unit was lab-tested to evaluate the accuracy of the sprayer at three travel speeds of 2، 4 and 6 km h-1. The effect of travel speed on spraying delay was not significant when using LabView®، while it was significant when MatLab® was used for image processing. A binary analysis algorithm showed that misclassification rates for plant (MCRP) and soil (MCRS) were (2. 4±1. 3) % [mean±SD] and (2. 8±0. 7) %، respectively and correct classification rates for plants (CCRp) and soil (CCRs) were (96 ±1. 1) % and (93. 8±1. 3) %، respectively. During the field test، three herbicide application treatments consisting of target patch spraying، conventional (uniform) spraying and no spraying (control) were compared at three levels of weed coverage (low، medium and high). In the patch spraying treatment، a spray mixture of 2-4-D (0. 35%) was sprayed only over the weed patches، while the conventional treatment plots received uniform and continuous applications of the same mixture. The result showed that the herbicide used in each patch spraying plot was proportional to the weed coverage level. On average، the target application resulted in 75% less herbicide consumption compared to the conventional application، while the patch spraying application was as effective as the conventional application for the eradication of weeds.

To evaluate effects of different soil moisture conditions namely، phosphorus (P) and zinc (Zn) application، on extractable Zn and Fe، two experiments were conducted in laboratory conditions based on a completely randomized design with a factorial arrangement of treatments with two replications. The first experiment was performed with the following factors; incubation time at four levels (1، 10، 30 and 60 days)، soil moisture at two levels (0. 6 FC and FC)، P fertilizer at two levels (0 and 60 mg P per kg of soil) and Zn fertilizer at two levels (0، and 20 mg Zn per kg of soil). The second experiment was conducted with two Zn levels (0 and 20 mg Zn per kg of soil)، two P levels (0 and 60 mg P per kg of soil) and three wetting-drying cycles (1، 10 and 20 cycles). The results showed that the extractable Zn and Fe decreased by time. The application of Zn fertilizer under FC conditions resulted in higher amounts of extractable Zn in all incubation times. The application of P reduced the extractable Zn and Fe in most incubation times and moisture conditions. By increasing the number of wetting-drying cycles and the duration of incubation time، the extractable Zn decreased significantly. There were no significant differences between constant moisture and wetting-drying cycles on the extractable Zn، except for the application of 60 mg P and 20 mg Zn per kg of soil under 0. 6 FC conditions.

The purpose of this study was to elucidate the effects of chemical thinning on seasonal variations of leaf and fruit mineral compositions of ‘Soltani’ apple trees. Treatments، including unthinned control، naphthalene acetic acid (NAA) at 5 and 10 mg L-1، naphthaeneacetamide (NAD) at 25 and 50 mg L-1، benzyladenine (BA) at 50 and 100 mg L-1 and carbaryl at 500 and 1000 mg L-1 were applied when fruit diameters were about 8 to10 mm. The results showed that leaf nitrogen (N)، phosphorus (P) and potassium (K) concentrations decreased، whereas calcium (Ca) and magnesium (Mg) increased during the season. Fruit mineral concentration changed with the age of the fruits. All nutrients decreased with fruit maturation. Most chemical thinners affected leaf concentrations of N and K but not P، Ca and Mg. Chemical thinning increased the fruits’ P، K and Mg concentrations. It is concluded that fruit chemical thinning may affect the accumulation of some nutrients، especially P and K in apple fruits and could improve fruit quality as well.