Iran Agricultural Research
Year:2001 | Volume:20 | Issue:2|Papers Count:8

Trials of several methods indicated that selective removal of ripe date fruits could be accomplished by shaking the bunch. The purpose of this research was to design and develop an experimental shaker for investigating the effects of shaking mode, frequency and amplitude on ripe date fruit detachment. The experimental shaker was powered by a continuous variable speed electric motor. The rotational speed of the electric motor could be continuously varied from 0 to 1400 rpm by means of an electric volume I control knob on a digital board. The rotating output power of the electric motor was transmitted to a small flywheel through a V-belt drive system, where it was converted to a reciprocating motion by a slider-crank mechanism. The eccentricity of the crank mechanism was adjustable to provide stroke lengths of 20, 40, 80, 100 and 120mm. The slider motion was transmitted to the shaker clamp by a 500 mm long boom made of 20mm steel tubing. The boom could reciprocate vertically and horizontally in a brass guide. Using this shaker, date fruit bunches can be oscillated in vertical, horizontal and hanging modes. At the vertical shaking mode, the resulting motion of slider-crank mechanism was transmitted to the fruit bunch clamped to the shaker. Frame, through a boom and a clamping-device. At the hanging shaking mode, the bunch stalk was clamped to the end of a rocking arm. - The prototype machine was constructed and tested for 'Shahani' date fruit bunches in Jahrom, a date growing town in Fars province, Iran.

A unique solar air heater with a transpired slatted glass sheet cover and transpired absorber was developed and tested. The idea was to suck the air through the air slots to recover part of the short wavelength radiation absorbed by the glass sheets. Furthermore, the long wavelength emission from the absorber could also be recovered thus minimizing the total heat losses. A mathematical model was developed to predict the effects of variations in the input parameters on the collector thermal efficiency. The theoretical results showed that the thermal performance of the collector was sensitive to air flow rate, ambient temperature, solar irradiance and absorber emissivity variations. The collector was tested under a solar simulator over a wide range of air flow rate. The experimental results were in good agreement with the theoretical ones. An absorbing efficiency as high as 86% could be obtained with a reasonably low air pressure drop across the slatted glass sheet cover The sensitivity analysis of the collector to variations in input parameters was also investigated.

A PTO-powered one-way disk plow was developed to plow paddy fields with excessive soil compaction. The plow was operated in the rice fields after paddy harvest at peripheral disk velocity to ground speed ratios of 3.0, 2.2 and 1.7 at four soil depths. The factorial experiments were conducted as randomized complete block design in three replications. The performance of the powered disk plow was compared to that of the standard disk plow and pre-till soil conditions. The study indicated that the rotary plow markedly decreased aggregate size since the clod fineness was improved by an average of 29.5% compared to the standard disk plow. Smaller clod mean weight diameters (MWD) were obtained at low levels of velocity ratio (higher tractor speeds). The cross section of the soil tilled with the powered plow exceeded the standard disk by an average of 25% for the speed range studied. The disturbed cross sectional area was larger at higher speeds. Average cone index reductions of 50 and 63 % were determined in depth ranges 10-15 and 15-20 cm, respectively. It was found that an increase in the tractor speed was associated with corresponding decrease in the soil cone index at 10-15 and 15-20cm depth ranges. Therefore, for better penetration, the tractor speed should be kept at the fastest possible level. The maximum working depth was 16 cm for the standard disk plow but was 20 cm for –the powered disk plow, i.e., a 25% increase. The study revealed that the powered disk plow resulted in a significant decrease in soil cone index and improvement of other factors as compared to pre-tillage conditions and the standard disk plow.

Producers' risk attitudes in Ramjerd district of Fars province were estimated by using the nonstructual approach. The results indicated that, at the population mean, these farmers were both Arrow-Pratt and downside risk averse. Risk-aversion coefficient can be used in the analysis of farmers' behavior and preparing risk-efficient strategies for water and other resources.

Seed dormancy of 'beneh' (Pistacia mutica F. & M.) rootstock was the subject of this investigation. Scarification with 98% cold sulfuric acid (90 min), stratification (10, 20, 30, 40 d at 5±1oC) and soaking in gibberellic acid (GA3) (100, 250, 500, 750, and 1000 mg1-1) were used to increase seed germination of 'beneh'. Scarification plus 20 d stratification at 5±1oC increased seed germination from 27.7% to 62.1 %. The highest seed germination occurred when seeds were soaked in GA3 at 500-1000 mg I-I Inhibitors extracted from 'beneh' seeds had properties similar to abscisic acid (ABA). Concentration of these inhibitors decreased as stratification time increased. The lowest concentration of inhibitors was found 20 d after stratification. A hard endocarp and internal dormancy were the main causes of seed dormancy.

A better understanding of some physico-chemical characteristics of saline soils, developed in playa margins, may be important to improve the study of soil salinity in playas using remotely sensed data. In this study, some important aspects of soil salinity in the Ardakan and Abarkooh playa margins in the central part of Iranian deserts were investigated. For this study, 115 soil profiles were excavated and soil samples from different intervals/horizons were analyzed for some physico-chemical properties. It was also attempted to study the accumulation of soluble salts in the soil profile, and relationship between some soil salinity parameters such as electrical conductivity (EC), soluble chloride (Cl- and sodium ions (Na+) with soil depth. The results obtained from the relationship between soil salinity parameters showed that the estimation of soluble Cl- and Na+ from EC (1:5) and electrical conductivity of soil paste (ECp) of surface samples has the advantage of saving time when high accuracy is not intended. The result Alovi Panah and De Dilpper also showed that EC and soluble Cl- and Na+ decreases rapidly at about 20 cm and that below this depth, soil salinity decreases gradually. Based on the results obtained, we generally concluded that the relationship Between soil salinity parameters might be useful to design a sampling plan more efficiently.

Pathogenic variability among four isolates of Phaeosphaeria nodorum, causal agent of glume blotch of wheat, was investigated. Aggressiveness of the isolates of the P. nodorum was examined by expression of components of partial resistance on six wheat cultivars. All isolates were pathogenic on all wheat cultivars. Significant differences in incubation period, latent period, and lesion type were found among isolates in intact leaf tests. There were significant differences among the six wheat cultivars in incubation, latent and maturation periods, and lesion type in the intact leaf tests. Significant correlation among some components of partial resistance was found. Lesion type was the best component to predict both aggressiveness of isolates and resistance of wheat cultivars. No evidence was found for the existence of races among the isolates of P. nodorum. However, based on differences in aggressiveness, different pathotypes could be recognized. Among the wheat cultivars, spring wheat '86ISWMN' 2137 had the highest resistance to the isolates of P. nodorum, measured components of partial resistance.