Iran Agricultural Research
Year:2002 | Volume:21 | Issue:1|Papers Count:9

One of the major problems in date (Phoenix dactylifera L.) harvesting is variable maturity. Selective hand-picking of individual rjpe fruits from each bunch is the most expensive and time consuming cultural operation. A 2 x 5 x 3 factorial experiment with a completely randomized design in three replications was conducted to investigate the effects of sbak.ng mode, frequency and amplitude on date fruit detachment. Five levels of shaking frequency (200, 300, 450, 600 and 750 cpm) and three levels of shaking amplitude (20, 40 and 60 mm) were investigated it two modes of fruit hunch vibration (vertical and banging).The experiment was conducted on 'Shahani' dates fruit bunches. The effects of shaking mode, frequency and amplitude were significant on fruit detachment. The most effective detachment of ripe fruits with minimum unripe fruit detachment occurred at 300cpm frequency and 60 mm amplitude. Also the results showed that the vertical shaking mode was more effective in detaching ripe fruits than hanging mode and in the vertical shaking mode the amount of detached fruits with calyx attached was less than in the hanging mode. The amount of detached fruits without calyx attached increased at the higher frequency and amplitude levels. Fruit pull tests showed that the average axial tensile force required to remove ripe fruits was about 35% of that needed for removing unripe fruits. Bunch shaker was capable of removing marketable ripe dates from the bunch without imparting any significant rubbing of bruising damage to fruits.

Straw from 20 winter and 20 spring cultivars of wheat collected from 6 experimental stations were evaluated chemically to determine if the feeding value of straw differed among cultivars and if straw nutritional quality components were associated with desirable agronomic characteristics such as grain yield, heading date and plant height. No significant differences were observed for crude protein (CP) content among winter and spring cultivars but there were significant differences for location, cultivars and cultivar x location interaction for the spring cultivars. A combined analysis for spring cultivars showed a significant difference between location, cultivar, and cultivar x location interaction effects for all the components tested except for hemicellulose. Average CP, neutral detergent fiber, acid detergent fiber, hemicellulose and in vitro dry matter digestibility percentage of all cultivars ranged from 1.4 to 3.9%, 73 to 79%, 45 to 50%, 24 to 29% and 33 to 54%, respectively. Agronomic characteristics were unrelated to most straw quality components. The data indicated that genotypic selection can be made for feed quality components without affecting agronomic characteristics.

Aqueous extracts of Ailanthus altissima Swingle leaflets, rachises and roots reduced radicle growth of garden cress. The growth inhibitory activities of aqueous root extracts were significantly higher than that of the leaflets and rachises aqueous extracts. Methanol extracts of leaflets were more toxic than the aqueous extracts, whereas the chloroform extracts exhibited very low inhibitory activities. The aqueous, methanol and chloroform extracts of leaflets at 50 g 1-1  inhibited growth by 63.1, 90.6 and 9.2%, respectively. In contrast, the chloroform extracts of rachises significantly reduced the radicle length in garden cress. At 50 g 1-1, the aqueous, methanol and chloroform extracts of rachises inhibited growth by 61.6, 90.2 and 84.3%, respectively. The Ailanthus leaflets and rachises had the highest seasonal activity in spring and early autumn such that phytotoxin synthesis apparently follows optimum temperatures for growth. Postemergence applications of aqueous extracts of leaflets on garden cress, pigweed, barnyard grass and maize exhibited broad-spectrum herbicidal activities by reducing growth to 58-71 % of the control. Aqueous extracts of leaflets and rachises significantly reduced peroxidase activity by up to 85% and respiration (O2 uptakes) in root pieces by up to 66% in all plant species tested. Ailanthus tissues aqueous extracts also decreased mitosis in onion root tips. In the presence of 50 g 1-1 of root extract, 90% reduction in mitosis was observed. These biochemical and physiological changes are probably among the various cellular targets for Ailanthus allelochemicals responsible for growth inhibition in higher plants.

Palygorskite is a mineral of great importance in arid and semi arid soils and sediments~ This fibrous clay mineral has been reported in Iranian Aridisols. The main objective of this study was to determine the presence and the origin of palygorskite in Rafsanjan soils in central Iran and to study the relationship between this clay mineral and geomorphic surfaces. Soils occurring on two perpendicular transects were studied. The first transect is located in Nough area, 30 km north of Rafsanjan, and the second one extends to Ali-Abad village 20 km south of Rafsanjan valley. Palygorskite, illite, chlorite, smectite, and quartz were observed in all soils using XRD; TEM, and EDX analyses. In the first transect, palygorskite crystals: decreased in number and size from east (rock pediment) to the west (mantled pediments and playas). A trace amount of smectite was found in rock pediment position; in contrast, there was more smectite in other soil profiles. Due to more precipitation in the area of second transect, CaCO3 illuviation has been occurring. Besides, palygorskite has easily been weathered and transformed to smectite. On the other hand, highly smectitic Marl formations resulted in greater amount of this mineral in the second transect as compared to the first one.

Typha latifolia L. is a widespread nuisance aquatic weed species. It is a harmful weed. in the Iranian freshwater systems, especially in the Anzali lagoon. The effects of frequent cutting at the different levels of water, competition and late application of glyphosate on dry weight shoot length, number of shoots and numbers of leaves per plants of T. latifolia were studied in the Anzali lagoon. T. latifolia dry weight and shoot length decreased significantly after cutting compared to the control plants. Dry weight was uniformly reduced in all treatments after 1, 2 and 3 cuttings. Three cuts during the growing season resulted in almost complete death of the plants. Water level and intraspecific competition did not have a significant influence on dry weight and shoot length. The best time for cutting was late June to early August, when carbohydrate reserves in the rhizomes were low, and just before the inflorescence appears. T. latifolia was susceptible to glyphosate at doses of 1.5 kg a.i. ha-1 and higher. Although, high rates (1.5, 2, 3, and 4 kg a.i. ha-1) of glyphosate provided excellent initial control of T. latifolia, long-term control of regrowth was not achieved. Late season application caused poorer control due to a lack of the moyement of photosynthate to areas of high metabolic activity.

Decision makers usually engage in the optimization of multiple goals rather than a single objective. So, management problems may need to be analyzed in the multi-objective framework. Multiple criteria decision making models have been proposed to solve multiple objective problems. This paper shows how weighted goal programming technique can be applied to farm planning problems. Data used in the current study come from a sample of 68 farmers, who were selected by a two-stage cluster sampling method, from the Sarvestan plain, Fars province. Cluster analysis method was used in order to classify sample farms into homogenous groups. Then, conventional linear programming and weighted goal programming models of the representative farms were compared with their existing farm plans. The modeling results indicated that goal programming is a more powerful and flexible technique, as compared to conventional linear programming, to analyze farm planning problems.

This experiment was carried out to study the effects of different carbohydrate sources (fructose, glucose and sucrose) at different concentrations (20, 30 and 40 g 1-1) on shoot multiplication of Persian walnut (Juglans regia L.). In vitro propagated shoot tips of J. regia L. cv. 'Serr' were cultured on DKW medium containing 1.0 mg -1 6- benzylaminopurine (BA) and 0.01 mg -1 indole-3-butyric acid (IBA) solidified with 2.2 g -1 Phytagel. No significant differences were observed among the different kinds of carbohydrates for shoot fresh weight and main shoot length. Maximum callus fresh weight at basal ends of shoots was obtained with glucose and this was significantly greater than fructose or sucrose. Explants cultured on media containing glucose produced maximum number of axillary shoots. Different concentrations of carbohydrates did not have any significant effect on shoot fresh weight and main shoot length. There was a significant difference among the three different concentrations of carbohydrates for callus fresh weight and axillary shoot numbers. The best micro shoots were obtained using 20 g -1  sucrose.

Soil erosion begins with detachment and transportation of soil particles from surface soil layers. In the evaluation of soil erosion, usually the volume or the weight of the soil losses is calculated, but the physical properties of the sediment are less often considered, Due to the selectivity of erosion process the clay particles are much more in the sediments than in the original soils. For estimating the clay enrichment ratio (CER) in the sediment resulting from erosion, a 4.83 ha watershect with a surface soil of silt loam texture was selected in the north-west of the College of Agriculture, Shiraz, Iran. Suspended sediment resulting from eight independent precipitation events was sampled and their particle size distribution was determined: The average CER for the selected rainfall events was 2.3 with a range of 1.5 to 3.1. No significant relation was found between CER and the properties of the precipitation and runoff such as magnitude, average, and maximum rainfall intensities. The following relation between, CER and the suspended solid in runoff from the watershed was obtained, CER=59 (SSa)-0.465, (R2=0.91), where, SSa is the average sediment concentration in suspension, mg 1-1. This equation shows that the CER decreases with an increase in the sediment concentration.