THE SCIENTIFIC JOURNAL OF AGRICULTURE (SJA)
Year:2006 | Volume:28 | Issue:2|Papers Count:18

A new device was designed for chopping fodder and for its automation. To feed the fodder into the jaws of the chopper, a coupler curve of a four-bar mechanism was used. The most efficient and time saving method of selection of the coupler curve was identified, accordingly an Atlas of these curves, for the first time in Iran, containing more than 8000 items was produced. The device can be operated manually as well as by an electric motor. It is shown that the performance of the designed machine is 9 times better than the commonly used choppers.

Physical and mechanical properties of fruits are undoubtedly of great importance in design and improvement of fruit production, processing, and packing systems. Most of the agricultural products are generally classified as viscoelastic materials. Although time-dependency is one of the basic characteristics of the viscoelastic materials’ behavior, the effect of loading speed on the mechanical properties of agricultural crops necessitates individual subtle studies on each of them. On the other hand, the relation between mechanical properties and fruit size as a physical property is unknown. The Importance of Date fruits and lack of fundamental data about their mechanical behavior is the motive for this study. Mechanical properties of two date fruit varieties, namely Zahidi and Estamaran including force and energy needed to deform the fruit, and the energy per unit volume of the fruit and the initial modulus (the first non-zero tangential modulus) neaded to be determined. The force, energy and energy per unit volume were determined at 10%, 20%, 30%, 40%, 50% specific deformations and at the point where the first crack in the fruit became visible. Independent variables included loading speed (30, 60, 90, 120, 150 mm/min) and fruit size (small, medium, large). Although the effect of loading speed on most force, energy and energy per unit volume values under different specific deformations was not significant for Zahidi variety, its effect was very significant for Estamaran dates. For both varieties, the initial modulus, force, energy and energy per volume at the rupture point were significantly affected by loading speeds. Fruit size did not affect mechanical properties of the dates except for the energy per unit volume which is quite logical given its very definition.

In order to evaluate and select the drought tolerant sunflower hybrids and their parents, two experiments were conducted under stress and non-stress conditions in the form of line× tester design at the Seed & Plant Improvement Research Institute of Karaj, Iran, in 2002. Both experiments consisted of 36 treatments including 3 lines with cytoplasmic male sterility, 8 restorers and 24 their hybrids and one open-pollinated variety (Armaviruski). The experimental design was a simple lattice design with two replications. All plots in stress and non-stress conditions were irrigated on the basis of 180mm and 60mm class A evaporation pan, respectively. Drought stress was applied at 6-8 leaf stage. Analysis of variance showed all traits were highly significant in stress and non-stress conditions. To study combining ability, line× tester analysis was used using procedures developed by Kempthorne (1951), Singh and Chaudhari (1976). Line mean square for traits such as seed filling period, days to the beginning and end of flowering and tester mean square for traits such as seed filling period and days to physiological maturity were significant under two conditions, which shows additive variance is significant. Where as line× tester mean square for traits such as seed filling period, days to the beginning and end of flowering and days to Reproductive Stage 8 was significant under one/two conditions; which shows that non-additive variance is significant. GCA/SCA variance ratio revealed that non-additive genetic variance was more important than additive variance for latter traits.

The residual effects of applied nitrogen to previous crops and cropping system were evaluated in southeast of England, for yield and quality of wheat grain yield in the following year. The experiment was carried out in Wye college farm, University of London between 1997-1998 one season for grain production. The experiment consisted of three rates of nitrogen applied to previous crop as a main plot (N0 = no nitrogen, N75 = 75 kg N ha-1 and N150 = 150 kg N ha-1) and four previous cropping system as a sub -plot (W = wheat sole crop, B= bean sole crops, bw = bean - wheat intercrop low density, and BW = bean-wheat intercrop high density). There were four replications.  Soil mineral NO3-1-N concentration, measured before sowing the subsequent wheat crop varied with applied nitrogen to the previous crop and also previous cropping system treatments. The previous bean sole crop and intercrops had a beneficial residual effect on the performance of the subsequent wheat crop. The highest mean grain yield of subsequent wheat was obtained following bean (Vicia faba) and following the intercrops encouraged a better wheat performance than following sole wheat. Thus inclusion of faba bean in rotation as a sole crop or intercrop could generally result in both higher yield and better nitrogen uptake in the following wheat crops compared to continuous wheat, mainly due to greater nitrogen supply.

Absorption capability of micronutrient elements such as Zn is important for optimum plant growth. It has been reported that zinc deficiency is the most common deficiency cationic micronutrient elements in calcareous and alkaline soils. Most of the sugarcane cultivated soils in Khouzestan- Iran have a high level of CaCO3 content ( > 40%) with a pH greater than 7.0. Hence, availability of zinc and maintaining mechanisms of this element in soil surfaces are important. One of the important mechanisms that had not been investigated in these lands is adsorption phenomena of the elements. Eight surface soil samples from the sugarcane cultivated soils (0- 30 cm) from two sugarcane agro industry were used to study the zinc adsorption characteristics in these soils. The absorption data were fitted to Freundlich and Langmuir adsorption isotherms and respective coefficients were calculated. The absorption data presented a highly significant fit to Freundlich and also to the two-surface Langmuir absorption. The results clearly showed that the Freundlich equation can explain the adsorption Zn in sugarcane cultivated soils much better than the Langmuir equation. The regression between the coefficients of equations absorption and some soil physical and chemical properties was established. The coefficients of both equations showed significant positive correlation with clay percentage and caution exchange capacity, and significant negative correlation with carbonate calcium percentage in sugar cane cultivated soils.

The allelopathic effects of chickpea root extracts were studied on germination and early growth of crops in rotation: Five accessions of chickpea were sown in pots and were followed by three crops (sorghum, soybean and sunflower). Crops were planted in three sowing intervals (immediately after physiological ripening of chickpea, two weeks later and four weeks later).  Experimental treatments were arranged as split-split plot and were compared in a Completely Randomized Block Design with three replications. Seed germination rate, germination percent, plant height, shoot dry weight and shoot/root ratio of crops were affected by different treatments. Seed germination rate of crops after chickpea line 5436 was significantly reduced after four weeks. Seed germination percentage increased as the crops were sown two weeks after chickpea physiological ripening. The crop height followed an increasing trend as they were sown later after physiological ripening of chickpea lines. The root extracts of line 4488 significantly reduced soybean biomass production. However, under the same conditions it enhanced biomass production of sorghum. The severity of chickpea root extracts inhibitory effects on crops were dependent on chickpea cultivar as well as the genetic characteristics of crops in rotation. Deferment in sowing date of crops from harvest time of chickpea decreased the deterious effects of chickpea root extracts on subsequent crops.

The study of climate change is pre-requisite for preparedness and mitigating the costs of such a change. In Iran, there is a little literature dealing with the identification of climate change in percipitation time series. Moreover, literature investigating the relationship between change point in climatic time series and Oceanic-Atmospheric Phenomenon was not found for Iran. The Mann-Whitney and cumulative sum tests were, therefore, conducted to reveal possible change point in percipitation (annual, biannual and seasonal) time series over southern and southwestern parts of Iran for the period 1951-1999. The results have indicated that the change point is mostly centered over the first half of the 1970s. It was shown that compared to the era before 1975, annual rainfall has increased for the period after this year for all sites studied. While rainfall in Shabankareh, Bandar Abbas and Bandar Lengeh has experienced the highest percentage of increase, the lowest increase rate has occurred in Boushehr and Shoushtar. In seasonal scale, although the percipitation has considerably increased during cold seasons (autumn and winter), the decline in spring and summer rain is a notable feature of climate change over the studied sites. In monthly scale, the highest increase rate (after 1975) was found for March. It has been found that the change point is SOI data is approximately coincided with the point in percipitation time series. The study has concluded that the recent increase in the frequency and duration of warm ENSO (El Nino Southern Oscillation) events is associated with positive trend in cold season percipitation over central south and southwestern parts of Iran.

In order to study the effects of cropping history on agronomic, biologic and chemical factors of wheat ecosystem, this experiment was conducted in the farms of Ramin (Molasani) agricultural faculty. Experimental design was RCD with rotation treatment in 6 levels. Evaluation and sampling of data were based on GIS method. The results shown that rotation and monocropping systems had different effects on agroecosystems. Legume crops had both nitrogen and non-nitrogen beneficial effects. Nonlegume crop sequences also had a positive effect on wheat yield but legume crop affects were higher than non–legume crops. Cropping history and previous crop had a significant effect on wheat grain and straw yield. Wheat grain yield was only yield component that was not affected by rotation systems. Both weed density and dry weight were higher in monocropping wheat than rotational one. Effects of crop sequence on SAR and soil organic matter was higher than other soil parameters. Based on the result of this research it can be concluded that non-scientific rotations could be an important biological stress.

In order to study the effect of planting pattern and plant density on grain yield of sweet corn (hybride ksc404) a field experiment was conducted in 2002 at Ramin Agricultural Research and Education Center at Shahid Chamran University. The design was a factorial in Randomized Complete Block Design with 4 replications. The plant density consisted of 3 levels (d1=60000, d2=75000 and d3=90000 plants/ha) and planting pattern (a1= single row on hill, a2 =single row on hill as zigzag and a3 = twin rows as zigzag). Results indicated that the highest amount of dry matter yield (1070.6 g/m2), wet cob yield (2293.7 g/m2), grain yield (383.83 g/m2), cob length (14.41 cm), kernel number in row and kernel number in cob was obtained with twin rows planting pattern. Also the results showed that plant density influenced dry matter yield, wet cob yield, grain yield, kernel number in cob, kernel number in row, harvest index (HI), 1000 grain weight, except length and diameter cob. The highest dry matter (1089.3 g/m2) and wet cob yield (2364.7 g/m2) were obtained by 9 plant/m2 density but highest grain yield (374.54 g/m2), HI (38.3 %) obtained at 7.5 plants/m2 density, however, by increasing plant density the other factors reduced.

In order to evaluate the effects of salt stress (concentration of NaCl, CaCl2, MgCl2, with EC = o, 3, 6.9, 12, 15 and 18 ds/m) on germination of four chickpea cultivars (Karaj 12-60-31, Kaka, Jam and Pirooz), a study was conducted in a Randomized Completely Block Design as factorial experiment. Seeds were germinated in lab condition. Results indicated that percentage and rate of germination were intensively infuenced and decreased by salt stress in all cultivars. Other parameters including shoot and root length , number of lateral roots, dry weight of roots and shoots increased at low levels of salinity (EC= 0 to 6 ds/m) and decreased at high salt. Among the cultivars, Karaj 12-60-31 was less sensitive than other cultivars.

The objectives of this study were to investigate and define suitable method for extracting liquid sugar or honey from date fruit. Major factors affecting the physicochemical characteristics of date fruit liquid sugar include the initial pH, extraction, clarification and decolorization methods were considered as variables. Different treatments were performed on liquid sugar accordingly. The effect of each variable on every production step was monitored by measuring the light transmission at 420 and 520 nm as color and clarity quality respectively as well as by measuring the total soluble solids. The results indicated that two decolorization methods (resins and bleaching earth) had a significant effect whereas the other two pectolytic enzymes and the two clarification methods (clarification aids and ultra filtration) had no effect on color quality. The same pattern was found about the effect of the above-mentioned variables on clarity but the significant difference was found between the two clarification methods. Decolorization step was the most effective stage in which the soluble solid matters increased particularly while bleaching earth was used. There were significant interaction effects between clarification and decolorization methods on color, clarity and soluble solid matters. No significant interaction effect was found between type of enzyme and clarification methods.

One of the best propagation methods of Tea “Camellia sinensis” is the use of stem leafy cutting, but unrooted cuttings in nursery of tea are extreme. Various factors as mother bush condition, environmental factors, cutting method, nursery management and different treatments could interfere in the reduction or increase of unrooted cuttings in nursery bed. A practical and scientific way for decreasing the unrooted cutting numbers of tea in nursery is a desirable nutrition of mother bushes and then preparation of cutting from them. Through nutrients, zinc, due to participating in indole acetic acid (IAA) and chlorophyll biosynthesis, has a significant value. In order to reduce the unrooted cuttings in tea nursery and study the zinc effect, the experiment was carried out in randomized complete block design with four treatments (including T1: Control, T2: NPK fertilizers, T3: NPK+ once zinc sulfate spray at 1% concentration and T4: NPK+ twice spray of zinc sulfate at 1%) and four replications. Callus volume, root weight (fresh and dry) and volume, young plant height, leaf numbers, stem diameter and percent of unrooted cuttings were measured. According to the results, callus volume, plant height, leaves number, root weight and volume showed a significant difference (at least in 5% level). Through treatments, T3 had the best effect on most of the characters. T3 decreased the rate of unrooted cuttings about 19% rather than control.

Truncated weirs are used to measure flow rate and control water surface upstream, in irrigation canals and laboratory flumes. The main advantages of such weirs are the ease of construction and the capability of measuring a wide range of flows with sufficient accuracy. The hydraulic performance of truncated weirs has not been widely investigated, and not sufficiently documented in the literature. This paper presents the results of an analytical and experimental study on flows over sharp-crested, truncated-900 triangular weirs with different side construction ratios (b/B= 1, 0.7, 0.5, 0.3). One-dimensional flow equation is presented from the integration of both analytical and physical based solutions. A coefficient of discharge has been introduced to represent the complex functions in the equation and to overcome any uncertainties. Intensive experiments were carried out to evaluate the discharge coefficient in terms of the most significant parameters such as: the geometry of the weir, upstream head and tail water levels, artificial aeration of the weir on downstream face. The results are presented in the form of non-dimensional figures from which the flow rate can be calculated in conjunction with the proposed flow equation. The present results indicate that (1) truncated weirs designed within the limitations from this study can be used as flow measuring structures with sufficient accuracy up to ±5%; (2) stability and accuracy of this measuring system are achieved where the threshold condition of  (h >20 mm) or (h/P1 >0.1) are provided; (3) weirs with side contraction of (b/B³ 0.5) are more efficient; (4) direct evaluation of discharge coefficient, Cd, is not recommended for the condition of submerged flow over the weirs; (5) modular limit of the flow over the weir has to be checked for an accurate evaluation of the flow. This limit is determined in terms of the weir geometry and head water level; (6) in case of the submerged flow, a reduction factor known as submergence coefficient,y , is introduced to evaluate the actual flow rate over the weir in terms of the relative tail and head water levels (t/h), and side contraction ratio (b/B); (7) these types of weirs are efficient enough by a degree of submergence up to t/h< 0.3; (8) artificial aeration has no significant effect on the flow capacity over truncated weirs.

Estimation of rivers sediment load is one of the most important problems for design of hydraulic structures. Feasibility study of dam constructions, hydropower plants, intakes, bridges and the other hydraulic structures without investigations on river sediment transport is not possible. Existence of numerous empirical methods for estimation of river sediment load, a wide range of calibration coefficients shows that a suitable analytical or empirical method does not yet exist to accurately estimate the sediment load. Therefore, the measured discharges and sediment concentrations in hydrometry stations are statistical analyses for an accurate estimation of sediment loads in rivers. In usual statistical methods a power function is generally fitted on the data sets of flow and sediment discharge and thus the total sediment load could be calculated using this function. These methods are not able to recognize and separate the specific data measuring conditions. Therefore, they are not only able to accurately estimate the sediment load, but also cannot show the temporal variation of sediment loads. In this paper the measured suspended sediment load, at 10 hydrometry stations of Karoon and Dez rivers, which are the most important rivers in Khoozestan province, are analyzed using the usual statistical methods and the results are compared with the corresponding values obtained from the fuzzy method. This research has shown that the temporal variation of sediment loads can be analyzed using a fuzzy method. Also the results obtained using the fuzzy method in comparison with the corresponding values obtained using the usual statistical methods show a better correlation with the observed values. In all stations the fuzzy method estimated the sediment loads more than the ones obtained using statistical methods.

During 1998–1999 syrphid flies were collected and compiled from various parts of Ahwaz region. The main tools for adult collection were white sweeping net, malaise trap and yellow watery traps. Specimens were mounted correctly and male genitalia were prepared. Figures of male genitalia, pattern of abdomen, wing venation and head profile were drown by drawing tube on Wild stereomicroscope. Species were identified with proper keys and investigated by Claussen from Germany .Syritta is one of the genera of the family found in 3 species: S. flaviventris; S. pipiens and S. vittata. The last species is new record from Iran. The key for identifying genus species were prepared.