Showing 2384 results for Type of Study: Research
Abdolhamed Dowlati Baneh, Mesbah Babalar, Mahmood Okhovat,
Volume 3, Issue 2 (7-1999)
Abstract
The effects of four levels of SO2 (0.0%, 0.06%, 0.125% and 0.25%) on the qualitative and quantitative characteristics of two Persian grape cultivars “Keshmeshi seedless” and “Shahroudy” were evaluated during the cold storage in 1995-1997. This research was carried out in a factorial experiment in a completely randomized design in cold storage at the laboratory of Horticultural Department, College of Agriculture, Tehran University.
The results showed that the effect of SO2 on decay was significant at 1%, and maximum control was obtained at 0.25%. No significant difference was observed when treated with 0.125% SO2 However, increasing SO2 concentration resulted in increased quantity and intensity of bleaching on the berries. At these increased concentrations, a linear relation was observed between bleaching on the berries and SO2 concentration so that the highest bleaching occurred at a concentration of 0.25%. Increased storage periods also increased bleaching. The effect of SO2 on weight loss, shattering, and rachis colour was also significant, decreasing rachis colour and shattering of berries.
Sayed Farhad Mousavi, Jafar Jamshidnezhad-Anbarany, Sayed Saeid Eslamian, Nasser Rostam-Afshar,
Volume 3, Issue 2 (7-1999)
Abstract
Estimation of flood flow rate represents a method of preventing damages associated with this natural phenomenon. This estimation is one basis in the design of various hydraulic structures, dam spillways, watershed management and flood control. The maximum flow rate of floods is determined by methods such as Creager, Jarvis-Meyer, Cypress-Creek, and rational method. Rational-probability method is an alternative to estimate peak flood rates, and is expressed as:
Q(y) = F. C(y). I(tc.y).A
where Q is maximum flood flow rate (m3/sec) y is the return period (year) C(y) is runoff coefficient with a return period of y A is watershed area (km2) I is rainfall intensity (mm/hr) for a specified return period equal to time of concentration of the watershed and F is the conversion factor equal to 0.278 when the above units are used. The basic concept of this method is the same as that in the rational method except that the return period is also included in the equation. Usually, runoff coefficient, C(y), is determined empirically from tables cited in the literature (e.g., Chow et al., 1988). In the present research, data from 18 hydrometry and 6 rainfall-recording stations (located in Caspian - Sea watershed) were analysed using TR software. The Caspian - Sea watershed (which covers eastern and centeral parts of Iran's No. 1 main watershed) has the sub-basins of Atrak, Tadjan, Chalus, Sardabrood, Siahrood, Gorganrood, Safarood, Kesilian, Babolrood and Neka. Runoff coefficients with return periods of 2, 5, 10, 25, 50 and 100 years were determined for these sub-basins and iso-coefficient curves were plotted. The results showed that computed runoff coefficients were less than the values given in the literature because they are determined from observed flow rate and rainfall intensity in each catchment. It was also shown that runoff coefficient increased with increasing return periods. Application of the computed runoff coefficients in three sub-basins of the area resulted in more accurate estimations of maximum flood rate than when the values for these coefficients cited in the literature were applied.
M. A Hajabbasi, A. F Mirlohi, M. Sadrarhami,
Volume 3, Issue 3 (10-1999)
Abstract
A two-year study (1996-97) was conducted to verify tillage effects on several soil properties and corn yield. The soil (fine loamy, Thermic, typic Haplargids) was treated by conventional (CT) and no-till (NT) systems. Soil organic matter (OM), mean weight diameter (MWD), penetration resistance (Cl), bulk density (BD), total nitrogen (TN) and aggregate size distribution at depths of 0-20 and 20-40 cm were measured.
No-till system caused the OM to be twice as much as that in the conventional tillage system. Total nitrogen in the NT and at depths of 0-20 and 20-40 cm were higher by 30% and 20%, respectively. No differences obtained in bulk density and penetration resistance, but MWD in the NT was 20% and 10% higher than CT in the 0-20 and 20-40 cm depths, respectively. Mean weight diameter of the aggregates in the CT was smaller than that in NT. Aggregates of less than 0.25 mm at 0-20 cm depths were almost 25% higher in CT compared to NT system. The yield in the NT system was significantly lower than CT. Although reduced cultivation could bring a better soil physical condition, low initial organic matter, weak structure and heavy-textured soil produced unsuitable conditions for the crop roots and, consequently, resulted in low yield. Therefore, no-till system in this region would not be recommended.
N. Tomanian, A. Jalalian, A. Zolanvar,
Volume 3, Issue 3 (10-1999)
Abstract
Gypsiferous soils, as the most characteristic soil in arid and semi-arid regions, are widespread in Isfahan Province. The north-west region of Isfahan is a closed basin and is surrounded by geologic formations. This area is a part of Zayandehrood watershed. The origin of gypsum in this area was investigated in this study. Considering the geologic distribution of gypsum, twenty-two locations, suspected to have been affected by gypsum, were selected for sampling. Natural and artificial excavations were used to discover their relationships. To distinguish the differences between fresh and weathered shales, some fresh samples were taken from the depth of Shemshak formations (a lead mine).
Field observations showed that in Shemshak and Nayband formations, gypsic crystals were present within the layers of weathered shales, and pyrite was observed only in the mine shales. In weathered red conglomerates (Lower Cretaceous), considerable amounts of gypsum had accumulated. In the hydrothermal veins of Shemshak and Nayband formations, gypsic crystals were found in matrix or between rock layers. In some parts, the Qom formation (Evaporate sediments) contained plenty of gypsum.
From field observations and analytical data, such as mineralogy of untreated and floated rock powders, determination of residual sulfides in shales, and the examination of thin and polished sections of rocks, we conclude that the origin and main resources of gypsum in our study area are as follows:
1. Gypsum being released from Cretaceous limes particularly from red conglomerates
2. Oxidation of pyrite and any sulfidic minerals existing in shales
3. Gypsum being released from evaporates (Qom formation and Oligomiocenic Marls)
4. Gypsum formed through hydrothermal reactions during late Tertiary.
R. Amiri, A. Rezai, M. Shahedi, S. Dokhani,
Volume 3, Issue 3 (10-1999)
Abstract
This study was conducted to evaluate the capability of reversed-phase high performance liquid chromatography (RP-HPLC) of wheat (Triticum aestivum L.) storage proteins, and their genetic variability in different winter and spring isolines, cultivars and landraces. Gliadin proteins were extracted from the flour of five randomly selected seeds of each genotype. In this method, Nucleosil C18 300 A column (250×4.6 mm ID), equipped with a guard column and acetonitrile containing TFA as mobile phase was used.
All selected conditions for RP-HPLC such as suitable velocity and resolution were sufficient to achieve the objectives of this study. Under these conditions, the number of gliadin components by RP-HPLC analysis was more than electrophoresis subunits. In addition, quantitative results of RP-HPLC facilitated the data analysis. Also gliadin analysis by RP-HPLC had a high potential in detecting rye (Secale cereale L.) genes, so that the presence of ω-secalins in the genome of Falat variety was easily detected. Therefore, it was concluded that RP-HPLC analysis of gliadin proteins is as efficient as electrophoresis, and could even replace it in some cases. The result of cluster analysis for gliadin polypeptides indicated the gradual increase of genetic variation from isolines to landraces. Generally speaking, among the landraces, Ali Abad, Aghda, Sefid Bafghi, Ghermez Bafghi, Shahdas and Sorkheh had greater genetic variations.
S. Chavoshi, S.s. Eslamian,
Volume 3, Issue 3 (10-1999)
Abstract
Designers of hydraulic structures are often faced with the problem of estimating flood frequencies at stream sites, where little or no flow information is available. A regional regression model is widely used which relates physical and climatological parameters to flow characteristics. In this study, a new method is used which is based on the station-year technique and combined records for several stream-flow gaging stations to make a single composite sample. This method, named ‘hybrid’, was proposed by Hjalmarson and Thomas (1992). It was applied to a group of records from 17 apparently homogeneous stream gaging stations to determine regional flood frequency equations. The study area consists of two adjacent basins, Gavkhoony and North Karoon in the central part of Iran. Using area and mean elevation of the catchments as the most important criteria in relation to peak discharge, the interactive process of the hybrid method was performed, resulting in two-parameter models of regional flood frequency. The performance of the hybrid method was evaluated by comparison with the regional relations determined from a multivariate regression. The comparison revealed that the accuracy of the hybrid method was significantly better than the regression method for low return periods.
B. Siahsar, A. Rezai,
Volume 3, Issue 3 (10-1999)
Abstract
In order to study the genetic and environmental variability of morphological and phenological characteristics and also to gain a better understanding of the morphological basis of yield variation in soybean, an experiment was conducted at Research Farm, College of Agric., Isfahan University of Technology, in 1996. The experiment was arranged in three augmented designs with 285 lines and 5 control varieties. There were highly significant differences among genotypes for all the characteristics studied. The phenotypic coefficients of variability were greater than the genotypic ones for all the traits although the differences for most of them were small. The highest phenotypic and genotypic coefficients of variation, in order of magnitude, were obtained for number of pods per plant, days to flowering, plant height, height of the lowest pod, and number of lateral branches. Heritability estimates and the percent of genetic improvement for these traits and seed weight were high but for seed yield per plant were low. The lowest coefficients of variability were related to number of seeds per pod and days to germination. The results of stepwise regression analysis indicated that the maximum variation in seed yield could be attributed to the number of pods per plant, number of seeds per pod, and 100-seed weight. Factor analysis in addition to emphasizing the importance of yield components, resulted in four factors which determined 97.34% of yield variation. These factors which were indicators of physiological sink and source, with respect to the traits contained, were named as photosynthetic sink, plant architecture, fixed capital, and weight, respectively. In general, it was concluded that in order to improve soybean cultivars, selection should be in favor of plants with stronger structure, higher number of leaves, nods and pods per plant, and higher seed weights.
B. Bahraini-Nejad, M.r. Khajehpour,
Volume 3, Issue 3 (10-1999)
Abstract
Combining herbicides for controlling broadleaf weeds and grasses in wheat farms has not been studied under Isfahan environmental conditions. Thus, this experiment was conducted in 1995-96 at the Agricultural Research Station, Isfahan University of Technology, in order to investigate the issue. In this study, 2,4-D+MCPA (U46 Combi Fluid 6), bromoxynil, metribuzin, diclofop-methyl and tralkoxydim and their combinations in 11 treatments plus weed-free and weedy checks were evaluated using a randomized complete block design with 4 replications. Goldbachia laevigata and Avena fatua were the dominant weeds. Cirsium arvense and Convolvulus arvensis were of less importance. Efficacy of bromoxynil on annual broadleaf weeds was higher than 2,4-D+MCPA, while 2,4-D+MCPA was more effective on perennial broadleaf weeds. Diclofop-methyl and combination of bromoxynil with tralkoxydim were the most effective on A. fatua, while differences between treatments containing diclofop-methyl or tralkoxydim on decreasing A. fatua numbers were non-significant. The most and the least visual damages to wheat plants were caused by metribuzin and bromoxynil, respectively. Wheat yield was not significantly affected by treatments. However, the highest yield was obtained by tralkoxydim + bromoxynil treatment, which produced the lowest total dry weight of weeds at terminal spikelet and heading stages of wheat. The results obtained here indicate that combination of bromoxynil with tralkoxydim might be the best treatment for the control of all annual weeds under conditions similar to this experiment. But if perennial broadleaf weeds and wild oat are dominant in the field, combination of 2,4-D+MCPAwith diclofop-methyl might be preferred.
M. Afsharmanesh, J. Pourreza,
Volume 3, Issue 3 (10-1999)
Abstract
An experiment was carried out to study the effect of different levels (3.06, 3.23, 3.4, 3.57 and 3.74%) of calcium and vitamin D3 supplementation (2000, 2200 and 2400 IU/kg diet) on the performance of laying hens. In a completely randomized design and in a 5 × 3 (15 treatments) factorial arrangement, two hundred and forty (240) white leghorn laying hens strain Hy-Line W 36, 26 weeks old, were divided into 60 replicates, four hens per replicate. The experimental period lasted 90 days, until the hens reached 38 weeks of age. The results indicated that calcium levels did not have any significant effects on the percentage of egg production, feed consumption, feed conversion ratio and egg mass. Egg weight significantly (P < 0.05) increased at 3.4% Ca level. Vitamin D3 had no significant (P < 0.05) effects on egg weight, feed consumption and egg mass, but feed conversion ratio significantly (P < 0.05) decreased and percentage of egg production raised significantly (P < 0.05) due to added vitamin D3. Interaction between vitamin D3and calcium on egg weight and egg production was significant (P < 0.05). The regression equations indicated that performance traits can be estimated from calcium and vitamin D3levels in diet.
M. Alikhani, G.r. Ghorbani,
Volume 3, Issue 3 (10-1999)
Abstract
To determine the best ratios of alfalfa hay to corn silage with similar dietary NDF, cation-anion balance, energy and protein content in the lactating dairy cows, eight mid-lactating Holstein dairy cows with average body weight of 570 kg, and milk yield of 22 kg/d with 3.5% fat, were assigned to each of four experimental diets with alfalfa hay to corn silage ratios of 100:0, 67:33, 33:67 and 0:100., in a 4 × 4 Latin square design with two replicates. Dry matter intake, digestibility, rumen degradability of DM, fat percentage and total solids in milk for diets one to four were 19.09, 19.94, 20.94, 20.90 kg/d 69.07, 65.75, 71.78, 49.82% 52.8, 49.6, 50.4, 46.7% 3.47, 3.53, 3.79, 3.93% 12.17, 12.17, 12.48, 12.60%, respectively. Diets containing 67% silage showed the highest dry matter intake, 3.2% FCM and digestibility. Degradability in rumen were highest and lowest in diets containing 100% alfalfa hay or corn silage, respectively. Increased ratios of silage to alfalfa hay corresponded to increases in milk fat and protein yield, milk protein percentage and total solids in milk.
G.h. Tahmasebi, D. Qujeq, R. Ebadi, M. Akhoundi,
Volume 3, Issue 4 (1-2000)
Abstract
An important and fundamental step in breeding honeybees is the separation of honeybee populations in Iran. During the years 1992-1996, several research works were directed towards the investigation of genetic populations of the Iranian honeybee (Apis mellifera L.), using biochemical methods. For this purpose, samples of worker bees were taken from 251 colonies of 115 apiaries in 84 cities in 21 provinces. The biochemical studies were conducted on thoracic proteins of worker bees using the horizontal electrophoresis.
The thoracic proteins of worker bees from the north and east populations isolated by electrophoretic techniques lacked a protein band having molecular weight of about 100,000 daltons. The results obtained from morphological and biochemical techniques and segregation of populations, indicate that breeding centers can be established in northern as well as western and central regions of Iran to improve genetic potentials of Iranian honeybee population.
M. Azimi, S. Massiha, M. Moghaddam, M. Valizadeh,
Volume 3, Issue 4 (1-2000)
Abstract
In order to study the genetic variation among local varieties of onion in Iran, an experiment was conducted in the Research Center, Faculty of Agriculture, Tabriz University. Sixteen populations were evaluated for agronomic characteristics and also total seed proteins via SDS-PAGE. Cluster analysis and principal component analysis were used to group the onion populations under study.
Analysis of variance showed significant differences among varieties for leaf color, leaf length, texture tightness, onion yield per plant, and number of edible layers. No significant differences were observed for the number of twin onions, bulb diameter, and onion dry weight. Hamadan (98-148), Arak (98-95, 98-96, 98-97, 98-103), and Zanjan (98-223) populations acquired the highest onion yield per plant. The significant differences between populations for the majority of characteristics proved the existence of genetic variation in the Iranian onion germplasm. The results from cluster analysis for agronomic characteristics were the same as those from the cluster analysis for the onion yield per plant. The 16 populations were divided into 4 groups. Cluster analysis for the electrophoresis banding pattern resulted in two groups, which was not similar to the dendrogram of agronomic traits. Using principal component analysis, the first principal components determined 97.57% of the total variation. Onion yield per plant was the most important trait in the first principal component and onion dry weight was the second trait in the rank.
M.r. Mosaddeghi, M.a. Hajabbasi, A. Hemmat, M. Afyuni,
Volume 3, Issue 4 (1-2000)
Abstract
Soil structure maintenance and stability is an important index indicating sustainable soil management. In this regard, components such as soil moisture and organic matter affect soil compactibility during farm machinery trafficking. Soils in Central Iran are commonly very low in organic matter (OM) and thus susceptible to compaction. This study was conducted to measure the effects of soil moisture content and manure application on soil compactibility. A randomized complete block design with four blocks (replicates) with the treatments nested (split-block) into the blocks was used in the soil (Typic Haplargids), located in Isfahan University of Technology Research Farm (Lavark). One-year aged manure treatments 0, 50, and 100 t ha-1 were incorporated into soil up to the tillage depth (20 cm) by a heavy disc. After five months (July-November), a two-wheel-drive tractor Universal Model U-650 was passed through the field at soil moisture contents of plastic limit (PL), 80% PL (0.8PL), and 60% PL (0.6L), either once (P1) or twice (P2). Bulk density (BD), cone index (CI), and soil sinkage (S) were measured as indices of soil compactibility and trafficability. Adding manure countered the effects of load and wetness on BD and CI, significantly. There was a significant difference between the effects of 50 and 100 t ha-1 of manure on BD but not on CI. Manure application reduced soil sinkage at high moisture contents (PL) but increased it at low moisture contents (0.6PL). Adding manure also reduced the BD and CI of subsoil. Repeating the passage of tractor (P2) increased compaction significantly. The significant increase in BD and CI did no occur at 0.6PL. When no manure was applied even at 0.6PL, there were limitations for trafficability, whereas this limit for 50 t ha-1 treatment was reached at 0.8PL. Results from this study indicate that the manure application at a rate of 50 t ha-1 reduces soil compactibility and increases soil moisture trafficability range.
T. Sohrabi, U.a. Khoshkhahesh,
Volume 3, Issue 4 (1-2000)
Abstract
The purpose of this research is to determine the application efficiency of rice irrigation plots and to analyze the reasons for low efficiency. The study will also try to determine the effective factors which could increase the application efficiency of rice fields. The selection of rice fields was based on climate, soil characteristics, and farmer management. Water application efficiency was determined by field measurements in three modern irrigation networks named Fouman (F), Rasht (G) and Lahidjan (D). In the meantime, a traditional network was included for comparison. In the study areas, the soil texture was heavy with an infiltration rate of less than 3 mm/day. The study was carried out under two different conditions: (1) without return flow and (2) with return flow. In the first case, the average application efficiencies in Fouman (F), Rasht (G) and Lahidjan (D) were about 51.2, 49.0 and 49.4 percent, respectively and the maximum and minimum values were about ((52.6, 49.7)), ((50.7 , 47.3)), and ((50.7 , 48.0)) percent, respectively. In the second case, the average application efficiencies for the above-mentioned regions increased to 73.4, 73.3 and 72.4 percent, respectively and the maximum and minimum values were about ((74.3, 72.4)), ((74.3, 72.1)), and ((73.0, 71.5)) percent, respectively. Runoff ratios in the above-mentioned regions were 30, 33 and 31 percent, respectively. During growing period (from transplanting to harvesting), the average applied irrigation water was about 1130 mm (11300 m3/ha) and the average evapotranspiration was determined to he about 561mm.
A. Nik-Khah, B. Abeshet,
Volume 3, Issue 4 (1-2000)
Abstract
Feed shortage is one of the most important characteristics of Iranian livestock industry. Therefore, the utilization of agricultural by-products in animal nutrition, especially for fattening animals, is of great importance. In order to study the effect of the four rations containing various levels of tallow (0, 2.5, 5, and 7.5%), on the performance of male Holstein calves (MHC), responding to the above treatments 1, 2, 3 and 4, twenty four MHC (191±32.1 kg) at age 6-7 months-old in a completely randomized design were used. The calves were fed individually for 195 days ad libitum.
Average daily gains (ADG) of the MHC fed diets 1, 2, 3 and 4 were 1.56, 1.61, 1.69 and 1.75 kg (P<0.05), respectively. Feed conversions (as DM) were 4.63, 4.31, 41.2 and 3.98 (P<0.05), respectively. Added tallow to the ration did not affect carcass, empty body weight (EBW), but increased warm carcass weight (P<0.05). The dietary treatments did not increase digestibility (D) of dry matter organic matter, crude protein and gross energy either, but decreased D of neutral detergent fiber and increased apparent crude fat (P<0.05).
M. Kavossi, M. Kalbasi,
Volume 3, Issue 4 (1-2000)
Abstract
High-yielding rice varieties are prevailing in Guilan Province which is one of the most important rice producing regions in Iran. However, little is known about K status in this region and no suitable extraction method can yet be introduced to the farmers. This experiment was carried out to determine the available K by 15 chemical extractants and also to examine the critical K levels in paddy soils of the region. The treatments included 23 soils and 2 K levels (0 and 300 mg/kg as KCl) in a factorial experiment in a randomized complete block design with three replications.
Results indicated that K application increased grain and straw yields, K concentration in straw as well as K uptake by rice. High correlation coefficients were observed between MgOAc, H2SO4, Morgan and 0.01 M CaCl2 methods with K concentration in straw (0, 0.83, 0.78, 0.8 and 0.78, respectively) and with K concentration in plant tops (0.79, 0.76, 0.75 and 0.73, respectively). Similarly, high correlation coefficients were observed between the same extraction methods with K absorbed by straw (0.83, 0.82, 0.78 and 0.76, respectively) and with total plant K uptake (0.79, 0.83, 0.74 and 0.71, respectively). Potassium critical levels by different extracting solutions were determined by Cate-Nelson procedure and were 38, 74, 160, 111, 36, 112 and 100 mg kg-1 for MgOAc, Morgan and Kelowana methods, Texas method H2SO4 0.01 M CaCl2 and NH4OAc without and with submergence of soil samples, respectively. In this study, available K was below the critical level in almost 75% of the soils.
J. Pourreza, H. Nasrollahi, A.h. Samie, M. Mohammadalipour, A. Assadian,
Volume 3, Issue 4 (1-2000)
Abstract
In order to study the effects of Total Dissolved Solids (TDS) in water on the performance of broiler chickens, preliminary data were obtained on water resources of Isfahan Province. Complementary tests and analyses were also performed including physical, chemical and microbial ones. Six different water qualities based on TDS contents of less than 1000, 1000-2000, 2000-3000, 3000-4000, 4000-5000 and more than 5000 ppm were selected. The main experiment lasted for 7 weeks (7-56 days), using 288 chickens in a completely randomized design, with 3 replications, while, the environmental and genetic factors were controlled in an identical broiler housing.
The results showed that using water with different TDS contents had the most negative effects on mortality rate (%) in the rearing period and up to 56.2% mortality was recorded at the highest TDS content. Water consumption showed high and positive correlation (P < 0.05) with TDS (r = +0.74). Correlation between TDS and bedding moisture was also high (r = +0.65) and significant (P < 0.05). The differences between final body weight of control chickens and highest level of TDS were significant (P < 0.05). Feed intake also was affected by different TDS contents and showed similar results as with body weight. Increasing the TDS level decreased the abdominal fat in the female chickens and ash content of tibia in the male chickens. It is concluded that water TDS should be considered for the development of broiler chicken farms. Therefore, it is recommended that higher quality waters (with a TDS content of 3000 ppm) must be used for this purpose. Otherwise, appropriate systems should be used to improve physical and chemical composition of the water.
A. Ghanbari, M. Maftoun, N.a. Karimian,
Volume 3, Issue 4 (1-2000)
Abstract
Different Extractants have been proposed to assess available P in different soils. Olsen method is widely used to determine available P in calcareous soils of Iran. However, it has not been compared adequately with other extractants. The main objective of this experiment was to compare this procedure with some other methods. Thirty nine calcareous soil samples from Fars Province with different physico-chemical characteristics were examined for available P by nine extractants. Furthermore, the effects of four P levels (0, 50, 100, 200 µgPg-1 soil) on growth, P concentration and P uptake by corn were studied in a greenhouse experiment using 20 soil samples. The results indicated that the amount of extractable P decreased in the order, anion-exchange resin > Colwell > Morgan > Olsen > Bray P1 (1:50) > Soltanpour & Schawb > EDTA > Bray P1 (1:7) > Water. The amounts of P extracted by all methods, except that by Bray method, showed significant correlation. However, the correlation coefficients between resin, Olsen, Colwell and water were higher than the others. Regression analysis showed that P extracted by all methods, except Bray, was affected by organic matter and native Zn. Moreover, P removed by Bray method was decreased with an increase in calcium carbonate equivalent. Correlation between top dry weight, relative growth and P uptake and P extracted by resin, Colwell, Olsen and water were highly significant. Although the correlation coefficients between growth parameters and P extracted by Morgan and Soltanpour & Schawb were significant, they were of lower magnitude. Plant phosphorus concentration showed significant correlation with P extracted by Olsen and Colwell methods. In general, resin, Olsen and Colwell methods seem to be appropriate extractants for available P in the present study. However, to select the appropriate extractants, more research is needed.
F. Noorbakhsh, M. Afyuni,
Volume 4, Issue 1 (4-2000)
Abstract
Field capacity (FC) and permanent wilting point (PWP) are important factors affecting irrigation scheduling and field management. FC and PWP can be estimated from some of the soil physical and chemical properties. Pressure Plate apparatus is usually used for determination of FC and PWP, but this is a time-consuming and laborious procedure besides, the apparatus may not be available in many laboratories. Samples were taken from 23 locations in Isfahan and Chaharmahal Va Bakhtiary provinces in central Iran. Soil texture, organic matter and cation exchange capacity were determined. Soil moisture at FC and PWP of the soils were measured with a pressure plate. Simple and multiple regression analyses were used to study the relationships between FC and PWP with sand, silt, clay, soil organic matter and cation exchange capacity.
Results indicated that FC significantly correlated with sand, organic matter and cation exchange capacity in a stepwise model (r=0.97**). The PWP of soil also correlated significantly with silt, organic matter, and cation exchange capacity in a stepwise model (r=0.95**). Available water capacity (FC-PWP) correlated with sand in a stepwise model (r=0.82**). On the whole, results showed that FC and PWP can be estimated from some soil physical and chemical properties.
A. Abdeshahi, G. Soltani,
Volume 4, Issue 1 (4-2000)
Abstract
Successful implementation of socio-economic projects depends on the degree of planners’ awareness of farmers’ risk coefficient. Because agriculture is a risky activity, knowledge about the farmers’ attitudes toward risk in each area is essential. This research investigated the farmers’ risk behavior in Homayjan district in Sepidan township. Cross-section and time series data were collected from a random sample of farmers and from Agricultural Department of Fars Province, respectively. In this study, the Safety First Rule (SFR), Generalized Stochastic Production Function (GSPF) and Target Motad models were used.
The results indicated that in this area, farmers are risk averse in crop production, but they have a low risk coefficient in the use of modern inputs. Signs of GSPF revealed that the use of modern resource input reduces risk. Target Motad risk programming model confirmed that farmers are risk averse because with increasing risk, crops like wheat that have relatively stable prices and yield enter the model, while crops like onion that have high instability in price and yield are omitted from the model.
