نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال پنجم شماره 1 (پیاپی 15، بهار 1380)

During recent years, worldwide concern has been focused on the potential for contamination of surface waters and ground waters by agrochemicals in runoff and soil water from irrigated fields. Given this perspective, it is very important to correctly evaluate the levels of different agrochemicals in water, both from human toxicological and environmental viewpoints and to develop management strategies for reducing agrochemical loads to acceptable levels in the environment. The main objective of this study was to assess the qualitative changes of tailwater due to the use of agrochemicals and thereby to determine contamination loads. Four farms (A, B, C and D) were chosen in the Foumanat region in the F2 unit in 1996. The areas of these fields ranged from 0.22 to 0.6 ha having a number of unequal successive basins with variable inflow and outflow rates. A quantitative analysis showed that the tailwater ratio in farms A, B, C and D ranged from 2 to 64% during the irrigation season. The outflow water was classified as C3S1. The changes in qualitative factors were not significant and did not follow any certain pattern during the irrigation season. The changes in SAR, EC, Cu, Zn, B, P, K and DO in the inflow and outflow waters were also insignificant. After fertilizer application, the increase in nitrogen concentration in the outflow was significant. The average pollution loads in the inflow and outflow were about 1618 and 1476 kg/day/ha, respectively. The remaining load in the rice fields was about 142 kg/day/ha, which was meaningful at 1% level. The fifth farm (E) located in Lahidjan was sprayed with diazinon. Water samples were analyzed each day for diazinon residues for 10 days after application. Sample analysis showed that the concentration of the insecticide was 93.08 mg/l immediately after application and gradually reduced to 0.98 mg/l ten days after spraying.

Bridge abutments are usually located in the floodplain zone of rivers where velocity and shear stress are not uniformly distributed. The influence of channel geometry and lateral momentum transfer in compound flow field on the scouring phenomenon has not been fully investigated and understood yet. The impact of lateral momentum transfer on the local scour at abutments terminating in the floodplain of a compound channel is presented in this paper. It is shown that, by accounting for lateral momentum transfer at small floodplain/main channel depth ratios (λa/H<0.3), estimates of maximum local scour depth are increased by up to 30%. Therefore, ignoring the influence of the lateral momentum transfer, in such circumstances, might result in unrealistic estimation of the scour depth. To draw a more general conclusion, more data are required to assess the influence of different parameters affecting the phenomenon in compound flow conditions.

In this paper, a numerical solution is presented for one-dimensional unsaturated flows in the subsurface. Water flow in the subsurface, however, is highly nonlinear and in most cases, exact analytical solutions are impossible. The method of reference-operators has been used to formulate a discrete model of the continuum physical system. Many of the standard finite difference methods and also the finite volume method are special cases of the method of reference-operators. Unlike elementary finite difference methods, the method of reference-operators may by used to construct finite difference schemes on grids of arbitrary structure. A one-dimensional model was developed to predict the soil-water suction (negative pressure head) and water content in a vertical column of a layered soil. The model was verified against some available analytical solutions and experimental results and, in all cases, it showed good agreement.

Experience has shown that all centralized planning, policy-making and decision-making which presuppose exclusion of public participation have never been successful in achieving their objectives. The goal of this research is to determine the driving and preventive factors of herders’ participation in rehabilitation designs of Aghghala ranges in Gorgan Province. The research method was direct observation in which measurement techniques were used. A questionnaire was used to divide the sample society into two categories: the experts who design the range management system, and the local herders. Results obtained from this investigation showed that according to the experts training, economic, planning and social parameters have the greatest effects on local herders’ participation while the herders maintained that planning, economic, training and social parameters have the greatest effect on decreasing their participation.

Qualitative land suitability evaluation is based on the physical parameters affecting the yield agricultural crops. The socio-economic factors are not considered in such evaluations. This study was carried out to assess the qualitative land suitability for irrigated wheat, barley, maize and rice in northern Baraan. Five soil series and 25 different phases were first delineated. Land utilization types commonly practiced in the region with intermediate input levels were considered. Physical requirements of the crops were determined and ranked using the available information. FAO framework and the proposed method of Sys were used for the evaluation. Qualitative evaluation was carried out according to both simple limitation and parametric methods by comparing land and climatic characteristics with crop requirements. It was shown that in addition to climatic factors, soil salinity, drainage and some soil physical properties such as texture, gravel and lime are the most limiting factors. Land physical suitability for rice production was very low in most land units. The results from physical evaluation by parametric method were very close to those from the simple limitation approach.

Evaluation of nutrient status in soil is important from nutritional, environmental and economical aspects. Potassium is a very important plant nutrient not only because of its large demand, but also because of its important physiological and biochemical functions in plant. In order to evaluate K availability and common K extractants in the central region of Isfahan Province, surface soil samples from 26 important soil series were taken, out of which 16 soil samples were selected for further study based on their ammonium acetate extractable K and texture. Available K was extracted from the soil samples by NH4OAC (4 methods), CaCl2 (2 methods), NaCl (2 methods), NaOAC, AB-DTPA, Mehlich I, Mehlich III, Morgan-Wolf and HNO3. A green house experiment using corn (Zea mays L.) variety Single-cross 704 as the test plant with 2 treatments (zero and 150 mg/kg K) and three replications was performed with the 16 selected soils to correlate K uptake with K extracted by different extractants. From XRD analysis, the dominant clay mineral was found to be Illite. Based on the amount of potassium extracted by these extractants from the soils the extractants used in this research may be divided into three groups: relatively weak extractants including CaCl2, Mehlich I and Morgan-Wolf relatively strong extractants including NH4OAC, NaCl (2N), Mehlich III, AB-DTPA, NaOAC and NaCl (1N), the strongest and weakest extractants in this group were NH4OAC and NaCl (1N), respectively and finally, a very strong extractant which includes only HNO3. In each group, the quantities of extracted K showed high correlation with each other. A high and significant correlation was observed between the quantities of K extracted by NH4OAC, AB-DTPA and HNO3. The amount of K extracted by 2N NaCl, 1N NaOAC, 1N NH4OAC, and AB-DTPA was significantly correlated with K taken up by plant and its K concentration. 2N NaCl and 1N NaOAC were selected as the most suitable extractants for K based on their high correlation coefficients with plant uptake (0.79** and 0.72**, respectively) and K concentration in plant (0.86** and 0.85**, respectively). Yield, relative yield and plant response were not significantly correlated with K extracted by different extractants indicating that available K of the selected soils was not a limiting factor for corn growth therefore, it was impossible to determine the critical level of K for corn by the selected extractant.

The effect of soil salinity on plant growth is due to two factors, namely, increase in osmotic pressure of soil solution and the ionic composition of salt. The present experiment was conducted to obtain information about the response of pistachio (Pistacia vera L.) to salinity and ionic composition of the salt. Salinity with different relative composition of sodium chloride and sodium sulfate were applied to two pistachio cultivars, Fandoghi and Badami. Yield (dry matter of leaf and shoots produced in each pot) of plants were compared by the analysis of variances method of F and Duncan tests. The yields of the cultivars were significantly different (P≤0.01) with Fandoghi cultivar producing less shoots and leaf and, consequently, lower total dry matter. Increasing the salinity level decreased the plant growth. Leaves were more sensitive to salinity. Increasing the ratio of sulfate salt alleviated the depressive effect of salinity such that when salinity was 100% sodium sulfate, the dry matter yield of shoots was 1.5 times and that of leaf was 1.7 times higher compared to the treatment where salinity was 100% sodium chloride. Leaf was more sensitive than shoots and, therefore, it showed a more positive response to chloride decreasing.

This study aims to evaluate land suitability for irrigated wheat in Falavarjan region (Isfahan) using the theory of fuzzy sets. This method differs from the usual land evaluation procedures in its use of weight for different land characteristics and in its method of determining land suitability index. The results were compared with those from parametric land evaluation method. The correlation between land indices and observed yield was higher for the fuzzy set method (r=0.35) as compared to the parametric method (r=0.14). The higher relationship given by the fuzzy set method illustrates its potential usefulness and applicability to land evaluation.

Soil loss due to erosion is a common problem in most parts of Iran. Reduced soil organic matter and lack of proper agricultural management have intensified the problem in recent years. Conservation tillage systems are becoming more widely used in corn production in other parts of the world because of soil losses due to wind and water erosion and energy inputs. Changes in tillage methods, however, create different environments for the germination, development and maturation of corn plants. Most corn hybrids have been selected and developed under conventional tillage systems but these hybrids mayor may not be well adapted to both systems. This study aims to evaluate the performance of five locally grown corn hybrids under zero and conventional tillage methods. The experiment was conducted for 2 years on a plot of land specified for this study. Experimental design was a split plot with randomized complete block arrangement and four replications. Seedling and juvenile plant growth were not affected by tillage method and were similar for all hybrids. Plant dry matter was affected significantly by the cropping system and was lower in no-till method. Plant leaf area index and stem diameter reduced significantly in the no-till system. Reduction was greater in the second year of the experiment. Also grain yields were significantly different among years, tillage method and plant genotypes. Yield reduction was highest in the second year of the experiment under no-till cropping system. There was no interaction between tillage method and corn genotypes, indicating that, usually genotypes perform similarly with regard to grain yield under both tillage methods. The results suggest that corn production under no-till system in Isfahan is probably associated with yield reduction.

Identification of easily measured physiological traits contributing to yield under specified environmental conditions would benefit genotypic selection for grain sorghum. A field experiment was conducted to determine broad-sense heritability and expected genetic advance, and to examine the relationships of grain yield with 11 physiological traits related to developmental periods, vegetative growth, growth rate, grain filling rate, and partitioning to the grain. Sorghum genotypes exhibited significant differences for all traits, except for grain yield. Broad-sense heritability estimates ranged from a low of 49.6 (for grain filling rate per unit area) to a high of 99.4 (for days to maturity). Expected genetic advance ranged between 9.2% (for days to transition of vegetative to reproductive phase, days to maturity and number of leaves) and 39.8% (for grain filling rate per grain unit). Generally, grain yield gave a significant negative correlation with physiological traits related to development and vegetative growth. But, this correlation was positive and significant for growth rate, grain filling rate, and harvest index. Grain yield was low in its coefficient of genetic variation and expected genetic advance. It is, therefore, concluded that indirect selection for grain yield via growth rate, grain filling rate per unit area and harvest index is efficient. Results suggest that use of easily measured physiological traits in sorghum breeding is possible.

An experiment was conducted in order to study the possibility of compensatory growth by changing dietary nutrients concentration in the female Arian broiler chicks using a completely randomized design by means of standard and diluted diets. By standard diet is meant diet recommended by Arian’s guide catalogue and by diluted diet is meant the diet used in Iran broiler farms. However, both diets contain the same nutrient/energy ratios. Chicks in the seven treatments received in their starter, grower and finisher stages standard and standard and standard, standard and diluted and diluted, diluted and standard and diluted, diluted and diluted and standard, diluted and standard and standard, diluted and diluted and diluted, standard and standard and diluted respectively. Furthermore each treatment contained three replicants and each replicant contained 30 chicks. This experiment was conducted in autumn using 630 female Arian broiler chicks for eight weeks. It was concluded that weight gain of chicks receiving standard diets during all stages of their growing period was the same as the chicks receiving diluted diet during their starter period and standard diets during grower and finisher periods. Feed consumption and feed conversion ratio of these treatments were statistically lower than other treatment groups. Furthermore, production index and percentage of mortality was better than other treatment groups. Likewise, viscera% and abdominal fat% remained significantly constant in all treatment groups. But the cost of feed per unit of live body weight was lower in the treatment receiving diluted diets in all three stages of their growing period.

The objectives of this study include the determination of the growth potential of Naeini lambs when fed with diets varying in energy and protein concentrations and also an investigation of the influence of level of energy and/or protein intake on carcass characteristics and composition. Ninety Naeini weather lambs (initial live weight 29.89 ± 2.9 kg) were used in a 92-day feeding experiment. Animals were blocked to each of nine dietary treatments. Diets contained either 2, 2.25 or 2.5 Mcal ME/Kg DM and 11.7, 13.2 or 14.7% CP diets were fed in a 3 × 3 factorial arrangement in randomized complete blocks. Lambs fed with high energy diets consumed significantly more feed (P<0.05) than lambs given the medium (ME) or low energy (LE) diets. The average final body weight and daily weight gain for lambs fed with HE, ME and LE diets were 41.4, 38.3, 34.5 Kg and 162, 124, 74 g/d, respectively, which were significantly different (P<0.05). Feed conversion ratio in HE group was significantly lower (8.3) than ME (10.4) or LE (14.3) groups. Energetic efficiencies and protein efficiencies were better for HE than for ME and LE diets. Increasing dietary energy significantly (P<0.05) improved energy and protein efficiencies of the diets. Dressing percentage, lean meat and eye muscle depth were significantly (P<0.05) improved with increasing levels of energy in the diet, but also increased dissectible fat. No significant changes were observed in bone percentage and body ash due to any changes in dietary energy. As the protein level of rations increased, feed conversion ratio and carcass meat percentage increased, but carcass protein percentage decreased.

Physicochemical characteristics of potato (Solanum tuberosum L.) are very important for storage and processing qualities. The amount of reducing sugars (glucose and fructose) and organic acids at harvest, during and after storage is the most important factor. In this study, three potato cultivars (Moran, Marfona and Agria) were collected, dry cleaned and graded into three sizes. They were analyzed for specific gravity and dry matter content. Potato tubers were stored at 4°C and about 85% R. H. for 15 weeks and then reconditioned at room temperature (25±l)°C for 4 weeks. During the storage period of tubers, sugars (sucrose, glucose and fructose) were analyzed on a weekly basis, but citric, D-malic and D-pyroglutamic were analyzed on a monthly basis by high performance liquid chromatography (HPLC). Data were analyzed statistically in a completely randomized design with sampling and Duncans multiple range test. The total sugar and organic acid contents of tubers significantly increased during the 15 weeks of storage at 4°C and decreased after reconditioning at room temperature. The size of tubers did not affect the accumulation of total sugars. Dry matter content and specific gravity of Agria tubers were higher than those of both Moran and Marfona. Also accumulation of reducing sugars was lower in Agria than in Moran and Morfona initially and after the storage and reconditioning periods. Therefore, Agria must be suitable for processing into chips or dry powder.

Molasses are produced in large amounts by sugar cane and sugar beet factories every year. However, they are considered as the waste product of the crystallization plants. Thus, although they contain significant amounts of materials with deep black colour which can be separated as food colour, molasses are very cheap and feasible to be used for this purpose. Aliquots of diluted molasses, after adjusting the pH, were passed through the column followed by extraction with acidified alcohol. The highest yield of extraction (76.3%) was obtained by using diluted molasses (10° BX) and 150 ml of Amberlite resins. The solvent was removed and the solid colour was obtained by evaporating the water using a freeze drying system. The colour was characterized by determining its solubility, amount of ash, and sugar content and its colouring ability. Also, the stability of the colour under different conditions of acidic pH, temperature, and visible light was investigated. In addition, the colour values of the colour solution were measured by Hunter lab system. The colour was compared with the imported caramel which is used in the black soft drinks of Zam Zam. Both had almost the same values of λmax. Also, their sensitivities to pH changes were similar. Samples of soft drinks made by using the prepared colour were compared with those made by caramel under different conditions of storage such as temperature and light. On the whole, the colour was found to be a very suitable replacement for caramel in the production of black soft drinks. Also the colour was used as partial replacement for cocoa powder in making chocolate milk. The taste panel showed that cocoa powder can be replaced by the colour powder by 20% with almost no detectable differences. The caramel from molasses is safe and can be used as a food colour. The cost of production was estimated at about 10 Rials per gram of caramel. Thus, from an economical point of view, industrial production of caramel from molasses is profitable.

The antifungal effect of sodium diacetate on inhibiting the growth of some bread spoiling molds was examined both in culture media and in flat bread “In situ”. In the first step, the antifungal effect of different concentrations of sodium diacetate: 0, 1000, 2000, 3000, 4000, and 5000 ppm were examined against Aspergillus sp., Aspergillus niger, Rhizopus sp., and Penicillium sp. The results indicated that as the concentration of sodium diacetate increased, the mold growth decreased. At 5000 ppm the mold growth was inhibited up to fifth day (the last day of experiment). Based on these results, the antifungal effect of different concentrations of sodium diacetate was evaluated in bread “In situ”. In this stage Aspergillus sp. was selected as the indicator mold. The results indicated that if 3000 ppm of sodium diacetate is used, not only mold growth is inhibited but bread staling can also be prevented. This concentration of sodium diacetate does not have any harmful effect on texture and flavour, and can increase bread shelf life up to four days. Higher concentrations of sodium diacetate can inhibit mold growth completely, but have negative effects on texture and flavour. Therefore, 3000 ppm of sodium diacetate is recommended for increasing bread shelf life.

This experiment was conducted to estimate genetic parameters of some of the important traits of silkworm in two populations, namely, Japanese and Chinese lines in Iranian Silkworm Rearing Co-Natanz. Based on single pair mating method, 9 male moths mated with 9 female moths and then raised under standard environmental conditions. Performance of 30 progenies of each pair was recorded. Heritability coefficients (parental full-sib method) of single cocoon weight (CW), shell weight (SW), pupal weight (PW) and shell ratio (SR) were estimated to be 0.209±0.123, 0.228±0.129, 0.174±0.109 and 0.044±0.042 in the Japanese race and 0.196±0.1l8, 0.234±0.132, 0.159±0.103 and 0.00, in the Chinese race, respectively. Genetic and phenotypic correlation between CW & SW were 0.645 & 0.957, CW & PW, 0.962 & 0.982, CW & SR -0.351 & 0.123, SW & PW, 0.496 & 0.871, SW & SR, 0.265 & 0.457, PW & SR, -0.446 & 0.169, respectively. Selection, based on heritability coefficients of single cocoon weight and shell weight, can be applied successfully to genetic-gain in this trait. Based on correlation coefficients between traits, selection for shell weight can be applied successfully to improve other traits such as single cocoon weight and shell ratio.

In order to study the parasitoid flies of Sunn pest in Isfahan, this research was conducted during the years 1997-1998. The results indicated that the dominant species of parasitoid fly is Phasia subcoleoptrata L. This species has two generations per year and over winters as pupae in soil under the shrubs of aestivation and hibernation places of Sunn pest and remains there until the following spring. The adults of the first generation of this parasitoid emerge from the pupae before the Sunn pest migrate to the grain fields and parasitize on the Sunn pest at the time of migration. About 6-8 days after the flies lay eggs in the body of Sunn pests, parasitoid larvae hatch from the eggs and grow in the body of their host. Larval period of parasitoid lasts about 15-20 days and then they fall on to the soil and pupate. In the laboratory, the length of pupal period for males and females is 17 and 18.5 days, respectively, for the first generation. Flies of the second generation of the parasitoid parasitize the fifth nymphal instar and the new adults of the Sunn pest.

In winter 1997 severely infested pistachio nuts were collected from orchards in Borkhar district of Isfahan to determine minimum threshold temperature and thermal constants. Minimum threshold temperatures were calculated according to rate of development or X-intercept method and the least coefficient of variation method. Thermal constants were calculated for different developmental stages in the laboratory and were initially compared to field information available. Results showed that minimum threshold temperatures for covered larvae in nut to 50% pupation, bare larvae to 50% pupation and larvae within nut and 50% pupation to 50% adult emergence according to X-intercept method were 7.69°C, 7.78°C, 9.52°C and 11.14°C, respectively. In the case of least coefficient of variation method, the values were 7.92°C, 7.59°C, 9.81°C and 11.99°C. Thermal constant for occurrence of 50% adult emergence and 50% pupation from overwintering larvae and from 50% pupation to 50% adult emergence and 5% adult emergence to 50% adult emergence with minimum threshold temperatures of 9.5°C, 8°C, 11°C and 11°C under laboratory conditions were 783±17.03, 609±1.7, 215.3±19.05 and 107, respectively, which, except for the last case, they were far different from the thermal constant under field conditions. With regards to the nature of the available data for field conditions, possible reasons have been suggested for these differences.