نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال دوم شماره 3 (پیاپی 5، پاییز 1377)

Physiographic characteristics of Atrak Watershed described by a number of parameters were used in regression models to estimate maximum daily discharges. These parameters were sub-watershed area, main waterway length, mean waterway slope, mean watershed elevation and mean watershed slope. Based on the results of correlation between the above parameters and their suitability for discharge estimation, three regression models were developed for further analysis. Model 1 applied area as the independent variable to estimate maximum daily discharge. In model 2 area and mean watershed elevation were the independent variables. Model 3 used area and mean waterway slope as the independent variables. Even though the results of testing did identified all three models as appropriate for application, further testing selected model 1 as the most appropriate. Recommendations were made for model application to similar watersheds lacking the necessary data.

To determine the effects of field slope, emitter discharge, irrigation water volume and soil texture on soil moisture profile and soil surface wetted shape from a point source, field data were collected on three different soil types, three emitter discharges (4, 8, and 12 lph), four slopes (0, 2, 5, and 10%), and five irrigation water volumes (10, 20, 30, 40, and 50 liters) with three replications. The results showed that the surface-wetted area increases as the emitter discharge increases. The surface-wetted area decreased with a corresponding increase in emitter discharge in experimental fields with light-textured soils. In experimental fields with heavy textured soils and slopes greater than 5%, the changes in surface-wetted area due to the emitter discharge increases, were higher compared to slopes of less than 5%. Since, a higher emitter discharge would result in higher surface-wetted area, the results showed that for an equal volume of irrigation water, the soil moisture profile was deeper for lower emitter discharge. In general, the volume of wetted zone was higher for greater emitter discharges. It was found that as the volume of irrigation water increased, the volume of wetted zone would increase correspondingly. This effect is more prominent than that of emitter discharge. In general, the depth of wetting front was lower and the wetted surface area was greater for heavy textured soils as compared to the light textured soils. The wetted-surface area and the shape of wetting front in the direction of slope were affected by the soil infiltration, emitter discharge and volume of irrigation water where these effects were more critical in higher sloping lands.

In order to study the effects of rate and time of nitrogen application on vegetative characters, i.e., yield and yield components of rice (Zayandeh-rood variety), an experiment was conducted at Isfahan University of Technology research farm during summer 1996. Four N rates including (60, 90, 120 and 150 KgN/ha) and four splitting form (1- all N applied before transplanting 2- 1/3 N applied before transplanting, 1/3 at the beginning of tillering and 1/3 at the emergence of first panicle in 50% hills 3- 1/2 at the beginning of tillering and 1/2 at the emergence of first panicle in 50% hills 4- 1/3 at the beginning of tillering and 2/3 at the emergence of first panicle in 50% hills) were evaluated in a factorial experiment which was arranged in a randomized complete block design with 3 replications. Plant height, number of tillers per unit area and days to heading and maturity increased with an increase in the rate of fertilizer application. Grain yield and number of panicles per square meter increased when the N rate was raised to 120 Kg N/ha, while application of 150 Kg N/ha resulted in the reduction of grain yield and number of panicles. Nitrogen rate increases did not have any significant effect on number of grains per panicle. The grain weight did not follow any particular trend at different application rates, but harvest index and percentage of filled grains were decreased as the N rate increased. The percentage of nitrogen content of plant was increased as a result of higher N - rate at heading and harvest times. Treatments containing base application of nitrogen resulted in an increase in plant height, number of tillers, plant dry matter, grain yield and number of panicles per square meter, although it caused a reduction in harvest index. The number of grains per panicle and grain weight did not follow any particular trend under the influence of time of application, although plant nitrogen content increased with a delay in time of fertilizer application.

Methods of seedbed preparation affect establishment, growth and yield of crops via manipulating physical and chemical properties of soil. These effects on wheat-mungbean double-cropping have not been studied in Isfahan. Therefore, the influences of various seedbed preparation methods on soil physical properties and nutrients content and on establishment of mungbean (experimental line 1-61-16) were studied in a wheat-mungbean double-cropping system during 1996 at the Agricultural Research Station, Isfahan University of Technology. Two residue management treatments (burned and unburned) along with four tillage systems (moldboard plow, disk, khishchee and no-till) were laid out in a strip plot design within a randomized complete block design with four replications. Bulk density and penetrability of soil at various depths were not affected by residue management at emergence. However, at the time of flowering, bulk density at 0-15 cm soil depth was lower and soil penetrability at 3-15 cm depth was higher in unburned treatment due to mineralization. Rate and coefficient of emergence of seeds were lower in unburned residue treatment. Soil bulk density at 0-30 cm depths was lower and penetrability at 3-21 cm depth was higher with moldboard plowing at both emergence and flowering time. In addition, lower soil N, P and K content at 0-15 cm depth at emergence and flowering time was obtained with moldboard plowing. Rate and coefficient of emergence were strongly lower in no-till treatment. Based on these results and considering sustainable agricultural goals, incorporating residue with disk tillage might be advantageous under conditions similar to this experiment.

Knowledge of the vegetative and reproductive characteristics of soybean cultivars with different growth habits and maturity groups is essential for the selection of a suitable variety as well as for providing optimum conditions for their growth. In 1994 in a field located in Kholenjan of Isfahan, Iran, nine indeterminate type cultivars belonging to different maturity groups, namely Williams, Wood Worth, Hack, Zane, Black Hawk, Bonus, Steel, S.R.F. and Harcor and one determinate cultivar belonging to maturity group III namely Hobbit, in a complete block design with four replications were evaluated. Indeterminate cultivars and higher maturity group cultivars produced more dry matter. On the whole, indeterminate cultivars with later maturity had longer main stem with more nodes, pods and grains. The determinate cultivar had more lateral branches, and more pods and grains in them but these traits did not show any specific trend in different maturity groups. Height of the first pod from ground surface in indeterminate cultivars was more than that of determinate cultivars. Number of pods per each node of main stem, number of grains per each pod of lateral branch and number of nodes per lateral branch showed no significant difference among cultivars. Classification of these cultivars based on the above characteristics showed that cultivars with different growth habits had basic differences and also that some cultivars showed some similarity to maturity groups which did not exist in the present study.

Immature embryo culture response of 28 durum wheat (Triticum turgidum</em> var. durum</em>) cultivars was studied using MS medium in Tissue Culture Laboratory of College of Agriculture, Isfahan University of Technology. Donor plants were grown in a recirculating hydroponic system and pots in a greenhouse. Regenerated immature embryos were recorded at 2, 4, 8 and 16 days after inoculation. Assessment of durum wheat cultivars for immature embryo culture was conducted by percentage and rate of regenerated embryo, using a split plot design arranged in completely randomized design with 5 replications. The analysis of variances showed that there were highly significant differences among cultivars for plant regeneration capacity. The highest potential and rate of embryo regeneration (two days after inoculation) were observed in “Shahivandi” which is a native cultivar of west Iran. “Awl1/Sbl4” with a mean of 48.5%, “Hagla” and “Ofen/Kil” with a mean of 80% have the poorest and the best mean of regeneration during the recording period, respectively. The high regeneration potential is important in view of reducing the time constrain and somaclonal variation in a breeding program.

Feeding high levels of barley to laying hens is accompanied with dirty eggs, decreasing the feed intake and egg size. To improve the diet with barley for layers, different chemicals including a commercial enzyme effective on barley (Fin Feed), cupric sulfate pentahydrate, sodium bicarbonate, magnesium sulfate and oxytetracycline antibiotic were supplemented to experimental barley based diets. It was found that the commercial enzyme had a significant effect on layer performance. Other treatments didn't have any considerable effects on their performances. Enzyme supplementation significantly (P < 0.05) improved feed intake, production rate and daily egg mass production of laying hens. No significant difference were observed in laying performance of mature birds fed with barley-based diet or soybean corn diet.

This experiment was carried out to study the effects of different levels of vitamin C (0, 150, 300 and 450 ppm) and cage density (3, 4 and 5 birds) on performance and egg shell quality of laying hens under high environmental temperature. In a completely randomized design with 3 × 4 factorial arrangement, one hundred and ninety two (192) 25 week white leghorn hens were divided into 48 replicates four hens per replicate. The experimental period lasted 90 days. The criteria measured were: percentage production, egg weight, egg output, feed conversion ratio, shell thickness, shell weight, shell calcium and albumin height. Daily egg production and biweekly egg weight, shell thickness, shell weight and albumin height were recorded. Shell c1acium was measured at the end of the experiment's period. The results indicate that, 150 ppm vitamin C significantly (P < 0.05) increased egg weight and shell calcium. Albumin height was significantly (P < 0.05) increased at 300 ppm vitamin C supplementation. Cage density had no effects on shell weight, thickness and calcium, and albumin height. Egg weight, egg production and egg output were reduced significantly (P < 0.05) due to increased cage density. Feed conversion ratio was also increased significantly (P < 0.05) as cage density was increased. Interactions between vitamin C and cage density on shell and egg weight were significant (P < 0.05).