نشریه علوم آب و خاک (علوم و فنون کشاورزی و منابع طبیعی)
سال سوم شماره 4 (پیاپی 10، زمستان 1378)

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</sup>/ha) and the average evapotranspiration was determined to he about 561mm.

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.

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</sup> 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</sup> 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</sup> treatment was reached at 0.8PL. Results from this study indicate that the manure application at a rate of 50 t ha-1</sup> reduces soil compactibility and increases soil moisture trafficability range.

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</sup> 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</sub> (1:50) > Soltanpour & Schawb > EDTA > Bray P1</sub> (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.

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, H2</sub>SO4</sub>, Morgan and 0.01 M CaCl2</sub> 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</sup> for MgOAc, Morgan and Kelowana methods, Texas method H2</sub>SO4</sub> 0.01 M CaCl2</sub> and NH4</sub>OAc without and with submergence of soil samples, respectively. In this study, available K was below the critical level in almost 75% of the soils.

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.

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).

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</em> 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.