مجله فنآوری زیستی در کشاورزی
سال هفتم شماره 4 (زمستان 1386)

Amount of fuel consumption and actual field capacity were measured by using of riding type and walking type rice transplanters in different times of puddlings. Statistical analysis was performed for a two-factor experiment with a completely randomized design. The two factors were transplanters and puddlings times, with two and three levels, respectively. The measurements were replicated 4 times. The six plots were selected and the plot length and width was 100 m and 3.6 m respectively. Four rows walking type and riding type rice transplanters were used. The hill distance adjusted on 16 cm. Transplanting speed were 1.9 km/h for walking type and 2.4 km/h for riding type. The puddlings were carried out by power tiller in one, three, and five times. The amount of fuel consumption (liter/hectare) was measured at beginning and end of transplanting operation. The results indicate that the rice transplanters (P<0.01) and puddlings (P<0.05) had a significant effects on the amount of fuel consumption. Also the factors of machines, number of puddlings and the interaction between them had a significant effects (P<0.01) on the actual field capacity. Based on the results, for increasing of field capacity and decreasing of total time, riding type transplanter is offered and also for decreasing of fuel consumption walking type tranplanter is offered.

Natural events like flood and drought waste a noticeable part of capitals in agriculture sector. Undesirable conditions caused by non-harmonious investment and depreciation and also distortion caused by natural events lead to intensified trend of decreasing gross fixed capitals in agriculture sector. Forests and pastures play different rules like as refining the weather, preventing soil erosion and providing wild ecosystem. Decreasing forest area and exploiting pastures used for fuel or grazing livestock lead to soil erosion and reduce agronomic lands fertility. Therefore, in order to correct national product, depreciation of natural resources should be subtracted from gross national product exactly like physical investment. In this research, depreciation of forests and pastures and their share in gross domestic product were measured in third economic, social and cultural development plan. Moreover, economic growth was adjusted based on environmental concerns (forest and pasture depreciation). Results showed that depreciation of forests and pastures reduce 4 percent in average over the period and gross domestic product growth was overestimated 0.6 percent. In addition, plans for reducing forest and pasture depletion did not perfrom proper results.

To collect complete data of snow depth from an area, intensive scale of spatial distribution of measurement is needed. But, difficulties are involved in measuring snow depth directly. Because of these difficulties, methods for predicting snow depth should be developed as alternative approaches. In the current research, an area of 5.2 located in Samsami Basin with an intensive data base of 258 measured points is studied to develop an alternative method. The cluster analysis model was applied to estimate snow depth for unobserved points in two models. The first model was applied to cluster the snow depth considering parameters including elevation, index of wind shelter and aspect using linear regression. The second model was used by Fisher's discriminate analysis. To do this, discriminate functions were used as estimator of snow depth. Statistical analyses showed that for elevation less than 2767 m, 61% of data variations were modeled using the first model. But, for the higher elevations, this model was unable to predict the unobserved data. However, the second model predicted 53% of data.

Study the Trend of Early and Late Frost Occurrences, Length of Frost-free Period and Number of Frost Day to reduce of Agricultural Damages in Several Climatic Regions of IranVarshavian, V., Ghahreman2, N., Khalili3, A. and Hajjam4, S. AbstractOccurrence of the early frost in autumn and the late frost in spring cause damage to crops in different climatic regions of Iran each year. Information about the probable dates of frost occurrence, helps farmers to avoid or reduce the damages caused by frost. In this study, high quality historical daily minimum temperature data in a 44 years period (1961-2004) from six synoptic stations, Tabriz, Tehran, Zahedan, Shiraz, Kermanshah, and Mashhad were used to derive agrometeorological indices i.e. date of last spring frost, SF (day), first autumn frost, AF (day), length of frost-free period, LFF (day), and number of frost day (1951-2005). These stations represent different climates of Iran based on Koppen climatic classification. First, time series (dates of frost, frost-free period and number of frost day) were checked for normality with the Kolmogorov-Smirnov test. Time trends for all variables were analyzed using parametric and nonparametric techniques. Zahedan (Steppe climate) didnt show significant trend. Tehran (As the other example of steppe climate) showed significant positive trend in length of frost-free period and date of first autumn frost and a significant negative trend in date of last spring frost and number of frost day. Among representatives of temperate humid climate, Tabriz showed significant negative trend just in the number of frost day. Analyzing Mashhad and Kermanshah showed a similar significant positive trend in both length of frost-free period and date of first autumn frost and a significant negative trend in number of frost day. Also Shiraz, similar Tehran, showed significant trend in all studied time series. Generally, except Tabriz and Zahedan, length of period that plant can develop without the risk of frost has increased. Also, except Zahedan, number of frost day in other stations has decreased significantly.

The experiment was conducted to test the effect of β-mannanase enzyme addation in broiler chicken diets contain three metabolizable energy levels on performance, carcass quality and intestine viscosity. This study was arranged by complete random design (CRD) in arrangement by factorial procedure (2×3). Six treatments were used that consist of two levels of enzyme (0 and 0.05%) and three levels of metabolizable energy (2850, 2900 and 3000 Kcal/Kg). The results of this study were shown that body weight was significantly increased by enzyme suplementation (2258.99 g) at 42 day of age (p<0.05) but energy level was not affected on body weight. The difference was appeared at 35 days of age in 3000 Kcal/Kg energy level. Reduction in feed intakes was indicated with enzyme supplementation at 21 days of age and feed intake was increased significantly by 2850 Kcal/Kg energy level (P<0.05). While the lowest level of feed was recognized in 3000+0.05 group (649.69 g) and highest levels were shown by treatments 2850+0 (716.54 g). No responses was found in feed intake at 35 and 42 days of age by experimental agents. Feed conversion ration (FCR) was significantly higher in 2850 kcal/kg ME (1.13) at 21 days of age compared with other levels of energy. This was lower at 35 and 42 days of age for 0.05% enzyme in comparison to zero level (P<0.05). Breast meat, abdominal fat and pancreas percentage wre not affected by experimental main effects, but breast and abdominal fat percentage were incresed in treatments 2850+0.05 (%4.25) and 2900+0.05 (%37.20) respectively (P<0.05). Viscosity was reduced by 2900 kcal/kg ME (1.73 cps) and 0.05% enzyme (1.84 cps). The results of this study were shown that in low energy level body weight increased, and feed intake, viscosity and FCR decreased with β-mannanase enzyme suplememtation.

In this study, the effect of different growth stages and cuttings on agronomic traits, chemical composition, and nutrient digestibility of sainfoin (Onobrychis viciifolia) in 2003-2004 cropping season was investigated. Chemical composition was measured by standard laboratory method and the nutrient digestibility by using 20 Mehraban male lambs. Agronomic traits and chemical composition data were obtained from a factorial experiment arranged within a completely randomized design. Nutrient digestibility coefficients were determined in a completely randomized design. The growth stages included full budding (I), early flowering (II), and full flowering (III), and the cuttings included first, second, third, and fourth cuttings. The bush height, wet and dry weight of forage, DM%, and NDF% increased with the advancement of plant age, and on the contrary the leaf: stem ratio, CP%, and NFC% decreased. There was significant difference for bush height at three growth stages and for leaf: stem ratio at stage I as compared with other stages (P<0.05). The effect of cutting on agronomic traits was significant, so that bush height increased from second cutting to fourth cutting and leaf: stem ratio decreased. Bush CP and NDF differed significantly between different cuttings and were 21.41% and 37.82% for stage I, 19.47% and 42.20% for stage II, and 18.21% and 48.79% for stage III, respectively (P<0.05). The crude protein of bush at fourth cutting (20.73%) was significantly higher than other cuttings and bush NDF at first cutting (40.68%) was significantly lower than other cuttings (P<0.05). The digestion coefficients of DM, CP, NDF, NFE, OM, CF and TDN decreased significantly with the advancement of growth stage (P<0.05). Results show that sainfoin at early flowering stage and third cutting has more desirable qualitative and quantitative capabilities.

Effect of Different Levels of Urea and Sulfur on Microbial Protein Synthesis, Nitrogen Retention, Some Blood Metabolites and Nutrients Digestibility in Mehraban SheepZamani, Z., Aliarabi2, H., Tabatabaei3, M. M., Zamani2, P., Saki3, A. A. and Zaboli4, KH.Abstract This study was conducted to evaluate the effect of dietary supplementation of urea and sulfur on microbial protein synthesis, some blood metabolites (urea and glucose), nitrogen retention, and nutrients digestibility in Mehraban sheep. Experiment was organized as 6×4 Uden square design with 3×2 factorial arrangement of treatments. Ingredients of diets were barley grain, soybean meal, urea, elemental sulfur and mineral supplement. Sulfur was supplemented at two levels of 0.13% and 0.2% on DM basis and urea was supplemented in three levels of 0, 0.25% and 0.5% on DM basis. Daily collections of feces and urine were made during the last 7-days of each period. Excreted purine derivatives (allantoin, uric acid and xantine plus hypoxantine) were measured after total urine collection during a digestibility trail to estimate microbial N supply to the duodenum. At the end of each period blood sampling was taken. Results showed that nitrogen retention, microbial nitrogen supplied to the duodenum, purine derivatives and purine absorption increased by simultaneous feeding of urea and sulfur. Plasma glucose levels and apparent digestibility of organic matter and neutral detergent fiber increased at high levels of urea and sulfur. Plasma urea levels decreased at the higher level of sulfur. It can be concluded that best combination of urea and sulfur might be 0.2% sulfur and 0.5% urea.

Aflatoxins (AFs) are groups of toxin fungus that are produced by different species of fungi of Aspergillus flavus and Aspergillus parasiticus. The experiment was conducted in order to study the effect of AFs on broiler chickens (400 strains Ross 308) in four treatments. Treatment 1 was fed the basal ration (corn and soybean meal), treatment two was fed the feed containing one ppm AFs, treatment three received the feed containing one ppm AFs and 0.25% Mycosorb absorptive and treatment four was given the feed containing 0.25% Mycosorb absorptive. Experiment was conducted in complete random design (CRD) with four replications in treatment and 25 chickens in each. Results were shown that adding of one ppm AFs in diet in comparison to control treatment caused to significant differences of total protein, uric acid and phosphorus in the end of rearing period (p<0.05). No significant differences were shown in serum cholesterol and glucose by Presence of AFs (one ppm) in diet comparison was to control treatment (p>0.05). Adding of 0.25% mycosorb on diet that contained one ppm AFs could not compensate harmful effects of AFs on total protein and uric acid in comparison to control treatment (p<0.05), but ameliorated the unfavorable effects of AFs on phosphorus of serum. Addition of 0.25% the mycosorb absorptive to the diet caused significant differences on incited parameter in comparison to control treatment (p>0.05).

Acyl-CoA: diacylglycerol acyltransferase-1 (DGAT1) gene has been mapped at centromeric end of bovine chromosome 14 and is known as a factor affecting fat content of milk. Our objective was to determine the relationship between the K232A polymorphism at the gene and milk traits in Holstein cattle of Iran. A 411 bp fragment including this polymorphism was amplified and digested with the enzyme CfrI to determine the genotypes of 206 Holstein cows. The estimated allele frequencies were 0.66 and 0.34 for the A (alanine) and K (lysine) alleles, respectively. Average allele substitution effects of the K allele for all traits in the first and second lactations were estimated, separately. The statistical analyses showed positive and significant effects of the K allele for fat and protein content traits, as well as for the fat yield in both lactations. In contrast, negative and significant effects were found for milk and protein yield. The relatively lower frequency of the K allele than the A allele may be due to selection for milk yield in recent years. Our results showed that the DGAT1 K232A polymorphism can be a source that underlies the reported quantitative trait loci for fat content trait in the proximal region of bovine chromosome 14.

This experiment was conducted to the examine effect of feeding single and multiple diets with different levels of nutrients on broiler performance. Birds were randomly assigned to five treatments including: control (two diets, high nutrients), 3H (three diets, high nutrients), 1H (single diet, high nutrients), 3L (three diets, low nutrients) and 1L (single diet, low nutrients). Body weight (BW), Body weight gain (BWG), feed, energy and protein intakes, carcass yield and gastrointestinal organs were recorded. Feed conversion ratio (FCR) and calorie conversion ratio (CCR) were calculated. BW of SL and SH groups and BWG for 1L, 1H and 3L groups were significantly lower than those of control group, however these treatments showed compensatory growth. Feed and calorie intakes of 1L group and protein intakes of 1L, 3L and 1H groups were significantly lower than those of control group. FCR and CCR for 1L and 1H groups were significantly higher than other groups. Weight of carcass, breast and leg for 1L group and breast for 1H group were significantly lower than those of control group. Actual weight of gastrointestinal organs for 1L group at 21 day decreased. Results showed that level of nutrients in the late stage of rearing period can be decreased without negative effect on broiler performance. However, single diet feeding program with low level of nutrients indicated decrease in performance of broiler and decrease in carcass yield was observed with single diet feeding regardless of level of nutrients.

Licorice is a leguminous and its root extract is used in industries of pharmacology. After extracting from the root, the remainder is called pulp. To determine nutritive value of the root pulp, its chemical composition and digestibility of DM, OM and energy were determined using in vivo method. Alfalfa and wheat straw were replaced with licorice root pulp at the ratio of 0, 13.5, 20 and 26.5 percent. Diets were isocaloric and isonitrogenous and C:F ratio was 33.33: 66.66. To compare effects of different levels of root pulp on average daily gain and feed conversion ratio, 32 Kordi lambs were randomly assigned to four treatments. DM, CF, EE, ash, CF, NDF, ADF, ADL, Ca, P and GE of root pulp were 91.4, 8.05, 0.7, 9.4, 38.0, 67.7, 46.7, 20.4, 0.87, 0.23 % and 4.4 Mcal/kgDM, respectively. Digestibility of DM, OM, and energy were 37.43, 40.02 and 38.08% and after subtracting associative effects were 42.20, 40.09 and 42.63% respectively. Average daily gain of lambes from T0, T1, T2 and T3 was 212.08, 207.00, 213.39 and 220.75 g/d and variation was not significant (p>0.05). Feed conversion ratios for treatment 1 through 4 were 7.69, 7.58, 7.46 and 7.29 which no significant difference was observed among them (P>0.05). It seems that licorice root pulp could be replaced for some part of roughage (Strow) in similar rations without any adverse effect on performance of animal.

This study was carried out to compare the effect of different treatments on in vitro solubility, in sacco degradability and in vivo digestibility of canola meal protein. Treatments were untreated canola meal (To), formaldehyde treated (T1), acetic acid treated (T2) and heat treated canola meal (T3). Canola meal was subjected to in vitro protein fractionation to find out the contribution of different protein fractions A+B1, B2, B3 and C. These fractions were determined on the basis of solubility of canola meal protein in three different solvents, phosphate buffer, neutral detergent solvents (NDS) and acid detergent solvents (ADS). Treatments were subjected to nylon bag technique at various intervals (0, 2, 4, 8, 16, 24, 48 hours) using two fistulated sheep. The N residue from nylon bags at any incubation time was determined to measure a, b, and c values and to estimate the effective degradability at different out flow rates. In vitro solubility study showed a significant (p<0.05) decrease in fraction A+B1 while B2 increased as the result of both physical and chemical treatments. Fractions B3 and C were not affected by treatments (p>0.05). Results of protein degradability showed that ' a ' was higher (5.74) and ' b ' was lower (76.32) for untreated canola meal than for treated meals (p<0.05). There was significant difference between untreated and treated meals in concern to ' c ' value (p<0.05). The effective crude protein degradability decreased significantly 15-19% as the result of either physical or chemical treatments. The effective degradability of To, T1, T2, and T3 was 63.28, 52.15, 53.65 and 51.50, respectively. Apparent CP digestibility was increased (p<0.05) due to physical and chemical treatments of canola meal. Crude protein digestibility was the highest for T1 (81.43) followed by T2 (80.42), T3 (78.84), and To (73.26). It can be concluded that chemical and heat treatments of canola meal increased the portion of un-degradable protein in the rumen by altering the potential degradable fraction (b) and the rate of degradation (c). Despite decline in protein degradability in the rumen, improved protein digestibility in total tract, significantly.

Based on meteorological conditions and also topography, frost is divided into two types of radiative and advective. Province of Khorasan Razavi in north east of Iran, is one of the places which is affected by advection of cold weather and always its agricultural productions are faced to many losses. So, determining the kind of frost in this province is very important. The aim of this studyis to consider and determine the type of the early fall and late spring frost and their probability in province of Khorasan Razavi. The meteorological data of twelve synoptic stations were collected and the date of temperature falling to 0°C (threshold) or lower for the first time in the fall and last time in the spring were determined. Then, the date of frost was given withquantitative values. To determine the type of frost, all atmospheric parameters were considered at observation date, the days before and after the first fall and last spring frost and then the dates were separated based on the kind of the frost. A statistical period of 13 years was selected and then probability of date of occurrence with 25, 50 and 75 percent were calculated. Results show that the earlier and later average of the starting date of advective frost happened in 20 of November and 17 of December in Ghouchan and Boshrouye station, respectively. The results also show that, the advective frost finish in 11th of March and 7th of April in Boshrouye station (South) earlier and in Ghouchan (North) latest respect to the other stations.

Infection with bovine viral diarrhea virus (BVDV) is endemic in cattle populations in most part of the world. The high prevalence in combination with the negative effects on reproduction and the general health condition in affected herds result in significant economic losses to the cattle industry globally. ELISA is better suited test for BVD screening of large series of samples. In this study, serological investigation was performed to determine the prevalence of bovine viral diarrhea virus infection of cattle in Hamedan erea. Blood samples were taken from 399 cattle (237 from industrial and 162 from non-industrial farms) and sera were stored at -70°C. The sera were tested by enzyme linked immunoabsorbent assay (ELISA) for detection of anti-BVDV antibodies. The antibodies against BVDV were showed in 309 (77.4%) of tested cattle. A total of 182 (76.8%) and 127 (78.4%) sera of industrial and non-industrial farms were positive, respectively. Statistical analysis of data by chi-square did not show any significant differences between age groups and also between the methods of husbandry.

During the last few decades, global climate change has been an important research task throughout the world and therefore its consequences have been addressed in many research works. In this research, the annual meteorological parameters such as air temperature, precipitation, relative humidity, wind speed and reference crop evapotranspiration (ET0) were analyzed to determine the temporal pattern of long-term trends of meteorological data. The trend analyses were carried out for two different climates: cold and warm climates, during the period 1966-2005. In this regard, Mann-Kendall test was used. The results showed that precipitation and wind speed parameters had the most variations to the average values in the study period respectively, whereas the least variation was observed in temperature data. In most cases, trends were observed in the both studied climates. Significant increasing trends were observed in air temperature data, while the trend statics revealed a significant decreasing trend for precipitation and relative humidity. Significant increasing trends were observed in air temperature and reference crop evapotranspiration data, while precipitation and relative humidity data revealed significant decreasing trends in all stations. The time series of annual wind speed data also showed negative trend in the majority of the stations. The results of such research are applicable in many sectors, including long-term water resources management and prediction of plant water demand in similar climates.

Generally in flood studies, two types of information will be offered which are namely as peak instantaneous discharge and flood hydrograph with different return periods. The main purpose of the present research is determination of regional coefficient Diken’s equation for calculation of peak flood with any return period. In this study, because of lacking measurement data in Sheyvand basin, the peak instantaneous discharge data of existing hydrometric stations in outline basins has been used. The outline rivers peak flow data was collected, controlled, validated and accomplished. The long set of peak flow data was analyzed by different statistical distributions. According to the results of statistical tests, the best distributions for each hydrometric station was selected and the floof peak values with different return periods was estimated by the selected distributions. By creating correlation terms between area parameters and flood data with any return period, one area- discharge equation was achieved according to Diken’s equation. By correlating between C & N parameters that are equation coefficients and return period, two equations for calculating both of the considered parameters were obtained. Replacing these equations instead of C & N in Diken’s equation, final equation in order to estimating flood amount in study region was achieved. Finally, flood values were estimated flood amounts with different return period for Sheyvand basin by this method.

In order to study the quality of sunflower in response to PGPR and different levels of urea under water stress condition, an experiment was conducted during 2006 growing season at the Eslam Abad-Gharb Agricultural Research Station, Kermanshah province, Iran. The experimental design was split-plot laid out in RCB with three replications. The main plots were three levels of irrigation [irrigation at 85% field capacity (I1), irrigation at 70% field capacity (I2) and irrigation at 55% field capacity (I3)] and sub plots were six levels of fertilizer [control (C), recommended rate of N (125 kg urea/ha) (N), inoculation with Azotobacter chroccocum&Azospirillum lipoferum (AA), AA+100% recommended rate of N (AA100), AA+75% recommended rate of N (AA75) and AA+50% recommended rate of N (AA50))]. Water stress significantly affected protein percentage but fertilizer treatment had high significant effect on this trait. The I3 and AA100 treatments significantly increase of protein percentage. The highest and lowest oil percentages were obtained from I1AA100 and I3C treatments, respectively. Combination treatments of I3C increased palmitic and stearic acid in seeds. The lowest percentage of palmitic and stearic were obtained from I1AA treatment. The I1AA50 and I1AA treatments significantly increased oleic and linoleic acid respectively, whereas these fatty acids decreased in I3AA100 and I3AA75 treatments, respectively. Overall, drought stress significantly decreased oil percentage, oleic and linoleic acids but increased palmitic and stearic acids in the seeds. Application of biofertilizers with urea significantly increased the oil, protein and unsaturated fatty acids in sunflower seeds. Because of the low price and positive effect of biofertilizers on sunflower seed quality, utilization of these fertilizers are therefore highly recommended in sunflower culture.

To evaluate the nitrogen fixation of annual medics in responce to Sinorhzobium meliloti strains four species of annual medics (Medicago truncatula, M. littoralis, M. polymorpha, M. rigidula) were grown in all combinations with four various strains of Sinorhizobium meliloti (Native, Hoomand, R95 and S13). There was also uninoculated check for each species. Control treatment (uninoculated) included mineral nitrogen (2.5 mMol nitrate). Pot experiment was conducted using a factorial completely block design with four replications in grow chamber at Forest and Rangeland Research Institute. Inoculation with suspensions of different strains was carried out when cotyledons were appeared. Nitrogen fixation in shoot was not significantly different among medics. There was a significant effect of sinorhizobium by medic species for shoot dry weight, height, nodule number, and shoot number. There was a good potential symbiosis with bacteria in M. truncatula and M. littoralis. There fore, it can be suggested that these species are suitable for all regions that medics can be grown. M. plymorpha has weak effective symbiosis with any of the strains though had highest nitrate use efficiency. It seems that this plant requires specific strain.

In order to study the effect of different amounts of nitrogen and plant density on dry matter yield and the rate of essential oil in leaf and whole plant of peppermint (Mentha piperita L.), a split plot experiment based on randomized complete block design was conducted with three replications over two cuts. Nitrogen was used as main plot in three levels (100, 150 and 200 kg/ha, two times, half for each cut) and plant density was considered as sub-plot in three levels (8, 12 and 16 plants/m2), then dry matter yield and essential oil percentage in leaf and whole plant were measured over two cuts. The results showed that nitrogen treatment were significantly affected the dry matter yield as well as essential oil in leaf and whole plant in both cuts, so that, with the application of 100 kg/ha nitrogen, the highest rate of dry matter yield and leaf essential oil was obtained from the first cut. In the second cut, the highest amount of dry matter yield and essential oil was obtained from leaf and whole plant when 200kg/ha nitrogen was used. The effect of plant density and also its interaction with nitrogen on essential oil percentage in leaf and whole plant was significant in the first cut only, so that, the highest rate of essential oil in whole plant was obtained when 75 kg/ha nitrogen was applied on 8 plants/m2. The results of this study were also analyzed for both cuts in total and showed that the effect of nitrogen on dry matter yield and the rate of essential oil in leaf and whole plant was also significant.

This experiment was carried out at Agric. Exp. Stn. of Gonbad. The experiment design was a Randomized Complete Block arranged in a strip-plot. Vertical factor consisted of four irrigation levels (I0= without irrigation, I1= Irrigation at flowering, I2= Irrigation at grain filling and I3= Irrigation at flowering and at grain filling). Four rates of N fertilizer (0, 30, 60 and 90 kg N (as urea)/ha) were horizontal factor. The results revealed that increasing N fertilizer significantly increased grain yield and protein content and yield, biologic yield, harvest index, while N.U.E. significantly reduced. The highest yield was obtained at 90 N kg/ha, however it had not any significant difference with 60 kg N/ha. Irrigation at both flowering and filling period (I3) significantly increased grain yield, grain per spike, grain yield and protein content and yield, N.U.E. while other traits reduced. Interaction of N fertilizer and irrigation was non-significant for all traits with the exception of protein content and N. U. E.

Soil conservation and sediment yield prevention is necessary for preservation and rehabilitation of renewable natural resources and integrated development of watersheds. The rate and type of sediment yield is generally a function of climatic conditions, topography, soil and land use characteristics out of which the importance of land use because of effective role of human is more than others. In the present study, the relationship between land use changes and sediment yield was studied in Manderijan watershed located in upstream of Zayandehrood dam basin covering an area about 23000 ha. The precipitation and the sediment data belonging to the period of 1979 to 2002 were respectively collected from Chadegan climatological and Manderijan hygrometry stations. The satellite images of MSS 1979, TM 1990, TM 1998 and ETM 2002 were also applied to map land use during study period. The relationship between sediment yield and annual precipitation changes were evaluated using five-years moving average and regression analysis. The assessment of relationship between land use changes and sediment yield was also made using regression equations for the periods corresponded on the time of available satellite images. The results of the study revealed that despite of significant variation in annual precipitation at the confidence level of 99%, it’s controlling role on sediment yield was found to be low owing to inconsistency of changes trend and their non synchronous variations. The analysis of regression equations was also verified the significant relationship in cubic form between irrigated agricultural land use and sediment yield with high determination coefficient of 0.99 and low estimation error of 12%.