جستجوی مقالات مرتبط با کلیدواژه « lettuce » در نشریات گروه « آب و خاک »

Today, by increasing industrial and agricultural activities and the subsequent increase in pollutants, soil and water pollution has become a serious environmental problem. The increase of pollutants in the soil in the conditions of dry climate and drought stress have adverse effects on the biological indicators. In this study the combined effect of cadmium at six levels (0, 5, 10, 20, 40 and 80 mg kg-1 soil) in the form of cadmium sulfate (CdSO4) and three irrigation intervals (2, 4 and 7 days) as a factorial experiment in the form of a completely random basic design with three replications was investigated on spinach (Spinosa oleracea) and lettuce (Lactuca sativa) in calcareous soil with silty clay texture. The obtained results showed that increasing the concentration of cadmium in the soil caused a significant decrease in the average dry weight of leaves and stems of lettuce and spinach. The average dry weight reduction percentage compared to the control at the highest level of cadmium was observed in lettuce leaves and stems as 63 and 46% and in spinach leaves and stems as 54 and 38%, respectively. Increasing the irrigation intervals decreased the dry weight of lettuce and spinach plants significantly compared to the control. The percentage of mean dry weight reduction in 4 and 7 days irrigation intervals compared to 2 days irrigation interval in lettuce leaf and stem was 23, 41, 31 and 63% and in spinach was 19, 39, 24 and 49%, respectively. The increase in cadmium levels increased the concentration of this element in the stem and leaves of lettuce and spinach plants, and by increasing irrigation intervals, the concentration and uptake of cadmium in the leaves and stems of spinach and lettuce decreased. The results of this research showed that the spinach plant absorb and transport cadmium metal more than the lettuce. The stress sensitivity index showed that the moisture stress has reduced the crop tolerance to cadmium. Based on the decrease in dry weight at different levels of cadmium, it can be said that the stem of two plants is more tolerant to cadmium than the leaf.

Current study was carried out as a pot experiment to investigate the effect of different irrigation levels (100% and 70% of crop water requirement) and seed priming with salicylic acid solution (zero, 0.5 and 1 mM) on the yield and water productivity of French lettuce in the greenhouse of Zanjan University Research Farm. The experiment was done from November 2019 to February 2020 as a factorial experiment based on randomized complete blocks design with three replications. The water requirements of the control treatment crops were determined by weight method. Based on the results, means of plant fresh weight, plant head diameter, shoot dimeter, relative water content and water productivity in plants was significantly reduced in plants irrigated as 70% crop water requirement by 46%, 19%, 24%, 8% and 35% (respectively) compared to the control treatment. Seeds priming with 1 and 0.5 mM salicylic acid solution, were significantly increased means of plant fresh weight (respectively 115% and 53%), plant head diameter (respectively 23% and 10%), shoot dimeter (respectively 10% and 6%), chlorophyll content (respectively 60% and 30%), relative leaf water content (respectively 59% and 41%) and water productivity (respectively 23% and 11%) compared to the control treatment (hydropriming with distilled water). The results of the interaction of the experimental treatments showed, the maximum and minimum mean of water productivity were in 100% water requirement-1 mM SA (8.9 kg/m3) and 70% water requirement-hydropriming (2.3 kg/m3). In areas like Zanjan with limited water resources where deficit irrigation should be done to save water, seeds priming is suggested to reduce the effects of drought stress on plants.

Biochar as a soil amendment can control bioavailability of heavy metals in contaminated soils and can reduce the hazard of their transferring to the food chain. In order to investigate the effects of biochar derived from the apple and grape pruning wastes and wheat straw on bioavailability of Cd and growth of lettuce plants an experiment was conducted in a completely randomized design under greenhouse condition with the facrors of: 1) the concentration of Cd (0, 10 and 20 mg kg-1), 2) type of biochar (apple pruning, grape pruning and wheat straw) and 3) biochar level (0 (B0), 2 (B2) and 5 (B5) % w/w) in 3 replications. At the end of the lettuce growth period, some parameters including shoot dry weight, root dry weight, Cd concentrations in root and shoot, translocation factor (TF), bio concentration factor for shoot and root (BCF), and bioavailability of Cd in soil were measured. The results showed that the increase of the soil pollution level, raised the   intensity of the Cd bioavailability, Cd concentrations of shoots and roots, bio concentration factor of shoot and root (BCF). Furthermore, with increasing the level of biochar in soil, bioavailable Cd, Cd concentrations of roots and shoots were decreased in treatments (B5> B2> B0). Bioavailable Cd concentrations in soil in biochar treatments including apple pruning, grape pruning and wheat straw at the level of 5% w/w were decreased, by 46.81, 65.96 and 76.59 %, as compared to control respectively. Therefore biochar impact on decreasing Cd bioavailability depended on its raw material, biochar amount and metal concentrations.

Nano in agriculture improves plants in absorption of food, fuel and other items. The aim of this study was to investigate the performance and efficiency of water consumption under low irrigation regimes and silica nanoparticles. The present study was conducted in 1398 in the greenhouse of the Faculty of Agriculture, Shahid Chamran University of Ahvaz. In order to achieve the above objectives, the present study on lettuce plant (Vivian baby lettuce cultivar) in three water levels (75, 85 and 100 water requirements of the plant) and three application levels of nanoparticles including 0, 50 and 100 ml per 100 g Liter is done as root feeding in three repetitions. This design was completed in the form of shredded strip cards with a basic block design. Based on the results, dehydration stress on the total yield, harvest index, leaf area and leaf area has a significant effect on the level is likely to exist if it is valid for one year and shows only on weight. In this study, the effect of using nanoparticles on any of the studied indicators was not found to be significant. The combined effect of dehydration stress and the use of nanoparticles on total yield was significant at five times the probability level, but this effect was not found to be significant on root weight, leaf area index, harvest, root length and leaf area. Records more than the lowest total performance parameter for the I100F100 team equal to 87.88 grams and the lowest amount in the I85F50 team with 47 grams. The lowest leaf area and leaf area index are observed in I100F50 team, the minimum leaf area in I75F0 treatment and the minimum leaf area level in I75F100 treatment. The highest and lowest harvest indices in this research are 74.68 and 52.61 of the budget results, respectively. Maximum and minimum root weight occurred at full irrigation. Root weight in I100F100 treatment is 27 grams and in I100F0 treatment is 18.42 grams.

The development of intelligent irrigation systems with the aim of providing the plant with water in a timely and adequate manner is an important strategy to increase the quantity and quality of agricultural products with minimal water consumption. On the other hand, determining the amount of water required by the plant largely depends on an accurate estimate of evapotranspiration in vegetation. In this study, neural network model was used to estimate the evapotranspiration in a lettuce hydroponic rotary culture system. The actual evapotranspiration of lettuce in the hydroponic cultivation system was estimated in order to design the irrigation system with the help of fuzzy logic model. Cultivation time was 30 days and data sampling time from temperature and humidity sensor was 10 minutes. According to the desired results obtained from the evaluation of the planted crop and water consumption, the efficiency of fuzzy model was proved. Therefore, it was used as a criterion for validating the neural network model of this study. The data volume for the neural network model was about 4500, which was randomly divided into three parts, 70% (training), 15% (evaluation) and 15% (test). Different ANN structures were evaluated to find the most suitable neural network architecture. The best result was achieved with BR algorithm with three hidden layers in an 8-10-10 topology and tansig transfer function in three hidden layers and output layer. For this architecture, the absolute error and coefficient of determination were 0.43 and 99.98%, respectively. Furthermore, considering a simple single layer network (one hidden layer), the BR algorithm with 8 neurons and logsig and tansig transfer functions for the hidden and output layers, were selected as the best model. The error and coefficient of determination of this structure were 0.79 and 98.84%, respectively. According to the sensitivity analysis, humidity and temperature were the most important parameters in predicting evapotranspiration, respectively.

This study aimed to investigate the efficiency of different chitosan composites on lettuce plant and mobility reduction of cadmium in the soil. For this purpose, a pot factorial experiment was conducted in greenhouse conditions using a completely randomized design.The proposed factors were soil cadmium levels (0, 8, 25 and 75 mg/kg) and types of adsorbent (chitosan, biochar, zeolite, nanomagnetite and composites of chitosan-biochar, chitosan- zeolite,chitosan- magnetite and control). Each adsorbent was applied to the soil at the rate of 0.5% W/W. The results showed that the shoot height, the shoot and root dry weight and the concentrations of phosphorus, potassium, iron and zinc in the shoot of lettuce decreased but the cadmium concentration of leaf increased as the concentration of soil total cadmium increased. The results also showed increasing the amount of adsorbents to the soil decreased the toxic effects of cadmium by adsorpting the part of soluble cadmium. As, by application of 0.5% W/W of chitosan-magnetite composite, the concentration of cadmium in the shoot of lettuce decreased about 24.22 mg/kg as compared to the control treatment. But the shoot height and the shoot dry weight increased by 29.57 and 43.6% respectively, and the concentration of phosphorus, potassium, iron and zinc increased by 72.22, 98.78, 267.77 and 128.10% respectively, as compared to the control treatment.

 Nitrification inhibitors are compounds that slow biological oxidation of ammonium to nitrite by reducing the activity of Nitrosomonas bacteria, without affecting the subsequent oxidation of nitrite to nitrate, either by inhibiting or interfering with the metabolism of nitrifying bacteria. The first step of nitrification is inhibited (i.e., the activity of Nitrosomonas bacteria) by the nitrification inhibitors, while the second step for oxidation of nitrite (NO2-) to nitrate (NO3-) is normally not influenced. In recent years, numerous compounds have been identified and used as nitrification inhibitors, particularly in agricultural soils. They are chemical compounds that slow the nitrification of ammonia, ammonium-containing, or urea-containing fertilizers, which are applied to soil as fertilizers, such as  thiourea, carbon Sulfide,  thioethers, ethylene, 3-amino-1,2,4-triazole, dicyandiamide (DCD), 2-amino-4-chloro-6-methyl pyrimidine, ammonium thiosulphate and 3,4-dimethylpyrazole phosphate (DMPP). These inhibitors reduce the losses of nitrogen in soil. Some nitrification inhibitors are very effective in the efficiency of the nitrogen fertilizers. Recently, a lot of attention has been paid to nitrification inhibitors from an environmental point of view. Some nitrification inhibitors are very expensive and not economically suitable for land application. Nonetheless, many farmers and researchers apply these compounds for many purposes in some specific places. On the other hand, there are many inexpensive natural nitrification inhibitors such as Artemisia powder, Karanj (Pongamia glabra), neem (Azadrachta indica) and tea (Camellia sinensis) waste which can compete with the artificial nitrification inhibitors such as 3, 4-dimethylpyrazole phosphate (DMPP), dicyandiamide (DCD) which are very common nitrification inhibitors. Applying 1.5 kg ha-1 of DMPP is sufficient to achieve optimal nitrification inhibition. 4-dimethylpyrazole phosphate (DMPP) can significantly shrink nitrate (NO3) leaching. 4-dimethylpyrazole phosphate (DMPP) may also decrease N2O emission and the use of DMPP-containing fertilizers can improve yield. The aim of this study was to compare the effect of 3, 4-dimethylpyrazole phosphate (DMPP), Dicyandiamide (DCD) and powder Artemisia (ART) at the presence of Urea, cow manure and Vermicompost.

 Effects of three nitrification inhibitors, (3, 4-dimethylpyrazole phosphate (DMPP), Dicyandiamide (DCD) and powder Artemisia (ART)) at the presence of three nitrogen sources (Urea, cow manure and Vermicompost) were investigated in a calcareous soil under lettuce cultivation in a greenhouse condition.  The changes in the soil mineral nitrogen (nitrate and ammonium), plant nitrogen, nitrate accumulation in leaves and some of growth characteristics such as lettuce chlorophyll content, leaf area index, leaf dry weight and root dry weight were determined. The experiment was carried out in a completely randomized factorial design with three replications. Soil ammonium and nitrate concentration were measured during the experiment. The growth characteristics of lettuce were also measured at the end of experiment. Nitrogen and nitrate contents were also determined in lettuce leaves. 

 The results of the experiment showed that soil nitrate decreased at the presence of three nitrification inhibitors but the soil nitrogen ammonium increased significantly. Application of nitrification inhibitors also reduced the concentration of nitrate in the lettuce leaves during two harvesting times. Moreover, the nitrogen concentration in the plant increased at the presence of nitrification inhibitors. The application of nitrification inhibitors influenced the plant growth characteristics and changed the lettuce growth characteristics. Chlorophyll content increased significantly in lettuce leaves. Leaf area index, leaf and root dry weight of lettuce increased notably when 3, 4-dimethylpyrazole phosphate (DMPP) and powder Artemisia (ART) nitrification inhibitors were applied to the soil samples. These growth characteristics, however, reduced significantly when dicyandiamide nitrification inhibitors was applied to the soil samples. In addition, the symptoms of toxicity were observed in lettuce plant when dicyandiamide nitrification inhibitors were applied to the soil samples. In general, the highest efficiency of nitrification inhibitors was recorded at the presence of urea fertilizer source and the greatest efficiency was observed initially for powder Artemisia (ART) and then for 3, 4-dimethylpyrazole phosphate (DMPP) and dicyandiamide, respectively, when urea fertilizer was applied to the soil samples. There was a positive correlation between soil nitrogen content and plant nitrate in the first and second harvest. The correlation between soil ammonium and plant nitrate (in the first and second harvest) and soil nitrate was negative.

Water deficiency or drought is among the most important factors in reducing crop production (Heidari, et al., 2013). Water deficiency or water stress occurs when transpiration is more than water absorption (Alizadeh, 2008). One of the methods that researchers have been studying to increase water use efficiency and performance over the last decade is the use of superabsorbent polymers and deficit irrigation (Khyrabadi, et al., 2014). The superabsorbent polymer is a kind of hydrocarbon, which absorbs water several times as much as its own weight. Due to the drying of the root environment, the water inside these polymers is gradually evacuated and placed at the disposal of the plan, thus the soil will remain moist for a long time without the need for re-irrigation (Abedi Kupai, And Sohrsb, 2005). Considering that the most important advantage of superabsorbent application is reducing the effect of drought stress, this study investigated the effect of deficit irrigation and different levels of superabsorbent on yield, yield components and water use efficiency of lettuce.

when the loss of water from the leaves by transpiration process exceeds the water in the root zone, water stress occurs. If water uptake reduction functions can predict the flow of water to the roots properly, with no need to field measurements, it is possible to determine the time of irrigation for maximum yield with the help of chemical and physical properties of water and soil and specific plant parameters. From a conceptual point of view, two main approaches of water uptake modeling exist, which differ in the way they predict the volumetric rate of root water uptake. The microscopic models describe the water flow towards the single root. Macroscopic models are based on the principles of energy and mass transfer and described water uptake by the entire root area, regardless of the impact of individual roots. In general, macroscopic models have been considered in plant growth and soil-plant-atmosphere models. The most important models of macroscopic water uptake can be referred to the model of Feddes et al. (1978), the Van-Genuchten model (1987), the Dirksen et al. (1993) and Homaee (1999). Saraei Tabrizi et al. (2015) with an evaluation of the water uptake reduction functions under water stress conditions on basil plant showed that the Homaee (1999) model was more suitable than other models. The purpose of the present study is to evaluate the four macroscopic water uptake reduction functions of Feddes et al., (1978), Van Genuchten (1987), Dirksen et al., (1993) and Homaee (1999) in order to predict water uptake by lettuce root and determining the most suitable model to predict the reduction of water uptake of lettuce under water stress conditions.  The experiment was conducted in a completely randomized design with three replications in 2017 in the research greenhouse of Agriculture Faculty, Shahid Chamran University of Ahvaz. The experiment consisted of irrigation water at three levels (I1:100%, I2:80% and I3:60% of crop water requirement). The soil texture was medium. The cultivation was indirect (seedling) in pots of diameter 22 and height 30 cm. For this purpose, 9 pots were used. The plant's growth period was about 70 days. The irrigation was done by the manual method and by the graduated bushel. During the growing season, treatments were irrigated fifteen times. The volume of water used for treatments I3, I2 and I1 were respectively 792, 1055 and 1320 )m3.ha-1(. The weighted method was used to determine the time of irrigation and the soil moisture characteristic curve was used to measure the matric potential. 12 pots were considered as destructive ones for measuring plant weight as it was not possible to measure the weight of plants per day. In order to evaluate the water uptake reduction functions, relative transpiration was plotted against the absolute value of matric potential and the best model was determined by fitting them, to the measured data. For this purpose, the statistical indicators of the Maximum Error (ME), coefficient of determination (R2), Root Mean Square Error (RMSE), modeling efficiency (EF) and Coefficient of Residual Mass (CRM) were used. Based on the results, the model of Homaee (1999) and the model of Van Gennuchten (1987) had the best fit on the whole range of measured data, respectively. Then, the model of Dirksen et al. (1993) and, the model of  Feddes et al. (1978) were  ranked. In addition, in models that |h| was smaller than 8000 cm, like Feddes et al. (1978), Van Gennuchten (1987), Dirksen et al. (1993) showed good fit and proximity to each other. Babaazadeh et al. (2017) in studying the effect of salinity and drought stress on the uptake of root water of  basil, concluded that the Homaee (1999) model had the best agreement with experimental data and increasing drought stress reduced the potential of water uptake by roots. Also Saraei Tabrizi et al. (2015) concluded that the Homaee (1999) model had the best fit with the measured data and the results were in accordance with the results of this study. Based on the results of this study, for simulation of water uptake, the models of Feddes et al. (1978) and Dirksen et al. (1993) are slightly overestimated and Van Gennuchten (1987) and Homaee (1999) models have slightly underestimated. Homaee (1999) in his research was conducted that in treatment of 70% water requirement supply for alfalfa, Feddes et al. (1978) model was overestimated and other models were underestimated which are close to the results. Homaee (1999) model was more consistent compared to other water uptake models because of considering two thresholds for the model. According to the results, Homaee (1999) model was better than other models (RMSE=9.14 and )‎. The results of the models of Feddes et al. (1978) with R2 =0.43 and RMSE = 16.46, Van Gennuchten (1987) with R2 = 0.51 and RMSE = 8.62 and Dirksen et al. (1993) with R2 = 0.48 and RMSE = 12.5 were closely related to each other.

Co-application of biological fertilizers and phosphate sources have greatly considered in calcareous soilsin recent years. In order to study the effect of phosphate solubilizing bacterium (PSB), phosphate sources and vermicompost on some growth characteristics of lettuce (cv. Ferdos), a greenhouse experiment was conducted with factorial arrangement in a completely randomized design with three replications and three factors. Factors consisted of two levels of phosphate solubilizing bacterium (Pseudomonas flouresence) (with and without inoculation), two levels of vermicompost (0 and 1% w/w) and four phosphate sources (control, rock phosphate, tricalcium phosphate (TCP) and triple super phosphate at 25 mg P kg-1 soil). Biological fertilizers significantly increased shoot fresh and dry weights (SFDW), but they didn’t have remarkable effect on lettuce height. Application of rock phosphate and tricalcium phosphate (TCP) increased dry and fresh weight, respectively. Application of triple super phosphate significantly increased SFDW and lettuce height. Co-application treatments of bacterium, vermicompost and phosphate sources (except super phosphate) significantly increased SFDW, leave numbers and phosphorus concentration of lettuce. Overall, the results indicated that phosphorus chemical fertilizers can be replaced by co-application of insoluble phosphate and biological fertilizers.

Phosphorus is one of the important macro nutrients. Available phosphorus in calcareous soils is low, due to high pH and calcium carbonate, and low amounts of organic matters and moisture, also phosphate minerals are insoluble in such conditions. Arbuscular mycorrhiza inoculation for improving plant growth and yield has become so attractive recently. The symbiosis between plant roots and arbuscular mycorrhizal fungi with increasing phosphorus uptake (through phosphorus uptake by extra and intraradical mycelia and also solubilizing inorganic and organic insoluble phosphates), other nutrients and water cause increase in plant growth. Vermicompost increases the growth of plants due to having nutrients, plant growth regulators and beneficial microorganisms. This research was conducted to evaluate the effect of arbuscular mycorrhizal fungi, vermicompost and phosphate sources on root colonization, shoot fresh and dry weights, number of leaves, chlorophyll index and phosphorus uptake of lettuce in a calcareous soil.
A greenhouse experiments was conducted with factorial arrangement in a completely randomized design with three factors and replications in a calcareous soil. Treatments consisted of two levels of arbuscular mycorrhiza (Claroideoglomus etunicatum (AM)) (with and without inoculation), two levels of vermicompost (0 and 1% w/w) and four phosphate sources (control (P0), rock phosphate (RP), tricalcium phosphate (TCP) and triple super phosphate (SP) at 25 mg P kg-1 level). Non sterile soil was used and its characteristics along with vermicompost were analyzed by standard methods. Seeds of lettuce (Lactuca sativa) cv. Ferdos were planted. After 10 weeks after planting, chlorophyll contents, leaves numbers, fresh and dry weights, root colonization and phosphorus uptake were measured. Data were analyzed with SAS statistical software.
Application of vermicompost increased root colonization and phosphate sources decreased it. The highest rate of root colonization was observed in co-application treatments of vermicompost and arbuscular fungus and in the absence of phosphate sources. Mycorrhizal inoculation increased shoot dry weight and phosphorus uptake. Vermicompost application increased shoot fresh and dry weights, number of leaves, chlorophyll index and phosphorus uptake. Application of SP increased shoot fresh and dry weights and decreased chlorophyll index and phosphorus uptake. Application of RP decreased chlorophyll index and increased shoot dry weight and phosphorus uptake. Co-application of mycorrhizal fungi, vermicompost and phosphate sources increased shoot fresh and dry weights, number of leaves and phosphorus uptake.
Application of biofertilizers (vermicompost and arbuscular fungi) along with insoluble phosphate source (RP and TCP) can be increased phosphorus uptake and plant growth and reduced the consumption of chemical fertilizers especially SP.

Application of organic amendments such as spent mushroom compost has received significant attention due to achieve sustainable production and healthy yield. This is very important in soil organic matter deficient soils. In this research, the effect of spent mushroom compost on growth indices and macroelements (N, P, K and Ca) uptake in lettuce (lactuca sativa L. cv Syaho) was studied based on completely randomized experiment with five replication in greenhouse condition. Experimental treatments were 0 (control), 10, 20, 30,40 and 50% of washed and unwashed spent mushroom compost (SMC) in a sandy loam soil. Some physicochemical properties and bioavailable concentration of macroelements were measured. After growing period, plant was harvested and growth indices like plant height, leaf number and surface, chlorophyll content and stomatal conductance of leaves, dry and wet weight and macro element concentration in lettuce were measured. Orthogonal comparison showed that washed spent mushroom compost in comparison to unwashed one had significant effect on measured parameters (p

Lettuce of Ahvaz (modified) with a scientific name Lactuca sativa varieties Romaine or Cos has one of the highest yields among the different types of country. In this study, the lettuce yield under different treatments was evaluated. The statistical method of this research is factorial design in a randomized complete blocks that major factor is irrigation frequency includes A1 and A2 (1 day and 2 days) and minor factor is irrigation regime that includes B1 and B2 (100% water requirement and 80% of the crop water requirement).This experiment was performed in 4 replicates.For this research,4 chasis in the greenhouse is devoted that plays a rol of replicate.Each block consists of the 12 plants on a row crop that were irrigated by a drip irrigation lateral tape type.For irrigate the crops was used the drip irrigation with tape type, emitters spaced 20 cm diameter of 20 mm.Soil moisture was measured with TDR device.In this experiment, lettuce height was measured during the growing season and the relationship between plant height and number of days were presented with a high correlation. Also water use efficiency was measured. Results showed that irrigation frequency under greenhouse conditions did not cause significant difference on the water use efficiency. Reduction the amount of irrigation water caused that water use efficiency increased significantly. So that the best water use efficiency was happened in the treatment of 80% water requirement with irrigation frequency 2 days to the amount 25.02 kg/m³ and the minimum water use efficiency was happened in the treatment of 100% water requirement with irrigation frequency 1 days to the amount 16.89 kg/m³.

In order to evaluate the influence of different irrigation systems on lateral movement of urea fertilizer and its effect on nitrogen-15 microplot design, an experiment was carried out during 2005-2006 in a randomized complete block (RCB) design (split plot) on lettuce and sugar beet with three treatments and replications. The plot area was 144 m2 and in the middle of each plot, an area about 1 to 3 m2 was selected as an isotopic subplot. The treatments were different irrigation systems (main factor) consisted of trickle fertigation (T1), sprinkler fertigation (T2), and furrow irrigation (T3) and different plant sampling areas (sub factor) consist of central part, first and second guard and non isotopic area. The crops were harvested in different parts of microplots and 15N/14N isotopic ratio was determined by the means of emission spectrometer NOI7. The results showed that, in lettuce culture, central parts of isotopic subplots and first guards were in the same statistical groups and 48% of fertilizers were supplied with the labeled materials. For sugar beet cultivation, central parts of isotopic subplots, first guards and non isotopic parts were situated in three different statistical groups and decreasing slope of nutrient absorption were 31% and 82% respectively. Therefore, for suitable design of isotopic subplots, increasing fertilizer use efficiency is quite necessary and by means of this methodology, low enriched fertilizers can be applied through the field experiment. It is also important to leave one row of plants (as guard) between isotopic and non isotopic rows to prevent lateral movement of nitrogen fertilizer. In this condition, area of isotopic subplots can be shrinked up to 0.56 m2 (in lettuce) and 1.12 m2 (in sugar beet). Under this condition, the efficiency of system can be increased up to the level of plastic barrier isotopic subplots. On the other hands, in furrow treatment, by presence of active rooting system (in accordance with absorption of nitrogen), liner movement of nitrogen were adjusted (along with irrigation channel), and this is the main reasons for similarity of system with drip and sprinkler fertigation methods. In the furrow irrigation system, movements of nitrogen-15 were more complicated. Therefore, the best place of sampling is 25 cm ahead of irrigation water pathway.

In order to investigate the effects of municipal waste compostapplication individually and enriched with chemical fertilizers on the micronutrient concentration in soil and lettuce (Lactuca sativa L.)a three years experiment was conducted with randomized complete block design with two factors and three replications at the experimental farm of Sari Agricultural Sciences and Natural Resources. The Main plot included 6 fertilizers treatments (control, chemical fertilizers, 20 and 40 ton.ha-1 of municipal waste compostindividually and enriched with 50% chemical fertilizers). The Sub-plots were considered as one, two and three-years application of fertilizer. The results showed that the effect of different treatments on Zn and Cu Content of soil, root Fe, Zn and Mn concentration and shoot Zn, Cu and Mn concentration were significant. The results also showed that concentration of the microelement in soil and root and shoot of lettuce were affected significantly by one year, two years and three years application of fertilizers. Interaction of two factors had significant effect on avaiable Cu content of soil and Fe, Zn, Cu, Mn concentration of shoot. Municipal waste compost promoted a significant increase in Zn and Cu plant concentrations in relation to chemical fertilizers. These results imply that municipal waste compost could be a suitable source of Zn and Cu for agricultural soils.

This experiment was conducted at research greenhouse of college of agriculture, Ferdowsi University of Mashhad in 1381-1382. The experiment was designed based on the splitted plots in the form of completely randomized design and in four replications. Irrigation intervals were in three levels of 12, 4, and 2 times per day at primary plots, and three substrates of new perlite, used perlit, and rice bran at secondary plots. We used Paris Island as the lettuce seed. Wet weight, dry weight, and height were influenced from irrigation interval. Accordingly which 4- and 12-day irrigation intervals resulted in 466.39 and 386.94 g corresponding to highest and lowest dry weight, respectively and 12-day irrigation interval arose increase in lettuce height. Significant differences for wet and dry weights were found under different substrates. High wet and dry weights were due to used perlit and rice bran substrates, respectively. There were no significant interactions between irrigation interval and substrate on all of the growth properties of lettuce.

A field study was conducted at the College of Agriculture, Ferdowsi University of Mashhad, to investigate the effect of irrigation with treated municipal wastewater on the yield and quality of lettuce and some soil characteristics. Five irrigation treatments were applied to a clay loam soil, classified as fine loamy mixed mesic Calcixerollic Xerochrepts, in a randomized block design with 5 replications. The treatments consisted of T1 (Irrigation with treated wastewater over all growing season), T2 (Alternate irrigation with treated wastewater and well water), T3 (Irrigation with well water and application of cattle manure), T4 (Irrigation with well water plus fertilizer N and P), and T5 (Irrigation with well water only as control). Chemical analysis of well water proved to be a suitable source for agriculture. The results showed that the yield was higher in T1, T2, T3 and T4 as compared to the control treatment. Maximum fresh and dry yields were obtained from T3 & T1 and T1 & T3, respectively. Plant tissue analysis showed an increase in macronutrients (N, P, K) and heavy metal concentrations in shoots and roots of lettuce in the first four treatments as compared to the control. In T1, iron concentration was maximum while that of cadmium was minimum. Furthermore, microbial contamination was considerably higher in T1 and T2. Soil analysis indicated that in plots treated with wastewater, electrical conductivity, total nitrogen, available phosphorus, soluble boron and heavy metal concentration increased. However, their values were all below international standards. More experiments seem to be necessary in this regard.

Land application of sewage sludge is potentially beneficial as an inexpensive nutrient source. However, problem with the use of sludge may exist from high soil concentrations and subsequent uptake of heavy metals by plant and entering of the metals into the human and animal food chains. A field study with lettuce (Lactuca sativa</sub> L.) and spinach (Spinacia oleracea</em> L.) was conducted to examine uptake of heavy metals from a sludge amended soil as affected by sludge rate and time of sludge application. Sludge rates were 0, 22.5, and 45 ton/ha. To determine the effect of time on heavy metal uptake, a year after the first plants were harvested, one third of each plot was planted without sludge application and to the rest of each plot sludge was added in the same rates as before. Total and EDTA-extractable Cu, Zn, Pb, and Cd concentrations in soil were determined. The metal concentrations in shoots and roots of the plants were determined separately. Total metal concentrations showed an increasing trend with addition of sewage sludge. Copper, Zn, and Pb EDTA-extractable concentrations in soil and concentrations of these metals in the plants increased significantly with sludge rate. Time of sludge application did not have any significant effect on EDTA-extractable and plant uptake of metals. Sewage sludge also increased the crop yields significantly.