Journal of Agricultural Science and Sustainable Production
Year:2011 | Volume:21/2 | Issue:2|Papers Count:14

Some crops have allelopathic effects that could be interested to study the effects on other crops, particularly in rotation and intercropping system. In this study, the allelopathic potential of bell pepper organs extract on seedling growth of cucumber, eggplant, bell pepper, and tomato was separately evaluated using a complete randomized design, in a hydroponic system under greenhouse conditions. The first variable was plant type (cucumber, eggplant, pepper, and tomato) and the second one was pepper organ type that extracted (leaf, root, and stem). Alcoholic extracts (5% w/v) of leaf, root, and stem of pepper were prepared. Then these extracts effects were investigated on all plant growth indices including number of leaves and flowers, root and shoot length, root and shoot fresh weight, and root and shoot dry weight. The results showed that all pepper organs extracts have similar effect on growth characteristics reduction of the other plants. Also, leaf extract had the most effect on reduction of growth of all the plants. It seems that the leaf had the most allelopathic effect as compared with the others. So, this effect may be related to production of allelochemicals in pepper leaves.

The influence of water stress during vegetative and reproductive growth stages on essential oil yield and composition of Iranian dill was evaluated in 2006 and 2007 at the Research Farm of Faculty of Agriculture of the University of Zanjan. Experiments were carried out as split plat design based on randomized complete block in four replications. Irrigation treatments were allocated to main plots and harvest times were assigned to sub plots. Irrigation treatments were full irrigation (control) to achieve 100% of field capacity (FC) during the growth season, two moderate (66% of FC) and two severe (33% of FC) water stresses during vegetative and reproductive stages. Three harvests were carried out at vegetative, full flowering and seed maturity stages. The essential oil contents of the leaves (H1), flowering shoots (H2) and mature seeds (H3) were isolated by hydro distillation and analyzed by GC and GC/MS.24, 29 and 25 compounds were identified from leaves, flowering shoots and seeds respectively. Both moisture availability and harvesting times had significant effects on essential oil content. The percentage and yield of essential oil contents of seeds (H3) and flowering shoots (H2) were much higher than those of leaves (H1) under all irrigation treatments. Essential oil percentage of leaves was increased with decreasing water availability. However, essential oil percentages of seeds and flowering shoot s were considerably high, when plants were subjected to moderate and severe water deficit at different developmental stages. In contrast, the highest essential oil yield (6.146 g/m2) was obtained from flowering shoots under moderate water stress during flowering and seed filling phases (S3H2), while the lowest essential oil yield (0.216 g/m2) was produced from leaves under severe water deficit during early growth stage (S2H1) in both years. The main oil constituents of the leaves and flowering shoot were a-phellandrene, b-phellandrene and b-pinene, while that of seeds oil was carvone (70.78%). The amount apiol increased under severe stress, while carvone content increased under moderate stress. The quality of b-phellandrene was unaffected by irrigation treatments, but the amount of a-phellandrene decreased under moderate and severe water stress.

An experiment was carried out to investigate the effects of different concentrations of gibberellic acid (GA3) as foliar application on growth and essential oil content and yield of lavender based on randomized complete block design with five treatments and four replications. The treatments consisted of different concentrations of gibberellic acid (T2=100, T3=200 and T4=300 mg/l), formulated (tablet) gibberellic acid (T5) and the control (T1=0). Essential oil of dried shoots and flowering stalks were extracted by hydro-distillation method using Clevenger type apparatus. Essential oil yield was calculated in milliliters per square meter based on the essential oil content. The results showed that the highest essential oil content and yield of both shoots and flowers belonged to the 300 mg/l GA3 application. Fresh and dry weight of leaves and stem attained their highest quantities at 300 mg/l GA3 application as well. In contrast, there was significant difference between treatments regarding flowering stalk (inflorescence) fresh and dry weight and the greatest amount for this trait was recorded in the control. GA3 application at 300 mg/l significantly (P<0.05) affected flower bearing plants and the highest number for this trait belonged to the highest level of GA3 i.e.300 mg/l. Like with many of traits, the maximal plant height was also belonged to T4 treatment. Overally, considering the whole results it seems that 300 mg/l GA3 was the most appropriate treatment for foliar spray of lavender plants regarding growth characteristics, essential oil content and yield.

No-tillage is a new approach to increase efficiency of activity inputs and conserving of natural resources. The role of driller and their furrow openers in this system is very important. Amount of soil translocation depends to opener shape which affects some characteristics of furrow such as moisture content in the slot. In this research magnitude of soil translocation and direction of movement for the soil located in the front of new opener were investigated. The new opener which was suitable for no-tillage system fabricated by adding two horizontal disks to traditional double-disk opener. The experiments were conducted with three levels of traveling speed (3, 6, 8 km/hr) and two bulk densities of soil (1.1, 1.4 Mg/m).The experimental design was arranged in a (3×2) complete randomized factorial design with three replications for each test. Few specified colored balls were used to trace direction of movement of soil particles. Results showed amount of soil translocation increased as traveling speed increased. Also movement in the less compacted soil was greater. In a specified condition lateral movement of the particles located in the shallower depth was higher. Although the particles which located deeper moved farther in the direction of traveling but their lateral scattering was smaller. Also, it was found that the direction of soil movement in the seed slot for the novel opener was upward. This can solve the problem of pushing drier soil of surface into seed slot due to using of double-disk opener.

Subsidy is one the important means in consuming agricultural inputs, but as the government is responsible for its costs the countries which have enough financial resources and the extension of economical activities depends on supplying cheap agricultural inputs, can pay for that. Surveying this problem, in this study we examine the effects of eliminating chemical fertilizer and seed subsidies on sugar beet production in Iran. This paper uses panel data for ten provinces during the period of 1379-86. First the sugar beet production function using econometrics methods is estimated, then elasticity of inputs are estimated and after that input’s demand functions are calculated using production function method. The results of input’s demand function indicated that the demand elasticity is low and farmers use water and chemical fertilizer in third area (uneconomic region). Therefore, the subsidy of seed had low effect on its consumption and sugar beet production, and it increased sugar beet production only up to 0.048 percent. According to chemical fertilizer result, it can be concluded that its subsidy even decreases sugar beet production 0.025 percent. Finally we can conclude that subsidy eliminating doesn’t assist to decrease input consumption and environmental damages but it can remove financial burden from government without having negative effect on production.

In order to investigate to the light extinction coefficient, the amount of light interception, leaf area index and the percentage of ground cover in additive intercropping, substitution and sole cropping of barley and vetch, an experiment was carried out in 2008 – 2009 farming year based on randomized complete block design with eight treatments and three replications at the Research Farm of Agricultural, University of Tabriz. The treatments were tested sole cropping of barley and vetch, additive intercropping in the ratio of 100: 15, 100: 30 and 100: 45 and substitution intercropping in the ratio of 2: 1, 3: 1 and 4: 1. The results showed that the most light extinction coefficient and percentage of light interception were related to 100: 30 additive intercropping treatment and the lowest was related to sole cropping. 100: 30 additive intercropping treatment, 20 percent has intercepted more light than sole croppings. Also, leaf area index and the percentage of ground cover in additive mixed treatment were more than sole cropping. This research showed that the additive intercropping treatments due to better utilization of light source is higher performance than substitution mixed treatments and sole cropping of barley and vetch. Also the greatest amount dry forage is 7030 kg/ha obtioned in 100: 15 additive treatment.

If the intercropping components have a complementarity effect in consuming environmental resources, the crop production will be more in intercropping compared to sole crops. A field experiment was carried out in during 2003 to investigate the competition and complementarity between intercropped components of corn and cowpea in nutrient uptake. A randomized complete block design (RCBD) was employed to compare the treatments including cowpea sole crop (Cp), corn sole crop (C), within-row intercropping (M1), alternate intercropping (M2) and mixed intercropping (M3). Intercropping was conducted as replacement method, where one corn plant was replaced by three cowpea plants. The results indicated that nutrient uptake by intercropping was more than sole crop which should be noticified for nutrient supply of the next crops. Cowpea was more competitive than corn in absorbing divalent cations (Ca and Mg) for its high root cation exchange capacity. However, corn was more competitive for phosphorus and potassium which is related to its expanded root system. For all intercrops, relative yield total (RYT) was significantly higher than unity, indicating that corn and cowpea were complement for nutrient consumption. This shows the advantage of intercropping in consuming an effective environmental resource for production, compared to sole crops.

To determination of thermal preferance range, the life cycle of an endemic isolate of each common entomopathogenic nematode species in Iran, Steinernema feltiae Filipjev and Heterorhabditis bacteriophora Poinar was studied, separately. One isolate of each species collected from Tabriz and its suburb soils, were evaluated under four temprature levels viz 4±1, 15±1, 24±2 and 30±1oC on Galleria mellonella L. last instar larvae for 13 days. The experiment was carried out twice, for each isolate. The life cycle of H. bacteriophora was completed at 30±1 and 24±2oC and IJs were appeared in 10th and 12th days post infection, respectively. At 15±1oC up to end of the experiment, only first generation (hermaphrodite females) of the species was appeared and after 312 hours, its life cycle was not completed. At 4±1oC, after 13 days (312 hours post infection) larval mortality due to nematode infectivity was not observed. For S. feltiae at 30±1oC despite insect infectivity, just first generation offsprings were emerged and second generation was not appeared. At 24±2oC the life cycle was completed and IJs observed in 8th day. At 15±1oC, mortality of G. mellonella larvae was occurred with one day delay compared to 24±2oC. The life cycle was completed and IJs appeared in 12th day. At 4±1oC, insect’s mortality due to nematode infection was not observed. Results of this study showed that the preference temperature for S. feltiae activity is lower than H. bacteriophora and the thermal preference ranges should be considered as they are used for biological control of insect pests.

In order to study the effect of nitrogen, vermicompost and nitroxin biofertilizer on quantity and quality yield of Sesame, a field experiment was carried out at Behbahan in summer of 2009. Treatments were arranged in a factorial experiment based on RCBD with three replications. Three rates of nitrogen fertilizer (50, 75 and 100% of region recommended nitrogen rate, equals to 25, 37.5 and 50 kg/ha nitrogen from urea, respectively) as a first factor, three rates of vermicompost (0, 5 and 10 t/ha) as a second factor and two levels of nitroxin biofertilizer application (seed inoculation and non inoculation) as a third factor, were used. Results showed that treatments had a significant effect on yield and yield components of sesame. Nitroxin application increased grain yield 8.5 percent. Interaction of nitrogen and vermicompost showed that the most grain yield (1352 kg/ha) was obtained with applying the 10 t/ha vermicompost with 37/5 kg/ha of nitrogen rate while the lowest grain yield (947 kg/ha) obtained from without vermicompost treatment with 25 kg/ha of nitrogen rate. The highest oil percent (45%) obtained with application of 37/5 kg/ha nitrogen with 10 t/ha vermicompost and the lowest of it (40 %) obtained in 50 kg/ha nitrogen with 10 t/ha Vermicompost. The oil percentage in 50 kg/ha nitrogen treatment, vermicompost application and Nitroxin inoculation decreased the significantly. By increasing nitrogen fertilizer, vermicompost and nitroxin, protein yield and percentage increased significantly.

In order to assess the soybean) Glycin max (L.) Merrill. (grain, oil and protein yield loss caused by interference of natural field weeds and the effects of weed management on weed dry weight loss a n factorial experiment was conducted based on randomized complete blocks design with 3 replications at Research Farm of the University of Tabriz in 2008. Two factors included Johnsongrass water extract spray at four levels as No-spray, one spraying at 15 days after emergence (DAE), two sprays at 15 and 30 DAE and three sprays at 15, 30 and 40 DAE and current weed control methods in four levels as two hand-weedings, Trifluralin (pre-planting application), Trifluralin plus two hand-weedings and weedy infested. Integrated application of pre-planting herbicide and Johnsongrass water extract spray had severe effects on percentage of weed dry weight loss in comparison to application of only herbicide. Also application of water extract at three times showed considerable increase in weed dry weight loss compared to other treatments. The relative damage coefficient (q) of Kropff and Spitters model showed that weeds were more competitor than soybean (q=1.001 and 1.002). The protein yield of soybean suffered a greater reduction as weed density increased. The response of grain, oil and protein yield loss with relative weed dry weight and weed density were linear and hyperbolic, respectively. Increasing of relative weed dry weight decreased oil and grain yield and increasing of weed density decreased protein yield. Results based on model showed that weed density at 9.5 and 20 plant/m2 and relative weed dry weight at 5 and 10.2 caused grain yield loss by 5 and 10 %, respectively. This information about yield loss related to density and relative weed dry weight can be used to determine the acceptable yield loss and weed economic damage threshold.

In order to study the influence of phosphorus biofertilizer on yield and yield components of potato cv. Savalan an experiment was conducted in agricultural and natural resource research center of Hamedan during 2009. The experiment was arranged on complete randomized block design with three replications. The treatments included control and ten other treatment including different levels of bio- fertilizer (biophosphor (BP) and golden biophosphate (GBP)) with or without triple super phosphate (TSP). The results showed that maximum number of tuber per plant (No mean 11.5), tuber weight per plant (1173 g), number of tuber in m2 (63.3) and total (67083 kg ha-1) and marketable yield (65657 kg ha-1) observed in TSP100+GBP300+Thio7.2 treatment. The amount of starch in tuber had positive and high correlation with variation level of phosphorus fertilizer. The highest starch percent in tuber was belonging related to fifth (TSP100+GBP300+Thio3.6) treatment and the lowest protein percent was observed in the T10 (BP10) and T7 TSP100+GBP300+Thio7.2 respectively. The maximum percent of tubers smaller than 35 mm diameter was observed in the T3 (TSP200) moreover tubers with bigger than 55 mm diameter and deformed tuber belonged to control treatment. The maximum percent of tuber with 35-55 mm diameter was observed in T5 (TSP100+GBP300+Thio3.6). Application of phosphate solubilizing microorganisms with mineral phosphor positively affected available and soluble phosphor in the soil.

One of the suitable methods for the movement in regard to sustainable agriculture and environmental conservation is intercropping. On this basis, an experiment was conducted in Station Research of Agricultural Faculty of Tabriz University in 2008. Intercropping pattern was additive series method. The factorial set of treatments was arranged within Randomized Complete Block Design with three replications. The first factor comprised common bean densities of 15, 20 and 25 plants/m2 and the second factor consisted of potato densities of 5, 7.5 and 10 plants/m2 with the same densities of sole cropping of two species. Results showed that the traits of tuber number tuber dry weight and tuber yield per unit area were significantly affected by potato and common bean densities. The highest tuber number was observed at the lowest densities of potato and common bean, but it was higher in 5 plants/m2 potato than that 15 plants/m2 common bean. The highest and the lowest tuber dry weight in per plant were achieved at 10 plants/m2 and 7.5 plants/m2 of potato and at 15 plants/m2 and 25 plants/m2 of common bean. The maximum tuber yield (T/ha) was produced at 10 plants/m2 of potato. Tuber yield was decreased as common bean density increased. Evaluation the advantage of intercropping using Land Equivalent Ratio (LER) showed that the highest LER was observed at 5: 15 (1.643) potato – common bean densities. The treatment combination of 5: 25 potato – common bean had the maximum RVT (Relative Value Total) (1.734). Therefore, in accordance with the high importance of yield economical value for farmers, it was concluded that the treatment combination of 5: 25 potato–common bean was more suitable than those other treatment combinations.