Iranian Journal of Soil Research
Year:2005 | Volume:19 | Issue:2|Papers Count:22

This study was conducted to determine the residual effects of P and K fertilizers applied to maize on the yield of wheat in rotation with maize during 1999-2002 at Safi-abad Agricultural Research Center, Dezful. The experimental design was a randomized complete block with three replications and a comparative plot for comparing the effects of fresh P and K fertilization with the residual effects of P and K in each replication. The treatments were four P fertilizer levels (0, 60, 120 and 180 kg/ha P2O5 as TSP) and four K fertilizer levels (0,100, 200 and 300 kg/ha K2O as SOP), which were applied prior to maize planting. The results showed that the residual effect of P on the grain yield and the thousand kernel weight was significant at 1% level, while K residual effect on the grain yield was significant at 5% level. Also, whenever more fertilizer was applied in previous planting, the residual effects of P and K on the grain yield and the thousand kernel weight increased. Also, the residual effect for each fertilizer level on the grain yield and the thousand kernel weight was greater than control plot which received no P and K before cultivation. The grain yield (4.60 tons/ha) resulting from the fresh P and K fertilizer in comparative plots was nearly equal to the grain yield (4.91 ton/ha) obtained with the residual effect of the highest P and K fertilizer levels (180 and 300 kg/ha P2O5 and K2O). The difference between the grain yield of fresh fertilization (100 and 150 kg/ha TSP and SOP, respectively) and the control plots was more than 1 ton/ha (4.6 vs 3.53 ton/ha). Therefore, application of P and K fertilizers in maize can provide some of the nutritional requirements of the next crop (wheat). This finding emphasizes the importance of soil testing rather than the application of general fertilizer recommendations in wheat-corn rotations      

The incidence of die-back in pistachios (Pistacia vera L.) is common in many pistachio producing countries including D.S., Greece, Italy, and South Africa. This problem also occurs extensively in pistachio orchards of Iran where it has caused yields to be low. In order to evaluate the spread, percent occurrences as well as to determine the causative factor(s) of this incidence, some 203 pistachio orchards located in Rafsanjan, Kerman, Yazd and Khorasan regions were visited during the period from 2002 to 2004. It was noted that from 4 to 90 percent, or on the average 28 percent of the trees, had been affected and that the rate of this incidence had increased by 60% during the ten year period from 1994 to 2004. Soil samples from profile depths of 0-40, 41-80 and 81-120 cm were collected in 31 randomly selected orchards for physicochemical analysis. Likewise, leaf samples as well as samples of irrigation water were collected in those orchards for chemical analysis. Then, correlations between the incidence of die-back and the examined factors were calculated. It was noted that the incidence of die-back in pistachios was positively correlated with soil EC, Na, K, SAR, Na/Ca and Na/K values. A stepwise regression analysis yielded the following equation: Y= 51.799-0.194 (K) soil+0.946 (SAR)soil --7 R2= 0.737 On the basis of our findings and the reports by others that the fungus Paecilomyces variotti was the causative agent for die-back in pistachios, a randomized complete block experiment was conducted with 4 treatments and 6 replications on a total of twenty four 25-year old trees of Fandoghi pistachio variety which were 30% affected by die-back problem to investigate the effect of balanced fertilizer application on preventing this incidence. The treatments included T1= the growers conventional method (ammonium sulfate+ triple super phosphate at the rate of 3 kg each per tree); T2=T1+ potassium at the rate of 3kg potassium sulfate per tree; T3= T2+calcium applied as gypsum at the rate of 40 kg/tree; and T4=T3+zinc applied as zinc sulfate at the rate of 1500 g/tree. The direct fungal inoculation of the trees followed two years of the fertilizer treatments. The results showed a significant decrease (at 1% level) in the incidence of die-backs with treatments T2, T3 and T4 as compared with the farmers conventional methods. In other words, the application of potassium, calcium and zinc sulfate reduced this problem by 63 percent.      

Nitrogen use efficiency (NUE) is usually lower in paddy rice (Oryza sativa L.) than upland crops. This is due to nitrogen leaching, denitrification and volatilization. Attempts have been made to increase NUE through the use of different nitrogen (N) carriers, rice cultivars and nitrification and urease inhibitors. Moreover, zinc deficiency is the most important nutrient deficiencies in waterlogged calcareous soils, which causes yield reduction. This greenhouse experiment was conducted to study the effect of four nitrogen sources [urea (U), sulfur-coated urea (SCU), ammonium sulfate (AS) and ammonium chloride (AC) at a nitrogen rate of 200 mg N.kg-1soil] and three Zn rates (0, 5 and 10 mg.kg-1 soil as zinc sulphate). The experiment was factorially arranged in a randomized complete block design with three replications. Application of 20 mg Zn kg-1 soil increased rice growth significantly. The highest top dry weight was obtained with SCU and was followed by AS, AC and U. The highest increase in N concentration was obtained with AS in comparison with other sources. Application of Zn increased N and Zn concentration and uptake. Nitrogen sources and Zn rates had no significant effect on chlorophyll content. Application of 5 mg Zn kg-1 soil, however, increased leaf area significantly.      

Carbon and nitrogen are the most important constituents of the media which help in the synthesis of protein, protoplasm, nucleic acid, enzymes and cell wall materials. The effect of different carbon and nitrogen sources on mycelial growth of Pleurotus eryngii isolates was investigated. Among the carbohydrates tested maltose and galactose were the most effective on mycelia growth of isolates number 80 and 65 respectively. Glutamic acid and peptone produced the maximum growth of isolate No 80. Asparagin and peptone showed maximum growth of No 65. Maximum growth were observed when maltose was used at 22g/lit on isolate No 80 and 20 g/lit on isolate No 65. Maximum growth was obtained when aspargine was used at 3 g/lit on isolate No 80; in case of isolate No 65 maximum growth was recorded at 3 g/lit. It was observed that in the case of the former isolate, the growth continued to increase significantly up to the concentration of 2.5g/lit and then showed a reduction with the increase in concentration up to 6 g/lit.      

A randomized compete block factorial experiment was carried out in East Azarbyjan province during 2003-04 in order to study the effects of rates and sources of nitrogen fertilizers on the yield and quality of two onion varieties. The first factor consisted of four nitrogen levels (50, 120, 180 and 240 kgN/ha) and the second factor consisted of four different sources of nitrogen, namely, urea, ammonium nitrate, sulfur coated urea, and urea-form; and the third factor consisted of two varieties of onions, namely, Qum Red and White Rey. The experimental plots were located at Khosrow Shahr Agr. Res. Station with the soil series as Fine mixed calcareous fluventic exerothents. The results revealed that there were no significant yield differences observed between NI80 and N240 treatment levels. In relation to the effect of nitrogen sources, the greatest yield was obtained with urea-form, but no significant differences were obtained between sulfur coated urea treatment, urea form and ammonium nitrate treatment. Urea-form and sulfur coated urea fertilizers performed considerably better than urea. The best yield of 78 tons/ha of white Qum onions was obtained with the application of 240 kgN/ha. The white Qum onion variety yielded higher than Red Rey onions. The greatest rate of onion spoilage was observed with nitrogen at the rate of N240. With respect to nitrogen sources, urea produced the highest rate of spoilage. The Red Rey onion produced more total soluble solids. The red onion contained the highest nitrate concentrations resulting from nitrogen rate of N240. As with the effect of variety, the highest nitrate concentration of 420 mg/kg was measured with white Qum as compared with the Red Rey variety. The longest bulb was obtained with nitrogen rate of N240. The sharpest taste based on pyruvic acid concentrations was also obtained with the nitrogen rate of N240.Similarly, sulfur coated urea produced the sharpest taste. The Red Rey onions produced sharper taste than the Qum variety. Finally, the largest onions resulted from the nitrogen rates of N240 and N 180.      

Nitrogen is vital for plant growth and influences yield and quality of agronomic and horticultural plants, but the presence of excessive amounts of this nutrient in water supplies has a negative impact on water quality. Sensitive crops may be also affected by nitrogen concentrations above 5 mg L-1. A survey was conducted to investigate nitrate pollution of well waters in Bahar area, Hamadan, western Iran. Nitrate concentration varied from 7 to 122 mg L-1 with an average of 41. Results showed that 18 % of samples had nitrate concentration of less than 25 mg L-1. Nitrate concentrations in 58 % of samples were in the range of 25-50 mg L-1, 18 % of samples were in the range of 51-75 mg L-1 and 6% of samples had concentrations above 75 mg L-1. This indicates that in 24 % of samples the concentration of nitrate is above the recommended guidelines of the World Health Organization (50 mg L 1 NO3 or 11.3 mg L-1 NO3-N). Nitrate concentration in shallow wells was higher than the deep wells. Results showed that concentration of NO3-N in 10 % of samples was less than 5 mg L-1 and 90 % of samples had concentrations in the range of 5 to 30 mg L-1. Improvement in the management of irrigation and fertilizer may reduce nitrate leaching and thus enhance ground water quality.    

Reproduction of selected strains is one of the most expensive stages in the process of inoculum production. Therefore, for large scale industrial production of rhizobiums, efforts are made to use the by-products of food industry plants directly or in combination with some other ingredients as culture media. In this experiment multiplication of S. meliloti in three culture media, namely malt sprout extract, dehydrated cheese whey, and the chemical base medium of yeast extract mannitol along with three nitrogen sources: ammonium chloride, potassium nitrate, and yeast extract; four carbon sources: mannitol, glucose, galactose, and sucrose at two pH levels of 6.8 and 7.0 was investigated. The experiment was designed as a randomized complete block factorial test with three replications. Isolates of SM-11 (S. meliloti) with population densities of 2×l05 cells/ml were transferred to 100 ml Erlenmeyer flasks containing the culture media mentioned before, followed by making plate counts on YMA, growth medium containing Congo-red. After two days of bacterial growth, the results of the experiment showed that the bacterial populations reached a level of 7.94×109 cells/ml in the malt culture containing mannitol as a carbon source and yeast extract as a nitrogen source with the pH of the medium adjusted to 7.0, while the population density in the same medium, but containing sucrose and potassium nitrate adjusted to pH 6.8 was measured to be 4.5× 109 cells/ml, as compared with 5.24×109 cells/ml for the standard YMB culture medium. Likewise, the population density of the bacteria in the chemical base culture at pH of 6.8, was 2.07×109 cell/ml after 3 days and in the same medium containing sucrose and yeast extract at pH of 7.0 was measured to be 5.24×108 cells/ml. These results indicate that, to reproduce this isolate inexpensively on industrial scales for inoculum production, the malt sprout extract growth medium containing sucrose and potassium nitrate is recommendable.    

A field study was conducted to evaluate the effects of bean nodulating rhizobia on the growth and yield of bean. The experiment was carried out in Karaj Soil and Water Research Station using ten strains of native rhizobia, two nitrogen levels (35 and 70 mg N/kg soil) and a control treatment in a randomized complete block design (RCBD) with four replicates. The strains were grown in YMB until the population density of 5×108 cfu/ml was measured then packed following the injection into 25 g samples of powdered perlite. The field soil was analyzed for chemical and physical properties as well as the number of native rhizobia. Seeds of bean (Cv Cos-16) were moistened with a 20% sugar solution and treated with the inocula before planting. N-fertilizer was used in two split applications. Plants were sampled at 50% flowering and at the end of the growth stage. The number and the dry weight of nodules, the shoot dry matter and total N-uptake of the shoots were measured at the first sampling time. With the second sampling, the seed yield, thousand kernel weight and protein content of the seeds were measured. Results showed that the inoculations increased the measured characteristics of plants. The superior strain improved the seed yield by 87% compared to the control.  

During the last decade, much research has been directed towards the potential use of plant growth-promoting rhizobacteria (PGPR). Among the non-symbiotic rhizobacteria, much attention has been given to fluorescent pseudomonas spp., from which many effective inoculants have been prepared. Fluorescent pseudomonads with respect to their ability to produce siderophores and other plant growth promoting characteristics are of first priority for researchers. In order to isolate and identify native pseudomonas strains, 52 soil samples were collected from different locations representing rhizosphere of wheat and were assessed in terms of pseudomonas bacteria. Two hundred and one strains were isolated with King'B medium as fluorescent pseudomonads. The populations of these bacteria ranged between 1.51 *105 to 6* 108 cfu (colony forming unit) per gram soil. To evaluate protein pattern, the isolates were compared by electrophoresis of soluble proteins on polyacrylamide gel. The isolates were classified into 16 electrophoretic protein-polymorphic types based on their protein patterns in SDS-P AGE. The results of physiological and biochemical tests showed that Pseudomonas putida making up 52.73% of the total strains was the dominant genus in the wheat rhizosphere while 44.27 and 3 % of isolates consisted of P. fluorescens and P. aeruginosa, respectively. Therefore, owing to effective colonization of putida and fluorescens strains on wheat rhizosphere, the isolates may be good candidates for making PGPR inoculants.    

Cation exchange capacity (CEC) has a major effect on soil chemical, physical and biological properties. CEC measurement, however, is time consuming and costly. Many attempts have been made to predict CEC indirectly from some easily available soil physical and chemical properties with reasonable accuracy. The objective of this study was to predict soil CEC by pedotransfer functions. Fifty soil samples were collected from Lorestan Province, of which forty samples were used for model development and ten samples were used for validation. CEC, particle size distribution, calcium carbonate and organic carbon percentage of soil samples were measured with ammonium acetate, hydrometry, acid neutralization and Walkly Black methods, respectively. The optimum combination of independent variables for estimation of CEC was selected by using stepwise regression method. The regression equation CEC=- 0.01 +0.233(CLA Y) + 0.00187 (SILT)2+7.69 (O.C)0.5 was obtained using multiple linear regression method. The results showed that there was a significant correlation (R2adj=0.873) between measured and predicted values. Statistical analysis for the evaluation of PTF indicated that GMER= 1.1 and GSDER =1.099. The results indicated that the presented function was valid.    

Seed germination and seedling emergence are two important plant phenologic growth stages. The plant survival, particularly in saline conditions, depends on these phenologic stages. To study the effect of salinity on the germination rate and seedling growth of sorghum (Sorghum bicolor L. Moench) in a natural saline soil and to compare the germination process in natural and artificially made saline water (NaCl + CaCl2 solution), a 3-phase experiment was conducted in randomized complete block design with 13 saline treatments and 3 replications. Germination in the first two phases was carried out in petridishes in an incubator (20°C) and included a non-saline water treatment (EC =0.3 dS/m) and 12 saline water treatments of 2 to 24 dS/m from two sources: natural saline water and NaCl + CaCl2 solution as a charge base. Germination in phase 3 was carried out in a greenhouse in pots containing natural saline soil, treated with saline water having the same salinities. The germinated seeds were counted at desired time intervals until full germination or until two continuous counting were identical. The percentage of germinated seeds and germination rates were then calculated and the results statistically analyzed. The calculated means indicated that germinated seeds and germination rates decreased with salinity increase. But this decrease was greater in natural saline water than in the NaCl + CaCl2 solution. Comparison of seed germination in soil and in incubator showed that the seeds could germinate at all the salinity treatments tested in incubator (in spite of a decrease in the rate of germination), but seed germination rates in soil continued in salinity levels of up to 4 dS/m and decreased with increasing salinity levels up to 14 dS/m. With time, seedling growth decreased with increasing salinity and sometimes fully stopped. The seeds could not germinate and grow in soil salinities more than 14 dS/m. Although seed germination was observed in all saline treatments in the incubator, it seems that sorghum is tolerant to salinity levels of up to 4 dS/m in the germination stage.

Infiltration is one of the most important parameters in irrigation performance. Also farm management affects this parameter directly. In this research the effect of two farm managements on furrow basic infiltration rate (f0) is evaluated in a clay-loam soil. In this study, there were four treatments with three replications in a randomized complete block test. Measurements of f0 were done at the initial, middle and final stages of the season. Blocked furrow method and inflow-outflow method were used for measurement of f0. Based on the results there is no significant difference between the treatments in the beginning and the end of the season. But there is a significant difference in value of f0 in the middle of season. The value of f0 with a 99% level of significance in planted furrows is greater than in non-planted furrows, being the same for both the mulched soil and un mulched soil. It was concluded that only the presence of plants causes this effect. On the other hand, plant roots create some preferential paths which carry water down more rapidly than the soil profile without roots. Also it shows that the f0 in mulched soil is significantly greater than that of the unmalched soil only in the middle of season. These changes are caused by improved soil porosity because of increases in soil organic matter. The results show that the f0 measurement method will have an affect on the value of the f0.    

This study was carried out in 2003 to investigate the effects of different water treatments (40, 60, 80, 100 and 120 percent of water requirement) and different amounts of nitrogen (60, 120 and 180 kg/ha) as well as their interaction on the yield and water use efficiency (WUE) of tomato (Var. Early Urbana). The experiment was performed on the research farm of agriculture faculty of Tehran University (semi-arid area) in a clay loam soil, using a split plot design with three replications (irrigation treatments as main plots and different amounts of nitrogen as sub plots). The results obtained from statistical analysis indicated that the different treatments of irrigation and nitrogen as well as their interactions have significant effect (1% level) on the yield and WUE of tomato. The maximum yield and WUE were obtained at 100% water requirement with 120 kg N/ha. Furthermore, it was observed that reduction of water consumption by 20, 40 and 60 percent reduced the crop yield by 20,57, and 74 percent, respectively.    

One of the relatively new surface irrigation methods is the surge method in which water flows discontinuously. Compared to classic methods, water moves at higher velocities and, as a result, the difference in the time of infiltration between the beginning and the end of the furrow will be minimized, with more infiltration uniformity along the furrow. One of the surface irrigation simulation models is SIRMOD. This model is able to simulate the surge irrigation according to the flow cross section characteristics, the parameters involved in Kostiakofs infiltration equation and other parameters of the surge. In an attempt to use the model, the effect of the variation of different surge parameters using silty loam soil, has been investigated and finally the optimum combination that gives the best efficiency and superior uniformity was identified. The simulation was conducted using four flow rates smaller than and one greater than the erosive flow rate cycle ratios between 0.25 to 0.75 and by fixing the cycle period and other input parameters. The results show that in silty loam soils, the maximum uniformity has been seen in cycle ratios of 2:3 and 3:4 and flow rate of 2 l/s and the maximum efficiency took place in 0.5 l/s with cycle ratio of 3:4.  

Reference evapotranspiration (ETo) is a term used for a grass/alfalfa medium under no-stress condition. ETo can be measured in lysimeters or estimated by the empirical equations. Due to lack of lysimetric data in Golestan province and taking FAO-Penman-Monteith (F-P-M) as a standard method, the radiation and humidity methods were compared with this standard method in synoptic stations of Golestan Province (Gorgan, Gonbad and Marave-Tappeh). In this evaluation, the data used were either raw data or corrected based on local and/or universal conditions. The results showed the accuracy order for these methods to follow the sequence Makkink, Turc, Jensen-Haise and radiation. The results also showed that Gorgan and Gonbad stations did not need any aridity correction, while the Maraveh- Tappeh had to be corrected. When estimated ETo values from radiation methods (e.g. J-H in Maraveh-Tappeh) were corrected by regression equation, the amounts obtained for these methods were applicable in Golestan. The humidity methods were not useful in Golestan, unless they were corrected by suitable regression equations in Gorgan and Gonbad stations.      

Declining ground water level and lack of adequate recharge are the most limiting factors for development projects. Knowledge about methods of water spread systems and their effects on ground water resources along with other natural factors influencing the recharge of aquifers is one of the most important activities that could be assessed in managing water spreading and aquifer recharge projects. The aquifer in Zanjan plain, in north-west of Zanjan City that is covered by the quaternary coarse material depositions of recent are has suitable ground water that can be recharged by the surface flows through the implementation of artificial recharge projects. In this study, the effect of volume of recharge floodwater in flood spreading station of Sohrain-Qarecharian, Zanjan, on the changes of qanat water delivery located in the spreading area has been investigated and compared with the delivery rate of a control qanat located outside of the area. Ground water level changes in the plain and in some observation wells were surveyed during the period 1995 2002. It was observed that during a 7 year period the water delivery of the qanat located in spreading area was highly affected by the amount of water spreading and showed large changes during the spreading times. However, the control qanat, despite having a larger basin, showed no changes. Ground water table changes in 3 observation wells around the spreading area showed that their levels were not affected by drought and rose about 0.5m due to the artificial recharge of groundwater. Whereas, in the control well, the drop in water table continued during this period and was measured to be about 4.5 m. The data on groundwater table of plain also showed no drop and, actually, rose by about 0.5 meter. Finally, this study showed that artificial recharge of aquifers in wet years can prevent water table from dropping and can lead to sustainable management for overcoming the water deficiency during droughts.      

Water exploitation methods, especially for surface water such as rivers, are varied so that every method has its special specifications and the assessment of these methods for different river conditions has an effective role in optimizing the exploitation method. Results of this research showed that, under the conditions where no water resource restrictions existed, diversion dams are more economical in comparison to other methods and are superior to other structures considering that diversion dams have a simple form and farmers are more familiar with them. Pumpage under the conditions where the high flow river sediments deepen, and riverbeds widen, diversion dams are not economical, so that the best method, and in some areas, the only method is the pompage method. Considering the restricted flow of tributaries Qezel Ozen and Rudshor in irrigation periods and geomorphological situation, small earth dams turn out to be suitable constructions, especially in some areas where the only way to control the surface water of tributary is by constructing diversion and proper distribution systems where they can provide enough water for small areas. According to the comparison of cost per unit of water and cost of construction for different methods of water supply, there is no significant correlation between water supply and its cost, and many other natural factors such as discharge of the river, the position of construction, and the situation of agricultural farms are important.