Iranian Journal of Soil Research
Year:2003 | Volume:17 | Issue:2|Papers Count:16

This experiment was conducted to study the effect of Zn-fertilizer on the yield and quality of soybean seed, and to determine the critical level of Zn in the soils of eastern part of Mazandaran Province. The soils had a wide range of CaC03 (5-39%) and DTPA extractable Zn (0.60-3.5 mg/kg soil). In each farm, the experiment was a randomized complete block design with two Zn treatments (0 and 40 kg zinc sulfate per hectare) and three replications. Twenty kg /ha urea as starter fertilizer was applied to all plots. Also, to the soils that had less than 15 mg P/kg (Olsen method) and less than 300 mg K/kg (Ammonium acetate IN pH7), 50 kg triple super phosphate/ha and 100 kg potassium sulfate/ha were added, respectively. The size of each experimental plot was 49 m2 and the planted variety of soybean was Perching. The aerial part of plants was harvested at the end of the growth period. Absolute yield and relative yields, Zn concentration and uptake, 1000 seed weight, number of seeds per plant and seed protein percent were used as plant responses. Parameters. The critical levels of Zn were calculated by Cate-Nelson and Mitcherlich-Bray methods. Application of 40 kg ZnS04 increased seed yield, Zn concentration in seed and Zn uptake by 18.7, 14.7 and 37 percent, respectively, and also 1000 seed weight, number of seeds per plant and seed protein percent were increased by 8, 5.7 and 3.5 percent, respectively. Based on the results, the critical levels of Zn in these soils were 1.25 and 1.30 mg/kg by Mitcherlich-Bray and Cate-Nelson methods, respectively. The results of the two methods were almost identical.

Recently, Bunch Fading Disorder of date palm has extended in important date producing regions of Iran (e.g. Jiroft and Bam). This disorder has only been reported from Iran. It has severely damaged the date growers. Although several investigations have been conducted to identify the responsible agent(s), so far, there has been no success. However, all researchers believe that unsuitable climatic conditions, such as high temperature and low humidity influence the incidence of this disorder. On the other hand, it is confirmed that calcium plays a specific role in cell wall stability and potassium has an important role in the resistance of plants against the environmental stresses, pests and pathogens. Also, balanced nutrition positively affects the plant health. In order to evaluate the effects of foliar application of potassium sulfate and calcium chloride with or without applying micronutrients (to soil) on date bunch fading, an experiment was carried out in randomized complete block design (RCBD) with 6 treatments and 4 replicates in 2002-2003 in Jiroft. The treatments were: control (only nitrogen fertilizer application) (T1); application of fertilizers containing the micronutrients (T2); foliar application of pure calcium chloride (5 kg/1000 . L) (T3); T2 + T3 (T4); foliar application of pure potassium sulfate (5 kg/1000 L) (T5); T2 + T5 (T6). The basin irrigation method was used, and the trees were irrigated every 5-7 days. Foliar applications were carried out at 2A 10 and 15 weeks after pollination. One half of N-fertilizer (as urea) was applied in January with micronutrients, and the next half used in May. The results showed that, foliar application of potassium sulfate and calcium chloride with or without micronutrients addition, were more effective in decreasing the damage of the disorder. Treatments containing potassium decreased the percent of faded fruits and bunches, and subsequently, increased the yield significantly. Foliar application of potassium sulfate with or without adding micronutrients lowered the percent of faded bunches from 69% in control to 19.7% and 21.2% and faded fruits from 66.5% in control to 7.5% and 10.4% and increased the yield by 46% and 65%, respectively. For the first time, these results reveal the useful effects of potassium sulfate application (with or without micronutrients) on decreasing the date bunch fading disorder in Iran.

Extensive areas of sunflower production lands are salt-affected in Qom Province, Iran. Optimum use of chemical fertilizers is necessary for increasing yield and oil seed content. During spring 2001, a field experiment was conducted to investigate the effect of potassium and magnesium and their interaction on growth and yield of sunflower (variety Record) in a saline soil. The treatments consisted of three potassium rates (0, 50 and 100 kg, K__2O ha^-1) and three magnesium rates (0, 75 and 150 kg, Mg O ha^-1) in a split plot experiment with a randomized complete blocks design and three replicates. Seeds of sunflower were planted in 3 f xm plots, and 20 1. xcm spacing. A uniform amount of nitrogen and phosphorus fertilizers) based on soil analysis) as well as the fertilizer treatments were applied in rows. At harvest, seed yield, plant height, head diameter, 1000 seed weight, oil seed content, as well as the concentrations of mineral elements (N, P, K, Ca, Mg, Na and Cl) were determined in sunflower leaves. Results showed that increasing K application significantly enhanced yield and oil seed content (p>0.05). Application of Mg O up to 75 kg ha^-1 level, decreased seed yield, but increased oil seed content; whereas 150 kg Mg O ha^-1 treatment increased seed yield and oil content. In low and middle rates, K and Mg had a positive and significant interaction on the seed yield, plant height, 1000-seed weight and oil seed content. The highest (3638 kg ha^-1) and lowest (2043 kg ha^-1) yields were related to K__100 Mg__0and K__0 Mg__0 treatments, respectively. Also, K and Mg had a positive and significant interactive effect on K/Na, Mg/Na and Ca/Na ratios in the leaf. Application of K decreased Na concentration in the leaf and, as a result, increased plant tolerance to salinity. The use of Mg fertilizer increased yield and oil content of seeds, even though its role in the increase of the yield was less important than potassium.

Wheat (Triticum aestivum L.) is sensitive to zinc deficiency, but less sensitive to iron and copper deficiencies. A series of experiments was carried out at Khosrow-Shahr Agricultural Experiment Station to evaluate the effects of various rates of micronutrients on wheat production under saline condition. The project included four completely randomized block experiments carried out in 10 m2 plots. Various rates of iron, zinc, copper or manganese were tested in three replications with the following treatments: 1control; 2- the recommended rates; 3- the nutrient rate at 50% below the recommended level; and 4- the nutrient rates at 50% above the recommended level. The analysis of variance showed no significant effects of Iron on the seed yield, straw yield, the weight of a thousand seeds, the number of spikes per unit area and on copper concentration in the wheat grain. But, there were significant effects (at 1 % level) due to various rates of iron on the number of seeds per plant, the grain concentrations of iron, zinc, and manganese, and the grain protein content (at 5% level). Also, the effects of various rates of zinc sulfate on straw and grain yield, and the number of spikes per unit area were significant at 5% level, and on the Thousand Kernel Weight (TKW), the number of seeds per plant, the grain protein and zinc contents were significantly affected at 1% level. The analysis of variance showed that the effects of the rates of manganese applications on the grain and straw yields were significant at 5% level and on the grain concentrations of iron and zinc significant at 1% level. Also, the effects of copper on the TKW, the number of spikes per unit area and on the grain iron and zinc concentrations were significant at 1% level and on the grain copper concentration at 5% level.

In order to evaluate the effect of wheat stubble disposal practices during fallow period on wheat yield, protein content, and soil properties, a field study was conducted on a clay loam soil at the Ghamlo station in Kurdistan Province. The experiment was arranged as a Randomized Complete Block Design with four replications. There were five treatments of stubble disposal practices, including control or stubble standing (A1), stubble removing (A2), stubble incorporated into soil (A3), stubble chopped and incorporated into soil(A4), and stubble burning (A5). Besides, two levels of nitrogen fertilizer, including 30 and 60 kg N/ha as Urea were applied in 3 wheat-fallow rotation periods. The results showed that stubble management had significant effect on grain yield, stubble yield and TKW. TreatmentA4 with 1543 kg/ha of grain yield, 3273 kg/ha of stubble yield and 40.7g of TKW was the best treatment. Nitrogen effects were significant on grain and stubble yield but were not significant on TKW. Therefore, N30 treatment was better than N60. Also wheat stubble management practices had positive effects on soil nitrogen and sulfate, grain protein and soil infiltration rate. Treatments A3 and A4 with soil nitrogen contents of 18.44 and 17.19 mg/kg, sulfate contents of 24.42 and 24.45 meq./liter, grain protein contents of 11.77 and 12.06 percent, and cumulative infiltration of 16.05 and 18.74 cm, respectively, were the best treatments in the experiment. Interaction effects of wheat stubble management practices and nitrogen levels were significant on grain yield, straw yield and TKW, such that A4B2, with grain yield of 1678 kg/ha and stubble yield of 3525 kg/ha was the best treatment, and A4B 1, with TKW of 41.07 g, was the best treatment with regard to grain size.

Fifty soil samples were collected from various locations in Gilan Province during 2001. Total populations of the bacteria, phosphate solubilizing bacteria (PSB), the total counts for fungi as well as phosphate solubilizing fungi (PSF) were determined in all 50 soil samples. Total bacterial counts varied from 10^6 to 10^9 cells /g soil, with an average value of 5.82 x 10^7. The PSB populations ranged from 0 to 10^7 cells/g soil with some 94% of the samples containing PSB organisms. The soil sample from Tutestan region contained the greatest PSB population equaling to 3.85 x 106 Cells/_ soil. The average ratios of PSB to total bacteria and to total phosphate solubilizing microorganisms were 3.98% and 88.04%, respectively. The total fungi counts varied from 10^2 to 10^6 cells/g soil, with the lowest count of 6.4 x 10^2 cells/g soil coming from a forest area, and the greatest population of 2.73 x 10^6 cells/ g soil coming from the fermenting residues of a tea processing plant. The average value for total fungi populations was calculated to be 1.92 x 10^5 cells/ g soil in the collected samples. The total fungi population in 82% of the samples was below this average value. Eighty six percent of the soil samples contained PSF ranging up to 10^6 cells/g. The greatest PSF population of 1.8 x 10^5 cells/g was also found in the fermenting residues of the tea processing plant. The average ratios of PSF to total fungi counts and the total phosphate solubilizing organisms were 15.3% and 9.96%, respectively. Bacteria comprised the greatest percentage of phosphate solubilizing microorganisms in the soil samples examined.

This study was carried out to compare the siderophore-producing ability of the native rhizobial strains for selection of superior specimens that could be used as "PGPR" for both legume and non-legume agricultural plants. For this purpose, 447 isolates of Rhizobia from different cross-inoculation groups were tested. The Rhizobia were isolated from important agricultural legumes, cultivated in different regions of Iran and identified according to the standard methods used for rhizobial authentication. In addition, 29 strains of P. fluorescens were used as positive controls (Sid^+). The potential of siderophore production of all bacterial strains was tested using chrom azurol S (CAS)-agar assay. Since the detergent HDTMA in CAS-agar has a tendency to inhibit growth of several microbial species, the usual direct culture onto this medium was compared with half- plate and overlay of two-layer methods. These media were inoculated by the drop plate method, using 7µl of fresh culture of each strain adjusted to 5X10^8 cfu ml^-1, with 3 replications per strain. After the periods of 7, 14, and 21 days of incubation, the diameter of each bacterial growth colony and the orange halo surrounding colony, were measured. The maximum diameter of halo, the ratios of halo to colony, as well as the rate of color-change (mm day^-1) were used as the criteria for comparison of the Sid-producing ability of the strains tested. The results showed that most rhizobial strains were unable to grow directly on CAS-agar plates. M. ciceri had the highest number of CAS + strains (77.3%) and S. meliloti the lowest number (7%). The half-plate method demonstrated the minimum inhibitory effect on the growth of these bacteria. On the basis of this method, around 86% of the tested strains were Sid-producing. However, their abilities were highly different, considering the measured criteria. The best Sid-producers were R__7 and R__38 strains of S. Meliloti, R__305 of R.1.bv phaseoli, R__237 and R__229 of Bradyrhizobium sp., which revealed the highest Sid-production abilities when compared with all strains of P. fluorescens used as the Sid^+ controls.

Qualitative land suitability evaluation is land efficiency assessment for specific utilization. The yield ratings and socio-economic factors are not considered in this evaluation; rather the results are determined by qualitative terms (land classes). In this study, the qualitative land suitability was assessed for irrigated wheat, barley and alfalfa cultivation in Chahshoor plain located in western Iranshahr. Detailed soil survey was carried out in the study area and 9 soil series and 15 different phases were delineated. The evaluation was based on FAO framework and the proposed method of Sys. Crop requirements of the land utilization types were determined using the tables developed by Sys et al. and by Givi. Finally, qualitative land suitability evaluation was carried out according to both simple limitation and parametric approaches by comparing land and climatic characteristics with crop requirements at detailed scale. It was shown that climatic characteristics are not the limiting factors for crop production in the study area. But, some of the soil and topographic characteristics are limiting factors. The limiting factors in wheat production include soil texture, gravel content, and topography. In some of the land units, the limiting factor is soil salinity. The limiting factors for barley production include soil texture, gravel content, and topography, and for alfalfa production include flooding, topography, soil salinity, texture, and gravel content. Also, all land units suitable for wheat production overlap with that of barley. The results showed that qualitative land suitability evaluation classes by the parametric approach are similar to those of the simple limitation approach.

Drought is a natural phenomenon that starts gradually, and extends tranquilly. However, it affects human activities drastically. This creeping disaster happens almost in any kind of climate all over the world, be it humid or dry, when there is a deficit in the precipitations of a certain time period in comparison to the normal precipitation of the same period. Study of drought periods of Mashhad over a 32 years period (1968 - 1999) demonstrates that drought periods in this region are recurring usual events. Almost in every 10 years, there is a severe and long (more than a year) drought period. The trend of 32 years precipitation data reveals that in the recent years duration and frequency of the drought events have increased for all time scales, but their severity has decreased. This study shows that from 1968 to 1999, the most severe one-year drought occurred in 1971, and the wettest one-year period occurred in 1992. Finally, the study proves that the combinations of smalltime-scale droughts, with short durations and great severities, forms large time-scale droughts, with long durations and moderate severities.

A pot experiment in randomized complete block design with four treatments and four replications was conducted to study the effect of different irrigation regimes on growth, yield, water relations and compatible solute; accumulation (proline and total soluble sugars) in basil (Ocimum basilicum). The treatments were: 100%, 85%, 70% and 55% of field capacity. According to the results of statistical analysis, irrigation treatments had significant effects on growth, yield, water relations and amounts of proline and soluble sugars. As the amount of irrigation water decreased, the plant height, stem diameter, leaf area, fresh and dry weight of shoots, fresh and dry weight of roots, leaf relative water content (RWC) and leaf water potential decreased but the root to shoot ratio, proline and total soluble sugars concentration increased. The results of this study showed that basil plant uses osmoregulation by increasing proline and soluble sugars level in order to tolerate the water deficit conditions.

Development of new irrigation technologies is one of the most important solutions to water crisis, especially in recent droughts. During the past years, irrigation technologies have been developed to improve agricultural water efficiency in Iran. The main purpose of this study was to examine the economical, social and technical problems influencing adaptation of drip and sprinkler irrigation systems by the farmers in Kohgiluyeh and Boyrahmad (KB) province. The experimental design was a survey research. The population consisted of the farmers who had the drip and sprinkler irrigation systems on their farms. Fifty-two farmers from 3 counties of KB province were selected with stratified random sampling method. Data were collected with questionnaire. Three extension and education specialists and two irrigation experts examined suitability and face validity of the questions. The Cronbach Alpha coefficient was calculated for determining the internal consistency of the questionnaire. Alpha coefficient for different questions varied from 0.70 to 0.94. The results indicate that responding farmers have little communication with agricultural college professors and agricultural center/station researchers. The results also showed that most of the economical problems that farmers confront with are due to the bank services. One of the main problems is lack of effective quality control of the farm equipments. Furthermore, support and services presented by the equipment suppliers are not adequate. The correlation between farmers^, satisfaction and their technical problems was negative and significant. There was a negative and significant correlation between farmers^, participation in extension/education programs and their technical problems.

Soil infiltration problems occur as a result of irrigation with saline-sodic waters. Knowledge of the soil infiltration parameters is necessary for efficient furrow irrigation. This experiment was carried out in the experimental farm of Tehran University at Karaj, in 2002. The method used for determination of the basic infiltration rate was inflow-outflow. The basic infiltrations were measured on twelve irrigation events using different water qualities (salinity-sodicity). Three water qualities as control (EC=0.6 dS/m, SAR=0.9), low salinity and high SAR (EC=2 dS/m, SAR=10) and high salinity and very high sodicity (EC=6 dS/m, SAR=30) were tested in furrows which were planted with maize. Irrigation water treatments were created by adding NaCl to irrigation water. Results showed that with increasing sodium adsorption ratio in waters, the basic infiltration rate at the end of period reduced markedly than control. Basic infiltration rate decreased about 41% in very high SAR compared with low SAR treatment (control). High SAR value adversely affected the basic infiltration rate. The observed results for these saline-sodic treatments were attributed to formation of a depositional seal layer, soil consolidation and different levels of irrigation water salinity and sodicity.