Iranian Journal of Soil Research
Year:2006 | Volume:20 | Issue:1|Papers Count:19

Plant analysis is a useful tool in monitoring nutritional status, recommending fertilizer rates and types, and maximizing fertilizer efficiency, if the chemical analysis results are correctly interpreted. Diagnosis and recommendation integrated system (DRIS) approach is a comprehensive system which does not have limitations of the critical value approach (CVA) and sufficiency range approach (SRA). Pomegranate (Punica granatum L.) is one of Iran's commercial tree crops for which there is no sufficient data available for making fertilizer recommendations. In this investigation the amount of nutrients in leaf samples and yield from 151 pomegranate orchards Throughout Yazd province were determined for two years (1996-98). According to the DRIS technique, the whole population was divided into two groups based on yield performance as high and low yielding sub-population with dividing line of 14 t ha-1 yields. The mean of each sub-population was calculated for various forms of expression. Variance ratios between yield of sub-population for all forms of expressions were calculated along with the coefficient of variation (CV). In order to select the best reference norms two factors were taken into account involving the largest of variance ratio (SB/SA) and the concentration of elements during growth stage. 45 reference norms were selected. DRIS indices for N, P, K, Ca, Mg, Fe, Mn, Zn and Cu were calculated using Quick Basic and Excel software. These reference norms as well as the DRIS indices are useful in determining nutritional problems of pomegranate trees.

This four year study was conducted in an orange orchard in Jahrom Agricultural Research Station to compare the effectiveness of iron sulfate whit iron chelate, as two different sources of iron fertilizer. Fruit yield decreases drastically in citrus orchards of the region, when iron chelate is not applied. So, application of iron chelate is a regular practice in Jahrom orange orchards. The objective of this investigation was a long-term comparison of broadcasted and localized application of iron sulfate, along with fertigation of an iron chelate. As we follow a practical viewpoint, only fruit yield and quality were determined for each treatment. Results showed that application of 100 grams of iron chelate, yielded 22240 kilograms of fruit per hectare. Localized application of 500 grams of iron sulfate, diminished yield 18 percent, to 18291 kilograms per hectare. There was no significant difference between fruit yield in broadcasted and localized application of iron sulfate treatments, results that differed from the findings of similar researches. This may be due to continuous application of organic matter to the soil and the development of tree roots near the soil surface as a consequence of drip irrigation. The iron fertilizer sources did not show any significant effect on fruit quality parameters including crust thickness, acidity, vitamin C and total dissolved salts.

To study the effects of N, P and their interaction on grain yield of safflower under dry farming conditions, a factorial experiment was carried out in a randomized complete block design with twelve treatments, three replications for two years. Treatments consisted of four rates of N (0, 30, 60 and 90 Kg N ha-1) and three rates of P (0, 40 and 80 Kg P2O5ha-1). Investigation on the results of combined analysis of variance showed that the effects of N, P and their interaction on grain yield was significant (α=0.05) and application of N and P increased grain yield. The effect of N, P and their interaction on head per plant was significant (α=0.01) and that the application of N and P increased this parameter. Considering the results of this experiment the application of 60 kg N ha-1 and 40 Kg P2O 5ha-1 for this variety of safflower should be recommended for such climatic conditions.

Lettuce (Lactuca sativa L.) is one of the important salad vegetables, which is consumed daily as contributing to nitrate intakes by humans. The lettuce nitrate contents depend on the plants growing conditions. For example the biochemical reactions within the plant are affected by light intensity and wavelength frequency to the extent that nitrate production and concentrations in the leaves are affected. Two separate experiments were carried out during the spring of 2003 to evaluate the effects of light spectra on the growth rate and nitrate concentrations of the lettuce plant. In the first experiment color filters (bright, blue, green and red) were used to create different light spectra, and in the second experiment different color light sources were used to grow the lettuce plant. The plants were grown under hydroponics conditions in both experiments with completely randomized designs and four replications. The results indicated no significant effects of light sources or filters on the yield of lettuce plant. The fresh weights of the stalks of the mature lettuce plants were significantly reduced by green light so that the ratio of lettuce leaf to stalk was 40 percent greater as compared with the control. The chlorophyll index for lettuce leaf improved in the blue light; however, other light sources had no significant effect on the leaf chlorophyll index as compared with the control. The concentrations of nitrate in lettuce were highest under green light or green filter, which were significantly different from those concentrations of the control samples. The lowest nitrate concentrations of 670 mg/kg were measured with red light and 800 mg/kg with bright filter, 1000 mg/kg for red filter, and 1300 mg/kg of fresh lettuce leaf with bright filter. It appears that the level of nitrate concentrations can not be controlled by color filters but more research in this area is recommended.

Corn (Zea mays L.) is one of the most important agronomic crops in Iran. Potassium and zinc are two essential elements for different crops such as corn. Corn requirement to K and Zn is relatively high. In order to study effects of Zn and different amounts and sources of K the yield and quality of silage corn, in 2002, a field experiment were conducted in Karaj Soil. & Water Research Station with soil K and Zn available 189 and 0.69 mg kg-1, respectively. In this experiment, 12 fertilizer treatments including three levels of K (0,50 and 100 kg ha-1 K2o), two K sources (chloride and sulfate) and two rates of Zn (0 and 10 mg kg-1 Zn) as ZnSO4 were compared by factorial in completely randomized block design with three replications. All of agronomic operations carried out based on research recommendations. The annual results showed that Zn and K application caused increasing in silage yield (14% humidity), Zn and K concentrations and total uptakes in silage significantly (α= 0.05%). But, in general, application of both Zn and potassium together to compare with application of each element alone had better effects on silage yield and the majority of related parameters. Maximum and minimum silage yield were 17,404 and 12,080 kg ha-1 respectively which produced from K50S2Zn10 (application of 50 kg ha-1 K2O as SOP and 10 kg ha-1 Zn at the same time) and control. In general, there was not significant difference between two potassium sources, although potassium sulfate had better effects.

Nitrogen is taken up by the higher plants in both nitrate and ammonium forms with different physiological impacts on the plant. An experiment was conducted to assess the effect of NH4:N03 ratio in nutrient solution on the yield and quality of hydroponically grown strawberry (Fragaria × ananassa Duch) cvs 'Camarosa' and 'Selva'. Six replications per treatment were involved in a randomized complete block experiment. Four nutrient solutions differing in NH4:NO3 ratio (0:100, 25:75, 50:50 and 75:25) were applied. The nutrient solutions had significant effects on the strawberry plants so that the highest leaf area was observed in the plant grown with 25:75 ratios. Flower and fruit number were not affected by the solutions however, the weight of individual fruit increased with 25:75 ratio. Both high ratios of NH4 and NO3 in the solution reduced the yield. The yield was reduced by 33% and 80% in cvs Camarosa and Selva respectively, when the NIL concentration increased from 25% to 75% in the solution. The highest and lowest photosynthesis (pn) rate in both cultivars was observed at 25:75 and 75:25 ratios, respectively. Increased NH4 ratio in the solution significantly reduced post harvest life of the fruits in both cultivars. Both higher leaf area and Pn rate appeared to be the reason for the increased yield and plant growth in the 25:75 ratios of NH4:NO3. Therefore, a combination of two forms of N in an appropriate ratio (25 NH4:75NO3) promote the strawberry plant growth, yield and quality.

Soil water retention curve is a key function that expresses soil vadose zone characteristics quantitatively. The direct measurement of this curve is time-consuming, laborious and costly. Therefore, many attempts have been made to predict water retention curve from other soil characteristics indirectly. Pedotransfer functions (PTFs) is one of the indirect methods. The objective of this research was to study the effect of geometric mean diameter (dg) and geometric standard deviation (σg) calculated the basis of three and nine soil particle size classes in the prediction of soil water retention curve and Van Genuchten equations parameters applying pedotransfer functions. Consequently, 40 loamy soil samples, including 35 samples for prediction and 5 samples for validation, were randomly collected from Karaj area. Particle size distribution, bulk density, calcium carbonate and organic carbon percentages were determined with the hydrometery, cold, acid neutralization and Wally and Blacks methods, respectively. Soil water retention curve was obtained using pressure plates. The best subset of independent variables for estimation of soil water retention curve and Van Genuchten equations parameters were selected by best subset regression command. Regression equations were obtained using multiple linear regressions. The results indicate that there is no significant difference in calculations in predicting point estimation PTFs by using dg or σg obtained from the data of three soil particle size classes or nine soil particle size classes. However, in the case of parametric estimation of water retention at tensions of 10, 33, and 100 kPa, using dg and σg obtained from the data of nine soil particle size classes and at tensions of 300, 500, 1500kPa than using dg and σg obtained from the data based on three soil particle size classes made more valid predictions. Statistical analysis indicated high validity of derived PTFs.

Iran is located in an arid part of the world and water shortage is considered to be the main problem that affects the yields of most agricultural products. One of the many solutions that are suggested includes improving water holding capacity and moisture retention properties of the soils by using hydrophilic polymers. These polymers (Hydrogels) swell in aqueous solutions up to several times their dry weights and thus increase available soil moisture to more favorable levels. Swelling behavior of these materials, including their potential for absorbing and desorbing water under different conditions has led to many applications for soil improvement, particularly in agriculture. When mixed with soil, hydrogel particles are capable of absorbing water. As a result this should efficiently improve the water holding capacity of the soil and promote optimal plant growth, thought controlled releasing of water. In this article the experimental results of ydrogels applications in several types of soils are presented. The effects of ions, and load, on swelling of super absorbent polymers are also evaluated.

Various water uptake models have been developed under salinity and water stress conditions. These models can be considered as useful tools in irrigation scheduling and management, because often they predict reliable crop response under stress conditions. Simulated relative yield of wheat from the five macroscopic water uptake models (Van Genuchten (additive and multiplicative), Dirksen et al., Van Dam et al. and Homaee) were evaluated against the measured results from field experiment that had been conducted during the wheat growing season of 2002 and 2003 north of Gorgan. The treatments consisted of four water quantities 50 (W1), 75 (W2), 100 (W3) and 125 (W4) percent of crop water requirement and four water qualities 1.5 (S1), 8.5 (S2), 11.5 (S3) and 14.2 (S4) dS/m. The experiment was laid out in a randomized complete block design with split plot plan with three replications. It was found that the yield decrease under combined salinity and water stress was additive. However, the effect of osmotic potential on wheat yield was not the same as metric potential. The effect of combined stresses on wheat yield was less compared to sum of the separate effects due to salinity and water stress. The results also indicated that reduction function of Homaee's model was more accurate than the other functions.

Increasing soil organic matter can improve plant growth due to its effects on physical, chemical and biological properties of soil. Transformation of essential elements from organic form under the influences of intra- and extra-cellular enzymes and other microbially mediated processes can increase plant growth. The aim of this study was to identify the effects of different rates and times of sewage sludge application on L-glutamines, alkaline phosphatase, arylsulfatase and ß-glycosidase activities, microbial biomass index and corn yield. Three levels of application (0, 25 and 100 Mg ha-1) and four consecutive times of sewage sludge application (1, 2, 3 and 4) were studied in a randomized complete block split plot design with three replications. Composite soil samples were collected from 0-15 cm depth at the end of 4th year of application. Results illustrated that application of sewage sludge increased soil organic carbon (SOC) and total nitrogen (TN) compared with control treatment. An increasing trend was observed in sac and TN, as the rates and times of applications increased. Increasing the times and rates of application also enhanced L-glutaminase, alkaline phosphatase, arylsulfatase, ß-glucosidase activities, microbial biomass index and corn yield, significantly. The lowest levels of enzyme activities and microbial biomass indices were observed in the control treatment. Four consecutive applications of 100 Mg ha-1 sewage sludge was associated with the highest levels of the bio-indicators. We concluded that functional biodiversity increased in soils that were amended with sewage sludge.

The influence of arbuscular mycorrhizal fungi (AMF) on the nutrition of plants is not well understood under saline conditions. An experiment was carried out in a randomized complete block design with two factors of fungi in three levels, MO (without fungi), Mi (Glomus interaradices) and Mm (Glomus mosseae) and salinity in eight levels. Two kinds of salinity effects were tested including four levels (dS/m) of salts mixture (S1-S4), S1=1.2, S2=4, S3=6.5 and S4=8 and four levels of NaCl (S5-S8), S5=1.2, S6=4, S7=6.5 and S5=8 The seedlings were inoculated separately with two fungi species. After one month, the inoculated plants were transferred to pots containing four kg sterilized sand and salinity treatments were initiated gradually. The results showed significant increases in dry weight of shoot and root, potassium and phosphorous content of shoot, root colonization percent, fruit weight and K/Na in the shoot of mycorrhizal plants in comparison with non-mycorrhizal plants (P<0.05). Although there were no significant differences between two species of fungi both fungi species (Mm and Mi) increased tomato yield (10% and 16%) respectively (P<0.05). The effects of salinity were significant (P<0.001) for the measured variables except for magnesium concentration of root. In comparable salinity levels, K/Na in shoot and Ca/Na in shoot and root were significantly (P<0.05) enhanced more by salt mixtures NaCl salinity.

The continuous use of agricultural machinery in the field results in soil compaction with many long term effects on the physical and chemical properties of the soil and in the case of improper field management may alter and deteriorate soil physical properties. For example the alteration of root depth that results from soil compaction influences water and nutrient uptake as well as the amount of energy and fertilizer used in crop production and eventually affects the environmental conditions, soil fertility and economic returns because soil compaction reduces nutrient uptake and hence decreases plant yields. Biological methods that employ symbiotic fungi (arbuscular mycorrhizae, AM) may be considered to reduce the stressful effects of soil compaction on plant growth. Based on these considerations two years of field experiments were conducted using different species of arbuscular mycorrhiza to reduce the effects of soil compaction on corn nutrient uptake and yield. The experiments were conducted in the research field of Soil and Water Research Institute in Meshkin-Dasht, Karaj using three levels of compaction (in the first year) and three species of arbuscular mycorrhiza in four replicates. In the second year, with regard to the first year's results, an extra level of compaction was added. Using a penetrometer, soil resistance for different soil compaction treatments at certain soil moistures was measured. Soil bulk density was also measured. Corn height, leaf fresh and dry weights and corn yield as well as concentrations of N, P, K, Fe, Mn, Zn and Cu in corn leaf were measured. The results demonstrated that compaction treatments were significantly different. AM treatments significantly increased corn growth parameters and yield. In AM treatments nutrient uptake increased at different levels of soil compaction, though the effectiveness of AM decreased with increasing compaction. It may be concluded that, through increasing nutrient uptake, AM decreases the stressful effects of soil compaction on corn growth resulting in increased corn yield, and this effect may be more pronounced in the medium levels of compaction.

This experiment was carried out at Karaj Soil and Water Research Station during 2002 and 2003 for evaluation of rock phosphate, sulfur, and Thiobacillus on the yield and quality of soybean and their residual effects on corn growth. The experiment was based on a randomized complete block design with six treatments and four replications. The treatments were: T1=control; T2=Triple super phosphate; T3=rock phosphate; T4=rock phosphate + sulfur; T5=rock phosphate + sulfur+ Thiobacillus inoculum; and T6=rock phosphate + sulfur + manure. No phosphorus fertilizer was applied in the control treatment (T1) during the first year, while in the second treatment (T2) 150 kg ha-1 of triple super phosphate was applied in a band below the seeds. Each one of rock phosphate and sulfur was applied in the form of powder at a rate of 300 kg ha-1. Thiobacillus inoculants were used at a rate of one kg ha-1 (108 cellsg-1 inoculum). Composted cow manure was also used at a rate of 10 tons ha-1. Soybean seeds of Williams variety were inoculated with a Bradyrhizobium japonicum before sowing. A SC 704 variety of corn planted in the second year in the same plots used for soybean. No phosphorus fertilizers were applied during the second year, while in T5, Thiobacillus inoculant was used. Soil samples were collected each year from 0-30 cm depth following harvest and leaf sampling. Results of first year indicated that the application of triple super phosphate improved the yield as compared with the control though not significantly (even at 5% level). Rock phosphate application also increased the yield though less than triples super phosphate. T5 increased the yield significantly as compared with the control but no significant differences (at 5 % level) were observed among yields of T5, T2 and T3. There were no significant differences among treatments respect with seed oil concentration. In the second year, the highest forage yield of 67190 kg ha-1 was obtained in T5 which was significantly (at 5% level) differ from T6. No significant yield differences were obtained with the other treatments at 5% level. T2 (triple super phosphate) improved the yield as compared with the control but this increase was not significant.

The potentials of non-symbiotic rhizbacteria for stimulating plant growth have been extensively used during recent decades. The objective of this investigation was to determine the potentials of some indigenous fluorescent Pseudomondas for siderophore production. For this purpose, some 201 strains of Pseudomonas putieda, Pseudomonas fluorescents, and Pseudomonas aeruginosa were studied. Also two imported PGPR strains belonging to the Pseudomonas genus (7NSK2 and GRP3) were used as positive controls (sid+), and MPFMI strain was used as negative control (sid-) The potentials of these strains for siderophore production were evaluated by chrome azorel-S assay (CAS blue agar) through color change. The blue CAS-agar medium was inoculated in a drop plate method with 5 microliter of fresh culture suspensions having a controlled population density of 5x108 CFU/ml in three replications. The diameter of colonies and orange halos around the colonies and their ratio were determined 24, 48, 72, and 96 hours after the inoculation. The results showed that 100% of the Pseudomonas strains were capable of growing on the CAS-agar medium and producing siderophore. The advance of color change was measured to be less than 15 mm/day for 25% of the strains, 15-20 mm/day for 61% of the strains, and more than 20 mm/day for 14% of the strains. A large percentage (75%) of the group with high potentials for siderophore production consisted of Pseudomonas fluorescents strains. Regarding the potential of these strains for siderophore production, the most abundant strain lay within the medium range (15-20 mm/day). The best strains FP136 and FP93 producing about 24 mmlday belonged to the Pseudomonasfluorescens strain. Furthermore, strains FP45, FP165, FP159, FP120, FP190, and FP106 from various species showed much greater potentials for siderophore production as compared with the strains 7NSK2 and GRP3. Considering the superior potentials of FP93, and FP159 strains for auxin production and for solubilizing insoluble phosphates, they are recommended for the production of PGPR inoculum.

Subsurface irrigation with porous pipes is among the microirrigation methods widely used in recent years. However consideration of the hydraulic properties of these pipes is part of the system evaluation. In this research porous pipes were tested under 6 different operating pressures. Relationships for discharge-pressure, discharge variation in lateral length, changing discharge with time, coefficients of variation, emission uniformity, and coefficient of uniformity were obtained. Data were analysed based on American. Society of Agricultural Engineers (ASAE) Standards. The results showed that the operating pressure and time had significant effects on tested parameters and that the porous pipes which are available in Iran are not acceptable for use in irrigation.

For agriculture, Municipal wastewater is marginal quality water and using this for irrigation can be an important consideration when its disposal is being planned in arid and semi-arid regions. In this study, secondary municipal effluent was used for irrigation of tomato. Five different irrigation treatments were designed with three replications. The treatments were: furrow irrigation with normal water (FN); surface drip irrigation with treated wastewater (DI); subsurface drip irrigation in 15cm depths with treated wastewater (SDI15); subsurface drip irrigation in 30cm depths with treated wastewater (SDI30); furrow irrigation with treated wastewater (FW). Crop water requirements were determined by ET-HS model. Also, chemical and microbiological haracteristics of soil, water and crops were analyzed. The results indicated that SDI treatments could control environmental contamination and in comparison with surface irrigation, decrease the pollution problems in the soil such as total coliform and Fecal coliform. The highest water use efficiency (WUE) was obtained with SDI15, which were about 13.15 and 11.64 kg/m3 for tomato and eggplant respectively. A part of this increased yield can be related to better soil moisture and increased available nitrogen in the root zone. Finally, among the sewage treatments, SDI15 produced the least amount of leaching nitrate and heavy elements into the soil. The concentration of these elements in tomato and eggplants samples show that based on the obtained results, and the critical limits, no excess accumulation of these elements was observed. Whenever good quality water is sca.

Canola is one of the oilseed crops, which is grown extensively in Khouzestan Province. As a newly adapted crop, there is not so much information about its water requirement. Its study is the first step in the determination of canola irrigation scheduling and water consumption. An experiment was based on a randomized complete block design with four treatments and three replications. It was carried out from 1379 to 1381 on the Shavoor Agriculture Research Station in Khouzestan province. The station characteristic is: elevation is 32 m from sea level, physiography unit is Alluvial Plain, soil taxonomy is fine mixed hyperthermic Aeric Haplaquepts, topsoil and subsoil textures are silty clay loam and silty clay, respectively. Soil salinity is 2-3 dS/m in topsoil (0-30 cm), pH and %OC are 7.6 and %0.8, respectively. The treatments were: 1) Irrigation interval based on 50 mm cumulative evaporation from class A Evaporation Pan (C.A.E.P) (11).2) Irrigation interval based on 75 mm cumulative evaporation from C.A.E.P (I2). 3) Irrigation interval based on 100 mm cumulative evaporation from C.A.E.P (13).4) Irrigation interval based on 125mm cumulative evaporation from C.A.E.P (14). Water use consumption during experiment will also present irrigation depth. Tilling operation, fertilizer and herbicide, applications planting and harvesting were carried out according to previous technical experiences. The day before irrigation, soil samples were taken to measure moisture content. Depth of irrigation water was calculated by parameters such as soil moisture content (θ), soil moisture content in field capacity (θfc), soil bulk density (ρ) and effective root depth (D). A pump was used for delivering irrigations water and water volume was measured by a flow meter. Grain yield, oil percent and oil yield were also determined. Analysis of variance and means comparison tests were done by Duncan method. So, results are as follows, the best interval of canola irrigation is 75 mm cumulative evaporation from CAE.P. Water use consumption of canola is about 350 to 400 mm for 1.5-2 ton/ ha yields.

In order to determine the water requirement of apricot trees and the best Irrigation systems, an experiment was carried out using a randomiged complete block design in four replications for 6 years. Irrigation water and irrigation systems were used in the following treatments: I1= water application based on 55% evaporation from class A pan; I2= water application at 75% evaporation from class A pan; I3=water application at 110% evaporation from class A pan. D1= Microjet Irrigation system; D2= Drip Irrigation system; and D3=Bobler Irrigation system. For establishment of apricot seedlings all young trees were irrigated uniformly for 3 years. Irrigation systems installed for the fourth year and tested. During the fifth and sixth years all of the trees were irrigated according to the experimental design. The amount of irrigation treatments (I1, I2, I3) were 4950, 6360, 8970 m3/ha in 1380 (2001) and 4650, 6240 and 9020 m3/ha, respectively. in 1381 (2002). Statistical analysis showed that the irrigation treatments highly significantly affected the fruit yield and water use efficiency (WUE) (p<0.01) According to the experimental analysis, the best treatment was I2D3 (application of water based on 75% evaporation from class A pan in Babler irrigation system). In this experiment maximum fruit yield was gained by the 75% accumulative evaporation from class A pan in Bobler irrigation system with 6295 m3/ha water applied