Iranian Journal of Soil Research
Year:2008 | Volume:22 | Issue:2|Papers Count:14

Effects of nitrogen, phosphorus, and interaction of these nutrients on grain yield of canola variety (Brassica napus L.), hyola 308 was studied under rainfed conditions ( mean annual rainfall of 450 mm) in a calcareous soil (Fine loamy, Carbonatic, Hyperthermic, Typic Calciusteps). The experiment was carried out in a factorial CRB design with three replications for two years (2003-2005). The content of organic matter, available phosphorus and potassium in soil was 0.78%, 10 and 252 mg.kg-1, respectively. Treatments included four rates of nitrogen (0, 30, 60 and 90 Kg N ha-1) and three rates of P (0, 45 and 90 Kg P2O5 ha-1). The results showed that the effects of N, P and N*P interaction was significant on grain yield at a=1%. It can be concluded that application of N, P increase grain yield. N and P application increased significant thousands kernel weight (TKW). According to the results of this experiment, application of 90 Kg N ha-1 and 45 Kg P2O5 ha-1 for similar conditions is recommendable.

Soil phosphorus (P) deficiency is limiting plant growth factors in many soils. The deficiency resulted from P ion exchange, precipitation and transformation. Soil moisture deficiency also limits P uptake by reducing P diffusion and plant root growth. Since, the response of different wheat varieties and genotypes in P and soil moisture uptake and growth might differ. Therefore, differences of wheat varieties for moisture from different depths and P uptake were studied. In order to do this study, experiment was conducted with 6 wheat varieties) Sardari, Azar 2, Sabaln, Ogosta/sefid and Fenkang15/Sefid and Pvn”A”/Bow”S”//Lira"S"/31 Shahi) with randomized complete block design (RCBD) with four replications in Maragheh research station for three years (1380-1383). Soil moisture fluctuations for different wheat varieties in three replications were also determined for two different depths (5-10 and 10-20 cm root zone). Data of different varieties for moisture, P uptake, grain and straw yield were collected and analyzed in Genstat 5. The results showed that soil moisture contents differed significantly (P £0.01) in two different soil depths 5-10 and 10-20 cm. Soil moisture level in 5-10 cm depth in morning measurement compared to afternoon were differed, which were higher than afternoon measurements. In addition, moisture content in root zone for different wheat verities varied. Wheat grain and straw yield, harvest index, P uptake were differed significantly (P£0.01). Sardari, Azar 2 and Ogosta compared to other wheat varieties had greater moisture uptake, leading to increased P uptake grain yield. However, to some extent harvest index was different for wheat varieties. It can be concluded that soil moisture contents were differed for all wheat varieties. Wheat varieties in moisture uptake from different soil depths, and P uptake and grain yield varied. Sardari, Azar 2 and Ogosta had greater moisture and P uptake, and grain yield compared to B31 and Fankang varieties.

Sewage sludge is widely used as a fertilizer and soil conditioner on agricultural lands. However because of high concentration of soluble salts in sewage sludge, it increases soil salinity. The objective of this study was to evaluate the residual and cumulative effects of sludge application on soil salinity. This study was conducted in Lavark experimental site with four rates (0, 25, 50 and 100 ton.ha-1) of sewage sludge. The plots received one, two, three or four years of sludge applications. Corn (Zea mays) and wheat (Triticum sativum) were planted in the first and second half of each year, respectively. Soil samples were collected at the end of wheat growing season at 20 cm increments to 100 cm depth from each plot. Soil samples were analyzed for EC, OC, Na, K, Mg, Ca, Cl, SO4 and HCO3. Sludge application significantly increased concentration of Na, Ca, K and Mg in the soil depths. Concentration of Cl, SO4 and HCO3 also significantly increased with sludge application. However, the effect of residual sludge application on soil salinity was minimal and because of leaching, soil EC did not reach the critical value that affect most plant growths.

Increasing population growth, necessity of food production, increase use of fresh water in industrial expansion, urbanization and cultivation expansion and ultimately low amount of rainfall in arid and semi-arid regions of the country increases the pressure for using saline waters in crop production. Application of proper saline irrigation water managements could maintain optimum crop production and moreover soil salt balance. In this study seven saline irrigation water management treatments were used on Varamin cotton cultivar (Gossypium.hirsutum) production in three replicate in RCBD for three years. The treatments consisted ;application of three saline irrigation waters of 2.9,6.3 and 10.2 dS.m-1 (M1, M2 and M3) during whole growing  season , irrigation with water salinity of 2.9 dS.m-1 in early season (the germination and establishment stages) followed by irrigation  water salinity of 6.3 dS.m-1(M4) or 10.5 dS.m-1 (M5) for the rest of growing season and two alternative saline irrigation water  application managements  of 2.9 dS.m-1 along with 6.3 (M6) or 10.5 dS.m-1 (M7). The results shows that  cotton lint yield reduction in M2 and M3 treatments were about 33 and 66 percent compare with M1 (2.9 dS.m-1) treatment, respectively. Cotton lint yield reduction in M4 and M5 irrigation water management treatments also were 21 and 49 percent relative to M1 treatment respectively. Alternative irrigation of fresh water (2.9 dS.m-1) and moderately saline water (6.3 dS.m-1) or high saline water (10.5 dS.m-1) caused 13 and 40 percent cotton lint yield reduction with respect to M1 treatment. As a result alternative managements of irrigation water application (M6 and M7) could save about 50 percent of fresh water (2.9 dS.m-1) and meantime maintain optimum amount of yield.  The linear regression analysis of the relationship between relative cotton lint yield (Ry) and average salinity of saturated soil paste extract (ECe) during growth period resulted the b ( line slope, expressing percentage yield depression per dS.m-1 ) and a (threshold value) equal to 8.2 and 6.5 dS.m-1 respectively (Ry=100-8.2 (ECe-6.5))with high correlation coefficient (R2=0.88).

Total copper (Cu) content of soil does not necessarily reflect its availability to plants. It is, therefore, important to find a suitable reagents which can predict the plant available Cu in soil to optimize fertilizer use. There is little, if any information available regarding Cu availability in calcareous soils of Iran. The availability of this nutrient is generally low in such soils. Therefore, it is very important to assess the status of Cu availability to plants by chemical extractants. In a greenhouse experiment, Nineteen surface soil samples (0 – 30 cm) with a wide range of physical and chemical properties from different filds in Fars Province for Determination of Available Cu for Rice were collected. The following extractants were used to extract available Cu: Mehlich-3 (MH3), ammonium carbonate - EDTA (AC-EDTA), ammonium bicarbonate-DTPA (AB-DTPA), ammonium acetate-EDTA (AA-EDTA), DTPA-TEA, ammonium acetate (AA), hydrochloric acid (CA), EDTA and Mehlich-2 (MH2). Copper extracted by AA and CA were lower than atomic absorption detection limit and thus was reported as nondetectable. The amount Cu extracted by other extractants were decreased in the following order: AC-EDTA > AA- EDTA > AB- DTPA > MH3 > EDTA > DTPA – TEA > MH2. Although, these methods removed different amounts of Cu from soils, they were significantly correlated with each other. However, the correlation between AC-EDTA and AB-DTPA was higher than the others. Multiple regression equations showed that the most influential soil properties affecting extractable Cu was organic matter (OM). The highest correlation coefficient was obtained between grain yield, and Cu concentration by the grain and top with DTPA. Inclusion of soil properties improved the coefficient of determination. Among the soil characteristics tested, cation exchange capacity (CEC), pH, calcium carbonate equivalent (CCE), and clay content correlated negatively with top dry weight and grain and straw yields. whereas, OM and pH related positively and CCE and CEC negatively with plant Cu concentration and uptake.

For assessment of auxin production from fluorescent Pseudomonads and effects of their inoculation on growth of canola seedlings, a study was conducted using 40 strains of Pseudomonads. Fifteen strains had been originally isolated from rhizosphere of wheat as well as two other strains GRP3 and MPFM were obtained from microbial culture collection of Soil and Water Research Institute (SWRI). Twenty – three strains were isolated from rhizosphere soil samples of canola fields from Karaj region. Bacterial strains were isolated by soil serial dilation culture technique on king B agar plates and were identified using morphological and biochemical tests. Two media, enriched TBS and DF minimal salt supplemented with 0, 50, 100 and 200 mg.l-1 of L-TRP were employed to evaluate the efficiency of strains for production of auxin. The strains were further tested for their effects on canola growth in a sand-based pot experiment. Results revealed that auxin biosynthesis was enhanced as L-TRP concentration was increased in culture medium. Strain P23 was the most effective in auxin production in DF medium supplemented with 200 mg.l-1 of L-TRP. Bacterial strains significantly increased growth of canola.The highest correlation was observed between auxin production in DF minimal salt medium with 50 mg.l-1 of L-TRP and shoot dry weight of plants. These findings imply that the inoculation with auxin producing fluorescent Pseudomonads could promote growth of canola.

In order to investigate the effects of salinity and soil phosphorus on respiration, microbial biomass and phosphatase activities in the rhizosphere of berseem clover (Trifolium alexandrinum L.), an factorial experiment was arranged in a randomized complete block design with four levels of salinity (S1= 0.12, S2= 2, S3= 6 and S4= 10 dS/m) and two levels of phosphorus (P1= 10 and P2= 30 mg/kg ) from KH2PO4 sources with four replications under greenhouse conditions. Different levels of salinity were produced by NaCl, MgCl2, Na2SO4 and MgSO4 with weight proportional 2, 1, 1 and 1 respectively. The traits such as Soil respiration, Substrate-Induced Respiration (SIR), Microbial biomass and activities of Acid and Alkaline phosphatase enzymes in the rhizosphere of berseem clover were measured. The salinity was applied using saline water with the above- mentioned electrical conductivities. The results show that an increase in soil phosphorus increases soil respiration but decreased microbial biomass, SIR and acivities of acid and alkaline phosphatase. All measured traits were reduced with an increase in salinity.

Drought is long periods when precipitation falls below normal, and consequently causes shortage of water resources in the affected regions. Drought results in serious economic, social and environmental impacts. Drought is known as a complicated natural hazard, which is very difficult to be understood fully or described Clearly. We tried to clarify the problem by investigating drought patterns and severity during a long period of 31 years (1970-2001), using climatic data for Khorasan province, I.R.Iran. The investigation showed that general changes for dry periods are more or less uniform over the province. We realized that drought (sever or moderate) occurs time and time in the region and actually is a part of the province climate. We also concluded that on average moderate/mild drought has occurred once every two years; while sever/extreme drought occurs once every 6 or 7 years. It should be noticed that drought severity and duration is different as one moves from the south to the central and northern parts of the province. It is, also, clear that droughts recurrences, severities and durations have been increased during recent years. The most sever drought has been occurred during 1970 and 1990. Comparing the index for different months, we concluded that a long duration drought is made of few merged short period droughts with different severities. Finally we realized that Palmer index is a suitable index for drought monitoring, even though there are some criticism, which challenge the index.

In order to study the effect of application of different quantities of natural zeolite and soil moisture depletion on yield of corn (Zea mays L.) single grass var. 704, a factorial pot experiment was conducted with 12 treatments and three replications in the experimental field of Agriculture Faculty of Tarbiat Modares University. In this study, zeolite was applied at four levels (0, 2, 4, 8 gr.kg-1 soil) while treatments of soil moisture depletion percentages were at three levels (45, 65, 85 % of soil water) during growing season. Soil moisture of pots was measured by weighting method. After harvesting, also same soil chemical characteristic, leaf area, stem height and leaf and stem total protein percentage were determined. Statistical analyses results indicate that zeolite had a significant effect on all measurement parameters but soil moisture depletion percentage didn’t have a significant effect on leaf and stem total protein percentage .Effect of interaction between zeolite and soil moisture depletion levels was not significant on leaf area and plant height, while had a significant effect on leaf and stem total protein percentage. Based on the results of this research, it was concluded that zeolite application at 8 gr.kg-1 soil with 85% soil moisture depletion produced the greatest water use efficiency.

Eeffects of water and nitrogen levels on the yield and nitrate concentration in potato tubers was studied in a field experiment in Agricultural Research Center of Semnan (Shahrood), during 2000 and 2001. In this research a split –plot design was used with two factors. The factors included water (main plot) at four levels (50, 75, 100 and 125 percent of water requirement) and N in subplots at four levels (50,75,100 and 125percent of recommended value based on soil testing). Irrigation requirement was determined using data of class–A evaporation pan. Plants were irrigated in furrows. Irrigation amounts at the aforementioned levels were, respectively, 4000, 6000, 8000, 10000 m3.ha-1 and nitration treatments used were 200,300,400 and 500 kg.ha-1, respectively .The results showed that the effects of water and nitrogen levels and their interaction had significant effects (a=1%) on the yield, such that the maximum yield was obtained with treatments of W125N75, W125N125, W125N100, W75N125 and W75N75 corresponding to tuber yields of 27.8, 27.7, 25.8, 23.7 and 23.5 tons per hectare, respectively. The effects of water and nitrogen on the quality characteristics, such as tubers N content, dry matter and protein percent of potatoes were significant. Maximum concentration of N in tubers was obtained for W 50, while W125 gave the minimum protein percent. Highest water use efficiencies were observed in W75N125 and W75N75, corresponding to 3.97 and 3.90 kg.m-3.ha-1 respectively. The W75N75 treatment was superior to other treatments in terms of higher WUE and lower N concentration.

In a RCB design, effects of deficit irrigation on Canola yield and water use efficiency (WUE) were investigated. Also phonologic stages sensitive to drought stress were determined at Mashhad Agricultural Research Station. Treatments included: I1= without irrigation. I2= irrigation at stem elongation, flower bud development, flowering and pod development stages. I3= irrigation at flower bud development, flowering, and pod development stages. I4= irrigation at stem elongation, flowering and pod development stages. I5= irrigation at flower bud development and pod development stages. I6= irrigation at flowering and pod development stages. Maximum grain yield (2837 kg.ha-1) was obtained from I4 treatment (Duncan’ test , a=0.05). Lowest yield was obtained in I1 treatment equal to 1746 kg.ha-1 .The same treatment also had the lowest percent of seed oil. Because of above-normal precipitation in the second and third year, I1 treatment had the highest water use efficiency as 0.6 kg.m-3 . According to our results, irrigating at stem elongation, flowering , and pod development is necessary for obtaining suitable yield and WUE.

Drinking water demand is presently putting pressure on the City of Rey authorities. With a population of about one million in central Iran, the city relies on groundwater sources to tackle its growing need for the potable water. The quality of the groundwater, which currently contributes up to 50% to the total drinking water demand, has become a major concern. In this research, groundwater contamination in the Rey province and its social health impacts has been investigated. In particular, the problem of groundwater contamination caused by nitrates and bacteria due to anthropogenic activities in the area has been addressed. The study has been encountered with several difficulties such as shortage in proper field data and measurements, the vast study area as well as the complexity of nitrate fate. The main focus has been to identify the contaminant sources in the area, classify the saturated zones, learn about nitrate transport mechanisms and estimate the quantities finally discharged into the groundwater. The employed mathematical groundwater model shows that during a representative simulated 7 years dry period (from 1382 to 1388) the mean groundwater level will drop about 9.5 meters. In the eastern regions the water surface will move from -1.5 to -5 meter, while in the central regions the water surface will fall from -5 to -11 meters. In some areas in the western regions the water surface will even drop more than 22 meter. Groundwater quality model shows that the Rey aquifer consists of several overlying layers. It has been perceived that during the representative dry period, the nitrate concentration will increase in the central and eastern regions. Bearings of an under construction sewage collection network and treatment, however, has not been included in the current study. The new sewage system seems to have some impacts on the nitrate concentration in the Rey province and will put the actual figures lower than that that reported by the current study. The employed mathematical groundwater model (PMWIN) is competent to predict the groundwater potentials for periods of about 10 years. With conventional quality groundwater models, it is only possible to provide predictions up to 2 to 3 years. Which is why the errors of quality groundwater model would be increasingly, mount after 3 years.