نشریه مدیریت خاک و تولید پایدار
سال دوم شماره 2 (پیاپی 4، پاییز و زمستان 1391)

Land use change from paddy soils to kiwi orchards in north of Iran is one of the most common problems in Mazandaran and Guilan provinces which is mainly caused by agricultural communities to compensate the damages caused by unstable rice marketing. Due to insufficient income of rice cultivation in this area, the conversion of paddy to kiwi orchard is inevitable which causes changes to soil physico-chemical, mineralogical and micromorphological properties. The experimental farm of Rice Research Station (West of Tonekabon, Northern Iran) was selected and 7 pedons were dug, described and sampled and their physicochemical, mineralogical and micromorphological properties were analyzed. Features such as roots rot due to very poor drainage, intense chlorosis and yield decrease of kiwi were the main consequences of incorrect land use change. Available iron and manganese amounts in paddy soils were higher while phosphorus and potassium contents were lower than the soils under kiwi plantation. This could be attributed to the reduced condition and different land management practices. Mineralogical results indicated that smectite was the most dominant mineral in the studied paddy soils while under kiwi fruit land use with moderately drainage condition, smectite content decreased and some vermiculite formed. Micromorphological results also indicated that due to unsaturated condition at the upper layers and high biological activities, pore volume increased and more developed iron features have been revealed after kiwi orchard establishment.

Sewage sludge contains abundant organic matter and essential nutrients such as nitrogen and phosphorus for plant. In addition to having economic benefits, using sewage sludge as fertilizer in agricultural lands is an excellent option for sewage sludge management problem. The main limitation of the use of sewage sludge is high concentrations of heavy metals such as lead and cadmium. The purpose of this study was to evaluate the effect of sewage sludge on soil properties, nutrient uptake, heavy metals and maize yield. Thus, a greenhouse experiment with different levels of sewage sludge application (0, 15, 20 and 25% w/w) was conducted as a completely randomized design with four replications. The Results showed that the application of sewage sludge leads to significant increase of of soil organic matter, electrical conductivity and significant decrease of soil pH at 1% level. Sewage sludge application increased significantly (at 1% level) maize yield, nitrogen, phosphorous and sodium concentration in maize. The results also revealed that the application of sewage sludge increased the lead concentration in maize above ground biomass, but this increase was statistically significant (at 1% level) only in 20% rate of sewage sludge in comparison with control treatment. The application of sewage sludge significantly increased (at 1% level) lead and cadmium concentration in roots.

Microorganisms in soil usually make up less than one percent of the total soil volume and their effect on soil is very high. One of the indicators of soil quality is a sufficient number of microorganisms and their activity in different soils which depends on soil properties. In order to determine the relationship between the bacteria and fungi, with some soil properties 50 soil samples were collected from different areas of Guilan province. Total population of bacteria and fungi and some soil properties were measured in soil samples. For counting the total bacteria and fungi a series dilution of soil and a tenth of milliliter of dilutions spread in three replicates on nutrient agar and martin Rose Bengal Agar petri dishes respectively for enumeration of total bacteria and fungi. Colony count of bacteria and fungi was carried out after a week of culture. The total population of bacteria and fungi were counted and their relationships with soil properties was investigated. Results showed that 50 percent of the samples with electrical conductivity less than or equal to 1 (dS m), their total bacterial population were more than 108 cells per gram. The total population of fungi in all electrical conductivity levels varied, mostly between 104 to 105 cells per gram. About 84 percent of the samples had moisture content of more than 10 percent. In this moisture range, the total population of bacteria of most samples (62 percent) were between 107 to 108 cells per gram. In different percentages of organic matter, in more than 50 percent of the samples the total population of bacteria varied between 107 to 108 cells per gram. In all of organic matter ranges, more than 50 percent of samples had the total population of fungi with 104 to 105 cells per gram. In all ranges of cation exchange capacity (except in less than 10 Cmolc per kg) most of the samples contained the total bacterial population against 107 to 108 cells per gram. In the cation exchange capacity range between 10 to 20 Cmole per kg, the total population of fungi varied in 69.2 percent of the sample between 104 to 105 cells per gram. In all domains of available phosphorous, total bacterial population in the most of samples was between 107 to 108 cells per gram. Distribution of total population of fungi in the range of available P between 10 and 15 mg kg, was higher than other domains.

Land use type is one of the most important factors affecting the soil quality. In this study for evaluating the effects of land use change on soil quality, 18 soil properties (TDS) were determined as soil quality indicators in 60 soil samples of agriculture and range lands with 1800 ha area in southern Mashhad (Iran). Also, pore size distribution curve for 40 soil samples was determined as another indicator of soil quality. The quantitative values of soil quality were calculated by six models (IQITDS, IQIMDS, NQITDS, NQIMDS, CR, and SI) for studied samples. The results showed that changing of land use from range land to agriculture decreased significantly the mean values of soil porosity, water stable aggregate (WSA), the slop of soil moisture curve at inflection point (Sgi index), mean weight diameter of aggregates (MWD) at P<0.01, and soil erodibility factor and plant available water content (PAWC) at P<0.05 and also caused the soil pore size distribution to be out of optimum range. Changing the land use by negative effect on soil physical properties degraded the soil quality. Also, it was shown the significant and positive correlation of macro aggregates (greater than 4 mm) with soil organic carbon percentage and Sgi index at P<0.01. Between studied models three models including IQITDS, NQITDS and SI were more sensitive to the land use change and had a significant difference in two land uses (P<0.01).

Iron-chlorosis is an important problem in peach trees in calcareous soils of Iran and affects over 60% of Iranian soils. In order to assess the status of iron and evaluation of common extractants used for the extraction of available iron for peach in orchard soils of Golestan province, 39 major soils and depths of 0-30 and 30-60 were selected and on the basis of tests and iron extracted with DTPA, 24 soils were selected for further studies. The iron was extracted by DTPA, AB-DTPA, Hydroxyl amin hydrochloride and Mehlich1. In garden studies of the various varieties of peaches that were under chlorosis the benchmark plant and three levels of treatments (Fe0, Fe1) of iron sequestrine-138 (6%) source in 0 and 10 Kg/he rates utilized in split plot experiment with four replications. The results based on the amount of iron extracted by DTPA and AB-DTPA extractant shows significant relationship with chlorophyll concentration in plants. Also Hydroxyl amin hydrochloride extractant showed a significant correlation with total iron concentration. The AB-DTPA was selected as the best extractant, because of its high correlation with chlorophyll content as well as being easy and economical. Also the critical level of iron was determined on the basis of Cate-Nelson GM with AB-DTPA for relative total iron concentration, active iron concentration and chlorophyll meter index was 13, 14 and 13 mg/kg, respectively.

Soil respiration is one of the most sensitive indices which affects soil quality and soil functions. Therefore, a field experiment was conducted in a randomized complete block design with four replications in 2010 on a research farm in Shahrekord University to study the effect of integrated and solitary systems of urea fertilizer, cattle and poultry manures on soil CO2 emission, carbon mineralization potential and dry matter production of sorghum. The treatments consist of control (without fertilizer and manure), solitary application of urea, cattle manure and poultry manure (as inorganic and organic sources, respectively), and three integrated combinations of cattle manure + urea, poultry manure + urea, cattle manure + poultry manure (as 50:50). The results showed that application of poultry manure gave the highest values for the cumulative soil respiration (141.39 gm-2) and respiration rate (3.8 gm-2day-1) and the lowest at the control treatment. The greatest dry matter of sorghum (11.16 Mg ha-1) was observed in solitary application of poultry manure, but there was no significant difference in dry matter between this treatment and treatments with urea. The carbon mineralization potential was not affected by the amendments. It is concluded that poultry manure due to significantly more nutrients compared to other fertilizer sources, has led to increase in dry matter of sorghum. Additionally, poultry manure positively affects soil respiration. Also, substituting the chemical fertilizer by poultry manure can reduce environmental pollution hazard.

Azotobacter is an important bacteria in crop rhizosphere. This research aimed the isolation of local Azotobacter under cultivation of soybean plant in Golestan province and their potential growth promoting-ability. After identification of 30 isolates their ability to molecular nitrogen fixation were tested with Acetylene to Ethylene reduction method. Their ability in auxin production and solubilizing the mineral P were tested with colorimetric method and sidrephore production potential was tested with Cas-agar medium. The maximum nitrogen fixation was in Az26 (428.23 nm.vial.h-1 ethylene) and minimum in Az27 (21.39 nm.vial.h-1 ethylene). Auxin production was highest in Az4 isolate (27.3 mg/l) and lowest in Az20 isolate (0.0157 mg/l). Also maximum sidrephore production was in Az9 and minimum in Az18 observed with diameter halo on colony of 6.36 and 2.24 in 72 hours respectively.

In order to evaluate the influence of different irrigation systems on lateral movement of urea fertilizer and its effect on nitrogen-15 microplot design, an experiment was carried out during 2005-2006 in a randomized complete block (RCB) design (split plot) on lettuce and sugar beet with three treatments and replications. The plot area was 144 m2 and in the middle of each plot, an area about 1 to 3 m2 was selected as an isotopic subplot. The treatments were different irrigation systems (main factor) consisted of trickle fertigation (T1), sprinkler fertigation (T2), and furrow irrigation (T3) and different plant sampling areas (sub factor) consist of central part, first and second guard and non isotopic area. The crops were harvested in different parts of microplots and 15N/14N isotopic ratio was determined by the means of emission spectrometer NOI7. The results showed that, in lettuce culture, central parts of isotopic subplots and first guards were in the same statistical groups and 48% of fertilizers were supplied with the labeled materials. For sugar beet cultivation, central parts of isotopic subplots, first guards and non isotopic parts were situated in three different statistical groups and decreasing slope of nutrient absorption were 31% and 82% respectively. Therefore, for suitable design of isotopic subplots, increasing fertilizer use efficiency is quite necessary and by means of this methodology, low enriched fertilizers can be applied through the field experiment. It is also important to leave one row of plants (as guard) between isotopic and non isotopic rows to prevent lateral movement of nitrogen fertilizer. In this condition, area of isotopic subplots can be shrinked up to 0.56 m2 (in lettuce) and 1.12 m2 (in sugar beet). Under this condition, the efficiency of system can be increased up to the level of plastic barrier isotopic subplots. On the other hands, in furrow treatment, by presence of active rooting system (in accordance with absorption of nitrogen), liner movement of nitrogen were adjusted (along with irrigation channel), and this is the main reasons for similarity of system with drip and sprinkler fertigation methods. In the furrow irrigation system, movements of nitrogen-15 were more complicated. Therefore, the best place of sampling is 25 cm ahead of irrigation water pathway.

Azospirillum and Pseudomonas bacteria are as plant growth promoting rhizobacteria that can stimulate growth and increase plant resistance to stress conditions such as drought and salinity. In order to evaluate the ability of different strains of these bacteria on the reduction of salinity in canola, three species of Azospirillum and two species of Pseudomonas isolated from the rhizosphere of canola were inoculated. This experiment was performed in the Department of Soil and Water Research in Agriculture and Natural Resources Research Center of Golestan in greenhouse conditions and in special glass containers (Jar Leonard) containing Hoagland's solution. A factorial experiment was conducted in completely randomized design with three replications. Factors include canola varieties at two levels (Hyola 401 and RGS 003), salinity at three levels (0, 80 and 160 mM sodium chloride) and bacterial isolates included six levels (Ba1=A. irakense DSM 11586, Ba2=A. irakense 49, Ba3=Azosprillum lipoferum 45, Ba4=P. fluorescens, Ba5=P. putida and control=not inoculated) respectively. The Results showed that with increasing salinity up to 160 mM NaCl, parameters as shoot fresh and dry weight, leaf number and leaf area per plant are reduced in the rapeseed plant. Both varieties of canola seeds inoculated with different bacteria reduced effects of salinity. The effect of salinity on seedlings inoculated with strain A. irakense DSM 11586 was less than the rest. The concentrations of Zinc and Iron in the inoculated cultivar with strain A. lipoferum 45 were higher. Manganese was the highest amount in plants inoculated with strain A. irakense DSM 11586.

Using microorganisms among the suggested remedies for oil pollution problembs and its destructive effects is a way which is used as the title of bioremediation in most developed countries. Using bioremediation to remove pollution from polluted areas is limited by means of some bioenvironmental parameters. Nutrients are one of these elements. In this study four types of bacteria were isolated from the Boushehr Soils. The mentioned kinds were nominated as Pseudomonas stutzeri, Chryseo bacterium Sp, Acinetobacter Johnsonii, Pseudomonas aeruginosa. These bacteria were studied from the aspect of their ability to degrade phenanthrene in different P concentrations and in different periods of time. The results showed that the best phosphorus concentration in biodegradation of phenanthrene equals to 2 mgr/lit, and the best performances is related to bacterial pseudomonas aeruginosa, and the best of time in biodegradation phenanthrene is 144 hours.