مجله مدیریت خاک
سال سوم شماره 1 (پیاپی 4، بهار و تابستان 1393)

A greenhouse study was conducted to compare the abundance and functional diversity of endorhizobacteria of pistachio seedlings grown in three soils with different chemical and physical characteristics. After two months, the abundance of endorhizobacteria and some important plant growth promoting-properties including Indole Acetic Acid (IAA) production, nitrogen fixation and ACC utilization as the sole source of nitrogen were determined. The results showed that the abundance of endorhizobacteria was the highest in soil 2, which contained the highest organic carbon content. Also, the abundance of endorhizobacteria isolated from soil 1, 2 and 3 were 48.5, 60 and 53 % for IAA production; 27.3, 62.9 and 50 % for nitrogen fixation; and 15.2, 48.6 and 16.7 % for ACC utilization, respectively. Based on high organic carbon content, high abundance of endorhizobacteria in soil 2 and their high capability in production of plant growth promoting compounds, it seems that there is a relationship between soil organic carbon and endorhizobacteria population and also the abundance of these bacteria.

The goal of research was to study the spatial structure and mapping the spatial distribution of some soil micronutrients using geostatistics. For this propose, 390 soil samples were taken from agricultural soils in Maragheh located in southwest of East Azarbayjan. Soil samples were analyzed using standard methods and the amounts of available Iron (Fe), Zinc (Zn), Manganese (Mn) and Copper (Cu) were measured. Nutrient semi-variograms were developed and then a suitable theory model was fitted to data. The information generated from the fitted models was applied to make use of ordinary kriging and estimating the value of micronutrients in unknown locations. The results revealed that distribution of micronutrient data sets had no random pattern and there was a spatial correlation between micronutrient. Zn had a strong spatial structure (Nug/Sill=10.87%), but Fe, Mn and Cu had a moderate spatial structure. Semi-variograms of all the nutrients were fitted to exponential and spherical models. The maximum and minimum ranges were found for Zn and Cu with 3540 m and 15000 m distance, respectively. Generated maps showed that the studied arable soils were suffered from Zn and Fe deficiency, had an optimum level of Mn and an excessive amount of Cu. These maps can useful for agricultural soil quality management especially in large scale.

Nowadays, nitrogen fertilizers are applied at very high rates in agriculture with a negative consequence for environment and groundwater contamination. Therefore, soil and fertilizer management practices are necessary to protect and conserve the soil and environment resources.The aim of this investigation was to study the consequence of NH4+-enriched zeolite application on the retention of nitrate and ammonium ions in two soils with different textures under wheat cultivation. In this greenhouse study, the effect of urea fertilizer in one level (100 kg/ha), raw zeolite in two levels (5 and 10% w), NH4+-enriched zeolite in two levels (5 and 10% w) on the amount of nitrogen leaching was investigated in two soils with clay loam and sandy loam textures during eight irrigation events. At the end of wheat growth and leaching stages, soil samples were obtained and the concentrations of nitrate and ammonium in soil, wheat plant and drainage water were measured. The study showed that nitrate concentration of drainage water in 10% NH4+-enriched zeolite treatment was 38.5% less than that in fertilizer treatments. Soil nitrate and ammonium were increased by 37.2 and 48.5%, respectively, without an effect on plant N. Therefore, adding NH4+-enrched zeolite to the soil, reduced nitrate and ammonium leaching and increased their retention in the soil.

Wheat is planted in several million ha of hummocky land of Zagros area. Considering high precipitation in this area, it is important to study nitrogen application management with respect to soil, water and environmental protection. This study was conducted in rainfed wheat fields located on different slope positions. Soil properties, crop yield, N uptake and residual soil N were determined in 100 points of rainfed cultivated wheat. The results showed that soil characteristics and crop yield varied in different slope positions. The highest and the lowest crop yields were obtained in toeslope and shoulder, respectively. Maximum and minimum N uptake and residual soil N were also observed in the same slope positions. Soil N in toeslope had a movement toward downhill and was higher than wheat requirement. Thus, residual soil N in this position may be exposed to the soil surface erosion and move on to the waterways and deep percolation to ground water during intermittent years, and thus the excess N in the soil would probably lead to soil and water contamination. Based on the results of this investigation and in order to prevent N losses, it is recommended that N application should be managed to use less N in all slope positions, especially in the toeslope, to split application of N fertilizers in appropriate times, and to use organic.

In order to investigate the effects of soil/water petroleum contamination on soil hydrophobicity, part of the green-landscape area around Isfahan Oil Refinery was selected. Due to poor management of green spaces, soil was polluted by oil sludge and some of trees were destroyed. The soils which have been contaminated with petroleum wastes and the reference (uncontaminated soils) were sampled. In addition, the well water in the area which was also contaminated with the petroleum compounds was sampled. In situ water drop penetration time (WDPT) test was done on the contaminated soils. To assess the effects of petroleum pollution of water, the soil samples were repacked and were undergone wet-dry cycles using the contaminated well water and uncontaminated water. Then, hydrophobicity tests including molarity of ethanol droplet (MED), water/ethanol sorptivity (Sorptivity W & E) and capillary rise method (CRM) were done on the soil samples. Results showed that soil petroleum contamination induced hydrophobicity, significantly increased water repellency index (R) and decreased cosθ (P<0.001). The effect of water pollution on R and cosθ was significant at 0.001 and 1%, respectively. Thus, the wetting/drying with the petroleum contaminated water intensified the soil hydrophobicity. Positive and significant correlations were obtained between organic indices and water repellency index and significant negative correlations were observed between cosθ and organic indices. Thus, both soil and water petroleum contamination have induced and intensified soil hydrophobicity in the studied area.

Understanding the consequences of application of organic and inorganic soil amendments is very usefull in management of low-fertile soils. The objective of this study was to evaluate the influence of addition of natural zeolite, cow and poultry manures on some chemical properties in soils cultivated with maize. Two series of experiments were conducted separately in a loamy sand soil and in a clay soil. The studied factors were zeolite (at three levels of 0%, 10% and 20%), manures at a rate of 20 g kg-1 of dry weight basis (no manure, poultry manure and cow manure) and soil sampling zone at two levels including rhizosphere and nonrhizosphere. At the flowering stage of maize growth, soil samples from the rhizosphere and nonrhizosphere zones were analyzed. The result showed that addition of zeolite and manures to both loamy sand and clay soils changed the soil chemical properties considerably, increasing soil pH only in clay soil and cation exchang capacity (CEC), exchangeable+soluble K and salinity in both soils. However, available P was decreased significantly in the light soil treated with zeolite and cultivated with maize. The addition of manures especially poultry manure increased the CEC of the light soil, and available P and exchangeable+soluble K in both soils. Rhizosphere soils compared to nonrhizosphere soils had significantly (P<0.05) lower pH and available P and exchangeable+soluble K but higher CEC and EC in all treatments.