نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و دوم شماره 1 (بهار 1397)

This study was carried out to evaluate the effects of soil and foliar applied chemical fertilizers and foliar organic acids (as leonardite; a mixture of humic and fulvic acids) on yield and yield components and nutrient uptake by wheat. The experiment was laid out in Gorgan University of Agricultural Sciences and Natural Resources Farm during 2013- 2014, using a split-plot design with four replications. Treatments included potassium application and without potassium in the main plots and foliar applications of nitrogen, potassium, and leonardite from two different sources (Humic Power, mega humat) and a control without foliar application in subplots. Maximum root length before heading was obtained by Humic Power (11.6 cm) and, at harvest, by megahumat (16.4 cm), both in potassium treated sub plots. Root weights also followed the same trend. This may be due to growth stimulating effects of humic acids. Greatest phosphorous uptakes were 19.2 and 48.75 kg.ha-1 by straw and grain, respectively, by foliar application of megahumat in soil potassium applied plots. Foliar applications of nitrogen and potassium also enhanced nitrogen and potassium uptake, respectively. The interactions between foliar and soil applied treatments on stem length and straw yield were significant by analysis of variance. Their combined application significantly improved plant height and straw yield. This research showed that yield by foliar application of leonardite (from both sources) was greater than yield by foliar use of nitrogen and potassium irrespective of soil potassium applications. Soil potassium applications enhanced yield and nutrient uptakes by foliar treatments.

Nowadays, due to limited water resources and low soil fertility, especially in arid and semi-arid regions, the use of water with low quality (such as saline water) and soil amendments such as biochar is essential. Biochar is a kind of charcoal produced from plant residue and animal manure, which improves soil physical and chemical properties due to its porous structure. Therefore, the current research was conducted to investigate the effect of different levels of saline irrigation water and biochar on soil chemical properties under faba bean cultivation. Four saline irrigation water treatments having EC values of 0.5, 2.5, 5 and 7.5 dS m-1 and four levels of biochar including 0, 1.25, 2.5 and 3.75 % w/w were applied based on completely randomized design with three replications. Chemical properties such as potassium, calcium, and sodium ions concentration, sodium adsorption ratio, and electrical conductivity of saturated extract were measured in two depths of 0-10 and 10-20 cm. The results showed that increase in salinity and biochar levels increased the amount of sodium, potassium, and calcium ions and also soil electrical conductivity. Further, all ions concentration, sodium adsorption ratio, and electrical conductivity in the depth of 0-10 cm were higher than 10-20 cm depth, due to soil evaporation and water and solute movement towards upper layer. According to the results obtained in this study, it can be concluded that the use of biochar as a rich source of plant nutrients can greatly increase availability of nutrients such as calcium and potassium in soil, but, the negative effects of biochar application, such as increasing salinity, should be considered.

Addition of plant species residues to soils can add high amounts of potassium (K) as well as carbon sequestration. In the current investigation, residues of three plant species including Ziziphus spina Christi L., Phragmites australis and Atriplex halimus L. were collected from Darab plain and converted to biochars at 500 °C for 3 h under oxygen-limited condition. The soil used in the study was collected from a field in Darab at depth of 0-30 cm. Experiment was done using a completely randomized design with 7 treatments (plant residues, their biochars and control) and 3 replicates. Three percent of plant residues or biochars was added to the soil. Soil samples were incubated for 2 months at FC moisture and 22 °C temperature condition. Then, pH, EC, CEC and the contents of soluble, exchangeable, and non-exchangeable K of soil samples were determined. Results indicated that application of Ziziphus spina Christi biochar, Atriplex halimus leaves and Atriplex halimus biochar significantly increased soil pH. All residues and biochars increased EC from 0.43 (Ziziphus spina Christi biochar) to 3.57 dS m-1 (Atriplex halimus biochar). Biochars had more effect on soil EC than residues. Biochars had no effect on CEC, but Ziziphus spina Christi L. and Phragmites australis increased it significantly. Application of residues and biochars significantly increased soluble (144-937 mg kg-1), exchangeable (354-1430 mg kg-1), non-exchangeable (379-607 mg kg-1) and HNO3-extractable K (1030-2918 mg kg-1) and biochars had more effect than residues. Generally, Atriplex halimus leaves were more effective than Ziziphus spina Christi and Phragmites australis residues on soil properties and K forms contents. Residues and biochars application concentrated K in the exchangeable form (34-49 %). For application of these compounds, especially in the case of Atriplex halimus L., their effects on soil salinity and pH should be considered.

Iran is one of the most important watermelon producing countries and globally ranks the second in terms of watermelon cultivated area. Kerman Province is in the southeast of Iran and ranks the first watermelon producing province in the country. However, in the last decade, drought, physical and chemical properties of soil, poor quality irrigation water, lack of proper and balanced nutrients have caused outbreak of blossom-end rot, leading to quantitative and qualitative losses in watermelon. Therefore, effects of simultaneous application of organic matter, potassium, and calcium on yield, chemical composition, and blossom-end rot of watermelon were investigated. The studied variables included organic matter (0 and 20 ton/ha of animal manure), potassium sulfate (0, 250. and 350 kg/ha) and calcium chelate foliar application (0 and 4 g/L). The project was conducted in Randomized Complete Block Design in Faryab in southeast of Iran. The irrigation water salinity was 2100 µs/cm. Results revealed that organic matter application and foliar calcium chelate caused increase in yield, calcium, iron and zinc concentration in the plant, and decrease in blossom-end rot of watermelon fruit significantly. Moreover, potassium sulfate led to yield increase, but its application more than 250 kg/ha caused concentration reduction in calcium, iron, and zinc in plant and increase in blossom-end rot.

The effect of zeolite as a soil conditioner that is used for improving physico-chemical soil properties, improving nitrogen use efficiency, and decreasing nitrogen losses has not been studied on leaching of nitrogen from different sources. Therefore, this study was conducted as a factorial greenhouse experiment using a completely randomized design with 3 replications. The objective was to evaluate the effect of 4 levels of zeolite (0, 15, 30 and 45 g zeolite kg-1 soil) on leaching of nitrogen from different nitrogen fertilizers (control and application of 150 mg N kg-1 soil from urea, ammonium sulfate and nano- N- fertilizer) in a calcareous soil under Ocimum basilicum (var. Green Ardestani) planting. At 4 stages, the leachate of experimental pots was collected and nitrate concentration was determined. After harvesting, ammonium, nitrate, and total nitrogen concentrations of postharvest soils were also determined. Application of 15, 30 and 45 g zeolite kg-1 soil increased ammonium concentration of soil by 16%, 13%, and 22 %, and nitrate concentration by 50%, 130%, and 170 % as compared to control, respectively. Application of 30 and 45 g zeolite kg-1 soil increased total nitrogen concentration by 42% and 28 %, respectively. Among the applied levels of zeolite, only application of 45 g zeolite kg-1 soil significantly decreased nitrate concentration in leachates at different stages. The amount of ammonium, nitrate, and total nitrogen were the highest for soils that received nano-N- fertilizer. Furthermore, nitrate concentration in leachate at different stages was the least when soils received nano-N- fertilizer. In general, zeolite increased nitrogen retention from the studied fertilizers and resulted in lower nitrate leaching through soils. Among the studied treatments, application of 45 g zeolite kg-1 soil and using nano- N- fertilizer were the most effective in nitrogen retention and decreasing nitrogen in leachate. Therefore, it is recommended that these treatments be used in field conditions if complementary field trials confirm the results of this greenhouse experiment.

The aim of this research was to determine the Ca concentration in citrus fruit peel and different vegetative organs, trend of Ca changes in fruit peel during growing season and the effect of its application in phonological key stages of Thomson Navel orange in increasing relative yield and fruit quality. Ca concentration was determined in leaves, shoots, roots and the fruits of internal and external parts of canopy. Furthermore, the effects of Ca(NO3)2 foliar application after fruit set, before physiological drop and at the end of the second phase of fruit growth was evaluated using a RCBD with 4 treatments replicated four times. The results showed that fruit diameter in internal canopy was more than that in external canopy, whereas the Ca concentration in fruit peel of internal canopy (about 0.43%) was lower than that in external canopy (about 0.52%). The trend of Ca concentration changes in fruit peel of internal canopy showed more fluctuation during the growth period. The highest yield, fruit diameter, fruit weight and Ca concentration in fruit peel was obtained with Ca foliar application after fruit set and before the fruit physiological drop. According to these results, the most suitable time for Ca foliar application to enhance Ca content of citrus fruits is the first stages of fruit growth. Therefore, Ca(NO3)2 foliar application after fruit set and before the summer physiological drop is highly recommended.
Trend of Calcium Concentration Changes in Fruit Peel and Effect of Calcium Nitrate Spray on Yield and Quality of Thomson Navel Orange

This study was conducted to investigate the effect of non-living Spirulina cyanobacterium (Arthrospira platensis) biomass as an organic matter and incubation time on the chemical forms of lead (Pb) in a calcareous soil. The experiment was conducted in a factorial with completely randomized design in three replications. Treatments consisted of two incubation time (one and two months at 25 oC), three Pb levels as Pb(NO3)2 (control (10), 200, and 400 mg kg-1 of soil) and three Spirulina cyanobacterium levels (0, 500 and 1000 mg kg-1 soil). Results showed that with increasing Pb levels, Pb concentration in all chemical forms (Ex, Car, Om, Fe-ox, Mn-ox and Res-Pb) significantly increased. Different levels of Spirulina cyanobacterium had different effects on Pb chemical forms over time but, in general, application of Spirulina increased Ex and Car-Pb fraction by 31% and 43%, respectively as compared to those of control, and increased Pb availability in the soil. Therefore, application of this cyanobacterium as an amendment should be done with caution; and more investigation at different incubation time and different soils are recommended.

Water repellency is one of the major problems of oil-contaminated soils and influences water redistribution via reduced infiltration, enhanced surface runoff and soil erosion, and preferential flow. The objectives of this study were to examine the effects of petroleum on water repellency and soil water content. Undisturbed samples were collected from sandy loam and clay loam textured soils and three levels of petroleum including 0, 0.5% and 1% (w/w) were added to the samples. The water drop penetration time (WDPT) test was used to measure the water repellency of soils. The soil water characteristic curve (SWCC) of the soil cores was measured using sandbox and pressure plate apparatus. The van Genuchten-Mualem model was fitted to the SWCC data and soil physical quality index (S) as defined by Dexter. Increment of petroleum increased the soil water repellency and sandy soils were most susceptible to water repellency due to low specific surface area. Petroleum contamination also changed soil pore size distribution, as the soil field capacity and available water content (AW) was increased due to development of soil microporosity. Although greater water repellency increased AW in the polluted samples, reduction in soil macroporosity could result in unfavorable condition for plant growth. Petroleum contamination affected the shape and slope of SWCC. Water retention in petroleum-contaminated soil of the two textures of sandy loam and clay loam was lower at low suction values due to decrease in macroporosity, while in clay loam soil it was higher at high suction values due to increase in microporosity. Petroleum significantly decreased the S index of both soil textures;but it was more severe in sandy loam texture. According to Dexter classification and results, water repellency due to petroleum decreased soil quality by reducing macro pores and S index (ranged between 0.02 to 0.035), which have unfavorable result for plant growth. Also, coarse textured soils could develop water repellency more readily.

With increase in fire frequency in the Zagros forests, long term and short term evaluation of soil quality is very important. In this study, changes in some physico-chemical and microbial properties of soils were compared in short, medium and long-term after fire. For this purpose, three post-fire treatments were selected and labeled as TSF=1, TSF=3 and TSF=10 years after fire. In the nearest neighbor of each fire treatment a relevant unburned area was selected as the control and labeled as C1, C3 and C10, corresponding to the post-fire treatments. Soil sampling was performed from the depth of 0-20 cm in 4 replications. Overall, 24 composite soil samples were collected for post-fire treatments and their relevant controls. Some physicochemical and microbial properties were measured in soil samples. Results showed no changes in soil texture. Soil saturated moisture decreased for TSF=1, while it was recovered for TSF=3 and TSF=10. Soil bulk density decreased both in TSF=1 and TSF=3, while no changes were observed for TSF=10 compared to C10. There was a significant increase in soil pH, CEC, EC, and P for TSF=1 compared to C1. However, for TSF=3 and TSF=10, pH and CEC were recovered to the pre-fire level and soil P and EC were significantly lower than their controls. Soil organic carbon and N remained significantly lower than their control in all treatments. No significant change was observed in soil C:N ratio in any treatment. Microbial carbon biomass significantly decreased for TSF=1 compared to C1, while no significant changes were observed for TSF=3 and TSF=10 compared to C3 and C10, respectively. Soil induced respiration increased significantly for TSF=1, while it decreased significantly for TSF=3 and TSF=10 controls. Soil basal respiration significantly decreased in all post-fire treatments compared to their controls. Metabolic quotient significantly increased for TSF=1 and TSF=3, however, it recovered in TSF=10 to the pre-fire level. There was a significant decrease in microbial quotient for TSF=1, however, it increased significantly for TSF=3 and recovered to the pre-fire level for TSF=10. All the treatments were significantly discriminated using multivariate analysis (discriminant analysis). It was concluded that EC, N, CEC, and P were the most important physicochemical properties while microbial biomass carbon, basal and induced respiration, and microbial quotient were the most important microbial properties of soil for discriminating treatments.

Many methods have been developed since the formulation of the FAO framework for land evaluation and several of them still remain in widespread use. The objective of this research was to determine land suitability (using FAO method) and inherent soil fertility quality (using fuzzy membership function) for rice crop in paddy fields of Fouman and Shaft counties in northern Iran. Based on results obtained from FAO method, after climate factor (the limitation of the ratio of sunshine hours to day length i.e. n/N, and mean temperature in the growing cycle[b1] ) which was the major limiting factor for irrigated rice cultivation in the study area, drainage was the most soil-limiting factor. Based on inherent soil fertility quality, thickness of the plow layer, which affected root penetration and available soil volume for nutrients, was the most important limiting factor. Based on FAO method SQRI, 92.4% of the study area were marginal and 7.6% were in moderate suitability class, however, according to CLI, all of studied lands were in moderate suitability class. Also, based on inherent soil fertility quality, most of the study area were in suitable (38%) and highly suitable (27%) classes. Correlation of the FAO (SQRI and CLI) and soil fertility quality calculated indexes showed that the indexes were significantly correlated with each other (r=0.7, p

Clay minerals constitute a fundamental fraction of soils and their quantitative information is important in soil management. Therefore, the objectives of this research were to evaluate the ability of vis-NIR spectroscopy to quantify the dominant clay minerals of soils and to determine the limitations of this approach. One hundred surface soil samples were collected from the Isfahan province. Semi-quantitative mineralogical analyses were performed by XRD. Soil spectral analyses were carried out by a field spectrometer using 350-2500 nm wavelength range. Partial least squares regression and continuum-removed spectra were used for modeling. Modeling by continuum-removed spectra could not precisely predict dominant clay minerals. Clay minerals estimation by partial least square regression was more accurate than continuum-removed spectra. It appears that mixing the clay fraction with each mineral (palygorskite, smectite and illite) significantly influences the special absorption features of mineral and makes it difficult to estimate clay minerals accurately. In arid and semi-arid regions, mineralogical diversity is high and the presence of gypsum and carbonates increases the complexity of the soil system. Therefore, information from spectra is difficult to obtain and clay minerals could not be accurately estimated.

In this study, soil hydraulic conductivity function was modeled based on fractal geometry and capillary tube models. The proposed model is expressed as a function of the pore diameter, apparent flow path length, pore fractal dimension and tortuosity fractal dimension. In this study, the relationships concerning calculation of the pore fractal dimension and tortuosity fractal dimension for unsaturated flow was presented as a function of the soil water content. The advantage of this model is lack of empirical constants. Van Genuchten soil water retention curve was used to calculate the pore diameters. In this research, the model was evaluated by using 40 soil samples with 11 different soil textures covering sandy, loam, and clay from the UNSODA database. Results of comparison of unsaturated hydraulic conductivity estimated with fractal model presented in this study and the reported amounts of Van Genuchten model showed that the root mean square error (RMSE) of van Genuchten model was less than the fractal model, while the ratio of geometric mean error (GME) and standard deviation error of fractal geometry model was less than the van Genuchten model. Van Genuchten model had the highest coefficients of variation, with the exception of RMSE parameters. In terms of GMER and GSDER, fractal model was more reliable than the van Genuchten model.