نشریه پژوهشهای خاک (علوم خاک و آب)
سال سی و چهارم شماره 3 (پاییز 1399)

Although there are numerous studies on the effect of soil and foliar application of Zn on rice yield, knowledge on Zn distribution in rice tissues through simultaneous soil and foliar application of Zn is limited. Therefore, The current experiment was conducted to explore the effect of soil and foliar application of zinc sulfate fertilizer on Zn and protein content of grain, and Zn content of rice (Oryza Sativa L.) tissues at different growth stages of Hashemi local cultivar. This filed experiment was carried out on two factors (soil application of Zn at three levels and foliar application of Zn at four levels) using complete randomized block design with three replications. The maximum grain yield (4283 kg ha-1) was recorded at simultaneous application of 20 kg Zn ha-1 (basal soil application) with foliar application of Zn solution at ripening stage, giving 32% increase compared to the control (2915 kgha-1). The highest increase in leaves and stems Zn content (2 times) was recorded at the combined treatments (10 kg Zn ha-1 and foliar spray at the maximum tillering stage). Also, the maximum increase in panicle and rice grain Zn (around 2.5 times) was obtained by application of 10 kg Zn ha-1 and foliar spray at the flowering stage. The highest linear correlation coefficient was found between grain and panicle Zn content (0.58**). Meanwhile, the grain protein content positively correlated with grain Zn content (0.68**), panicle Zn content (0.64**) and Zn content of stem (0.64**). Among the aerial parts, the highest linear correlation coefficient was found between Zn content of panicle and leaves at ripening stage (0.69**), Zn content of leaves and stems at flowering stage (0.65**), Zn content of stems at ripening stage and root Zn content at flowering stage (0.45**). The fitted stepwise multiple regression analysis  among protein content of rice grains and Zn content of all rice tissues at different rice growth stages indicated that grain Zn content, Zn content of leaves and stems at ripening stage had positive significant relationship with protein content of grains. According to adjusted coefficient of determination, these characters demonstrated 56% of protein content variations. It can be concluded that soil application of 20 kg Zn ha-1 in combination with Zn foliar application of  0.5% Zn sulfate at flowering stage of rice plant enhance grain yield and quality.

Application of organic fertilizers such as biochar is one of the most effective techniques to avoid immobilization of P chemical fertilizers in soils. In order to evaluate the effect of rice bran biochar (produced at 550º C) alone, biochar mixed with P, and that enriched with P on some chemical properties of soil and yield of corn plant, a field experiment was conducted based on a completely randomized design with 7 treatments and 3 replications. The treatments included a control, triple superphosphate (350 kg ha-1 TSP), biochar at 2 levels (2 and 4 t.ha-1), biochar enriched with TSP (2 and 4 t.ha-1 biochar enriched with, respectively, 350 and 700 kg TSP), and 2 ton ha-1 biochar mixed with 350 kg TSP. To determine the chemical properties of soil and yield of corn, soil sampling was done three times during the growing season while plants were sampled 120 days after sowing. The results revealed that pH value decrease and soluble and available phosphorus increased in almost all treatments including biochar. The biochar with TSP was the best treatment (soluble and available P increased by 190% and 105%, respectively, compared to the control).  Grain yield was the lowest in the control (9.1 t.ha-1) and the highest in 4 t.ha-1 biochar enriched with TSP (15.9 t.ha-1). The treatment including 4 t.ha-1 biochar showed the highest P concentration in corn root (0.47%) and grain (0.79%). It is concluded that although TSP alone was able to increase available P in the soil, but its effects will decrease in longer times. Application of biochar mixed with TSP had the best effect on the P availability and its uptake by the plant. In general, for soils with low content of  P and organic matter, treatment of 4 t.ha-1 biochar enriched with 700 kg TSP is recommended to obtain the highest grain yield. However, environmental issues caused by the overuse of phosphorus fertilizers and the costs imposed on farmers must be considered.

The purpose of this study was to investigate the effect of soil characteristics on sugarcane yield and to revise the “Table of Soil and Landscape Requirements for Sugarcane”. For this purpose, 120 points in different areas under sugarcane cultivation in Khuzestan and Mazandaran provinces were studied based on diversity in soil characteristics. Parametric methods were used in this study to determine the land index. For data analysis, multivariate regression by stepwise method and simple regression were used. Sugarcane yield was considered as a dependent variable and factors including salinity, percentage of exchangeable sodium, soil acidity, gypsum, lime, clay, sand and silt, as independent variables. Then, by examining the simple regression between important and effective land characteristics with sugarcane yield, the relevant equations and diagrams were drawn and soil properties were rated by FAO method. The results showed that exchangeable sodium, clay, lime, acidity, and salinity, in decreasing order, had a significant correlation with yield of sugarcane, while and the variables of sand and silt had no significant correlation. Multivariate regression coefficient analysis showed that the variables entered in the model were able to explain 67% of the variance related to the dependent variable. In simple regression equations, soil salinity, exchangeable sodium content, and lime had a decreasing effect on yield. The variables of exchangeable sodium percentage and soil salinity had the greatest effect on sugarcane yield. The proposed table on sugarcane soil and landscape requirements was evaluated and validated by using soil data and yields of 30 sugarcane fields that had not been used to extract this table. The coefficient of determination between the sugarcane yield and the land index was about 0.81, indicating the acceptable accuracy of the table.

With the growth of industries and technologies, the entry of pollutants, especially heavy metals, into the soil has raised the international community's concern about food security. The aim of this study was to investigate the effect of cadmium on some growth indicators and nutrient concentrations of different wheat cultivars. For this purpose, a factorial pot experiment was conducted in greenhouse conditions using a completely randomized design with three replications. The studied factors included five levels of soil contamination by cadmium (zero, 10, 25, 50, and 100 mg Cd/kg of soil) from the source of cadmium sulfate [3Cd (SO4).8H2O] and four wheat cultivars (Zare, Pishgam, Mihan, and Orum). The results showed that different levels of soil cadmium significantly reduced wet and dry weights of the aerial part and root, leaf chlorophyll index, plant height, as well as nitrogen, phosphorus, potassium, iron and copper concentrations of different wheat cultivars. The highest levels of these traits were obtained from the control treatment (without cadmium contamination), and the lowest from the treatment with 100 mg Cd/kg of soil. Different wheat cultivars reacted differently to various levels of soil cadmium. Pishgam and Orum cultivars showed the least sensitivity and Mihan cultivar showed the highest sensitivity to soil contamination by cadmium.

This study was conducted to evaluate the soil physical quality (SPQ) indices of topsoil and subsoil of wheat and sunflower fields in Urmia plain. Principal component analysis (PCA) was used to distinguish the effect of soil layer and cultivation type on SPQ. Soil samplings and measurements were done in two layers (topsoil and subsoil) of 30 agricultural fields (15 wheat fields and 15 sunflower fields). Soil water retention and penetration resistance curves of undisturbed samples were determined using sand box and pressure plate, and micro-penetrometer, respectively. Then, least limiting water range (LLWR), integral water capacity (IWC), and Dexter’s index of soil physical quality (S-value) were calculated. There were significant differences (p < /em><0.05) in the mean values of physical quality indices between the topsoil and subsoil. The relative bulk density (RBD) values of subsoil were bigger than topsoil. Also, the IWC, LLWR, and S values of subsoil were much smaller than those of topsoil, indicating poor physical quality of subsoil layer in the studied fields. This might be related to conventional tillage with heavy machinery, especially under high soil moisture conditions in last decades, which induced some compaction effects in the subsoil. These findings recommend improving of tillage systems and continuous monitoring of cultivation effects on SPQ in the studied area. Evaluating the SPQ indices of wheat and sunflower fields, using the means comparison and PCA, showed that wheat fields had better soil physical quality compared to sunflower fields. The difference of root systems and more human trafficking in the sunflower fields could be the main reasons of lower soil physical quality in sunflower cultivation compared to wheat cultivation.

Mass-fractal models have been frequently used to quantify soil particles size distribution. Since fractal dimension has numerous capabilities to predict different soil properties, this study aimed to determine the best soil primary particles size groups in estimation of fractal dimension of soil primary particles size. This study was done with 186samples of calcareous soils in southern parts of Iran located in Fars province. Soil particles size distribution was determined using combination of wet sieving and modified hydrometer method. Fractal dimensions were calculated using three methods including Tyler and Wheatcraft (DT), Sepaskhah and Tafteh (DS), and Kravchenko and Zhang (DK). Then, the relationship between DT and DK with contents of soil primary particles in different size groups were established. Results showed that regression relationship (power 2) between DT and DK was very strong (with determination coefficient of 1). In addition, DS regression relationship (linear) with DT and DK was strong. Results also revealed that mean values of DK and DS were significantly higher and lower than DT, respectively.As the particles size became smaller, accuracy of regression relationships between smaller particles size percent of a specific diameter and soil fractal dimensions (DT and DK) becomes more, and the maximum accuracy was observed in logarithmic relationship between fractal dimensions and clay percent. R2 of training data and that of test data, normalized root mean square error (%), and Nash-Sutcliffe coefficient statistics were 0.99, 0.98, 0.6, and 0.95 for logarithmic model between clay content and DT, and 0.98, 0.99, 0.25, and 0.94 for logarithmic model between clay content and DK, showing very strong relationship between clay content and fractal dimensions. Therefore, it is possible to calculate Tyler and Wheatcraft and Kravchenko and Zhang fractal dimensions by using clay content and very simple equations in a wide range of calcareous soils with different mechanical components. Thus, those fractal dimensions can be used to estimate physical, chemical, and especially hydraulic properties of calcareous soils, whose measurements are complex, expensive, and time consuming.It should be pointed out that the proposed relations are valid when primary particle size distribution of soil is determined using the method used in the present study. Otherwise, the relations should be tested and validated.

Exploitation of oil reservoirs enhances the seepage of petroleum hydrocarbon contaminants to the soil. This phenomenon causes environmental damages and detrimental changes in soil chemical, physical, mechanical, and biological properties. In this study, effects of Bagasse biochar and zeoplant as organic-mineral amendments were investigated on some oil-contaminated soils around Ahvaz city (exploitation area of Karoon oil and gas). Soil sampling was carried out using completely randomized in the block, then, the soil samples were put in pots (7 kg) and the treatments were applied at rates of 2%, 4%, and 6% by weight. Afterwards, the soil moisture was adjusted in the pots (25% and 50% of FC) and all samples were incubated for 100 days. After incubation, penetration resistance, tensile strength, and shear strength were measured using the standard methods. Also, Alkanes and total petroleum hydrocarbons (TPHs)were determined using Gas Chromatography (GC). Results revealed that application of biochar and zeoplant at 2% and 4% levels enhanced the shear strength, whereas application of 6% level at 50% FC decreased the shear strength (0.4 Kpa). Application of biochar and zeoplant increased tensile strength, and at 6% level of biochar (at 25% FC) the highest tensile strength was observed (18 Kpa). The lowest penetration resistance was recorded for 6% of biochar application and at 25% FC. Addition of organic and organic-mineral amendments improved the soil structural and mechanical properties, therefore, their application is a convenient management strategy to amend the oil-contaminated soils.

Vermicompost, as a nutrient-rich organic amendment, contains most nutrients in plant-available forms and can influence soil fertility and plant growth significantly. The objective of this study was to investigate the availability and release rate of potassium (K) in six vineyard topsoil (0-30 cm) with different textures (loam, clay loam, and sandy clay loam) treated with 2 % of cattle manure vermicompost (VC), through successive extractions with 0.01 mol L-1 CaCl2 over periods of 0.25-72 hours. The results showed that VC addition to soils increased the K availability. The average cumulative K released after 72 h from the control and treated soils was 526.9 and 547.9 mg kg−1, respectively. Due to the conformity of data to the Simple Elovich Equation it was suggested that process of K release from soils was affected by diffusion processes. Simple Elovich rate constant values in soils ranged from 34.9 to 132.1 mg kg−1h-1.The VC had different effects on K release rate in soils. In clay loam soils with high clay content, low organic matter and K fixation capacity, VC increased K release rate, while in loam and sandy clay loam soils with low clay, high organic matter, and low K fixation capacity, it decreased K release rate. Overall, VC had a balancing effect on K release rate. It could be related to VC interaction with soil particles, especially clays. Due to the importance of K in grape nutrition and K deficiency in some soils, the use of VC in vineyards is recommended.