نشریه مدیریت خاک و تولید پایدار
سال دوازدهم شماره 2 (پیاپی 40، تابستان 1401)

Climate and topography are two important soil-forming factors that affect the genesis, evolution, and classification of soils. Topography may influence soil evolution through attributes such as the direction, shape, and percentage of the slope, the amount of precipitation, penetration, and runoff, the rate of erosion, as well as the difference in the drainage conditions. On the other hand, organic carbon, the amount and type of clay, soil color, calcium carbonate, base saturation, leaching depth, and solubility of salts in the soil are closely related to the climate. Hence, this study aimed to investigate the effect of climate and topography on changing physicochemical, mineralogical, and micromorphological properties of soil.

This research focused on two regions including, Sardooeyeh and Bam. The Sardooeyeh region, with the soil moisture-temperature regime of xeric-mesic, is about 3500m above sea level. However, the mean elevation in the Bam region, with the aridic-thermic regime, is 900m. Eight representative pedons on the extrusive igneous parent material with an intermediate composition were selected, sampled, and described. Physicochemical, mineralogical, and micromorphological analyses performed on the soil samples, and the soils were classified using Soil Taxonomy and World Reference Base for Soil Resources (WRB). Soil pH, particle size distribution, electrical conductivity, equivalent calcium carbonate, cation exchangeable capacity, and gypsum were measured, then eight samples were selected for clay mineralogy investigations. A Bruker Dh8 Advance X-ray diffractometer at 30 mA and 40 kW was used to analyze the samples. Scanning electron microscopy was performed. The undisturbed soil samples from horizons were selected for micromorphological observations.

The results revealed the increase in the clay percentage, cation-exchange capacity, organic carbon, and equivalent calcium carbonate in the elevations with the xeric regime. On the other hand, an increase in the amount of electrical conductivity and gypsum percentage in the aridic regime was determined. Thus, changes in soil properties caused different soils, including a range of Mollisols and Alfisols (xeric regime) to Aridisols (aridic regime) in the Soil Taxonomy and the Chernozems, Luvisols, and Calcisols (xeric regime) to Solonchaks, Gypsisols and Cambisols (aridic regime) in the WRB system to be classified. One of the strengths of the WRB system compared to the Soil Taxonomy is the classification of buried soils and the use of the "Raptic" qualifier to indicate the lithologic discontinuity within the pedon. The results of clay mineralogy elucidate the presence of illite, palygorskite, chlorite, smectite, kaolinite, vermiculite, smectite-vermiculite interstratified minerals, and quartz. In the xeric regime, the illite mineral decreased, and vermiculite and smectite increased. However, the amount of illite increased in the aridic climate. Furthermore, the simultaneous presence of palygorskite and smectite-vermiculite interstratified minerals can be the result of the presence of polygenetic soils in this region. Calcite infilling, nodule, and calcite internal hypo-coating, with clay coatings, clay bridges, and link clay capping were among the dominant micromorphological pedofeatures observed in the xeric moisture. On the other hand, the simultaneous presence of calcite and clay coatings and infillings together with gypsum infillings and the interlocked gypsum plates prove the role of paleoclimate in soil formation.

Results of this study showed that the current climate, the paleoclimate prevailing in the region, and topography have key roles on the intensity of weathering, the amount of clay minerals, and the type of pedofeatures in the region. Besides, due to the lack of carbonate in the parent material, it seems that the increase of weathering in the xeric regime part of the area significantly influenced on the alteration of plagioclase mineral which in turn, increased secondary calcium carbonate.

The amount of macronutrients content is affected by various environmental factors such as severe water stress occurs after anthesis. Using of Azospirillum brasilense as a biofertilizer and crop residues for increasing soil organic matter are the two methods for reducing water stress in the farms. However, despite the favorite effects of Azospirillum brasilense and crop residues application for reducing negative effects of water stress, a few studies have been performed on regarding the effects of these factors on macronutrients uptake of barley in the warm and arid regions of Southern Iran. Therefore, the aim of this study was to investigate the effects of Azospirillum brasilense and wheat residues applications on macronutrients uptake of barley.

This research was conducted at the experimental farm of the Darab Agricultural College of Shiraz University. A split factorial experiment in a randomized complete block design with three replicates were carried out in 2017 - 2018 growing season. Treatments included: two levels of irrigation as the main plots [normal irrigation (IRN): irrigation based on the plant's water requirement up to the physiological maturity and the other factor was deficit irrigation (IRDI): irrigation based on the plant's water requirement up to the anthesis stage (cutting of irrigation after anthesis)]. Also, sub plots were two levels of crop residues [1. without residue, 2. returning 30% of wheat residues to soil] and four fertilizer sources [N0, no nitrogen fertilizer (control); N100, 100 kg N ha-1 (as urea); Bio + N50, Biofertilizer (Azospirillum brasilense) + 50 kg N ha-1 (as urea) and Bio, Biofertilizer (Azospirillum brasilense)].

Interaction of residue × nitrogen (N) source on barley grain N content showed that the highest and the lowest grain N content (161.7 and 43 kg ha-1, respectively) were achieved in without residue and the Bio + N50 and in with residue and Bio treatments, respectively. Also, the straw N content was affected by the interaction of irrigation regime × residue × N source. The highest N content of straw was obtained in IRDI, with residue and N100 treatments (62.9 kg ha-1) and the lowest was achieved in IRDI, with residue and N0 treatments (5.7 kg ha-1). The highest grain and straw phosphorus (P) content (1.35 and 1.12 kg ha-1, respectively) was obtained by the Bio + N50 and N100 treatments, respectively. The irrigation regime × residue × N source interaction showed that the highest and the lowest grain potassium (K) content (12.6 and 4.0 kg ha-1, respectively) was belonged to IRDI, without residue and N100 treatments and IRDI, with residue and N0 treatments, respectively. Also, irrigation × N source interaction showed that the highest K content of straw (114.4 kg ha-1) was achieved in IRN and Bio + N50 treatments and the lowest K content of straw (33.3 kg ha-1) was observed in IRDI and Bio treatments.

Based on the findings of this experiment, the Bio + N50 treatment is appropriate for achieving the maximum macronutrients content of barley in IRN conditions. Therefore, with respect to environmental and economic considerations and achieving high levels of barley macronutrients content, this fertilizer regime is recommended.

Soil salinity is an increasing problem in agricultural soils that mycorrhizal fungi in saline soils increase plants tolerance to salinity by symbiosos with their roots and improving their growth. In addition, mycorrhizae contribute to agglomerate stability through two main mechanisms, physical stabilization by trapping individual soil particles by extensive hyphae networks and chemical stabilization by adhesive-like secretions. Therefore, the aim of this study was to compare the root effects of three different plants, clover Terifoliom alexandrinum L., onion Allium cepa L. and parsley Petrocelinum crispum L. with and without mycorrhizal on soil aggregates stability in saline soils.

In order to investigate the effect of mycorrhiza fungi and different salinity levels on morphological characteristics, nutrient concentrations and soil aggregate stability in three plants: clover, parsley and onion, a factorial experiment in a completely randomized design with 3 replications were conducted in the greenhouse of Agricultural sciences and natural resources university of Khuzestan in 2018. factors were included mycorrhiza at two levels (no inoculation with mycorrhiza (NM), inoculation with mycorrhiza (M)), salinity at three levels (salinity 1 dS m-1 (S1), 3 dS m-1 (S2) and a 6 dS m-1 (S3)) and three levels of plant type (clover (TA), parsley (PC) and onion (AC)).

Accourding to the results, salinity stress caused a significant decrease in growth indices and plant colonization percentage, but inoculation with mycorrhiza fungus increased them significantly. Salinity stress in clover, parsley and onion reduced shoots dry weight 31%, 35% and 96% respectively, but inoculation with mycorrhizal faungus increased this factor 69%, 67% and 93% compared to non-mycorrhizal treatments. The increase of root dry matter of these three mycorrhizal plants compared to their non-mycorrhizal treatments was 65, 65 and 93%, respectively. Salinity stress also caused a significant decrease in the macronutrients (phosphorus and potassium) and micronutrients (iron, zinc and copper) concentration, while sodium concentration increased significantly. Mycorrhizal treatment increased phosphorus concentration significantly in clover, parsley and onion by 26, 27 and 41%, while salinity stress reduced it by 22, 24 and 26% respectively. Mycorrhizal inoculation increased iron concentratin 6, 12 and 66% in the above three plants, respectively. The results showed that the highest aggregate stability in clover, parsley and onion were seen with an average of 0.81, 0.75 and 0.93 mm in mycorrhizal low salinity level treatment and and the lowest aggregate stability by an average of 0.41 , 0.39 and 0.35 mm were obtained in non-mycorrhizal high salinity level treatment.

Based on the results of this study, salinity stress has a negative effects on plant growth characteristics and nutrient uptake by clover, parsley and onion, but mycorrhizal fungi inoculation reduces these negative effects. Also, the negative effects of salinity stress on aggregate stability in mycorrhizal treatments were less than non-mycorrhizal treatments. Among the studied plants, the highest amount of aggregate stability in mycorrhiza inoculation conditions was related to onion and the lowest amount of aggregate stability was seen in parsley. Its obvious from the results that onion, which has a higher mycorrhizal dependency, can further increase the aggregates stability. Thus, the use of mycorrhizal fungi, especially in saline soils, can increase the stability of aggregates and thus improve quality and soil physiacl properties.

Splash and interrill are two important types of rain-induced erosion in agricultural lands. In many parts of the country, erosive winds can increase soil erosion rate by intensifying rain erosivity. One of the most important conservation practices to control erosion is the use of plant residue mulch. The aim of this study was to investigate the effect of different percentages of wheat straw mulch in addition to different wind velocities on soil losses due to interrill and splash using simultaneous rain and wind simulator instrument.

For this purpose, an experiment was done in a completely randomized design based on three factors including wind velocity (0, 6 and 12 m s-1 at height of 40 cm), wheat straw mulch (0 (as control), 30, 60, 90%), and soil type (namely C2mm and C4.75mm) each at three replicates. A constant rainfall intensity of 40 mm h-1 was applied on the treated soils for a period of 40 minutes. Interrill erosion as well as up- and down-ward splash materials were measured separately. Finally, the efficiency of different mulch percentages in reducing soil erosion compared to the control (bare soil) at different wind velocities was determined.

The results showed that with increasing the percentage of soil coverage, the soil loss due to interrill and splash was significantly reduced. Also, with increasing wind velocity, interrill erosion and downward splash increased, whereas upward splash decreased, significantly. The efficiency of plant residue mulch in reducing interrill erosion was ranged between 30.7 and 92.8 %, while its efficiency in controlling upward and downward splash varied from 3.3 to 81 % and 78.9 to 99.9 %, respectively. The 60 % coverage was introduced as the best mulch percentage.

The findings of this study showed that in wind-driven rains, interrill erosion rate increased with increasing wind velocity. However, it could be reduced by an appropriate coverage of plant residues. In other words, by increasing the percentage of wheat straw mulch, the soil surface is protected from the direct impact of raindrops and hence, interrill and splash erosion rates are reduced, significantly. It was concluded that the efficiency of plant residue in reducing downward splash was more than that in reducing upward splash. In addition, in the presence of plant residue, the downward splash was reduced more than interrill erosion rate. The results of this study indicate the importance of plant residue as an effective conservation agent in controlling soil erosion in agricultural lands.

Most of the Iranian soils are poor in organic matter due to poor management; including monoculture system and lake of crop rotation, removal of plant residues from the field, arid and semi-arid climates and non-utilization of organic fertilizers and organic amendment. Improper use of chemical fertilizers to increase agricultural production has initiated environmental issue and diminish soil fertility. Nowadays, with the development of organic farming, the use of organic amendments to replace the application of chemical fertilizers took a pay attention. The sugarcane is a plant that accumulates silicon. The poor management of sugarcane cultivation can reduce available silicon. Biochar is one of the most important organic compounds for improving soil properties, carbon content and improving the concentration of available silicon. The aim of this study was to investigate the effects of biochar types application on the concentrations of silicon and some essential elements of the sugarcane field soil.

In order to investigate the effects of biochar types application on the concentration of silicon and some essential nutrients in the sugarcane field soil, an experimental design was carried out as a factorial experiment based on a randomized complete design with two factors including biochar and chemical fertilizer in a completely randomized design with three replications in the greenhouse of Imam Khomeini Agro-Industrial Company in Khuzestan. The applied biochar was included sugarcane bagasse, rice husk, rice straw, wheat straw and dicer wood chips, which were produced at 300 °C for 3 hours in a pyrolysis furnace. Experimental treatments included the control (soil without any biochar or chemical fertilizers), biochar, chemical fertilizers and mixture of biochar and chemical fertilizers. Biochar was added to the soil based on one percent weight and the treatments were incubated for three months in the field capacity water content. At the end of the incubation period, the concentrations of nitrogen, phosphorus, potassium, silicon, iron, manganese, copper and zinc were measured.

The results showed that the effects of treatments on the concentration of nitrogen, phosphorus, potassium, silicon, iron, manganese, copper and zinc in the soil was significant. The mixture of rice straw biochar and nitrogen, phosphorus and potassium from chemical fertilizer sources (RSB + NPK) treatment had the highest available concentration of nitrogen, phosphorus and potassium in the soil. The highest available soil silicon concentrations were related to the treatments of mixture of rice straw biochar and nitrogen, phosphorus and potassium from chemical fertilizer sources (RSB + NPK), mixture of rice straw biochar and nitrogen and phosphorus from chemical fertilizer sources (RSB + NP) and mixture of rice straw biochar and phosphorus from chemical fertilizer sources (RSB + P). There was no significant difference between these treatments and treatments of rice straw biochar along with phosphorus and potassium (RSB + PK) and rice straw biochar (RSB).

In general, the results of this study showed that treatments with biochar (either biochar alone or mixture of biochar and chemical fertilizer) increased the available concentration of soil nutrients more than treatments without biochar (control and chemical fertilizer). Among the biochars, rice straw biochar, sugarcane bagasse biochar and rice husk biochar were most useful to increase the available concentration of nutrients. In general, it can be concluded that because biochar is a rich source of the nutrients and has a positive effect on soil properties, Hence, it can be used as useful material factor to improve soil fertility.

Nowadays, fertilizers are one of the factors affecting the yield of plants, but their high use, especially when combined with inappropriate management practices such as burning of plant residues, drastically reduce soil organic matter. Long-term use of chemical fertilizers also results in the leaching and contamination of groundwater. Using biofertilizers to reduce chemical fertilizer use and increase crop yields is an important strategy to move towards sustainable agriculture. So far, no research has been conducted on the effect of vermicompost and vermiwash on the growth and development of African daisies. Therefore, the present study was conducted to investigate the effects of vermicompost and vermiwash on growth and development of African daisies plant.

The present study was conducted to assess the effect of vermicompost and vermiwash on morphological and physiological properties of African daisies (Gazania rigens L.) in 2018. For this purpose, vermicompost was applied at 4 levels (control, 20, 40, and 60 % V/V), and vermiwash was applied at 4 levels (control, 50, 100, and 200 mg/l) as a factorial based on randomized block design. Plant height, number of flowers, flower diameter, root volume, fresh and dry weight of shoot and root, chlorophyll content, insoluble sugar, K, N and P concentration were studied. Statistical analysis of the data was performed using SAS software version 9.1 and comparison of means by Duncan’s Multiple Range Test at 5% probability level.

Vermicompost and vermiwash treatments had significant effects on morphological and physiological properties of African daisies. Interaction effect of vermicompost and vermiwash was significant for all studied traits except P concentration. The highest number of flowers (10) was observed in 60% vermicompost and vermiwash treatment at 100 mg/l. There were no significant differences between 40 and 60% vermicompost volume and also between 100 and 200 mg/ l vermiwash in flower number and diameter. Therefore, increasing the amount of vermicompost and vermiwash to some extent increase the reproductive properties of the plant and higher than that amount can even reduce related traits. By increasing the volume of vermicompost from 20% to 40%, the root volume of African daisies significantly changed. The fresh and dry weight of shoots also showed a similar response to vermicompost and vermiwash treatments. By increasing vermicompost volume from 20 to 40%, the soluble sugar increased significantly in African daisies. Vermicompost and vermiwash increased chlorophyll content in African daisies. The highest amount of chlorophyll b was observed in vermicompost treatment at 60% volume and 50 mg/ l vermiwash.

According to the results of the experiment, vermicompost and vermiwash, with effective nutrient absorption and high water absorption and storage capacity, increased the reproductive traits of African daisies. The effect of vermicompost was higher than vermiwash on studied traits. Treatment of 40% vermicompost and 200 mg/l vermiwash was the best treatment for improvement of African daisies growth