sepideh abrishamkesh

Forests have important role for ecosystem maintenance, and deforestation is one of the factors in degradation of soil quality.  In this study, using multivariate analysis, soil quality index was evaluated in three land uses including forest, grassland, and cropland at two depths of 0-10 and 10-20 cm in Sidasht of Guilan Province, Iran. The weighted additive soil quality was calculated using two methods (1) Minimum data set (MDS1) and (2) Revised minimum data set (MDS2). Also, each feature’s variance and communality and two scoring methods, namely, linear and non-linear, were compared and evaluated. In MDS2, the effects of land use on soil quality index (SQI) indicated that the mean values calculated by the non-linear scoring method was significantly more precise than the linear one. Soil quality indices in forest and grassland had the maximum values when compared to cropland. SQIW2-MDS2-NLS had the highest sensitivity index (SI= 3.14). In MDS2, the soil properties including silt, Mean Weight Diameter, pH, CaCO3 and available phosphorus were selected. Efficiency ratio of MDS2 was 80% and in soil quality assessment, MDS2 had higher efficiency than MDS1. Soil condition and change of soil management practices were reflected in MDS2 more clearly than in MDS1. Accordingly, SQIW2-MDS2-NLS method was the best means for evaluating the effects of deforestation on soil quality in the studied area.

Soil erosion in upstream areas has an important role in sediment entry to dams. Sediment accumulation result in decreases of dam service life, environmental problems, and acceleration of floods. In addition to climate, topography, vegetation cover and land management, soil erosion amount depends on soil characteristics and its erodibility.  In this research, soil erodibility factor and its special distribution was assessed by using of various pedotransfer functions including KUSLE, KEPIC and KDg in a part of Aliabad watershed of Roodbar, located at upstream of Sefidrood dam. The soil samples were collected from 0-10 cm depth and size distribution of soil primary particles, organic carbon content, and aggregates stability were measured. The KUSLE was calculated in two ways without codes of soil structure and permeability, and with respective codes, named as KUSLEi, and KUSLEf, respectively. The results showed that studied soils generally had coarse texture, and KUSLEi was estimated low to moderate in range of 0.11 to 0.040 ton h MJ-1 mm-1. The least soil erodibility factor belongs to KDg, which was significantly lower than the soil erodibility factors calculated by other pedotransfer functions. All of the calculated erodibility factors had significant negative correlation with mean weight diameter of aggregates which KUSLEi and KDg showed the most and least correlation with MWD, respectively. All of the erodibility factors had moderate spatial dependence, however KUSLEi showed strong spatial dependence. Therfore, it generally can be concluded that zoning map of KUSLEi  generated via kriging can be a suitable indicator of the studied soils erodibility.

Soil is one of the important parts of ecosystem. Land use change and developed agriculture can lead to soil loss and land degradation because they have damaging effects on soil properties including soil organic carbon, aggregate stability and soil erodibility factor. Soil erodibility factor can be measured by different methods including experimental plots. It shows that the problem should be dealt directly and it demands high amount of cost and time. The factor can be calculated by soil properties such as soil organic matter and particle size distribution. They play a crucial role for sustainable ecosystem and decreased soil erosion. Since a few decades ago, deforestation has caused increased soil degradation and it has had devastative effects on soil surface and subsurface properties. This study investigated soil erodibility factor by different methods in three land uses including forest, grassland, and cropland at two depths in Sidasht of Guilan province. Soil quality index was calculated for evaluation of effects of land use on soil quality degradation.

The study area is located in Tootkabon in Guilan province (latitude 36º 50' 10" N, longitude 49º 39' 15" E). Parent material is limestone and geomorphologic units that are comprised of hill land and plateau. The soil moisture and temperature regimes are xeric and thermic, respectively. In order to reach the goals of the study, samples were collected from three land uses of forest, grassland, and cropland at two depths of 0 to 10 and 10 to 20 cm in regards to parent material, slope class, and equal slope aspect. Soil samples were prepared in two categories: the disturbed soil and the undisturbed ones. After becoming air drying, the disturbed samples were sieved by a 2 mm sieve. Soil properties such as soil texture, bulk density, soil organic carbon, CaCO3, and soil stability were measured. Soil erodibility factor is calculated by nomograph, Vaezi and Ostovari methods. Also sensitivity index and stratification ratio were taken into account. Soil quality index was determined using linear and nonlinear scoring methods based on minimum data set. All soil parameters were tested using one-way analysis of variance and the differences among means were analyzed using Duncan's significant difference test at the probability level of 0.05.

Results showed that the effects of land use and soil depth on bulk density, soil texture and soil erodibility factor using nomograph method were non-significant (p ≤ 0.05). The amount of organic matter, soil structure stability index and soil erodibility factor of Vaezi method were significantly decreased by increasing the depth. MWD and GMD at forest were higher than cropland, and CaCO3 and soil erodibility factor of Ostovari method at forest were lower than cropland. In comparison with other methods, soil erodibility factor of Ostovari method demonstrated that the effect of land use was significant (p ≤ 0.05). Soil properties including bulk density, MWD, organic matter, and soil erodibility factor of Ostovari method were selected as the minimum data set. Results of nonlinear scoring method were better than linear scoring method because the linear scoring method just showed the effects of soil depth on soil quality index (p ≤ 0.05). The soil quality index using linear scoring method was decreased by increasing the depth. However, soil quality index using nonlinear scoring method in forest was higher than cropland, and it was decreased by increasing the soil depth. It was found that non linear scoring methods are superior to linear and soil quality index using the nonlinear scoring method showed better the soil quality among different land uses.

Sensitivity index and stratification ratio values showed that land use change and soil depth effect on soil properties including CaCO3, organic matter, structure stability index and MWD. The stratification ratio values more than 1.5 for organic matter and soil structure stability index can be stated that these properties can show the degradation of soil quality due to land use change. Soil quality evaluation showed that in relation to the effect of land use on soil quality index, nonlinear scoring method is superior to linear scoring, so that forest and agricultural land use had the highest and lowest soil quality index by nonlinear scoring method, respectively. Therefore, due to the high sensitivity of soil quality to land use change, preventing land use change is one of the necessary measures for sustainable soil management in the study area.

Land leveling is a conservation solution to create a uniform slope to integrate, facilitate irrigation and drainage of paddy lands. Despite the positive effects of land leveling, it destroys the physical properties of the soil. The purpose of this study was to investigate the impact of land leveling on the physical characteristics of the soil. This work compares traditional and leveled lands, Balagafsheh and Limuchah areas, which have been leveled for two and five years, respectively. A total of 80 samples were taken, 20 soil samples from each traditional and land leveled plot in the two areas at depth of 0-20 cm by a grid method with dimensions of 20 by 20 meters.  Mean comparison was performed using an independent t-test and SPSS software. The results of comparing the mean showed a significant increase in the percentage of clay, bulk density, penetration resistance in the leveled lands of Limuchah, but in Balagafsheh area, the opposite results were observed. In general, the results indicated changes due to land leveling, such as changes in particle size distribution, structure destruction, and soil compaction without proper management after the implementation of the project, and the reversibility of soil properties is not adjusted solely by relying on the role of the time factor.. Proper management practices such as growing cover crops and returning them to the soil, such as the Balagafsheh area, can exploit the benefits of the land consolidation plan and control the destructive effects of it.

Main portion of organic wastes usually is burned or left in fields or landfills, which leads to pollution of soil, water, and air. The use of organic wastes for biochar production can be considered as a solution for the above-mentioned problems. Biochar is a rich carbon material which is produced via pyrolysis of various biomasses in anaerobic or limited oxygen condition. Inspire of world attention to biochar application in soil, effects of particle size, and method of biochar application has also been studied in a few pieces of research. Biochar is mixed with surface soil without the selection of a given class of particle size in most researches. Furthermore, olive kernel is considered as the main waste in agro-industrial integration, which often has no special use and is left in nature. Therefore, the use of olive kernel as a feedstock for biochar production can be a great approach for the management of these wastes and improvement of soil quality. Therefore, the purpose of this research is: 1- biochar production of olive kernel and its characterization and 2- A study of biochar addition effects with different particle sizes as the suspension on soil physical and erosion related properties of an erosion- prune soil.

An erosion-prone slit clay soil was sampled as undisturbed via metal cylinders (diameter and height of 25 and 15 cm, respectively) from 0 to 10 cm of soil located at Rudbar, Southern of Guilan, Biochar was produced of olive kernel at 650 C○ and 2 hours and 45 minutes. Biochar yield was calculated based on produced biochar per unit weight of feedstock (olive kernel). pH and electrical conductivity of olive kernel was determined at 1:5 (olive kernel powder : water) and 1:20 (biochar : water). Carbon, hydrogen, and nitrogen content and Fourier Transform Infrared Spectroscopy of olive kernel and biochar were assessed through Elemental Analysis and Fourier Transform Infrared Spectroscopmeter, respectively. Biochar was milled, and with particle size of 53-250 and 250-500 micron at 1 and 2 weight percent as a water suspension was injected to cylinder containing undisturbed soil. Four cylinders without biochar was also considered as a control treatment. Soil cylinders were located at a greenhouse at 20-25 C○ for 10 months (300 days) and their moisture was held approximately at 70 percent of field capacity. At the end of the tenth-mont of incubation, samples were provided of cylinders, and some soil properties and soil loss were studied.

The studied soil had a silt clay texture. Containing an abundant amount of silt can increase sensitivity of soil to surface crust formation. Carbon and hydrogen content was increased and decreased 44 and 69 percent, respectively as a result of olive kernel transformation to biochar. Result of Fourier transform infrared spectroscopy also showed olive kernel transformation to biochar has led to decrease of volatile organic components and increase of carbon and nitrogen content.
Results of this study showed that biochar with coarser particle size (250-500 micron) led to more increase of hydraulic conductivity compared to ones with finer particle size (53-250 micron). Although, biochar application result in aggregate stability improvement and runoff production decrease, biochar with particle size of 53 to 250 and 250 to 500 micron had no significant difference compared to each other. Runoff delay time and sediment yield were more and less, respectively in all biochar treatments in comparison with control (without biochar). The most increase of runoff delay time (5.65 minutes) was also was observed at 2 percent biochar application level of 250 to 500 micron. Biochar with particle size of 53 to 250 and 250 to 500 micron result in more decrease of sediment yield at 1 and 2 percent biochar application levels, respectively.

Generally, the results of this research showed that the transformation of organic wastes such as olive kernel can be considered as a useful approach to manage this kind of wastes. Olive kernel biochar with having less hydrogen to carbon molar ratio compared to feedstock (olive kernel) has long-term persistence in soil.  Furthermore, olive kernel biochar application as a suspension in an erosion-prone clay slit has positive effects on improvement of aggregation and hydraulic conductivity, and potential erosion decline.  Therefore, biochar production of olive kernel and its application as a suspension not only prevent soil degradation in time of application in soil but also lead to long-term carbon sequestration, improvement of important properties influencing soil quality, and sustainable use of unused wastes. A Study of biochar particle size and application-level also showed a specific type of biochar does not exert similar effects on different properties of a given soil, and particle size and level of biochar application must prescribe according to the desired goal.

Addition of biochar to soil has been recently considered as an amendment to reduce soil erosion. Biochar contains pyrogenic carbon, which is produced by heating residue of various crops, woods (or in other words various biomass) in restriction or absence of oxygen. Biochar can affect soil organic matter level and aggregate stability. Reduction of soil erosion through maintenance and  the increase of organic matter, increase of aggregate stability and improvement of hydraulic conductivity, and enhancement of moisture retention as a result of biochar application should be considered as an important achievement. It is important to study the effect of the different methods of biochar addition to the soil. The method of uniformly mixing biochar with surface soil which has been used in most studies can disturb the natural structure and lead to soil degradation. Therefore, it is an important issue to introduce a practical method that is associated with minimal soil manipulation, especially in erosion-prone soils. The effect of the biochar addition as suspension in water has never been reported in previous studies. Therefore, the aim of this study was to investigate the effects of adding different levels of biochar produced from two types of feedstocks (horticulture and agriculture wastes) in form of aqueous suspension on the properties of two types of erosion-prone soils in southern Guilan.

Two erosion-prone soils which were undisturbed, were sampled by metal cylenders (diameter and height of 25 and15 cm, respectively) of marl lands located in southern guilan. These soils were named as SL and L. Texture of SL and L were sandy loam and loam, respectively. Two types of biochar were produced from different feedstocks including pruned branches of ash tree (Fraxinus excelsior) and rice husk by slow pyrolysis at a temperature of 550 °C in a muffle furnace, titled as WB and RB respectively. The yield of biochar was determined based on weight of biochar produced per unit weight of raw material. The amount of ash in the biochar was determined by heating five grams of biochar at 500 °C for more than 8 hours and weighing it again. The pH and electrical conductivity were measured in a mixture of biochar and deionized water with a weight ratio of 1: 20 (biochar: water). The total amount of carbon, hydrogen, and nitrogen in biochars was determined by dry combustion. Two types of produced biochars were milled with a particle size of 63-250 microns, at levels of 0.7 and 1.4% by weight. Three repetitions in the form of aqueous suspensions were added to the cylinders containing undisturbed soil. Three cylinders of soil without biochar were also considered as control treatment. Soil cylinders were placed in a greenhouse for six months at a temperature range of 20-25°C and underwent several cycles of drying and wetting. At the end of incubation period, soil samples were obtained from cylinders. Soil properties including pH, electrical conductivity, organic carbon, hydraulic conductivity and aggregate stability were also measured. Thin sections were also taken out of soils and state of soil structure and voids were studied. The effect of two factors, including biochar type and biochar application level were analyzed as factorial in a completely randomized design by SAS statistical software. The comparison of the means was done by Duncan's test at the probability level of five percent.

The WB compared to RB, had a higher yield, and less ash content, pH, electrical conductivity and H/C and O/C. More mineral ash in biochar is likely to provide more electrical conductivity in RB. Both biochar had an alkaline pH (more than 7). The biochar used in previous studies were usually alkaline, but biochar can be produced with any pH in the range of 4 to 12. The raw biomass has a H/C  molar ratio of about 1.5, but with the pyrolysis, this ratio decreases. WB had less H/C compared to RB. Therefore, it can be concluded that WB had more aromatic carbon and it can probably be a more effective tool for carbon sequestration in soil. Presence of a lot of pores in biochar, especially WB which were visible in SEM photos, are very effective on vital soil functions such as aeration and hydrology. The organic carbon content of SL and L soils were significantly higher at biochar treatments compared to control. The hydraulic conductivity of SL soil at both application levels of WB and RB was significantly lower than the control. However, both application levels of WB and 1.4% of RB led to significant increase and decreases of hydraulic conductivity of L soil, respectively. The mean comparison showed no difference between bulk density of treatments and application levels of biochar to control treatment of SL soil. However, Bulk density of biochar treated L soils were less than control. Biochar treatment also result in significant increase of: mean weight and geometric mean diameter and decrease of fractal dimension of aggregates in L Soil.

WB and RB biochars had no significant effects on indexes of soil aggregate stability and bulk density of SL soil, but they led to significant improvement of bulk density and aggregate stability of L Soil. Although, assessment of thin section showed partial improvement of soil structure of both SL and L soils. Therefore, more time than 6 months of incubation probably is needed to significant improve of aggregate stability of SL. Application of both biochars led to increase of organic carbon of both SL and L soils. Hydraulic conductivity was decreased in SL soil as result of both biochar application which can lead to the increase of water retention. Although the increase of hydraulic conductivity of  L soils due to WB can be considered as a suitable approach for the decrease of  the runoff, Generally, it can be concluded that due to the significant effect of feedstock type on biochar characteristics and different characteristics of soils, various types of biochar do not have a similar effect on a particular soil, therefore, a type of biochar cannot have the same effect on different types of soil.

Biochar application as a strategy for long term carbon sequestration has recieved worldwide attention. In addition to long term carbon sequestration and global warming mitigation, biochar application in soil can result in improvement of soil properties, enhancement of plant growth and sustainable management of agricultural, garden and industrial biomass wastes and residues . Most of reports about positive effects of biochar have been done in acidic soils and there is little information about biochar effects in non-acidic soils. Therefore this research was conducted to investigate the effects of production condition of two type of rice husk biochar on their properties and accessing these biochar effects on plant biomass production in a two plant (lentil-wheat) cycle in an alkaline soil in greenhouse condition.
Biochar 1 and 2 were produced of rice husk at temperature range of 250-300 and 450-500 C, respectively and they were compared with each other. 0.4, 1.6 and 3.3 weight percent (B0.4, B1.6 and B3.3) of biochar 1 and 2 were added to pots. At first, lentil was seeded and then wheat was seeded after lentil harvest. Effects of type and application rate of biochar on biomass production were compared with each other and control (without biochar) treatment.
Molar hydrogen to carbon ratio and infrared spectrum of biochars showed more aromaticity in biochar produced at higher temperature. Increase of temperature led to smaller particle size, increase of electrical conductivity, pH, nitogen, potassium, calcium and phosphorus content of biochar. Two biochar effects on dry above and below ground biomass of lentil and wheat were not significantly different. But dry above ground biomass of wheat and dry below ground biomass of lentil and wheat in biochar 1 and 2 treatments were significantly higher in compared to control treatment. Effect of biochar application rates on dry above ground biomass of lentil were not significantly different with each other and control treatment. But dry below ground biomass of lentil in B3.3 was significantly more than other biochar application rates (B0.4 and B1.6) and control treatment. Dry above ground biomass of wheat in B1.6 and B3.3 was significantly more than B0.4 and control treatments. Dry below ground biomass of wheat in B1.6 was significantly more than B0.4, however it was not significantly different in comparison with B3.3. Shoot to root ratio of lentil in B1.6 and B3.3 was significantly less than control treatment. Shoot to root ratio of wheat was significantly less than control in all biochar application rates, however biochar application rates did not have significant difference with each other.
More aromaticity of biochar 2 (produced at temperature of 500-450 C˚) in comparison with biochar 1 (produced at temperature of 500-450 C˚) means more long term carbon sequestration potential. Biochar application had positive effects on biomass especially below ground biomass. Biochar effects were not only limited to first growth cycle (lentil) but also exist in second growth cycle (wheat). Generally it can be concluded that biochar production of rice husk can improve plant growth even in alkaline soils.