H. Bagheri; H. Zare Abyaneh; azizallah izady
Abstract
Introduction: Vermicompost is a type of biological organic fertilizer obtained from earthworm activity. Vermicompost is used in sustainable agriculture due to its beneficial effects on diversity of plant nutrients and physical-hydraulic modification of soil. However, high presence of solutes ...
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Introduction: Vermicompost is a type of biological organic fertilizer obtained from earthworm activity. Vermicompost is used in sustainable agriculture due to its beneficial effects on diversity of plant nutrients and physical-hydraulic modification of soil. However, high presence of solutes in the structure of vermicompost causes soil salinity, increases soil sodium content and changes soil pH. Soil flushing is one of the well known strategies to minimize the mentioned disadvantages of vermicomposting. Although flushing can reduce the soil salinity and sodium content, it leads to transportation of some soil substances such as nitrate, dissolved organic carbon and colloids which their tracing is necessary because of soil quality monitoring and possibility of water resources pollution. The objective of the current study was to investigate the effects of vermicomposting on soil chemical, physical and hydraulic properties and its role on the amount of soil total dissolved salts (TDS), sodium, nitrate, dissolved organic carbon and leaching behavior of colloids.
Materials and Methods: To treat the soil, 1.45 weight percent of vermicompost (17.68 tones/hectare) was mixed with regular soil. Physical, chemical and hydraulic properties of soil were determined. PVC columns with length of 20 cm and internal diameter of 5.95 cm were used and filled with soil to perform leaching during 24 hrs in saturated condition experiment. The effluent of columns were collected at various interval times, and their sodium, nitrate, dissolved organic carbon, TDS and colloid contents were measured and the cumulative amounts of them were calculated at 6 and 24 hrs. All experiments were carried out in three replications, and the mean comparison of leaching parameters was done according to Duncan's multiple range test at probability level of 5%.
Results: Vermicompost increased the studied soil chemical properties i.e, organic matter, organic carbon, extractable nitrate, soluble sodium, soluble and exchangeable sodium, EC and TDS to 12.42, 12.9, 118.96, 80.43, 44.48, 109.4 and 109.4 %, respectively and decreased soil pH to 2.35 %. Soil bulk density reduction to 3.81 % and enhancement of soil porosity, saturated hydraulic conductivity and the pore water velocity to 1.38, 7.25 and 5.6 %, respectively are the other results of vermicompost application. The used vermicompost fertilizer caused displacement of soil water retention curve to more moisture around of saturated and permanent wilting points and reduction of air entry potential. In this regard, vermicomposting increased all of soil hydraulic coefficients of van Genuchten model including θr, θs, α and n, and its effect was specially more on θr and α. The result of leaching experiments showed that the amounts of leached TDS, sodium, nitrate, dissolved organic carbon and colloid in vermicompost-containing soil during 6 hrs were 491.4, 65.22, 116.71, 47.68 and 24.86, and during 24 hrs were 946.3, 72.16, 146.26, 95.11 and 41.97 mg/Kg, respectively. For the natural soil, these amounts during 6 hrs were 240.9, 11.84, 20.08, 23.2 and 15.11, and during 24 hrs were 665.6, 15.69, 44.48, 58.34 and 29.39 mg/Kg, respectively. Therefore, vermicompost significantly increased the amounts of leached TDS, sodium, nitrate, dissolved organic carbon and colloid, because of containing more contents of solute, sodium, nitrate and organic matter in its structure. It also increased the porosity and hydraulic conductivity of soil, and made changes in soil water retention curve (P<0.05). The presence of more sodium in vermicompost together with its effect on soil porosity enhancement increased the colloid dispersion and consequently its leaching. In addition, the leaching rate of all of parameters at 24 hrs in comparison to 6 hrs decreased significantly due to high amount of solute leaching through mass flow at initial time of leaching experiment and leaching residual solute by time-consuming process of diffusion.
Conclusion: Although vermicompost can enriched the soil due to increasing nitrate and organic matter contents, it leads to soil salinity and increases sodium contents. Flushing the soil treated by vermicompost removed the amounts of TDS, sodium, nitrate to 10.4, 76.2 and 44.6 % during 24 hrs. Therefore, leaching had a considerable effect on soil sodium reduction and a little effect on soil salinity reduction. Moreover, in comparison to chemical fertilizers, the high nitrate fraction of applied vermicompost resulted in sustainability of soil fertility. It is expected soil salinity and nitrate leaching fraction of vermicompost will be reduce by managing leaching methods, treating vermicompost before using and reducing fertilizer application rate. Thus, the results of current study warn the farmers who used vermicompost in soil to control the soil salinity, ground water pollution and vertical colloid migration.
Iman Nikravesh; Saeid Boroomand Nasab; AbdAli Naseri; Amir Soltani Mohamadi
Abstract
Introduction: Organic matter is considered as the main element for soil fertility by improving the condition of agglomeration, porosity and soil permeability. One of the most useful ways to use plant debris is to turn it into Biochar and Hydrochar. Biochar is a kind of coal produced from plant biomass ...
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Introduction: Organic matter is considered as the main element for soil fertility by improving the condition of agglomeration, porosity and soil permeability. One of the most useful ways to use plant debris is to turn it into Biochar and Hydrochar. Biochar is a kind of coal produced from plant biomass and agricultural waste that is burned in the presence of low oxygen content or its absence. The hydrothermal process involves heating the biomass or other materials in a pressurized in the presence of water at a temperature between 180 and 250 C, and the result of this reaction is coal (Hydrochar) and soluble organic matter. Biochar and Hydrochar have several advantages such as climate change mitigation through carbon sequestration, soil cation exchange capacity (CEC) increasing, soil fertility, plant growth and root development, improved soil structure and stability, increased soil moisture storage capacity and soil pH adjustment. Coarse soils have large pores and they have low ability to absorb the water and nutrient. The aim of this research was to determine the optimum temperature of wheat straw Biochar and Hydrochar production, and to investigate the effect of these materials on bulk density, total porosity and moisture curve of Sandy Loam soil.
Materials and Methods: In order to produce biochar, at first the wheat straw was washed and dried in the oven. Then it was grinded and was made at different temperatures (200 to 600 ̊ C) inside a furnace for four hours. Similar to biochar, for producing hydrochar, after washing and drying the wheat straw it was grinded into particles ranges from 0.5 to 1 mm. Then it was placed in a stainless steel autoclave with deionized water. The autoclave was heated at different temperatures between 140-230 ̊ C for four hours. The optimum temperature for producing of biochar and hydro-char was determined by using stable organic matter yield index (SOMYI), and it was used in this study. The pH and EC of the biochar and hydro-char samples were measured by combining 1 g of a sample with 20 mL DI water. The cationic and anionic exchange capacity were determined by replacing sodium nitrate with hydrochloric and potassium chloride (Chintala et al., 2013). Surface area was obtained using methylene blue method. A CHNSO Elemental Analyzer (Vario ELIII- elementar- made in Germany) was used to determine the content of C, N, H, S and O in the samples. Potassium and sodium content were measured by flame photometer and calcium and magnesium were measured by titration with EDTA. Biohchar and hydrochar treatments were applied at three levels of 2, 5 and 10 mg / kg soil in three replications in 21 lysimeter. The bulk density, total porosity and moisture curve of soil were measured after four-month irrigation period.
Results and Discussion: According to the calculated value of stable organic matter yield index (SOMYI) at various temperatures in this study, the maximum thermal constancy of wheat straw biochar was 16.20 at temperature of 300 ̊ C and for hydro-char was obtained as 6.13 at the temperature of 200 ̊ C. So, the temperatures of 300 and 200 ̊C were determined as the optimum temperature of sustainable carbon biochar and hydro-char production and were used to continue the experiments of this study. The results showed that addition of HW2, HW5, HW10, BW2, BW5 and BW10 to soil compared to control treatment significantly decreased the bulk density of the soil, 8.97, 11.77, 15.17, 7.9, 10 and 13.10 percent respectively. Also, results showed that addition of HW2, HW5, HW10, BW2, BW5 and BW10 to the soil as compared to control treatment increased soil porosity by 8.8, 11.48, 15.77, 6.48, 9 and 22.13 percent, respectively. The reason for reducing the soil bulk density and increasing the total porosity of soil can be due to the mixing of the soil with materials with a lower bulk density and the effect of increasing the organic matter of the soil due to the use of Biochar and Hydrochar. Based on statistical analysis, wheat straw Biochar and Hydrochar had a significant effect (P
I. Nikravesh; Hadi Moazed; S. Broomandnasab; AbdAli Naseri
Abstract
Many of irrigated agriculture problems are resulting from chemical and physical composition of irrigation water. The irrigation water quality is effective on soil moisture characteristic curve by effect on soil structure, pore size distribution and continuity of them. The aim of this study was to evaluate ...
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Many of irrigated agriculture problems are resulting from chemical and physical composition of irrigation water. The irrigation water quality is effective on soil moisture characteristic curve by effect on soil structure, pore size distribution and continuity of them. The aim of this study was to evaluate the effect of different water salinity in the presence of constant turbidity on the soil moisture curve. The salinity treatments at five levels (1, 2, 4, 6 and 8 dS/m) with constant turbidity (200 NTU) were applied. These treatments were investigated at three depths of soil (0 to 15, 15 to 30 and 30 to 45 cm) with a silt-loam texture with three replications in a randomized complete block design. Soil water retention curve was determined by using pressure plate method. The results were statistically analyzed with MSTATC software. The results showed that the water percent of the soil of S2, S3, S4, S5 treatments of irrigation water quality increased to values 13.65, 20.20, 23 and 30 percent compared to S1 treatment. Comparison of water percent of soil at various depths showed that the depth of the second and third compared to the first decreased to 1.40 and 2 percent.
