Document Type : Research Paper

Authors

1 Department of soil science, Faculty of Agriculture, Rafsanjan University

2 Department of Soil Science, Faculty of Agriculture, Shahid Chamran University of Ahvaz, Ahvaz, Iran

3 Soil Science Dep. Faculty of Agriculture, Jiroft University

Abstract

Introduction
Soil is the upper layer of earth in which plants grow and is consequently very important for organisms and human nutrition. The protection of the soil against degrading processes, such as soil salinization and alkalization, is one of the main challenges in sustainable land management. Soil salinization and alkalization are two major environmental concerns leading to soil degradation especially in arid and semi-arid regions across the world. The balance of organic carbon in the soil is important for soil sustainability. Intensive cultivation enhance soil organic carbon (SOC) depletion. In order to alleviate the detrimental effects of SOC depletion, carbon-rich organic amendments such as biochar or compost are often applied to the soil. Therefore application of organic amendments to soil is an effective strategy to improve soil properties and to mitigate the negative impacts of inappropriate management strategies. Biochar is a carbon-rich compound produced by the pyrolysis of biomass in oxygen-limited conditions. Its use as an organic amendment to soil with specific inherent characteristics has been recognized. In this regard recent studies have shown that application of biochar to soil as an organic amendment can improve soil physical properties and help to keep the carbon balance in the soil. Moreover, compost as an organic amendment is capable to improve soil properties and increase the soil productivity.

Methods and Materials
The soil sampling was carried out near Kabutar Khan in Rafsanjan, Iran (56°22′N, 30°18′E), on a saline-sodic soil with Silty Clay soil texture (42% silt, 50% clay and 8% sand). The biochar was obtained from three different feedstocks consist of Conocarpus erectus, bagasse of Sugarcane and hard shell of Pistacia Vera. The obtained feedstocks were pyrolyzed at 400°C for 2 h with increasing rate of 7 °C/min in a sealed reactor to prevent O2 input (Muffle Furnace, SEF-101 Model). Afterwards the produced biochar was cooled slowly to the room temperature, then the EC, pH, specific surface area and CHNS of biochars were measured using the standard methods. The required amounts of soils and biochars were weighed by a total 5000 g dry weight of sample and mixed in the dry state. The soil samples were received three doses of biochar (0, 2, 4 % biochar, w/w). The mixtures of soil and biochar were packed into pots and controlled a bulk density of about 1.5 g cm-3 by artificial compaction. Treatments were replicated three times. The soil without any biochar was used as the control. The mixtures were wetted at three soil moisture contents (25, 50 and 75% field capacity) during incubation time (120 days). The treatments were kept at a temperature-controlled glasshouse. After 120 days of incubation, the untreated soils and biochar-amended soils were taken for physical and chemical analyses.
Particle size distribution was measured by hydrometer method and soil organic carbon by oxidation method with potassium dichromate. The consistency limits (liquid limit and plastic limit) of soils were determined according to the ASTMD4318 procedure. The field capacity was measured using the pressure plates with the standard rings in the lab. Mechanical strength is a sensitive indicator of the soil physical condition and has been commonly used to evaluate soil water erosion, structural stability, tillage performance, and root penetration. Higher strength found in saline-sodic soil often impedes seedling emergence and root penetration.

Results and discussion
Our results revealed that application of organic matter in the form of biochars and compost was effective on soil aggregation. The formation and stability of the soil aggregates play an important role in the crop production and soil degradation prevention. Moreover, the biochar application showed two main effects including direct and indirect effects. Our results confirm the addition of biochar to soil can cause a substantial and significant change in the soil physical characteristics of the strongly acidic Ultisol, namely a significant increase in LL and PI, higher water-holding capacity, and reduction in mechanical strength. These changes are undoubtedly associated with the particular properties of biochar and in particular with its high porosity and low bulk density. The beneficial effect of biochars on soil physical properties is mainly due to the dilution effect of biochar with higher porosity and lower density. When the biomass is heated, volatile matters may release out of the biomass to create micropores on the surface, and meanwhile those trapped inside the biomass are evaporated to expand the microstructure. Thus, the resulting biochar has much higher surface area and porosity. These properties are particularly useful for soil application of biochar especially for enhancing soil water-holding capacity, reducing mechanical strength, and increasing soil aggregation. The dilution effect can be attributed to the increased volume of pores as well as the decreased particle density in soil amended with biochar. The effectiveness of different biochars in improving the soil physical properties can be explained by their porosity and bulk density.

Conclusion
Our results depicted that application of biochars and compost as an organic amendments improved mechanical quality of the saline and sodic studied soil. Indeed all organic treatments decreased bulk density and enhanced soil aggregate stability while the biochar of Conocarpus illustrated the greatest effectiveness on soil physical and mechanical properties. Therefore it is a possibility to apply this biochar to the soil in the field scale but regarding the accessibility of biochar of Pistachio skin in the study area therefor we have another alternative to utilize in the soil. This research was conducted in the small scale and in a short time. Therefore, it is suggested that supplementary studies are carry out on farm scale for a longer periods.

Keywords

  1. Adekalu, K.O., and J.A. Osunbitan. 2001. Compatibility of some agricultural soils in south western Nigeria. Soil and Till. Res. 59:27-31.
  2. Ali, Sh., Rizwan, M., Qayyum, M.F., Ok, Y.S., Ibrahim, M., Riaz, M., Arif, M.S., Hafeez, F., Al Wabel, and Shahzad, A.N. 2017. Biochar soil amendment on alleviation of drought and salt stress in plants: a critical review. Environmental Science and Pollution Research, DOI 10.1007/s11356-017-8904.
  3. Alipour Babadi M., Moezzi, A.A., Nouruzi Masir M., and Khademalrasoul, A. 2018. Effects of feedstock and temperature of pyrolysis on some chemical and physical properties of biochar. Iran Journal of Soil Water Research, 49(3): 537-547.
  4. Amini, S., Ghadiri, H., Chen, Ch., and Marschner, P. 2015. Salt-affected soils, reclamation, carbon dynamics, and biochar: a review. Journal of Soils and Sediments, DOI: 10.1007/s11368-015-1293-1.
  5. Barzegar, A.R. 2004. Advanced soil physics. Shahid Chamran University press.
  6. Brown, R. 2009. Biochar production technology. Biochar for environmental management: Science and Technology, 127-146.
  7. Demirbas, A. 2004. Effects of temperature and particle size on bio-char yield from pyrolysis of agricultural residues. Journal of Analytical Applied Pyrolysis, 72, 243–248.
  8. Ekwue, E. I., and Stone, R. J., 1995. Organic matter effects on the strength properties of compacted agricultural soils. Trans. ASAE, 38: 357-365.
  9. Ekwue, E.I. 1990. Organic matter effects on soil strength properties. Soil and Tillage Research, 16: 289-297.
  10. Fang, Y., Singh, B., Singh, B.P., and Krull, E. 2014. Biochar carbon stability in four con-trasting soils. European Journal of Soil Science, 65:60–71.
  11. Gao Lu, S., Fang, S.F., and Tong, Z.Y. 2014. Effect of rice husk biochar and charcoal fly ash on some physical properties of expansive clayey soil (Vertisol). Catena, 114: 37-44.
  12. Herath, H.M.S.K., Camps-Arbestain, M., Hedley, M. 2013. Effect of biochar on soil physical properties in two contrasting soils: an Alfisol and an Andisol. Geoderma, 209–210, 188–197.
  13. Herrick, J. E., and Jones, T. L. 2002. A dynamic cone penetrometer for measuring soil penetration resistance. Soil Science Society of America Journal, 66: 1320-1324.
  14. Ippolito, J.A., Novak J.M., Busscher, W.J., Ahmedna, M., Rehrah, D., and Watts D.W. 2012b. Switchgrass biochar affects two Aridisols. Journal of Environmental Quality, 41, 1123–1130.
  15. Kemper, W.D., and Rosenau, R.C. 1986. Aggregate stability and size distribution. Methods of soil analysis: Part 1 physical and mineralogical methods, 5.1, second edition. SSSA book series.
  16. Klute, A. (Ed.) Methods for soil Analysis. Part6. Physical and Mineralogical Methods. 2nd Editon. Agron. Monog. 8 ASA/SSSA, Madison, WI. pp. 524-552.
  17. Khademalrasoul, A., Naveed, M. , Heckrath, K.G.I.D., Kumari, L.W., de Jonge, L., Elsgaard, H., Vogel, J., and. Iversen, B.V. 2014. Biochar effects on soil aggregate properties under no-till maize. Soil Science, 179:273-283.
  18. Khademalrasoul, A., Nikolaus, J.K., Elsgaard, L., Hu, Y., Iversen, B.V., and Heckrath, G. 2019. Short-term effects of biochar application on soil loss during a rainfall-runoff simulation. Soil Science, 184: 17-24.
  19. Lehmann, J., and Joseph, S. 2009. Biochar for environmental management: an introduction. In: Biochar for Environmental Management: Science and Technology. J. Lehmann, and S. Joseph (eds.). Earthscan, London, UK, pp. 1‒12.
  20. Lohrasbi, H., Khademalrasoul, A., and Farrokhian Firuzi, A. 2019. Effects of biochar and zeoplant on physical and mechanical properties of erodible soils (Case Study: Bostan). Journal of Water and Soil, 33 (5), 723-737.
  21. Luo, X., Liu, G, Xia, Y., Chen, L., Jiang, Z., Zheng, H., and Wang, Z. 2016. Use of biochar compost to improve properties and productivity of the degraded coastal soil in the Yellow River Delta, China. Journal of Soils and Sediments, DOI 10.1007/s11368-016-1361-1.
  22. Ohu, J. O., Ekwue, E., and Folorunse, O. A. 1994. The effect of addition of organic matter on the compaction of a vertisol from Northern Nigeria. Soil Technology, 7: 155-162.
  23. Qu, J., Li, B., Wei, T., Li, C., and Liu, B. 2014. Effects of rice-husk ash on soil consistency and compatibility. Catena, 122: 54-60.
  24. Rajkovich, S., A. Enders, K., Hanley, C., Hyland, A., Zimmerman R., and Lehmann., J. 2012. Corn growth and nitrogen nutrition after additions of biochars with varying properties to a temperate soil. Biology and Fertility of Soils, 48(3): 271-284.
  25. Sheng-Gao Lu, Fang-Fang Sun, Y-Tong Zong, 2013. Effect of ricehusk biochar and coal fly ash on some physical properties of expansive clayey soil (Vertisol). Catena, 114 (2014) 37–44.
  26. Sohi, S., Krull E., Lopez-CapelE., and Bol, R. 2010. A review of biochar and its use and function in soil. Advances in Agronomy, 105: 4-82.
  27. Sombroek, W., Ruivo, M.L., Fearnside, P.M., Glaser, B., and Lehmann, J. 2003. Amazonian dark earths as carbon stores and sinks. P 125-139, In: J. Lehmann, D.C. Kern, B. Glaser and W.I. Woods(Eds.), Amazonian dark earths: origins, properties, management. Dordrecht: Kluwer Academic Publishers.
  28. Tejada, M., and. Gonzalez, J.L. 2006. The relationships between erodibility and erosion in a soil treated with two organic amendments. Soil and Tillage Research, 91: 186–198.
  29. Thies, J.E., and Rillig, M.C. 2009. Characteristics of biochar: biological properties. Biochar for environmental Science and Technology, 1, 85-105.
  30. Zhang, A., Bian, R., Pan, G., Cui, L., Hussain, Q., Li, L., Zheng , J., Zhang ,X., Han, X., and Yu ,X. 2012. Effects of biochar amendment on soil quality, crop yield and greenhouse gas emission in a Chinese rice paddy: A field study of 2 consecutive rice growing cycles. Field Crops Research, 127: 153–160.
  31. Zong, Y., and Chen, D. 2014. Impact of biochars on swell-shrinkage behavior, mechanical strength, and surface cracking of clayey soil. Journal of Plant Nutrients and Soil Science, 177: 6. 1-7.