Fatemeh Hassani; Ataallah Khademalrasoul; Hosein Shekofteh
Abstract
IntroductionSoil 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 ...
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IntroductionSoil 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 MaterialsThe 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 discussionOur 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.ConclusionOur 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.
Parstoo Aslani; Masoud Davari; Mohammad Ali Mahmoodi; Farzad Hosseinpanahi; Naser Khaleghpanah
Abstract
Introduction Soil quality is one aspect of sustainable agroecosystem management. The application of zeolite minerals alone or in combination with other soil amendments (organic and inorganic fertilizers) can, directly or indirectly, affect soil quality indicators. Considering the unique characteristics ...
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Introduction Soil quality is one aspect of sustainable agroecosystem management. The application of zeolite minerals alone or in combination with other soil amendments (organic and inorganic fertilizers) can, directly or indirectly, affect soil quality indicators. Considering the unique characteristics of zeolites, such as the low-cost and abundance of its mines in Iran and the large area of wheat cultivation in Kurdistan province, the need to study the effect of zeolite application on soil properties and wheat yield becomes apparent. Although there is a lot of research on the impact of zeolite on improving soil properties and increasing the yield of various crops, few studies have been done on its residual effects. Therefore, in this study, we investigated the effect of zeolite and nitrogen (N) application on some basic soil properties, N efficiency, and wheat yield under field conditions after two years of zeolite application. Materials and MethodsBefore conducting the research, a composite soil sample from the soil surface (0 to 30 cm depth) was collected and analyzed to assess the farm's soil properties. The experiment was laid out in a split-plot based on a randomized complete block design with three replications at the University of Kurdistan research farm in Dehgolan. The main plots consisted of natural zeolite at four levels (0, 5, 10, and 15 ton. ha-1). Within each main plot, subplots were subjected to nitrogen applications at five levels (0, 50, 100, 150, and 200 kg. ha-1). Urea fertilizer was used to supply the required nitrogen. Zeolite was only utilized in 2018 and mixed into the surface layer of soil. The experiment was repeated in 2019 except for no addition of zeolite. The field was under potato cultivation in the first year of the experiment and followed by wheat crop in the second year. Wheat cultivation (Pishgam cultivar) was done in 2019 by grain seeders in plots with dimensions of 4.5 × 8.25 m. At the end of cultivation season, harvest was done from each plot, and some plant traits (grain protein, thousand-grain weight, spike number, grain number in spike, an economic yield of the plant, biological yield of plant, harvest index, and chlorophyll concentration) were measured. In order to investigate the effect of zeolite on basic soil properties, soil samples were collected from plots in the second year after harvest, and a number of physical and chemical properties of the soil were measured (dry bulk density (ρb), particle density (ρp), total porosity (f), saturated hydraulic conductivity (Ks), electrical conductivity (EC), soil reaction (pH), cation exchange capacity (CEC), and total soil nitrogen (TN)). Statistical analysis of data was performed using SAS 8.02 software.Results and DiscussionThe results from the second year indicated that the applications of zeolite or nitrogen alone or in combination with each other decreased dry bulk density and particle density of soil, but increased total porosity, saturated hydraulic conductivity, electrical conductivity, soil reaction, and cation exchange capacity. The porous structure of zeolite helps improve soil structure and increase porosity, thereby reducing the bulk density of the soil. Also, zeolites can affect the soil hydraulic conductivity due to channels in their structure. Zeolite is not acidic but marginally alkaline, and its use with fertilizers can help buffer soil pH levels. The very open structure of the zeolite and the similar pore network create a high specific surface area for the storage and exchange of nutrients. Therefore, different salts can be absorbed or desorbed from the zeolite structure. Desorption of salts from the zeolite can increase EC in the soil. The high cation exchange capacity and porosity of zeolite increase soil CEC, which increases the soil's ability to retain nutrients such as ammonium. The results also revealed that the grain protein, thousand-grain weight, spike number, grain number in spike, an economic yield of the plant, biological yield of plant and harvest index, with mean increasing about 37%, 6%, 30%, 15%, 43%, 26% and 7%, respectively, compared with the control, were significantly affected by zeolite and nitrogen applications, and also zeolite and nitrogen interaction. However, the chlorophyll concentration was not meaningfully influenced by them. Increased grain yield can be attributed to reduced nitrogen leaching and increased soil water holding capacity in the presence of zeolite, which improves nitrogen status and the availability of water for growth. Drought stress significantly affects grain yield, harvest index, thousand-grain weight, spike number, grain number in spike, and plant height. The use of zeolite can maintain soil moisture for a longer period and mitigate the adverse effects of drought stress on the crops.ConclusionThe improved agronomic traits and enhanced grain yield potentials induced by zeolite amendment were related to decreased drought stress in wheat crops and the increase in soil quality indicators and N uptake. The zeolite application probably enhanced NH4+–N retention in the topsoil and prevented NO3-–N from leaching into the subsoil. In general, the results showed that the combined application of zeolite and N can be a beneficial approach for increasing nitrogen fertilizer efficiency and improving the sustainability of agricultural systems.