Plant Nutrition, Soil Fertility and Fertilizers
Sepideh Raeisi; Nafiseh Rangzan; Naeimeh Enayatizamir
Abstract
Introduction: Zinc (Zn) is a vital nutrient for plants, needed in small amounts for their reproductive and physiological functions. Zinc deficiency is common in soils with high pH, low organic matter, and high calcium carbonate. Soil salinity is one of the most important and common environmental stresses ...
Read More
Introduction: Zinc (Zn) is a vital nutrient for plants, needed in small amounts for their reproductive and physiological functions. Zinc deficiency is common in soils with high pH, low organic matter, and high calcium carbonate. Soil salinity is one of the most important and common environmental stresses in the world. The impact of salinity on the forms of zinc and its availability in soil has varied. Among the chemical forms of zinc, the soluble and exchangeable forms have the highest mobility and availability for plants; whereas the residual form, associated with the crystalline lattice of soil minerals, appears to be very inactive. Depending on the physical and chemical properties of the soil, the carbonate forms, those bound to iron and manganese oxides, and the organic forms of elements are relatively active and have the potential to be available for plants. Organic materials like carbon black can alter zinc distribution. Zinc-solubilizing bacteria enhance zinc availability by converting insoluble forms into absorbable ones. This study examines the effects of carbon black and growth-promoting bacteria on zinc forms and soil properties under varying salinity levels.Materials and Methods: In this study, to investigate the effect of carbon black and inoculation of a mixture of two bacteria on the distribution of chemical forms of zinc under salinity stress, a pot experiment with four replications was conducted as factorial with three factors: salinity (2, 5, and 8 dS m-1), carbon black (0, 4% by weight), and a mixture of two bacteria (inoculated and non-inoculated). The bacteria included Enterobacter cloacae and Bacillus sp., which were obtained from the microbial collection of the Soil Science Department at Shahid Chamran University of Ahvaz. The experiment was carried out in a completely randomized design in 2023 in the greenhouse of Khuzestan Agricultural Sciences and Natural Resources University. In 5-kilogram pots, 10 corn seeds were planted, which were reduced to 6 plants per pot after ensuring germination. Two months after planting, soil samples were taken from the pots, and after removing the roots and passing through a 2-millimeter sieve, they were transferred to the laboratory to determine the chemical forms of zinc. The sequential extraction method was used to determine the chemical forms of zinc. The fractions—exchangeable, carbonate, iron and manganese oxides, organic, and residual—were determined. The concentration of zinc in the extracts obtained from the various stages of sequential extraction of the soil was read using an atomic absorption device. Some biological properties of soil, such as microbial biomass carbon via fumigation-extraction method, catalase activity via the titration method, and soil respiration by titration of residual NaOH, were measured.Results and Discussion: The interaction effect of carbon black× inoculation× salinity on chemical forms of Zn was significant. The results showed that the inoculation of a mixture of two bacteria and addition of carbon black in soil significantly increased the soluble and exchangeable, carbonate, iron and manganese oxide, and organic forms of zinc. Inoculation of a mixture of two bacteria and carbon black to the soil at a salinity level of 2 dSm-1 resulted in an increase in EXCH-zinc from 1.02 to 1.38 mgkg-1 compared to the control, which is equivalent to a 35% increase. Inoculation of the bacterial mixture and the addition of carbon black to the soil increased all forms of zinc except the residual form. With increasing salinity level, the amounts of soluble and exchangeable, carbonate-bound, and oxide-bound forms increased, while the organic-bound form decreased. The highest amounts of microbial biomass carbon, catalase activity, and soil respiration were measured in the treatment with bacteria, carbon black, and at a salinity level of 2 dS m-1, with values of 19.9 mg-Cmic 100g-1, 0.95 mLKMnO4g-1h-1, and 70.2 mgCO2 100g-1day-1, respectively. There was a positive correlation between soil respiration and all forms of zinc, except the residual form, but the correlation between soil respiration and the residual form of zinc was negative, indicating the influence of microbial activity on different forms of zinc.Conclusion: The addition of a carbon black to the soil and inoculation of a mixture of two bacteria caused zinc to convert from residual form to soluble and exchangeable, carbonate, oxide, and organic forms, increasing the availability of zinc in accessible fractions at various salinity levels. Overall, zinc-solubilizing bacteria offer a promising solution for enhancing zinc availability in saline soils, promoting plant health, and contributing to sustainable agricultural practices.
Land Evaluation and Suitability
Nazanin Khakipour
Abstract
Introduction: Soil is a dynamic natural system and interface between land, air, water, and life, which performs vital services for human sustenance. The increasing population growth has led to the excessive use of this natural resource to provide food, clothing and other human needs. This has led farmers ...
Read More
Introduction: Soil is a dynamic natural system and interface between land, air, water, and life, which performs vital services for human sustenance. The increasing population growth has led to the excessive use of this natural resource to provide food, clothing and other human needs. This has led farmers in different parts of the world to improper exploitation of inferior and marginal lands such as pastures and forests located on sloping lands. However, on the one hand, these lands have low potential and on the other hand, they have a high potential for erosion. Soil quality is usually introduced as the ability of the soil to interact with the ecosystem maintain the productivity of the quality of different parts of the environment and thus improve the health of plants, animals and humans. The quality of soil and its importance for the development of sustainable agriculture are more important nowadays. Land use change is one of the most important current problems of our country, especially in the Hyrcanian forest lands in the north of the Iran. The objectives of this study were to evaluate the effects of land use change on some soil quality indicators in north of Iran. Materials and Methods : A part area in the south of Lahijan was selected including 3 land uses: Natural Forest (NF), Tea plantation (TP) and paddy rice (PR) cultivation. In each land use 10 soil samples were collected at 0-20 cm depth and transferred to the laboratory. Undisturbed soils samples by core was taken for measurement of bulk density. A part of sample passed through the 4 mm sieve for measurement of aggregate stability and three indices comprised mean weight diameter: MWD, geometric mean diameter: GMD and water stable aggregates: WSA were calculated. Other soil properties such as pH, Calcium carbonate equivalent (CCE), soil organic matter (SOM), particulate organic carbon (POC), and soil respiration also measured.Results and Discussion: The statistical results in this study showed that due to the change of land use from forest to tea and rice cultivation, the amount of organic carbon decreased, while the amount of pH and calcium carbonate increased. As a result of changing the use of forest land to other two land uses, the indicators of stability of soil aggregates (MWD, GMD and WSA) have significantly decreased, and as a result, the bulk density of the soil has increased. The amount of MWD was 1.95 mm in the forest, 1.2 mm in the tea plantation, and 0.45 mm in the rice cultivation. The amount of particulate organic carbon as one of the indicators of soil quality in forest lands was observed in the maximum amount. In addition to the reduction of particulate organic matter, this change is also caused by the excessive traffic of machines. Soil microbial respiration was analyzed as a soil biological indicator. The results showed that the average microbial respiration in the natural forest was equal to 300 mg C/ day.g soil, and in the two other land uses of tea and rice cultivation, it was calculated as 200 and 120 mg C/ day.g soil, respectively. Positive and significant relationship between SOM and MWD confirmed that soil organic matter had high contribution for soil aggregate formation and its stability. Conclusion: This research was conducted to investigate the impacts of land use changes in the north of Iran in Gilan province on some soil quality indicators. The results of this research showed that the soil’s chemical, physical, and biological characteristics have shown significant differences due to land use change. In forest soils, the highest amount of organic carbon, and the lowest amount of pH was observed, which is due to the high accumulation of organic matter and high leaching of cations. Due to the degradation of organic carbon in the other two uses, the bulk density and aggregate stability indicators have decreased. The intense cultivation operations in the other two uses, especially in the paddy fields, have destroyed the soil structure. Also, more organic carbon in forest soils has led to more microbial respiration. In total, all soil quality indicators have decreased with the change in land use in the study area. Therefore, land conversion and especially deforestation in the studied region should be avoided. In total, the results showed that land use change in the study area has caused land degradation and reduced the soil quality and soil health indicators, and it is necessary to consider it in land use planning, land improvement, and sustainable land management.
