Soil Biogeochemistry and its Role in Plant Growth
Introduction
Sustainable food production has been one of the challenges in the world today due to an ever-growing human population. With increasing pressure on the soil, productivity reduces significantly due to consumption of nutrients. In some cases, methods for achieving sustainable high yields have been found. Most of the methods previously focused on the study of the weather and climatic conditions for crop suitability and the use of strategies such as soil rotation and intensification of land use. While these strategies help to increase crop yield, there have been arguments that they may not be sustainable due to the impacts that intensive crop growth and overuse of agricultural chemicals have on the soil. Soil biogeochemistry plays a crucial role in enhancing plant growth and it is believed through research that it could be the best alternative to maintaining sustainable agriculture. Studying soil biogeochemistry helps in developing an understanding of key soil characteristics which are crucial for ensuring effective and productive plant growth.
Various studies have been conducted on the subject of soil biogeochemistry. Similarly, most of these studies focus on the interrelationship between soil biogeochemistry and plant growth. However, many of these studies are also conducted in specific areas and with specific crops and/ or types of soil. The specificity therefore limits application of such studies to the general context. In the present study, the key objective is to determine how soil biogeochemistry influences plant growth and the factors that affect the soil biogeochemistry in various ways. To achieve these objectives, the study was carried out based on two key research questions which include:
- What role does soil biogeochemistry play in plant growth?
- What are some of the factors that can result in the variation of soil biogeochemistry?
Achieving these objectives will be crucial to geology due to the potential of the study to increase knowledge on the aspect of sustainable agriculture. This implies that it contributes to the subject in academia as well as in practice. In the ensuing sections, a review of relevant pieces of literature is conducted. This is followed by discussion of each of the research questions and the final section of conclusion which recaps the entire study paper.
Literature Review
Soil biogeochemistry is an inescapable topic in the discussion of sustainable agricultural practices. Various authors touch on the subject and its relationship to plant growth. The plants discussed include both food crops and other wild crops, trees, grass and others. According to various studies, soil biogeochemistry influences the type of ecosystem that a soil develops for the plants and the microorganisms it supports. In essence, the biogeochemical properties of the soil enable it to support particular plants whose nutritional demands are at par with what the soil provides.
Soil Biogeochemistry and Plant Growth
In several studies, the nature of interactions between the soil and the plant roots are reported to be dynamic and complex and incomprehensible by limiting studies to the soil only. For instance, Philippot et al (2013) assert that an understanding of soil biogeochemistry can only be fully accomplished when the links between the soil, microorganisms it contains and the plants it supports are understood. In regards to this, Hargreaves et al (2015) outline various roles associated with each of these key players. This is such that the microorganisms are responsible for varying the nutrient loads in the soil and with it the biogeochemical properties. On the other hand, the plants carried by the soil are responsible, together with the soil itself for the creation of an ecosystem that is supportive of the survival of microorganisms. This makes it essential to conduct studies on plant and land suitability prior to engaging in any agricultural land use practices. Other authors such Smith et al (2015) also describe soil biogeochemical characteristics as essential in determining how suitable a particular soil is for its key agricultural purposes. In their article, Smith and others suggest that while conducting studies on soil biogeochemistry, it is imperative that various biogeochemical cycles such as the carbon cycle, nitrogen and water cycles be understood deeply in order to be able to fully comprehend the extent of the role played by soil biogeochemistry on plant growth.
The focus on the role of soil characteristics on plant growth is not limited to the mention of the need for studies on the area. Several authors also maintain the belief that soil biogeochemistry affects plant growth, probably more than other factors that are considered similarly strong in determining agricultural productivity. In their work, Basso and Ritchie (2015) describe the importance of understanding soil biogeochemistry in agriculture. According to these authors, most of the strategies used for enhancing agricultural productivity such as the use of industrial chemicals to boost soil nutrients and the rotation of soils are not as suitable as taking advantage of the soil properties. Similarly, the use of other methods like studying the climatic conditions may not be exactly effective. Basso and Ritchie argue that these methods are more likely to cause intense pressure on the soil and thus soil biogeochemistry studies form an essential mode for improving plant growth and productivity.
Others have also mentioned particular reasons why soil biogeochemistry proves to be an important determinant of plant growth and productivity. From the argument developed by Hargreaves et al (2015), maintaining agricultural sustainability requires land use filtering first by plant characteristics then by soil properties. Other factors such as nutrient additions take a back stage in this. It is only through this method that an effective soil ecosystem can be developed for the growth and productivity of both plants and microorganisms as each of these plays a crucial role in maintaining the soil characteristics. Philippot and others present their views in a different manner by saying that understanding soil evolution and cycling of soil characteristics is necessary for effective development of agricultural sustainability (2015). The authors further suggest that several methods could be used to determine soil characteristics so as to facilitate agriculture that only allows for the proliferation of plants and microorganisms which are beneficial to the soil for the long term. Smith et al posit that the soil supports key geochemical cycles such as the carbon and nitrogen cycles hence it is essential to understand soil characteristics for the information of agricultural policy makers today.
Other arguments have also supported the application of crop characteristics as well as soil properties for ensuring sustainable plant growth. In their own study, Zhang et al (2002) recognizes a limitation of most of the studies on the subject in that they focused on the crop characteristics. However, the authors proposed a model which incorporates crop characteristics and the soil properties in planning for sustainable agriculture. In the model proposed by Zhang et al, crop characteristics to be considered during planning include respiration and photosynthesis capacities; nutrient assimilation and accumulation and leaf area index among others. The authors suggest that understanding these properties can be critical in determining the plant demands and therefore matching the plant to the soil where the demands can be met easily. In terms of the soil, the characteristics that are considered crucial in ensuring effective plant growth include: nitrogen and carbon contents, soil moisture content and plant biomass among others. These properties are crucial in agricultural soils as they also determine the plant carrying capacity of the soil.
Schroder and others (2016) also discussed the key characteristics of soil that are associated with plant growth and productivity. From their developed works, the authors present features such as nutrient carrying capacity, the ability to carry and deliver nutrients to plants, ability to extract excessive nutrients from plants and the ability to support plants in up taking nutrients as crucial in ensuring that sustainable plant growth is achieved. As such, studying soil biogeochemistry entails a consideration of these factors to facilitate effective nutrient cycling where there is need to do so. In another article by Zhao et al (2010), the authors exemplify the concept of soil characteristics and the role it plays in plant growth and productivity through a study of sandy soil on Hainan. In this study, Zhao et al confirm that sandy soils are more likely to result in lower crop yield due to characteristics such as poor moisture retention, lower nutrient carrying capacity and poor nutrient cycling capacities due to the low number of microorganisms that can be supported by the soil. Through a comparison of different areas with similar soil characteristics, the authors also managed to show that although soil characteristics is the greatest determinant of agricultural productivity, other factors such as rainfall are also crucial in ensuring that the achieved productivity is sustainable.
Factors Affecting Soil Biogeochemistry
As observed in the previous section, many of the studies focus on soil biogeochemistry and its importance to plant growth and productivity. On the other hand, very few studies explore factors that could result in variations in soil biogeochemistry. According to the study by Schroder et al (2016), soil nutrient cycling is one of the key features of soil that determines its effectiveness in crop growth. It is also because of nutrient cycling that crop rotation is often practiced as a method of enhancing sustainable agricultural productivity. In the discussion on nutrient cycling, several aspects have been mentioned to be responsible for nutrient cycling in the soil. Authors such as Leff, Ramankutty and Foley (2004) discuss how major crops are distributed across the world. In the research conducted by the three authors, the distribution of major crops is indicative that there are factors beyond climatic conditions that influence crop growth and suitability to particular soils. On the other hand, their work also shows that the soil characteristics may not be similar entirely through a section of the land. As such, it is crucial to understand how nutrient cycling occurs in order to pursue ways other than through the use of agricultural chemicals in order to improve the soil characteristics.
Schroder et al purport that nutrient cycling can occur effectively through the application of various nutrients borne in water and other wastes. The authors, while conducting their study, showed that most of the municipal and industrial wastes are laden with nutrients, particularly mineral elements such as calcium that are required by plants for growth. The ability of the soil to assimilate such nutrients from the wastes depends on soil characteristics and could be similar in any way to the assimilation of nutrients from agricultural chemicals. As such, those wasters require treatment to only reduce toxins and junk. This is however not the only way through which nutrient cycling can occur.
In an effort to explain the negative effects of intensification of land use and crop rotation, Didham et al (2015) reported that such strategies may not be effective for nutrient preservation. While land use intensification reduces the soil capacity in terms of nutrients, crop rotation is not a sure way for retaining nutrients in one area. This is because crop rotation depletes nutrients in one area leading to the spillover of nutrients from the surrounding areas. In the long run, there is nutrient reduction in the crop area as well as in the surrounding areas. This makes it necessary to find ways of boosting the land nutrient content while also maintaining the positive form of crop rotation. Intensification on the other hand may have to be explored to its full potential. There is the probability that land use intensification results in variation of soil nutrients especially where both livestock and crops are kept on the same small piece of land.
Other factors that result in nutrient cycling are mentioned by Quinton in an undated article. In this article, the author suggests that previous studies have ignored the impacts of factors such as lateral movement of soil and soil erosion. He opines that such should not be the case and that the movement of soil has more detrimental effects on such biogeochemistry and should be considered when determining plant suitability to soils. Some of the impacts of factors such as soil erosion and lateral movement include: carbon sinking in the eroded soils, lateral movement of minerals from the eroded to the deposition points and impacts on the soil’s primary productivity. These impacts can be adverse and can result in more negative outcomes on plant growth. In conclusion, Quinton argues that while undertaking studies on the role played by soil biogeochemistry on plant growth and primary productivity, it is essential that a consideration be made of the factors that may result in negative outcomes as this also has the potential of negative the expected positive outcomes from the consideration of soil characteristics.
Discussion
The role of Soil biogeochemistry on plant growth and productivity
From the review of literature conducted above, it is evident that soil biogeochemistry plays an important role in the enhancement of productivity. This is based on the understanding of what soil biogeochemistry entails. The studies reviewed affirm that soil characteristics play a role that may be higher than that played by factors such as climatic conditions and crop characteristics. As such, understanding the soil biogeochemistry is imperative if sustainable agriculture is to be achieved. Most of the other strategies such as land use intensification, climatic conditions alignment and crop rotation have shown limitations that can only be overcome through understanding the soil characteristics. For instance, intensification has been shown to cause a strain on the land through excessive consumption of nutrients. On the other hand, other methods such as crop rotation have shown the potential for resulting in nutrient cycling. While this other outcome may seem to be allowable, this is not so as cycling results in unreliability of soil test results due to variations in nutrient loads. Similarly, the use of other nutrient loading activities such as extraction of nutrients from wastes and agricultural chemicals can be argued to be unsustainable as not all nutrients can be obtained from these sources. Determination of soil biogeochemical properties therefore appears to be the most suitable method of improving primary agricultural productivity with straining any of the resources in application. Variation of climatic conditions also plays a significant role in agricultural productivity albeit not as strong as that played by the soil characteristics. This could be because the weather also helps to determine the soil characteristics to a significant degree.
In the discussions pertaining to soil characteristics, many authors have also mentioned specific features of soils which make the soil an important determinant of agricultural productivity and plant growth. The role played by the soil in carbon, nitrogen and water cycles comes in at the forefront of the factors that make soil characteristics important in planning sustainable agriculture. Features such as nutrient carrying capacity, water retention and moisture content are all important in soil characteristics studies. This is because the ability of soil to result in productivity depends on its ability to carry and deliver nutrients and water to the plants as well as on its ability to extract excess nutrients and water from the plants.
Factors that result in Soil Biogeochemistry Variation
While many studies focus on the role that soil biogeochemistry plays in agricultural productivity, very few studies have concentrated on the factors that can result in its variation as Quinton mentions. From the study findings, it is clear that nutrient cycling is an inevitable part of soil biogeochemistry. This occurs naturally in most cases through the microorganisms found in the soil ecosystem. Nutrient cycling is essential for plants if controlled and if the nutrients in question are sufficient for plant growth. This is enhanced through methods such as crop rotation which may or may not be beneficial to the plants. On the other hand, forceful modes such as lateral soil movement and soil erosion are not favorable for nutrient cycling as they have other detrimental effects such as carbon sinking and lateral nutrient flux. Both of these impacts can hinder effectiveness in primary productivity.
Conclusion
In the study, the objective of determining the role of soil biogeochemistry on plant growth and productivity has been accomplished satisfactorily. Similarly, it has also been shown that besides natural processes that result from microorganisms and crop rotation, other processes such as soil erosion and lateral movement of soil have proved to be harmful to the soil. Most of the studies reviewed show that soil biogeochemistry is a crucial determinant of plant growth and productivity capacity of a soil due to various reasons. This makes it necessary for studies to be conducted on soil characteristics before engaging in agriculture in order to achieve increased productivity. Although the study has achieved its objective, it is evident that more needs to be done pertaining to the subject of soil biogeochemistry.
References
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Didham, R., Barker, G., Bartlam, S., Deakin, E., Denmead, L. Fisk, L. et al. (2015). Agricultural Intensification Exacerbates Spillover Effects on Soil Biogeochemistry in Adjacent Forest Remnants. PLoS One, 10(1).
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Philippot, L., Raaijmaker, J., Lemanceau, P. & Van der Putten, W. (2013). Going Back to the Roots: The Microbial Ecology of the Rhizosphere. Nature Reviews Microbiology, 11(11).
Quinton, J. (n.d). The Impact of Agricultural Soil Erosion on Biogeochemical Cycling. Lancaster University Press.
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Smith, P., Cotrufo, F., Rumpel, C., Paustian, K., Kuikmann, P., Elliott, J. et al. (2015). Biogeochemical Cycles and Biodiversity as Key Drivers of Ecosystem Services Provided by Soils. Soil, 1: 665- 685.
Zhang, Y., Li, C., Zhou, X. & Moore, B. (2002). A Simulation Model Linking Crop Growth and Soil Biogeochemistry for Sustainable Agriculture. Ecological Modeling, 151: 75-108.
Zhao, Y.G., Zhang, G.I., Wen- Jun, Z. & Gong, Z.T. (2010). Soil Characteristics and Crop Suitability of Sandy Soils in Hainan, China. Session 1: Global Extent of Tropical sandy Soils and their Pedogenesis. Retrieved from ftp://ftp.fao.org/docrep/fao/010/ag125e/ag125e03.pdf