Actions To Improve Soil Organic Matter Content And Its Impacts In Soil Sustainability

3013 Sustainable Management of Soil and Water

Importance of Healthy Soil for Crop Production

Title: Actions To Improve Soil Organic Matter Content And Its Impacts In Soil Sustainability.

Soil is the building block of food system by producing healthy crops. In order to get healthy crops, healthy soil is required. Soil provides fertility to the crops and plants and feeds them with matters and minerals (Blanco-Canqui, 2013). Unfortunately, due to some practices done by humans, the soil has been losing its fertility and some have even become barren. Farming also disturbs natural soil process and even disturbs the nutrient cycle, where nutrients are taken and released.

Organic matter and Minerals

Organic matter are materials obtained from remains of animals and plants which moves to the soil after decomposition. Other than that, it gives food to living organisms in soil and provides nutrients. Organic matter also helps in water retention capacity in soil. Mostly soil contains 2 to 10% of organic matter in it. Exchange of nutrients between soil, water and organic matter are required to maintain fertility in soil for sustainable production (Lehmann and Kleber, 2015). However, during the production of crops, soil is exploited, and no organic matter and nutrients are restored leading in loss of fertility, breaking the nutrient cycle and destroying the balance between agriculture and ecosystem.

Organic matter in soil is the addition of decomposition of plants and animals in soil. The fertility in soil needs to be maintained and to maintain this fertility, content of organic matter in soil should be maintained (2 to 10%). Different scientists are researching in order to improve organic matter in soil and maintain it so that fertility of soil remains intact and no problems arise during production of crops and soil safety is maintained (Senesi and Loffredo, 2018). It has become a major issue as lands are becoming barren and finding a solution to this problem is very important in order to prevent other remaining lands to become barren.

Scientists throughout the past decade has been working on how to improve and maintain organic matter content in soil. While some of them have been successful, some of them are still working on it. There are different methods/process by which organic matter content in soil is maintained or increased which is going to be discussed below.

Population increase led to increase in crop production and in order to fulfil the demands of the population, large amount of fertilizers and pesticides are used, results in losing of fertility in soil and leading to the land being barren (Powlson et al, 2014). Strategies of sustainable land management should be adopted (Bender et al., 2016). Conservation agriculture causes minimum damage to soil and should be adopted. An important aspect of agriculture conservation is conservation tillage (3013 Sustainable Management of Soil and Water: Busari et al., 2015). Tillage is the process of preparation of agriculture in soil by mechanical agitation.

Types of conservation tillage

Role of Organic Matter in Soil Sustainability

Tillage could be classified as:

No or zero tillage: Cultivation of land with no or less soil disturbance, disturbance only occurs while planting.

Minimum tillage: Less level of manipulation of soil like ploughing.

Mulch tillage: Soil is prepared in such a manner that plants and other residues are left on the surface as much as possible.

Ridge tillage: Crops are planted in rows in both sides during the beginning of cropping season.

Contour tillage: Tillage occurs at right angle to the direction of slope.

Zero tillage and minimum tillage reduces soil disturbances and provides better soil conditions (Scotti et al., 2015).

Research reports showed positives of conservation tillage than conventional tillage with chemical, physical and biological properties of soil and yield of crops (Greenland, and Hayes, 2016).

Physical properties of soil

Among all the tillage systems discussed, no tillage has higher soil surface coverage as compared to other systems. Physical properties of soil are more favorable in no tillage than tillage based system. According to reports, drained soils (texture is light to medium and humus content is low), responds most to conservation tillage and minimizes soil erosion (Król et al., 2013). No tillage also shows high porosity. When minimum tillage was compared with conservation tillage, it showed improvement in stability as well as increase in concentration of soil organic carbon and nitrogen in upper portion (5 to 8 cm) of soil. No tillage also showed more water retention capacity as compared to other tillage systems and highest water retention capacity occurred in top soil. Water efficiency was high in reduced tillage. Soil water quantity in zero tillage was 25% more than minimum tillage.

A study was conducted in South West Nigeria for a period of 6 years to check which method of tillage system was most effective (Busari and Saako, 2012). At the end of first year, high unsaturated water flow and infiltration rate was observed under conservation tillage, minimum tillage and zero tillage.

Toward the finishing of second year, zero tillage had higher infiltration rate and water flow compared to conservation tillage. It is due to fast draining micro pores created by conservation tillage which facilitates infiltration momentarily. As a result (Table 1) of soil aggregates repackage and there is reduction in fast draining micro pores.

Chemical properties of soil that that affect tillage systems are pH, cations exchange and nitrogen content in soil. Chemical properties of layer in surface are more favorable in no tillage compared to other tillage systems (Greenland and Hayes, 2016). No tillage system over a long period helps in maintaining and enhancing the chemical properties of soil, especially soil organic carbon content. Observation showed organic carbon content is higher in soil with no tillage than untilled soil and high amount of organic matter in top soil. Loss of nitrogen was observed under no tillage as compared to that of conservation tillage. Leaching rate was high implicating reduction of inorganic carbon and nitrogen. Tillage techniques showed no effect in pH of soil, even though pH in soil is lower in no tillage system than conservation tillage. Exchange of calcium, magnesium, potassium are higher in soil surface under no tillage compared to that of ploughed soil. In tillage, plot values of soil N, P, K, Ca, Mg was low which could be due to ploughing where top soil is removed and subsoil is present which is less fertile with possible leaching.

Methods To Improve Soil Organic Matter Content

 A study was conducted in South West Nigeria for a period of 6 years to check which method of tillage system was most effective (Busari and Saako, 2013). At the end of two years it was observed that soil organic carbon and cation exchange capacity was found to be significantly high under zero tillage than conservation tillage. However, it was found that minimum tillage has resulted in higher pH and soil organic carbon than conservation tillage at the end of each year (Table 2). It suggests that less disturbance in soil can help in retaining chemical quality of soil.

Natural properties of soil are most influenced in soil natural carbon content by tillage. Earthworms are principle segments of soil small scale fauna as they give ripeness to soil. Its burrowing action helps in improving soil water penetration and air circulation (Sw?drzy?ska et al., 2013). Population of earthworms are affected by tillage practices, mainly ploughing. A six year study showed high population of earthworm under no tillage soil than ploughed soil (Zhou et al., 2014). Due to tillage, there is disruption of mycelia (fungi) and decrease in biomass of fungi and increase in biomass of bacteria.

Phosphate solubilizing microorganisms ways to deal with oversee phosphate inadequacy in agrarian soils. The most key component for soil after nitrogen is phosphorous. Phosphorous is abundant in soil, yet in both natural and inorganic structures and mostly happens in insoluble structure (Otieno et al., 2015). Phosphate content in soil is 0.05% (w/w) yet just 0.1% of all out phosphate is accessible because of poor solvency and its obsession. Phosphorous is required in early periods of plant advancement. It assumes a significant job in expanding root repercussion and quality. It helps in seed arrangement and early development of harvests like vegetables and grains. Inadequacy in phosphorous lessens the size of plants and their development. Phosphorous contains 0.2 to 0.8% of dry load in plants. For prerequisite of supplements in crops, phosphorus is included as substance manure. However, chemical fertilizers have severe  adverse impact on environment (like soil fertility, carbon foot prints and many more).

Plants can utilize just a limited quantity of this compound phosphorous, despite the fact that 75-90% of the phosphorus included is accelerated by the metal and ends up fixed in the dirt. Because of this explanation, phosphate solubilizing microorganisms is the most eco neighborly strategy to give nourishment to crops.

Several bacterial (Pseudomonas and Bacilli) and fungal strains (Aspergillus and Penicillium) under in situ conditions are not found reliable. So they need to be modified. They can be modified by either co-inoculation techniques or genetically modified strains.

Tillage Systems and their Impact on Soil

Gypsum disposal

Aggregation of Cd and other substantial metals in soil

Microorganisms play an important role in phosphorous cycle in soil. Phosphate solubilizing microbes  through different methods of solubilization and mineralization can convert it to organic and inorganic phosphates respectively. It could help in growth and development of plants as well as development of plants as well as keep the fertility of the soil.

Phosphorous fixation tells us the reactions which removes phosphorous from soil solution into soil solid phase. Two types of reactions occur

• Phosphate ingestion on surface of soil minerals
• Phosphate precipitation by free Al3+ and Fe3+ in the dirt arrangement

The productivity of phosphorous manures in substance structure is over 30% as a result of its obsession, as iron/aluminum phosphate in acidic soils or as calcium phosphate in unbiased or soluble soils. One of the fundamental qualities of phosphorous biogeochemistry is that just a single percent of complete phosphorous is brought into living plant biomass in each developing season, mirroring its low accessibility for plant take-up in soil.

Throughout the previous two decades, works done and information on phosphate solubilizing microorganisms has expanded altogether. Microorganisms are disconnected utilizing society procedures (Bashan, Kamnev and de-Bashan, 2013). Bacterial (Pseudomonas and Bacilli) and parasitic strains (Aspergillus and Penicillium) are utilized. In soil, phosphorous solvent microorganisms is 1 to half while in the event of phosphorous dissolvable growths, it is 0.1 to 0.5%. They are separated from rhizosphere and non rhizosphere soils (Teotia et al., 2016). One of the serious issue of phosphorous solvent organisms is the wellspring of insoluble phosphate. Determination consider utilized this characteristic is tricalcium phosphate (TCP). Since soils vary in pH and numerous other concoction properties, no metal phosphate compound could be utilized as regular determination factor for phosphorous solvent microorganisms. Determination of metal phosphate relies upon soil type (perhaps basic or acidic or natural rich) where phosphorous solvent microorganisms are utilized. Both parasitic and bacterial strain display phosphorous solubilizing action and shows radiance (indications of solubilization) around the settlements in a strong agar media. When disconnection is distinguished, further tests are led to sustenance in phosphorous plant. It helps underway of bio manures and looks after saltiness, pH, dampness, temperature.

Large number of microbial species have the capacity for potassium solubilization including bacteria, fungi, actinomycetes, cyanobacteria, VAM and many more. Examples of each species are given which acts as potassium solubilizers (Etesami, Emami and Alikhani, 2017).

Name of Species	Examples
Bacteria	Alcaligenes sp., Aerobactor aerogenes, Achromobacter sp., Actinomadura oligospora, Agrobacterium sp., Azospirillum brasilense, Bacillus sp., Bacillus circulans, B.cereus, B.fusiformis, B. pumils, B. megaterium, B. mycoides, B. polymyxa, B. coagulans B,.chitinolyticus, B. subtilis, Bradyrhizobium sp., Brevibacterium sp., Citrobacter sp., Pseudomonas sp., P putida, P. striata, P. fluorescens, P. calcis, Flavobacterium sp., Nitrosomonas sp., Erwinia sp., Micrococcus sp., Escherichia intermedia, Enterobacter asburiae, Serratia phosphoticum, Nitrobacter sp., Thiobacillus ferroxidans, T. thioxidans, Rhizobium meliloti, Xanthomonas sp.
Fungi	Aspergillus awamori, A. niger, A. tereus, A. flavus, A. nidulans, A. foetidus, A. wentii. Fusarium oxysporum, Alternaria teneius, Achrothcium sp. Penicillium digitatum, P lilacinium, P balaji, P. funicolosum, Cephalosporium sp. Cladosprium sp., Curvularia lunata, Cunnighamella, Candida sp., Chaetomium globosum, Humicola inslens, Humicola lanuginosa, Helminthosporium sp., Paecilomyces fusisporous, Pythium sp., Phoma sp., Populospora mytilina, Myrothecium roridum, Morteirella sp., Micromonospora sp., Oideodendron sp., Rhizoctonia solani, Rhizopus sp., Mucor sp., Trichoderma viridae, Torula thermophila, Schwanniomyces occidentalis, Sclerotium rolfsii
Actinomycetes	Actinomyces,, Streptomyces
Cyanobacteria	Anabena sp., Calothrix braunii, Nostoc sp., Scytonema sp.
VAM	Glomus fasciculatum

Source: (Sharma et al, 2013)

The significant procedures of soil phosphorous cycle that influences soil answer for phosphorous (Alori, Glick and Babalola, 2017)

Phosphate Solubilizing Microorganisms for Enhancing Soil Sustainability

(1) disintegration precipitation (mineral balance)

(2) sorption–desorption (activities between phosphorous in arrangement and strong surfaces in soil) and

(3) mineralization–immobilization (natural changes of phosphorous among inorganic and natural structures)

The fundamental systems include:

(1) arrival of perplexing or mineral dissolving mixes, for example natural corrosive anions, siderophores, protons, hydroxyl particles, CO2

(2) freedom of extracellular compounds (biochemical phosphorous mineralization) and

(3) arrival of P during substrate corruption (natural phosphorous mineralization)

In this way, microorganisms assume a significant job in these significant segments of phosphorous cycle in soil. Natural acids are created by phosphate solubilizing microorganisms by

(i) Lowering pH

(ii) Enhancing chelation of the cations with phosphorous

(iii) Competing with phosphorous for adsorption destinations on the dirt

(iv) Formation of dissolvable edifices with metal particles with insoluble phosphates (Ca, Al, Fe) and in this manner phosphorous is discharged.

Natural and inorganic phosphates are solubilized. Phosphate solubilizing microorganisms could be a solid segment of reasonable horticulture. It could be utilized as bio composts (Aggani, 2013) in future in various soil conditions which could transform into the real world. It could satisfy the needs for nourishment and horticultural difficulties. Better return could likewise be gotten. Future research should concentrate on overseeing communications among plants and microorganisms, uncommonly their method of activity and flexibility under extraordinary conditions to profit the plants (Mazid and Khan, 2015). Also, few issues should be tended to by researchers like how to improve viability of bio composts, how to balance out microorganisms in soil framework and improving wholesome angles in plants (Gupta et al., 2015). To put it plainly, biotechnology of phosphate solubilizing microorganisms could give in creating eco well disposed bio manures as an option in contrast to synthetic composts.

Conclusion

It can be concluded by saying that in order to provide sustainable productivity of agriculture, organic matter level in soil and optimization of the nutrient cycle is necessary. Both of them are closely related to biological activity between plants and living organisms present in soil, which provides fertility. Even though soil contains 2 to 10% of organic matter, it is the main component that provides fertility to the soil. As discussed earlier tillage methods and phosphorous solubilizing microbes (PSM) are the main methods by which organic matter content in soil can improve and has an impact on soil sustainability. Research works are being conducted in conservation of soil and improving organic matter content. It is known that excess use of fertilizers and pesticides has made the soil lose its fertility and eventually turn into barren lands. As discussed earlier about bio fertilizers, it could be one of the best alternatives for fertilizers and pesticides. The work done on bio fertilizers is still ongoing and it still needs some major modifications. Future aspects about bio fertilizers shows that soluble phosphorous are more effective and helps in growth and development of plants as well as maintains stability in soil. These methods needs to be adopted to conserve the soil for future. 

Aggregation of Cd and Other Heavy Metals in Soil

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