Under the long-term effects of soil, rocks and organic materials, climate, organisms and topography, a certain amount of water, which consists of the products of various degrees of physical decomposition, chemical and biological decomposition, contains a large community of living things, serves as a stop and food source for plants. It is an active, dynamic, three-dimensional natural substance consisting of layers with different properties, containing air and air.
The natural structure of the soil consists of solid, liquid and gaseous substances. The ratios of these substances in the soil mass vary depending on the landform, geological structure, climatic conditions and seasons.
A loamy soil suitable for plant growth theoretically consists of 50% solid, 25% air and 25% water.
Although soil organic matter constitutes the least part (5%) by mass, it is the part that most affects soil quality, in other words, the ecosystem services produced by the soil.
In addition to humus, which is colloidal soil organic matter, it also includes microscopic organisms of soil microbial life. Soil organic matter is critical for the balance of soil structure, supply of plant nutrients, maintenance of water holding capacity and climate regulation effect; it is therefore one of the key indicators not only for agricultural productivity but also for environmental resilience.
In summary, soil organic matter is the active element that makes soil soil.
Since organic matter is a source of energy and nutrients for microorganisms in the soil, its presence increases the activity of microorganisms and increases the availability and uptake of plant nutrients. In particular, it acts as a storage source for nitrogen, phosphorus and sulfur. By binding the sand, silt and clay particles in the soil, it provides the formation of clusters ( aggregate formation ) and improves the soil structure ( structure ). As a result, it increases the soil's resistance to erosion, reduces the formation of a cream layer in the soil, and allows more infiltration of rain water into the soil. It reduces soil compaction and regulates the movement of water and air in the soil. It increases the soil temperature, the water holding capacity of the soil and the water uptake of the plants. It reduces the loss of nutrients from the soil, increases the cation exchange and buffering capacity of the soil, allowing plants to benefit from more nutrients. It reduces salt damage in plant production by increasing its buffering feature against changes in soil reaction and soil salinization. It increases the resistance of plants against diseases and pests.
In order for the physical, chemical, biological properties and yield potential of agricultural soils to be at the desired levels, the organic matter content should be at least 3% of the soil weight. Only 1% of Turkey's agricultural lands are above this value in terms of organic matter content.
Intensive tillage, erosion, monoculture agriculture, chemical fertilizers and pesticides reduce soil organic matter. As can be seen from the table below, while the rate of soils containing insufficient (very little, little and medium) soil organic matter in 1990 was 92%, this rate increased to 99% in the analyzes made in 2011-2014. Soils with good and high soil organic matter decreased from 7.2% to 1%.
Soil organic matter improves the physical properties of the soil, increases the water holding and cation exchange capacity, enriches the nutrient content of the soil when it decomposes, encourages plant root development and increases soil fertility due to its regulating effect on soil pH.
82-84% of the variability in corn yield is explained by the soil organic matter content. A decrease in the amount of organic matter in the soil from 1.4% to 0.9% may cause 50% yield loss in grain production. For this reason, the amount of fertilizer to be used increases as the amount of organic matter decreases. In response to the increasing amount of fertilizer use, the crop production per unit fertilizer (fertilizer efficiency) is decreasing.
Between 1960 and 1995, the amount of fertilizer used in wheat production increased 7 times , but while an increase of 70 kg/da was achieved from 1 kg of nitrogen used in wheat production in the early 1960s, this amount decreased to 25 kg/da in 1995.
The use of chemical fertilizers alone, without the addition of organic matter, also causes faster mineralization of valuable organic matter in the soil. Thus, instead of being a carbon sink, soils become a source of emission and contribute to the progression of the negative balance in the atmosphere/earth carbon (C) balance.
Chemical fertilizers have an important place among the factors affecting agricultural product yield and their use is increasing. Although the total agricultural area in Turkey decreased by 2.4 million hectares between 2011 and 2015, the amount of fertilizer consumed increased by 16% compared to 2007 and reached 5.9 million tons . However, the return of the increase in yield achieved by the use of increased chemical fertilizers has been the deterioration of the physical, chemical and biological properties of the soils, especially the decrease in the organic matter level.
Chemical fertilizers cause changes in the physical and chemical properties of the soil, the pH of the soil goes beyond the plant's will, ionic toxicity to the plants by creating a salt effect, the decrease in soil biological diversity, the decrease in the resistance of the plants to diseases and pests, the deterioration of the nutrient balance of the products, the pollution of the water, the heavy metals in its composition into the soil. They can cause heavy metal accumulation in the soil as a result of mixing.
For example; As a result of excessive and one-way nitrogen fertilization in Nevşehir in the last twenty-five years, the pH of the soils where potatoes are grown has decreased by up to 2 units, and the acidity, in other words, has increased 100 times. This drastic change has almost zeroed the productive power of the lands, causing the village population to leave their lands.
Similarly, 88% of the soils became very acidic and fell below the pH level desired by the tea plant, due to the use of ammonium sulphate compound and acidic chemical fertilizers, which increased rapidly and excessively since the 1970s in tea gardens.
Chemical fertilizer applications without soil analysis and without taking into account the physical, chemical and biological properties of the soil cause nitrate pollution in waters as well as deterioration of soil properties. Nitrate compounds are carried by rain water to wetlands, seas and underground waters. Eutrophication , which occurs with the increase of nitrate accumulation in the waters, causes the oxygen in the water to decrease and the water quality to deteriorate, affecting the aquatic ecosystems.
Nearly 50% of the wells in Antalya's Kumluca and Demre districts have nitrate pollution above the threshold values. 20-60% of the nitrogen given to the field plants and 40-80% of the nitrogen given to the forage plants can be used by the plants. In this case, 20-80% of the nitrogen in the fertilizers used can be used by plants, some of the remaining part evaporates from the soil and turns into Nitrogen oxides, which are among the greenhouse gases, and contributes to global warming.
Nitrogen are a strong greenhouse gas and 45-50% of greenhouse gas emissions from agricultural activities are attributed to Nitrogen oxide. In addition, these gases have a role in the depletion of the ozone layer. The high nitrogen content of the food produced also affects human health. Nitrate pollution in drinking water causes blue baby syndrome in babies over the age of one. There are research results on the fact that nitrogenous compounds taken with water and foods with high nitrogen content can cause cancer by being converted to nitrosamines and adversely affect the thyroid gland.
The basis of sustainable agricultural practices is based on practices that protect and improve soil organic matter and soil organisms.
The most important issue that is ignored in agricultural practices today; Agricultural production is closely linked to the vital components of the biosphere (life sphere) such as soil, water and air, and the interrelationships between them, and that any problem occurring in these basic elements directly affects agricultural production, biological diversity, and ecosystem balances.
The dissemination of sustainable agricultural practices in order to prevent soil degradation and environmental damage caused by industrial agriculture based on intensive tillage, chemical fertilizer and pesticide use is among the top priorities of agriculture today. Soil management in sustainable agricultural practices, as it improves the physical and chemical properties of the soil, increases the water capacity and aeration of the soil, the availability and uptake of nutrients depending on the activity of microorganisms in the soil; It is based on practices that preserve and improve the amount of organic matter.
In order to increase soil fertility and to prevent soil degradation that threatens the food security of future generations, sustainable agricultural practices should be widespread, and organic material sources that can be used to increase the organic matter level should be evaluated effectively.
When we use our organic material resources effectively, approximately 112 million tons of organic fertilizer can be obtained annually.
With these organic fertilizers and green fertilization, organic matter will be added to the 5 million hectares of land, which constitutes approximately 25% of the areas where we cultivate, and it will be possible to increase the yield potential of the soils and the yield and quality of the grown plants. In order to achieve this, the producers should be informed about the importance of the organic matter content of the soil, the organic matter sources that they can use in their soils and how they are used.
It is one of the most important organic matter sources of our soils. However, although burning is prohibited and there are penalties for those who burn, stubble is burned in at least 25% (3 million hectares) of our approximately 12 million hectares of grain cultivation area every year. Studies show that the average amount of stubble per hectare is 3.29 tons . In this case, approximately 10 million tons of stubble is burned every year.
The leading sources of organic matter are the wastes of cattle, sheep and poultry. Besides being organic matter, they are an important source of nutrients. Considering the animal wealth in Turkey, 87 million tons of mature manure can be produced, and by using the produced mature manure on 3 million hectares of land, it can be ensured to increase the yield and quality of the grown plants; For various reasons, these resources are not used correctly and effectively.
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Animal wastes are generally turned into uncontrolled heaps and used as organic fertilizers in agricultural areas after a largely anaerobic and long-term decomposition process. Methane, one of the greenhouse gases considered to be responsible for global warming, is released from uncontrolled anaerobic heaps, plant nutrients are lost through long-term decomposition and washing, and microbiological disinfection cannot be achieved. For these reasons, it reduces its effectiveness as a fertilizer and causes environmental pollution. As a result of these wastes being kept in unsuitable conditions or randomly applied to the land, a significant amount of nutrients are lost by washing and evaporation, and the expected benefit in terms of soil fertility and agricultural production cannot be fully achieved. In addition, it can pollute surface and underground water resources.
The production of biogas by decomposing animal wastes in an airless environment, obtaining energy from biogas, and using the remaining materials as organomineral fertilizers are considered as good waste management to prevent environmental damage as well as benefits.
Tree leaves, pruning wastes, mown grass wastes, greenhouse production wastes, plant stems and residues from which fruit or seeds have been removed, spoiled feed, straw and silage wastes in parks and gardens can be turned into compost and applied to the soil. After plant production, approximately 12.8 million tons of organic waste is released and most of them are wasted.
On the other hand, it is reported that 1.5 kg of garbage is generated per person per day in our country. Assuming that half of this garbage has an organic character and our population is close to 80 million, 11 million tons of quality compost can be produced from approximately 22 million tons of organic waste per year.
By applying the compost to be produced from plant and city wastes to the soil and increasing the soil organic matter content, a significant amount of economic gain will be achieved due to the protection or improvement of soil health, as well as the water savings to be achieved by increasing the water holding capacity of the soil and the decrease in the use of chemical fertilizers due to the nutrients it contains.
E.g; From the Şanlıurfa Harran Plain , 3,900,000 tons of agricultural organic waste is evaluated and applied to the soil (30% of the weight of the organic matter will store water, 55% of the organic matter will be carbon and organic carbon:nitrogen:sulfur:phosphorus ratios 100:10:1). ,5:1.5) It is calculated that the income to be obtained with the prices of 2017 will reach 2.663 million TL .
With the increase in environmental awareness, the amount of treatment sludge remaining from the treatment of waste water in the treatment plants, which have become compulsory to be established and operated, is gradually increasing. Today, it is of great importance that the treatment sludge be disposed of in an environmentally compatible manner in order to protect the natural environment and maintain it sustainably. In cases where organic resources cannot be adequately provided and these resources are limited, the use of wastewater treatment sludge seems to be an alternative.
Due to the organic matter they contain, sewage sludge initially provides an increase in the insufficient organic matter content of the soils. In addition, it is considered as a suitable material that can increase plant growth and soil fertility due to the content of some nutrients, especially N and P. However, sewage sludge contains toxic elements harmful to the environment, pathogenic microorganisms and eggs of parasitic organisms, as well as plant nutrients, and their contents vary depending on the characteristics of the wastewater they are obtained from and the processes applied. For this reason, it is necessary to determine the chemical properties of the treatment sludge before it is applied to the soil. In order to determine which soils and at what rate it should be applied, the total and useful N and P content of the sludge must be taken into account.
There are some drawbacks and limitations in the application of sewage sludge to soils, depending on the sludge properties. For this reason, the “ Regulation on the Use of Domestic and Urban Treatment Sludges in Soil ” dated 3 August 2010 and numbered 27661 was issued.
Although there are many restrictions regarding its application to soils in this regulation, treatment sludge is used irregularly and uncontrolled. Irregular and uncontrolled use of sewage sludge should be prevented, and multi-year trials should be conducted on the use of sewage sludge in soils in order to prevent the negative effects on soil ecosystem, environment and human health.
The nitrogen needed by the plants can be met by adding mineral fertilizers to the soil, as well as by binding the atmospheric nitrogen to the soil by bacteria. Plants and microorganisms cannot directly benefit from N2 gas, which is 78% in the atmosphere. However, some groups of microorganisms bind the free nitrogen gas in the atmosphere and turn it into ammonia form that plants can benefit from. This phenomenon is known as biological nitrogen fixation .
Nitrogen-fixing microorganisms in nature, especially Rhizobium spp. The importance of biological nitrogen fixation, which is realized as a result of the symbiosis of bacteria with leguminous plants, is increasing day by day. Microorganisms, which play a role in nitrogen fixation, reduce the mineral nitrogen input, both provide nitrogen to the soil in a cheaper way and minimize the problems that may be caused by mineral nitrogen.
The amount of nitrogen fixed in the soil by legumes is 70-300 kg/ha per year. Forage crops such as clover, vetch and clover draw attention as prominent plants in green manure.
It has been determined that the ratio of organic matter and nitrogen in the soil increases from year to year in 3-5-year crop rotation systems in arid areas that are poor in terms of organic matter, where the grain -fallow system is applied.
Leonardite is a stratified clayey organic sedimentary rock as a result of the decomposition, humification, oxidation and metamorphosis of plant and animal remains in prehistoric times in aquatic environments such as lakes and swamps and under the influence of volcanic movements under pressure, temperature and anaerobic conditions. It has a high humic acid content and every lignite deposit is a potential source of leonardite.
It is estimated that Turkey's loenardite reserve is 5 million tons , while 7-8 million tons of humic acid can be produced from low quality lignite deposits.
It is reported that 1 liter of liquid humic acid is equivalent to 8 tons of animal manure, and 1 kg of solid humic acid is equivalent to 30 tons of animal manure.
For this reason, leonardite is widely used in organic agriculture as soil improver and fertilizer.
The use of natural organic fertilizers and organomineral fertilizers in order to eliminate the negative effects of the unbalanced use of chemical fertilizers on humans and the environment constitutes one of the backbones of sustainable agricultural practices. Organic fertilizers can differ due to the fact that natural fertilizers have different degrees of decomposition and decomposition, they generally break down and decompose slowly, and the distribution of nutrients they contain is variable depending on the source material.
Organomineral fertilizers, on the other hand, contain the plant nutrients and organic matter found in chemical fertilizers together, so that the nutrient contents can be presented in a more standardized form. In organomineral fertilizers, plant nutrients such as Nitrogen (N), Phosphorus (P), Potassium (K), Sulfur (S), Zinc (Zn) and humic-fulvic acid and compost-derived organic matter are used together as a base fertilizer. Organomineral fertilizers, produced as "organic matter + mineral fertilizer" by utilizing the positive effects of organic materials on soil fertility, on the one hand reduce the loss of nutrients by washing and on the other hand increase the efficiency of the minerals used by improving the fertility elements of the soil.
Organic matter content should be at least 3% of the soil weight in order for the physical, chemical, biological properties and productivity potentials of agricultural soils to be at the desired levels.
According to the results of soil analysis made in recent years, 99% of our soils contain organic matter below this value. Organic matter deficiency is one of the most important problems in terms of the productivity of agricultural soils in Turkey.
There are many sources of animal excrement, agricultural plant residues, urban organic wastes, leonardite, green manure, slaughterhouse and meat combine wastes, humic acid and other organic materials to compensate for the organic matter deficiency of soils. However, in our country, these resources cannot be evaluated correctly and are wasted.
Although it is one of the most important indicators of soil quality, the importance of soil organic matter is not known enough today. For this reason, producers should be informed about the importance of organic matter content of the soil, the animal and vegetable organic matter sources that they can use in their soils and their use.
The Ministry of Agriculture and Forestry should provide incentives for practices aimed at raising the level of organic matter and increasing soil fertility, and should be more active and active in the widespread and serious implementation of good agricultural practices, which have important contributions in this direction.
The practices made in the process of obtaining compost , which is an important source of organic matter for soils, should be in a way that ensures that it is healthy and beneficial. The use of hybrid systems to produce high quality and legal compost yields positive results. Incorrect fertilization based on soil and plant analyzes, not in accordance with greenhouse/field trials and calibration studies, without considering soil, climate, plant and fertilizer characteristics, causes both a decrease in fertilizer efficiency and environmental pollution.
In particular, excessive and improper use of chemical fertilizers can cause salinization and heavy metal accumulation in the soil, deteriorate the physical, chemical and biological properties of the soil, cause pollution of surface waters and groundwater as a result of infiltration, eutrophication in aquatic ecosystems, and even human and animal poses health risks.
Organic and organomineral fertilizers seem to be a good alternative for reducing the negative effects of chemical fertilizers and increasing the organic matter content of the soil. In general, organic and organomineral fertilizers are viewed positively in the world. Producers should be encouraged with the support to be provided in order to spread the use of organomineral fertilizers, which have a significant advantage both in terms of being a source of organic matter and containing the minerals that plants need immediately.
Sources
Serkan SEZEN