Presentation on the topic "agrocenoses and agroecosystems". Presentation on the topic "agrocenoses and agroecosystems" Soil section monolith

Surface area and annual production of major ecosystems Ecosystem type Tropical forest Temperate forest Tundra Cropland Area,% Net production,%

Popular wisdom: Without an owner, the earth is an orphan. Return the debt to the earth - it will help. Where there is water, the garden will bloom. In good times, you will gather a mountain of bread. A lot of snow means a lot of bread. The earth takes labor and gives back pounds. Do not spare your efforts, there will be more pounds. Live and learn.

Difference between agrocenoses and biogeocenoses In agrocenoses: - reduced species diversity; - species cultivated by humans cannot withstand competition with wild species without human support; - significant use of additional energy (muscular strength of humans, animals, agricultural machinery) to maintain plant yields; - food chains are short (in the natural community - branched food chains); - the circulation of substances is incomplete; - agrocenosis is an unstable system, and natural biogeocenosis can exist for a long time.

Increasing the productivity of agrocenosis: - application of fertilizers, their scientifically based use; - watering; - selection of crops; maintaining proper crop rotation; - use of high-yielding varieties taking into account natural and climatic conditions; - protection of plants from diseases, pests and weeds

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If every person on a piece of his land did everything he could, how beautiful our land would be. (A.P. Chekhov)

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Agrocenoses

Biocenoses that arise on agricultural lands.

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Agrocenosis

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Target: introduce students to the system of organization of artificially created ecosystems - agrocenoses.

• formation of knowledge about the structure and functions of agrocenoses;
• develop skills in working with additional literature;
• cultivate a careful attitude towards soils, as one of the most important components of agrocenoses.

Equipment: articles from periodicals, photographs or reproductions illustrating agrocenoses and agroecosystems, signs with inscriptions of the roles of conference participants; presentation.

During the classes

I. Organizational moment

On the screen (from the presentation): “If every person on a piece of his land did everything he could, how beautiful our land would be.” (A.P. Chekhov).

To hold a press conference, it is necessary to assign roles in advance and select appropriate questions; The teacher offers a list of literature.

II. Learning new material

The teacher acts as the host of the press conference. Teacher's opening remarks:

Agricultural ecology, or agroecology, studies issues of rational environmental management in agriculture. A properly organized farm produces environmentally friendly products and does not pollute the atmosphere or water. At today's press conference there are specialists who will help us understand issues related to agrocenoses.

What is agrocenosis?

Chief agronomist of the state farm "Harvest without nitrates"

Agrocenosis is an anthropogenic biocenosis. Agroecosystems are agricultural land created and maintained by humans.

Man determines their structure and productivity: he plows part of the land, sows crops, creates hayfields and pastures in place of forests, and raises farm animals. Agroecosystems are autotrophic: their main source is the sun. The additional energy they receive does not exceed 1% of solar energy.

Producers in the agroecosystem are cultivated plants, grasses of hayfields or pastures, and garden trees. At the same time, weeds - companions of cultivated plants - are also producers.

The decomposers in the agroecosystem are mainly bacteria. They maintain soil fertility.

All components of the agroecosystem are closely connected, but complete ecological balance does not arise in it. Man himself must maintain balance in the agroecosystem.

What role do microorganisms play in maintaining soil fertility?

Chief Researcher at the Institute of Soil Science

Soil is the main resource of the agroecosystem. Soil fertility depends on the supply of organic matter - humus, the content of nutrients available to plants, structure, and moisture supply. Humus is formed by microorganisms - gummifiers from the remains of plants and animals. The reserve of the humus layer depends on the thickness of the humus layer and the percentage of humus in it. Other microorganisms release nutrients from humus into the soil solution. Among them, there are macroelements (nitrogen, phosphorus, potassium), which plants require in larger quantities, and microelements (manganese, boron, copper), which plants require in small quantities.

Nitrogen can be supplied to the soil as a result of the vital activity of microorganisms - symbiotrophs, freely living in the soil or in nodules on the roots of legumes. To increase biological nitrogen fixation, the area under crops of peas, soybeans, alfalfa, etc. is expanded.

The structure of the soil is the shape and size of the lumps into which it breaks up. The best structure is finely lumpy. Inside the lumps, conditions are created for the activity of microorganisms - hummifiers that form humus, and between the lumps - for microorganisms that decompose humus into mineral compounds accessible to plants.

Laboratory report "Composition and properties of soil" (presentation)

Are there environmental problems associated with agriculture?

Employee of the Institute "Expert - Ecology"

The agricultural development of Russia is 13%, 2/3 of this territory is arable land (131.7 million hectares), but this area is decreasing from year to year.

Every year, more than 1 million hectares of agricultural use are lost as a result of erosion and 100 thousand. hectares are “eaten up” by ravines. Every year, Russian soils lose more than 0.5 tons of humus per hectare. Out of 5.9 million. hectares of irrigated land, more than half of these soils are secondary saline and produce extremely low yields. Every fourth hectare of arable land has acidic soils due to acid rain and the use of fertilizers, which also reduces yields. The area of ​​arable land is decreasing as a result of urban sprawl, construction of roads and industrial facilities. Over the years of reform, the situation in Russian agriculture has worsened. The application of organic fertilizers was reduced by 2 times, and mineral fertilizers by 3.5 times.

What impact does agricultural pollution have on human health?

Candidate of Medical Sciences, Institute of Nutrition

A very dangerous agricultural pollution is pollution with pesticides (substances that are used in agriculture to control weeds and pests). Pesticide residues can end up in water (especially during irrigated agriculture and rice cultivation), into the atmosphere, and into food products. Most pesticides and their incomplete decomposition products are toxic and adversely affect human health.

Nitrates are dangerous food contaminants. Once they enter the human body with food, they disrupt the normal functioning of the circulatory system, which is especially dangerous for infants. Nitrates form complex compounds called nitrous compounds. Nitrous compounds are carcinogenic, i.e. they can cause the development of cancerous tumors.

To prevent nitrates from accumulating in vegetables, it is necessary to limit the use of mineral nitrogen fertilizers and use them simultaneously with organic fertilizers (manure). Nitrates accumulate in plants when there is insufficient light.

It is useful to know how nitrates are distributed in vegetables. Thus, in beets, nitrates are concentrated in the upper part of the root crop. Carrots have more nitrates in the central yellow part than in the surrounding red part. The most dangerous part of cabbage is the stalk. During fermentation, nitrates evaporate. Potatoes have more nitrates in small tubers than in large ones. In addition, they are concentrated under the peel.

What role do crop rotations play in increasing the productivity of agrocenoses?

Agronomist of the farm "Agricultural Resource"

Crop rotations that are organized correctly help restore soil composition. Features of crop rotations depend on climatic and soil conditions and on the economic task: they can be grain, fodder, beet, potato. The crop that was grown in the field last year is called the predecessor. Peas, which enrich the soil with nitrogen, are an excellent precursor for grain and row crops. Winter rye clears fields of weeds due to its rapid development in the spring and early harvesting, which allows for early autumn plowing and triggers the germination of weed seeds. After rye, you can sow an additional green manure crop, which is then plowed into the soil as green fertilizer. Spring grains (wheat and barley) are good precursors for peas, sugar beets, sunflowers, and rapeseed.

Typically, crop rotation includes fallow fields, the soil of which is, as it were, resting from intensive use. Couples can be clean and busy. Clean vapors are useful because they store moisture, which is absorbed into well-loose soil. But this is not economically profitable, because a person is deprived of an area from which to obtain a harvest. Vapors increase nitrogen deficiency. These disadvantages do not exist in occupied fallows, when a soil-improving crop is grown on the fallow field. This crop produces a harvest. There is no erosion on occupied steam, but no moisture accumulates. If the next year is dry, the harvest will decrease. Different pairs are used in different areas. In the steppes, it is more advisable to have clean fallows, since the main thing for the future harvest is the supply of moisture. Busy fallows are used in areas with high rainfall and forest soils that are poor in nutrients.

How is insect pests and diseases controlled in agrocenoses?

Candidate of Biological Sciences

In natural ecosystems there are no problems associated with pests, weeds, or diseases. In human-created agroecosystems, ecological balance is not formed on its own. The weak competitive ability of cultivated plants contributes to the massive development of weeds. With the massive development of weeds, the yield decreases. People are forced to use special methods to control the density of weed populations in order to protect crop plants.

Weed control is carried out using agrotechnical methods. At the same time, cultivation and autumn fall tillage of the soil are carried out. This treatment provokes the germination of weed seeds, and they die from frost. Biological methods for controlling weeds, pests and diseases also play an important role. Crops with a dense canopy, for example, perennial grasses, cope with weeds themselves, and in order to help weaker cultivated plants withstand competition with weeds, they use mycoherbicides - fungal spores that attack certain types of weeds. Insects are very effective in the fight against weeds - pests that eat away their flower buds and flower ovaries.

In agroecosystems, agroecologies strive to form an ecological balance, similar to natural ecosystems. The main thing in the formation of such balance is the creation of a system of useful symbiotic connections. The main links of such a system are birds of prey and insectivores. For their reproduction, shelters are created in agroecosystems.

The teacher asks the students to solve a problem: in the spring, collective farmers are preparing potatoes for planting, but a pest, a nematode, has been lurking in the field since last year. They can wait in their cocoons for more than one year, and as soon as they smell the potato juice from the tubers damaged during planting, they will crawl out of the cocoons and get to the delicacy - potatoes. You can treat fields with chemicals, but pests adapt to them. In addition, it is harmful to animals. What should I do?

Answer: A few days before planting, potatoes are watered. Mixed with the juice of rotten potatoes. This forces pests - nematodes to get out of their cocoons, counting on the abundance of food.

III. Summing up the conference

Students summarize the results of the conference and draw conclusions.

• Agrocenoses differ from natural biogeocenoses in that the species composition in them is much lower than in the natural community.
• Biogeocenoses use only solar energy, while agrocenoses use additional energy inputs: the energy of machinery, associated energy of fertilizers, irrigation costs, etc.
• Agrocenosis is an unstable system, because crops are constantly being removed and the cycle of substances is not fully supported.
• The degree of self-regulation of agrocenoses is much lower than that of biogeocenoses.
• Agrocenoses cannot exist independently. A person must control and change the influence of natural factors.
• Cultivated plants cannot resist weeds and pests due to reduced species diversity in the system.

The teacher notes the most interesting questions and student answers and gives marks.

IV. Homework

Paragraph 70; solve the problem: during sowing, a lot of trouble is caused by birds that fly into the fields and peck a lot of seeds. In the old days, the Romans used scarecrows to scare birds. What to do now, because the fields have become huge?

Agrocenosis (from Greek agros -field) -

biocenosis that occurs on agricultural lands.

Examples of agrocenoses include:

• Buckwheat field

• Potato field

• cotton field

• Rice field

• Garden

Similarities between agrocenosis and biocenosis:

• Availability of producers
• Availability of consumers
• Presence of decomposers
• Plants are the initial link in the food chain
• Food connections between organisms
• Cycle of substances
• Diurnal and seasonal changes

Differences between agrocenosis and biocenosis:

• Reduced species diversity
• Short food chains
• The cycle of substances is incomplete (primary production - harvest, taken by humans)
• Species cultivated by humans cannot compete with wild species without human support
• Unstable system
• Significant use of additional energy (muscular power of humans, animals; agricultural machinery) to maintain plant yields

Ideal agrocenosis

Consists of one single type

Ideal food chain of agrocenosis

• plant - person
• plant - animal

In agrocenoses, various communities are formed of species that can survive in conditions of constant anthropogenic impact

Food chains of 3–4 links are formed, competitive interactions and other types of relationships between species arise

Inhabitants of the potato field

Wireworm

Common potato aphid

Inhabitants of the potato field

Golden potato nematode

Colorado beetle

Inhabitants of the wheat field

cornflower

Cockle

Sow thistle

Wild oats

Inhabitants of the wheat field

Field slug

grain moth

Vole mouse

Gopher

Inhabitants of the wheat field

Viper

Lun

Viper

Quail

Boomerang effect

In agriculture, a variety of chemical plant protection products are used in abundance - pesticides.

That. the regulatory connections that arise in agrocenoses are disrupted.

The remaining part of the pests gives a new, even higher outbreak of numbers.

Biological control method

Biological control method

Equestrians and egg eaters are human assistants in the fight against agricultural pests: top left and bottom left – female ovi eaters on the eggs of the host insect; top right – aphid rider; bottom right – dead aphids after the development of parasites in them

Food chain in agrocenosis

Bread mosquito

grain moth

Wheat

Lun

Meadow mint

Agroecosystem –

a territory deliberately planned by man, in which the receipt of agricultural products and the return of its components to the fields are balanced

Created by man to obtain a high yield - pure products of autotrophs (producers)

Properly planned agroecosystems include:

1) arable land

2) pastures (or meadows)

3) livestock complexes

Features of agroecosystems:

• Plant nutrients removed from the fields along with the harvest are returned to the biological cycle system along with organic and mineral fertilizers.

• Biological diversity is maintained through special landscape planning: alternation of fields, meadows, forests, coppices, shelter belts, ponds, etc.

• The diversity of species in the fields is maintained by the rotation of crops not only in time, but also in space.

• Humans control the operation of agroecosystems, introducing a significant amount of additional energy into them (tillage, watering, fertilizers, pesticides, etc.)

Describe the proverbs by connecting them with the topic studied

• What goes around comes around

• It’s not a problem that there’s quinoa in the rye, but it’s a disaster that there’s neither rye nor quinoa

Make food chains using the suggested organisms:

• wheat
• mouse vole
• quail
• kite
• polecat (ferret)

• grain moth
• meadow chased
• viper
• fox

Answer the questions:

• Explain why cultivated plants cannot compete with weeds.

• Indicate ways to return nutrients to the soil.
• Why is soil quickly depleted in agrocenoses?

Homework

• Lecture notes
• Answer the questions:

• Indicate the importance of agrocenoses for providing the population with food and developing the national economy.
• What are the ways to increase the productivity of agrocenoses?