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4.2. Answer the questions:

1. How is the water applied to the ground in subirrigation?

2. What is the application efficiency of this method?

3. What kinds of soils does subirrigation require?

4. In what way does moisture reach a plant in subsurface irrigation?

5. What should the topography of subirrigated lands be?

6. What are the principles involved in subirrigation?

7. Why is an artificial water table created over a natural barrier?

8. In what ways is water introduced into the soil profile?

9. What are mole and tile drains? In what soils can they be used?

10. What methods of subsoil irrigation have found a wide application in recent years?

4.3. Ask your groupmates questions in English about:

– в чому полягає суть підґрунтового зрошення;

– якими є передумови для успішного функціонування підґрунтового зрошення;

– яка структура розподільчої системи підґрунтового зрошення;

– чи є застереження щодо використання даного методу зрошення;

– яке основне призначення методів крапельного та дрібнодисперсного зрошення та імпульсного дощування.

4.4. Fill in the gaps from the words given below:

1. Subirrigation permits water to be applied … the ground.

2. Sprinkling is known to have some … over surface irrigation.

3. To get high … it is necessary to irrigate this field.

4. Application of new irrigation … has improved the methods of watering.

(yields, machinery, beneath, advantages).

4.5. Get ready to speak on the following topics (3-5 sentences):

1. Types of soil suitable for subirrigation.

2. The means of introducing water into the soil profile.

3. The most commonly used methods of subirrigation.

4.6. Write down your annotation of Text A.

V. Additional text

5.1. Memorize the following words:

medium

засіб, спосіб

predetermined depth

заздалегідь визначена глибина

to permit

давати можливість (змогу)

upward

спрямований угору

broad valley

широка долина

salting

просочування сіллю

top-soil

верхній шар ґрунту

infrequently

рідко, нерегулярно

seepage

інфільтрація, просочування

adverse weather

несприятлива погода

to penetrate

проникати, просочуватись

obstruction

перешкода, перепона

to hinder

заважати, перешкоджати

farm operations

сільськогосподарські роботи

valuable land

родюча земля

to take up

зайняти, забирати

except

крім, за винятком

repair

ремонт, лагодження

interference

втручання, завада

adjacent

суміжний, сусідній

5.2. Read the text. Text b. Subsurface irrigation.

1. Subsurface irrigation permits the direct watering of the root zone of the crop from below. The application and control of the water is by medium of the soil itself. The water passes under the ground surface either naturally, as the water table, or artificially, by means of pipes or drains.

2. Natural subsurface irrigation maintains a water table at a predetermined depth, suited to the crop, by means of field laterals. These are filled with water and seepage from them then raises the water table.

3. Moisture reaches the plant through upward capillary movement. The soil profile is important, the most favourable condition being a sandy soil over an impervious clay. Water applied at the highest points seeps down to the clay layer upon which it travels, sometimes for considerable distances, within reach of the plants’ roots.

4. Natural subirrigated lands are located in broad valleys where streams supply water beneath the surface to irrigate the crops on the flats.

5. Subirrigation has many advantages because its cost is low and there is little evaporation from the water, which is applied directly to the root zone. The disadvantage is that control of the water table may be difficult because of drainage problems and the danger of salting.

6. Adverse weather, with heavy rain, may make control of the water table difficult and expensive. In practice there are few areas with the special combinations of favourable soil profile, topography, and weather that are necessary.

7. Artificial subirrigation consists of supplying water in underground mains to the root zone of the crop. Its success depends upon the soil profile. An ideal one has an impervious subsoil and a top-soil capable of lifting moisture into the root zone.

8. Agricultural drains with perforated pipes should have a moderate slope so that water may move slowly and penetrate the soil uniformly.

9. From the theoretical point of view, this method is ideal because water is supplied to the crop where it is needed without losses by evaporation or in distribution. There are no surface obstructions to hinder farm operations or take up valuable land.

10. In practice, however, the method has proved disappointing except in particular soil profiles. Tile lines are expensive to provide, lay, and maintain. Faults are difficult to locate and their repair involves interference with the crop. Roots of the crops and adjacent trees tend to collect in, and clog the distribution lines.

11. Mole drains are sometimes used in heavy soils both for drainage and the supply of water. Usually they are at least 2 feet below the surface to prevent collapse by overhead operations. This method is used infrequently and only in certain soils.

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