Text 13 soil and soil fertility

All plants grow in the soil. If you want to have high yields of grains, fruits and vegetables you must have a fertile soil. All crops grow well in a good soil. They cannot grow well if the soil is poor. People who have vegetable gardens must work hard there. They must dig the ground with a spade and loosen it with a rake. They may apply some fertilizers. They must water the plants and weed their vegetable gardens.

All vegetables and other crops respond to fertilizers very well. Agricultural soils must have some organic matter and some mineral matter.

Crops cannot grow well if there is not enough water, plant .food, heat and air.

Collective farmers work many hours in the fields and they get good yields of wheat, rye, oats, barley, corn, millet, buckwheat, cabbage, beet, carrot, beans, peas, lettuce, onion, radish and other crops.

Soil fertility is very important for agricultural crops.

Text 14 plant life

Plants are very important for man's life. They supply us with different food products and fibre. Domestic animals use plants as fodder.

Plants grow and develop in the soil. They obtain the necessary nutrients from the soil and air.

Minerals and nitrogen are obtained by the plants from simple salts in watery solution. Carbohydrates are synthe­sized by plants from carbon dioxide which is in the atmosphere and water. The source of energy for the process of photosyn­thesis is sunlight.

The principal parts of the plants are the root system, stems, leaves, flowers, fruits and seeds. All these parts have different functions but they are all very important for plant growth and development.

Plants may be annuals, biennials and perennials. Annual plants produce seeds the first year. Biennials produce seeds the second year. Perennials produce seeds during many years. Seeds germinate at different temperatures. The optimum tem­perature for rye, wheat, oats and barley is about 20°—25°C. In order to grow and develop well plants must have good soil and climatic conditions. They must have enough water, nutrients, heat, air and light.

One of the most important tasks of the collective farmers is to properly till the soil.

Text 15 the soil

Soil Formation. Soil is produced from rock by the pros of weathering and by the activities of plants, animals, and man. Primitive or igneous rocks,¹ formed by the soli­dification of the magma in the process of the cooling of the earth consist of aggregates of mineral crystals which are large or small according to the rate at which cooling took place. Each mineral is a chemical compound with specific chemical and physical properties. As soon as igneous rocks are exposed to changing temperatures, moisture, etc. slow processes of disintegration and decomposition begin.

The weathering of a rock is generally due to a combination of physical and chemical actions. The weathered products of rock alone do not constitute a soil. Plants estab­lish themselves very soon after weathering begins, and the mineral material thus becomes mixed with plant remains. These remains, in the process of decay, form an addition to the products of rock weathering. Soil is therefore a mixture of organic and inorganic material containing a large and com­plex population of living things.

The general character of a soil depends to a considerable extent on the nature of the parent material. Thus a coarse-grained sandstone will generally produce a sandy soil, and a stratum of shale a "heavy" soil.