Some physiological bases of agricultural and gardening practice. Loss of water by plants

you are: Some physiological bases of agricultural and gardening practice

At a single plant all leaves will be transpirirovat as they are surrounded by rather dry air. However in the conditions of field culture the bottom leaves are surrounded by mainly damp air as a result transpiratsii other leaves. only the top leaves adjoin directly to drier atmosphere. Besides, the leaves located below the top layer, so limit air movement that between plants it becomes sated with a moisture. Therefore the bottom leaves possess much lower intensity transpiratsii. Molecules of water steams diffundirujut from the sated air bed in crops in dry air over crops, and at rather equal surface of planting (as, for example, in crops of cereals) effective transpirirujushchej the crops surface, instead of all separate leaves (fig. 14.3) becomes a surface, in essence. Then it is indifferent, how many plants in crops or how many leaves on a plant; If the sheet bed curtains cover all soil, water loss will be defined by the crops area. Such crops lose rather a lot of water - in the afternoon approximately as much, the open water table, such, as lake how many evaporates. As at night the majority of plants closes the ustitsa, limiting thus transpiratsiju, daily loss of water by crops a little below evaporation from a surface of an open reservoir. As return of water by each culture makes usually certain share of evaporation from an open water table, she can be calculated on this evaporation or by quantity of solar heat which can be spent for evaporation. Such data now can be received from meteorological stations.

Growth of plants inevitably depends on the water necessary for creation tourist's mountain in growing cages. Therefore productivity of culture is directly connected with quantity of the water accessible to a plant, which most part transpiriruetsja. As during the long period water arrival should be equal to its expense, knowledge of a quantity of water, transpiriruemogo culture, allows to define norm of an irrigation (loss by a way transpiratsii + infiltration - rain deposits=norm of an irrigation). It allows the farmer to make an irrigation only if necessary and thus to avoid unnecessary expenses of water and energy. In an ideal water inflow should counterbalance always it transpiratsiju, but it is often almost impracticable. Plants differ on ability to transfer water deficiency without growth oppression. However to prevent crop losses, the irrigation should compensate losses on transpiratsiju before shortage of water will start to limit growth.

Depending on biology of the given culture of loss of a moisture can vary from very small size to the quantity exceeding evaporation from a water table. The naked surface of soil quickly dries up, limiting to that loss of water from underlaying layers. That is why for water preservation in areas with the limited amount of precipitation and without an irrigation soil leave under steam. Thus in soil it is possible to keep the most part of annual deposits. When plants start to grow, roots can get water from underlaying layers of earth. Losses of water then increase until crops will not close completely soil and will not generate transpirirujushchuju a surface.

Transpiratsija at rjadkovoj culture or fruit-trees can exceed water loss by equal crops as they have big transpirirujushchuju a surface, than the earth area on which grow. Besides, between rjadkami the wind can blow, mixing dry air with the damp. Therefore the norm of an irrigation for rjadkovyh crops can be more than for continuous, and it depends basically on the general surface of crops.

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