Deficit irrigation

Under deficit irrigation refers to the agricultural irrigation with a consciously recognized below the optimum water requirement of the crop water quantity. It is at once ways to increase water efficiency in agriculture.

Principle and Mechanism

The deficit irrigation aims to produce in the crops targeted drought stress in those phases which have an insignificant effect on the crop yield. Finally, a small yield reduction will be taken at high water savings in purchasing. The strategy of stabilization and optimization of agricultural output stands at maximizing water productivity (ie, increasing the economic proceeds in proportion to the water removal from the wild ).

In addition one can make the following physiological context advantage: About the transpiration of leaves most of the water discharged from plants goes back into the earth's atmosphere. The amount of water discharge from the leaves is controlled by the opening of the stomata, the water discharge at the same time in addition to regulate the uptake of carbon dioxide, which is important for the photosynthesis and for the fabric construction. One of the essential scientific knowledge, which underpins the deficit irrigation is that can the regulatory mechanisms of stomata and thus the plant metabolism consciously controlled by different watering.

Could Based on these considerations, in the last decade irrigation strategies are being developed to lower water volumes which lead to similar yields and thus significantly improve the water use efficiency. These strategies even lead partly to higher plant health and have a beneficial effect on the quality of the products produced from.

Various approaches to deficit irrigation

Meanwhile, different strategies of deficit irrigation can be distinguished, which are initially mainly used in fruit growing and viticulture International Websites:

• Regulated deficit irrigation (RDI )
• Partial drying of the root zone (PRD, partial root zone drying )
• Sustainable or sustained deficit irrigation (SDI, sustained deficit irrigation )

Regulated deficit irrigation

In many types of fruit, but also in some grains the size of the fruit affects their content of ingredients. For example, did so with red grapes, berry size a significant impact on the content of tannins and flavors of the wines. In addition, small berries produce a lower juice percentage in relation to the color, tannins and aromas contained in the grape skins.

In addition, a slight drought stress at the beginning of the mature phase of the grapes is important for a high wine quality in red wines. The best wine quality always came from vines whose grapes had little berries.

In viticulture, therefore, can be set up as a rule: It should be avoided to optimally supply the grapes during the period of fruit set, otherwise the berries are too big in the fall. In order to keep the berries small, is therefore reduced from the heyday until shortly before maturity start supplying water to the vines targeted to a minimum. Before color change is then irrigated intensive in order to fit in a second drying phase to maturity beginning ( right after the color change); from the mid- maturation phase again more is then irrigated. Because of the drought stress thus generated in the plant promotes the formation of abscisic acid.

In cases of intentional handling the growth of the shoot comes through the " Regulated deficit irrigation " to a halt; while the berries remain smaller and contain more components and also have lower pH values. However, this method also lower yields are expected.

Partial drying of the root zone

This strategy of deficit irrigation based on the fact that, for example, the roots of grapevines produce in a slowly desiccating soil chemical messengers such as abscisic acid, which are forwarded to the above-ground Rebteile. The above-ground parts of the vine is signaled by the fact that the water supply of the plant is scarce. Then the leaves reduce transpiration and thus water consumption by closing the stomata. This reduces both the gas exchange; as the assimilation capacity of the plant and the other leaf and shoot growth declines slowed or comes to a standstill in the extreme. In this situation, the plant is preferably supplies the grapes. As long as a part of the roots of the vine still can replacement delivery so much water that the vital functions of the plant to be maintained, therefore, will not occur drought damage, even if vegetative growth is reduced as a whole.

If the soil is severely dehydrated, the Abscisinsäureproduktion the roots come in the dry soil areas to a standstill. However, the root tips in the dry soil does not die, but remain in the inactive state. During the night the vine consumes no water; all plant parts, the roots in dry soil, are supplied with water at this time. Thus, the roots in the dry area for long periods can last provided that a portion of the roots of the vine plant will subsequently supply is still sufficient water. If the dry soil moistened again, found there roots are active again and can take over their duties again; also can now photosynthesis achieve the full performance and thus use a shoot growth.

Not only in experiments but also in practical tests have shown in viticulture that this irrigation strategy, both the grape and wine quality advantageously altered. Compared with the traditional irrigation drip irrigation amount can be approximately halved, without changing the amount of revenue.

Sustained deficit irrigation

Of the two irrigation strategies described so far, the sustained deficit irrigation significantly different (SDI ). Here the irrigation period is given less and less water in the barrel; at the same time takes over the Vegetationspersiode the available water in the soil from the next. This takes the water stress to the plants slowly, and they can adapt to this. This strategy is due to the earnings trend for wheat, sunflower or corn better than for millet or cotton. The cultivation of adapted varieties makes more sense than the high-yielding varieties.

Implementation

In recent years, increasing the agricultural management of water demand is considered as an important tool to achieve a balance between demand, supply and optimized use of water. By application of deficit irrigation of agricultural water consumption per unit of land can be reduced. This allows either the expected scarcity of water meet in many irrigation regions of the world, or expand the irrigated area. According to the models and operating Experience has shown that the gross profit margin of farmers will be greater for deficit irrigation than at full irrigation.