In the face of severe and deteriorating grassland degradation in China, grassland irrigation is an effective grassland improvement and grassland production increase. In general, irrigation of natural grassland can increase production by 1 to 15 times, and irrigation of artificial grass can increase production. ~ 30 times. Because grassland irrigation and even grassland irrigation research started late, in the face of rapid technological advancement, many theories and technologies have yet to be studied and improved. Exploring the mechanism of drought adaptability for pastures, making full use of the strong anti-drought potential of pastures, and optimizing the irrigation system will undoubtedly increase the management level of irrigated grassland and increase the effective use of grassland water.
1 Mechanism of Draught for Drought The area of ​​pastoral areas in China is 4.16 million km2, accounting for 43% of the country's land area, of which grassland area is 247 million hm2. They are mostly distributed in arid and semi-arid areas with a precipitation of less than 400 mm. The water environment in these areas is poor. Forages grow year after year in a water deficit environment, forming a strong adaptability and resistance to deficient water environments. Although the same as grass, but in the state of natural precipitation, with the water from habitat change from poor to excellent drought resistance from strong to weak.
Based on the analysis of the physiological characteristics, morphological characteristics, and physiological and biochemical changes of forage grasses during drought, we studied the drought-resistance changes of pastures, that is, when pastures were exposed to drought, they were able to adapt to a relatively low water environment through the following evolution. The whole process of evolution. First of all, the normal physiological and biochemical changes, starch, protein hydrolysis, proline, abscisic acid, ethylene and indole acetic acid increase, in order to improve the ability of cells to absorb water, stabilize metabolic function, accelerate the old leaves yellow, fall off and root growth. Along with this, the physiology of herbage changes accordingly, the hydrophilicity of cell colloids increases, the viscosity of protoplasm increases, and the osmotic potential decreases.
2 The economical water consumption of forage grasses is generally parabolic-related between water consumption and yield. When grassland soil moisture reaches a certain value, grasses can absorb water and grow. The grassland water consumption in this state is called initial survival. The water consumption and the initial survival water consumption is called the survival water threshold. With the improvement of soil moisture, the grassland consumes more water. The water consumption of pasture is related to stomatal opening. When the stomata is opened, both the photosynthetic rate and gas exchange of forage grasses are accelerated, and the transpiration and water consumption of the plant body are suppressed to a certain extent. At this time, the transpiration efficiency of forage grass is the highest, and the water consumption is the most effective. The corresponding grassland water consumption is called the economic water consumption, and the area of ​​economic water consumption is called the high efficiency water consumption threshold. Within this water consumption range, the increment of grassland production caused by the increase of unit water consumption is the largest.
When the grassland water supply condition continued to improve, the cellular turgor pressure in the forage grass tissue reached its maximum and the stomata was fully opened. There was no inhibition on the photosynthetic rate and gas exchange, and the water consumption was also maximized by the action of the small hole mechanism. In addition, the soil moisture on the surface of the grassland is strongly evaporated under the influence of the strong water potential difference at the interface, and the water consumption of the grassland is the highest. At this time, the non-beneficial consumption of water is more. The grassland water consumption in this state is called the limit water consumption, the threshold of the limit water consumption is called the high production water consumption threshold, and the water consumption between the initial survival consumption and the high efficiency water consumption threshold is the effective consumption of pasture. Water threshold. The water consumption between the high consumption threshold and the high production water consumption is the high water consumption threshold of pasture.
3 Conclusion In the pastoral areas of northern China, pasture has long-term survival and reproduction in the deficient environment, resulting in a series of physiological and ecological aspects of drought evolution, such as high viscosity of the original biomass, strong colloidal hydrophilicity, thick cell wall and large elastic modulus, and high bound water content. . Making full use of this feature of pasture and exploring its high-efficiency water threshold will provide a theoretical basis for grassland water-saving irrigation.
The high-efficiency water threshold corresponding to the life activities of herbage is the economical water consumption threshold of grassland, and the grassland water consumption in this range can be referred to as economic water consumption. In this case, the unit water consumption gives the maximum photosynthetic rate and the highest dry matter yield. The general economic water consumption is only 65 to 80% of the high-yield water consumption, while the amount of grass production is only reduced by 5 to 15%.
The grassland sensitivity index was the largest in the vegetative growth period of the pasture (or forage community), followed by the reproductive growth period. Among them, the sensitive index of natural grass pasture community is smaller than that of artificial pasture, and one of the reasons is that forage grass has strong drought resistance, and the second is the complementarity of many pasture species in the community.
The application system engineering optimization method can be used to optimize the decision-making of the irrigation system. The dynamic programming is the reverse order optimization of the positive-sequence decision-making, which can better solve the series of water-use management under the condition of insufficient water resources. Generally optimized to save 25 to 35% of water. In the case of the same amount of water, the total efficiency or total output can be increased by 20 to 30%.
1 Mechanism of Draught for Drought The area of ​​pastoral areas in China is 4.16 million km2, accounting for 43% of the country's land area, of which grassland area is 247 million hm2. They are mostly distributed in arid and semi-arid areas with a precipitation of less than 400 mm. The water environment in these areas is poor. Forages grow year after year in a water deficit environment, forming a strong adaptability and resistance to deficient water environments. Although the same as grass, but in the state of natural precipitation, with the water from habitat change from poor to excellent drought resistance from strong to weak.
Based on the analysis of the physiological characteristics, morphological characteristics, and physiological and biochemical changes of forage grasses during drought, we studied the drought-resistance changes of pastures, that is, when pastures were exposed to drought, they were able to adapt to a relatively low water environment through the following evolution. The whole process of evolution. First of all, the normal physiological and biochemical changes, starch, protein hydrolysis, proline, abscisic acid, ethylene and indole acetic acid increase, in order to improve the ability of cells to absorb water, stabilize metabolic function, accelerate the old leaves yellow, fall off and root growth. Along with this, the physiology of herbage changes accordingly, the hydrophilicity of cell colloids increases, the viscosity of protoplasm increases, and the osmotic potential decreases.
2 The economical water consumption of forage grasses is generally parabolic-related between water consumption and yield. When grassland soil moisture reaches a certain value, grasses can absorb water and grow. The grassland water consumption in this state is called initial survival. The water consumption and the initial survival water consumption is called the survival water threshold. With the improvement of soil moisture, the grassland consumes more water. The water consumption of pasture is related to stomatal opening. When the stomata is opened, both the photosynthetic rate and gas exchange of forage grasses are accelerated, and the transpiration and water consumption of the plant body are suppressed to a certain extent. At this time, the transpiration efficiency of forage grass is the highest, and the water consumption is the most effective. The corresponding grassland water consumption is called the economic water consumption, and the area of ​​economic water consumption is called the high efficiency water consumption threshold. Within this water consumption range, the increment of grassland production caused by the increase of unit water consumption is the largest.
When the grassland water supply condition continued to improve, the cellular turgor pressure in the forage grass tissue reached its maximum and the stomata was fully opened. There was no inhibition on the photosynthetic rate and gas exchange, and the water consumption was also maximized by the action of the small hole mechanism. In addition, the soil moisture on the surface of the grassland is strongly evaporated under the influence of the strong water potential difference at the interface, and the water consumption of the grassland is the highest. At this time, the non-beneficial consumption of water is more. The grassland water consumption in this state is called the limit water consumption, the threshold of the limit water consumption is called the high production water consumption threshold, and the water consumption between the initial survival consumption and the high efficiency water consumption threshold is the effective consumption of pasture. Water threshold. The water consumption between the high consumption threshold and the high production water consumption is the high water consumption threshold of pasture.
3 Conclusion In the pastoral areas of northern China, pasture has long-term survival and reproduction in the deficient environment, resulting in a series of physiological and ecological aspects of drought evolution, such as high viscosity of the original biomass, strong colloidal hydrophilicity, thick cell wall and large elastic modulus, and high bound water content. . Making full use of this feature of pasture and exploring its high-efficiency water threshold will provide a theoretical basis for grassland water-saving irrigation.
The high-efficiency water threshold corresponding to the life activities of herbage is the economical water consumption threshold of grassland, and the grassland water consumption in this range can be referred to as economic water consumption. In this case, the unit water consumption gives the maximum photosynthetic rate and the highest dry matter yield. The general economic water consumption is only 65 to 80% of the high-yield water consumption, while the amount of grass production is only reduced by 5 to 15%.
The grassland sensitivity index was the largest in the vegetative growth period of the pasture (or forage community), followed by the reproductive growth period. Among them, the sensitive index of natural grass pasture community is smaller than that of artificial pasture, and one of the reasons is that forage grass has strong drought resistance, and the second is the complementarity of many pasture species in the community.
The application system engineering optimization method can be used to optimize the decision-making of the irrigation system. The dynamic programming is the reverse order optimization of the positive-sequence decision-making, which can better solve the series of water-use management under the condition of insufficient water resources. Generally optimized to save 25 to 35% of water. In the case of the same amount of water, the total efficiency or total output can be increased by 20 to 30%.
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