Gary Peterson, Colorado State University

Professor Gary Peterson is a man not only deep knowledge, but also an outdoor interlocutor who can captivate practitioners with original ideas and simplicity of clear thought. At the conference in Dnepropetrovsk, where Peterson read this report, he instantly fossious friends and new acquaintances, he was invited to visit, in the farm, and he responded sincerely, because he had enough of his stay on this earth to love Ukraine.

Precipitation and atmospheric need for evaporation

In arid conditions, natural precipitation is the only available source of moisture. Semi-sore regions, such as Eastern Europe and Western Asia, receive a non-permanent and limited amount of precipitation. Therefore, the successful cultivation of crops on non-argue soils depends on the adequate accumulation of water in the soil to maintain the culture before falling out the following precipitation. Cultures on inevitable lands are relying exclusively on water in the soil accumulated between the fallout of precipitation, and due to the unreliable precipitation due to the accumulation of water in the soil is extremely important for cultivating crops on non-irrooked lands.

There are three principles of moisture accumulation:

1) the accumulation of water - the preservation of precipitation in the soil;

2) Water retention - conservation of water in the soil for later use by cultures;

3) water use efficiency - efficient use of water to obtain an optimal crop. Only recently we have a technology that has significantly changed the approach to the precipitation on rapid lands. When the mechanical soil treatment was the only way to control the weeds and the preparation of the seed box, the management of precipitation accumulation and their holding in the soil was very laborious. The processed fields were not covered at all and were largely affected by the wind and water erosion. Intensive soil treatment has many negative effects on the soil itself, including a decrease in the amount of organic matter and damage to the soil structure. The use of abbreviated processing and no-till allows us to effectively collect water and save it. In most cases, when the abbreviated processing systems and NO-TILL are properly debugged, they lead to more sustainable cultivation of crops on non-irrooked lands. This article will consider the principles of capturing precipitation and maintain them in the soil.

Water accumulation

Water conservation begins with accumulating random precipitation (rain or snow). Water accumulation must be maximized within the framework of economic limiters of a certain situation. Principles that control the properties of the soil that affect the ability to accumulate moisture, the following: the structure of the soil, the formation of aggregates and the size of the pores. We will also consider the interaction of the accumulation and retention of water compared with evaporation. For example, reducing the time for the caution of water on the surface of the soil and moving moisture inland reduces the possibility of evaporation. This is especially important in the regions where, after raining the rain, there is a great evaporation potential.

Visualization of sediment trapping

We must try to make the water contained in a drop of rain, immediately got into between the soil units and was held there for further culture use. To begin with, let's imagine the capture of precipitation from the point of view of the rain drop, which hits the surface of the soil and penetrates deep into (Fig. 1). Note that the longer the gaps between the soil units are open, the less water has obstacles and is absorbed faster, therefore, the accumulation of precipitation will be excellent.

The flow of water into the soil, at first glance, looks like a very simple process when the incoming water simply displaces the air present in the soil. However, in fact, this is a complex process, because The rate of water infiltration into the soil is affected by a plurality of factors, such as soil porosity, water content in the soil and the permeability of the soil profile. Water holding is a complex phenomenon, since the maximum rate of infiltration is achieved at the beginning of precipitation, and then quickly decreases, as water begins to fill the spacespace on the surface.

The soil texture strongly affects the speed of infiltration, but with the help of the management, the soil texture cannot be changed. A large number of macropores on the surface (large pores), as well as those present in soils with a rough structure (sandy loams, etc.), increase the rate of moisture infiltration. Soils with fine structure (dusty loam and heavy clay loams) usually have a smaller number of macropores (small pores), and, consequently, the rate of infiltration on such soils is less than soils that have a rough structure.

Soil aggregation also controls the size of the soil. Thus, the soils with the same structure, but with varying degrees of aggregation can differ significantly in terms of the size of Macopup. Fortunately, and unfortunately, the degree of soil aggregation can be changed using managerial methods, for example, NO-TILL, adding plant residues that help restore aggregation. It is extremely important to remember that soils with a small structure, for example, dusty loams or heavy clay loams, remained well-structured to exist open passages to move water down. Remember, any technology that reduces structural size will reduce the pore size on the surface, and, therefore, limit the penetration of water into the soil. The best thing in this regard is a structure that can resist changes. Soils with a weak structure quickly lose their ability to absorb water if the structural units fall apart, and the pores on the surface of the soil are becoming less. This can occur either due to too intensive soil processing, or by virtue of natural phenomena, for example, rain.

Directly the surface of the soil must be of interest to management, because The conditions arising on the surface of the soil predetermine the ability to capture moisture. When working in drought conditions, our goal is to use such methods that lead to an increase in the degree of infiltration with a realistic and cost-effective way within a certain culture cultivation system.

Rain drop imaging

What really happens when the drop falls on the surface of the soil? The size of the drops depends on the strength of the thunderstorm, which, in turn, is predetermined by the climate of a certain geographic region. Diameter drops varies from 0.25 to 6 mm (medium - about 3 mm), and now compare the diameter of the drop with the diameter of soil units, in which this drop falls, and the soil, in turn, is not covered with anything; The size of soil aggregates is usually less than 1 mm. When a drop of 3 mm with a diameter, flying at a speed of 750 cm / s, is hitched into the unit with a diameter of less than 1 mm, the damage is often very significant. If we give it to the relative mass, then this phenomenon is similar to the fact that a car weighing 1600 kg, which moved at a speed of 27 km / h. Rain with the wind, which accelerates the speed of the drop, leads to more effects, because The droplet accelerated by the wind carries the charge of energy 2.75 times more than the rain at the pile. It is quite obvious that soil aggregates will be destroyed, especially if rain drops are constantly hit in the thunderstorms of any duration. The energy of raindrops adversely affects the structure of the soil surface, literally "exploding" soil units. When the aggregates explode, the remaining small particles clog the space of the soil, and the rate of infiltration decreases (Fig. 2). Obviously, during a short or non-mounted thunderstorm, the effect of rain drops will be less. NO-TILL gives the solution to this dilemma, because With such technology, plant residues remain on the surface, protecting the surface of the soil from the effects of rain droplets.

Protection of soil units from the influence of raindrops

Water holding can be carried out at an adequate level if we can save the pores on the soil surfaces open. Therefore, the protection of soil aggregates from the effects of rain droplets is the key to maintaining the maximum degree of water capture for a specific situation on the soil (Fig. 3).

NO-TILL technology, in which plant residues remain on the surface, is a partial response to how to protect the soil aggregates. In Figure 3, you see how plant residues absorb the energy of raindrops, and therefore soil units remain intact. Thus, water infiltration passes in normal mode. Due to the control over the weeds with herbicides, we can simply control weeds without machining, leaving our soil as protected from the effect of rain energy.

With no-till, soil cover is saved all year round, because The total degree of soil coating is the amount of the cover formed by the growing culture itself, and the cover created by plant residues. Obviously, the soil coating is very dynamically and can vary from 0% to 100% within the same vegetation season, depending on which culture is now growing and which soil processing technology is used. During the sowing, for example, the soil coating consists only of plant residues. As the culture grows, the coating is already mainly carried out by the foliage of the culture itself. When the cover created by the most culture itself takes on the hit of the rain drops, as well as plant residues, the water smoothly rolls on the surface of the soil with a much smaller energy charge, so soil units are subject to a smaller degree of destruction, the pores on the soil surface remain open, and Infiltration is supported at the appropriate level. As the culture grows, the number of plant residues decreases, because There is a natural disintegration due to the activity of microorganisms. When the cover created by a growing culture begins to decrease, plant residues are again becoming the main means of protection of the soil, and the cycle is completed. Remember that the mechanical processing of the soil, during, and after the growth of crops, reduces the number of plant residues on the surface, and, consequently, the protectedness of the surface of the soil.

The benefits of the accumulation of water due to the cover is the most sensible in the regions with summer sediments; For example, corn growing cycles (Zea Mays L.) or grain sorghum in the great plains of North America falls for the period when 75% of annual precipitation falls. On the contrary, inevitable regions where there are not very many precipitation (the north-west of the Pacific coast in the USA), do not have a well-developed cover, when most of the precipitation falls. However, the early formation of cultures sitting in the fall to obtain at least partial cover of the soil is recognized as good defense of the soil and the way to combat water outflow during the winter months.

Another impact of plant residues

In addition to the absorption of the energy of the droplets and the protection of soil units from the destruction of plant residues physically block the outflow of water, reduce the levels of evaporation during the rain, allowing water to go into the soil profile before the start of the outflow. The total infiltration of water is a consequence of how long the water will be in contact with the soil (the possibility of the possibility) before it starts to flock down the slope. An increase in this time component is a key management tool in water accumulation. The basic principle of increasing the "time of opportunity" is to prevent the outflow of water, slowing it, and that the possibility of being able to be in contact with the soil, and, therefore, to absorb. Plant balances on the surface of the soil increase the "time of opportunity", because physically blocked and slow down the outflow of water. The contour sowing also increases the benefits of plant residues in the slowdown of water outflow, because Combs play the role of mini terraces.

Duley and Russel (1939) were one of the first, who recognized the importance of soil protection by plant residues. In one of its experiments, they compared the influence of 4.5 t / ha's laid straw with an equal amount of exhaust straw and with uncovered soil on the accumulation of moisture. The accumulation of moisture was 54% of precipitation at a coating consisting of laid straw, compared with 34%, when the straw was embossed, and only 20% with uncovered soil. Their experiment did not provide for the separation of the influence of plant residues on such components as the protection of the soil, evaporation and blocking water, but comments suggest that the preservation of porosity and physical blocking of water significantly reduced moisture outflow during the thunderstorms and were the main components of the increase in water accumulation during the time Season.

MANNERING and MAYER (1963) research data explicitly show the protective mechanism of plant residues affecting the rate of infiltration on dusty loams with a slope of 5%. After four rain simulations for 48 hours of the soil coated with 2.2 t / ha plant residues, there was a final level of infiltration, slightly different from the initial one. The researchers found that straw absorbed the droplet energy and spread it, preventing the surface of the soil from covering the crust and blockage.

Demonstration of negative effects of machining

Soil aggregation decreases with an increase in the intensity of the soil processing and / number of years of cultivation (Fig. 4). Mechanical soil treatment adversely affects soil units for two main reasons: 1) physical grinding, which leads to a reduction in the size of the aggregates; 2) an increase in the oxidation levels of an organic matter, which arises due to the destruction of the macroaggers and the subsequent opening of organic compounds by soil organisms. Dragging the size of the aggregates is also changing in such a way that the microporosity increases due to the macroporosis, which leads to a decrease in the rate of infiltration. The extent to which mechanical processing affects infiltration is regulated by the complex interaction of the type of treatment, climate (especially precipitation and temperature) and time, together with such characteristics of the soil, as a structure, organic structure and organic matter content. Therefore, long-term treatment of any soil reduces the resistance of the aggregates to physical destruction, for example, the impact of rain droplets and mechanical processing of the soil of any kind. However, both clay minerals in the soil and organic matter stabilize soil aggregates and make them resistant to physical destruction. A decrease in the amount of organic matter reduces the stability of the aggregates, especially if it is so low.

Of these two main properties of the soil, regulating the formation of aggregates, the mechanical processing of the soil in any form affects the content of the organic matter. The degree of practicality of changes in the level of organic matter varies depending on the conditions, because The level of organic matter is largely determined by two processes: accumulation and decomposition. The first is determined mainly by the amount of organic organic, heavily dependent on precipitation and irrigation. The second is mainly temperatures. The purpose of preserving or increasing the levels of organic matter is easier to achieve in cool, moistened conditions than in hot and dry.

"Freshness" of the compounds of organic matter is necessary for the stability of the units. In soil ecosystems, newly added or partially decomposed plant residues and their decay products, also known as "young humin substances", create a more "mobile" array of organic matter. Older or more stable humic substances that are more resistant to further decay, create a "stable" array of organic matter. It is generally recognized that the mobile array of organic matter regulates the feed strength of nutrients in the soil, especially nitrogen, while mobile and stable arrays affect the physical quality of the soil, for example, the formation of aggregates and structural stability. The formation of mobile and stable arrays is a dynamic process that is regulated by several factors, including the type and amount of organic making and its composition.

There was a great interest in determining how soil treatment affects the structural development and maintenance of the soil relative to the content of organic matter, especially in connection with the advent of NO-TILL technology. Increased soil processing intensity increases the loss of organic matter from the soil and reduces soil aggregation.

Snow accumulation and hold of melt water

Many unrohakable land receive a significant amount of annual precipitation in the form of snow. Effective accumulation of snow water has two characteristics: 1) Snow trapping in itself and 2) trailing melt water. Since snow is often accompanied by the wind, the principles of snow trapping are the same as the principles used in defense of soils from wind erosion. Vegetable roasting remains, windproof strips, drive treatment and artificial barriers were used to maximize snow trapping. The basic principle of these devices is to create areas where the wind speed is reduced from a leeward side and barrier, which leads to the capture of the snow particles on the other side of the barrier. Repeating barriers, for example, a root rut, hold the wind over the surface of plant residues, and, therefore, the "caught" snow remains unattainable for subsequent wind movements.

Studies of scientists with the Great Plains of the United States showed that the Kiranny Stern retained 37% of winter precipitation, and the fields under the ferry without plant residues retained only 9%. The proportion of the field covered with plant residues to the root, obviously affects the capture of snow. Scientists studying the influence of the height of the sunflower cutting on the holding of snow discovered a high correlation between the stored moisture in the soil and the cutting height: the higher the cut, the more snow is captured.

The introduction of NO-TILL technology made it possible to significantly improve the trapping of snow with the help of plant residues for the root. Prior to the use of NO-TILL, the mechanical processing required for the control of weeds led to a decrease in the proportions of plant residues to the root and the total proportion of soil coating by plant residues, and, consequently, to a decrease in snow trapping.

Snowfall removal remains the easiest part of the accumulation of snow moisture resource; Calming melt waters is much less predictable and manageable. For example, if the soil freezes to snowfall, the water is less likely to absorb, compared with cases where the soil has not frozen. On the northern latitudes, the soil is usually freezed before the snow falls. Moreover, the depth of the soil freezing depends on the amount of water in the soil in the fall, as well as from the insulating effect of snow, which increases with increasing the depth of the snow cover. Dry soils are frozen deeper and faster than wet, but frozen dry soils reduce water outflow compared to wet soils.

Maintaining infiltration at the proper level when the soil freezes to the snowfall and / or before the winter rain falling, it is difficult. The levels of infiltration of frozen soils are determined by two factors: 1) the structura of frozen soil, i.e. Small granules or large units similar to concrete, 2) water content in the soil during frosts. Soils that frozen with a low level of moisture content do not interfere with the penetration of water, because The aggregates leave enough space for infiltration. On the contrary, the soils, frozen with a large content of water freeze into massive, dense structures (as concrete) and practically do not give water to penetrate inside. Sharp thaw and rain on such soils can lead to a large outflow and erosion. The accumulation of winter precipitation can be maximized using the following principles: 1) Snow capture with the help of plant residues; 2) maximizing macropores on the surface in those periods when the soil is frozen.

Synthesis of water accumulation principles

Favorable conditions for infiltration on the surface of the soil and a sufficient amount of time for infiltration - the keys to the effective accumulation of water. However, the most important principle is to protect the surface of the soil from the energy of the drop. During the winter months in the zones with a temperate climate, when there are no big leaves for the energies of the droplet and flow of water, vegetation (vegetable residues) perform a function of reducing outflow levels. The coating absorbs the energy of the drop, protects the soil units and increases the size of macropores, and this, in turn, reduces the outflow. Moreover, during the growth season of the culture, the water content in the soil in small quantities provides a good level of infiltration.

Holding water in the soil

After the water was collected, the evaporative property of the air begins to "pull out" it outwards. Therefore, even if no cultures are present on the field, soils lose moisture due to evaporation. In this section, we will demonstrate how No-Till affects the holding of water in the soil, after we collected a sufficient amount of moisture during precipitation. The protective property of plant residues increases infiltration, because They not only protect the soil aggregates, but at the same time affect the rate of evaporation, especially during the initial stages of evaporation, after falling out of precipitation.

Demonstration of evaporation of water from the soil

Evaporation occurs, because The need for air in water is always high, even in winter, with respect to the ability of the soil to hold water. In other words, the air potential is always negative in relation to the potential of the soil. The warm air has more ability to hold moisture than that of cold. Thus, with increasing temperature, the potential of evaporation increases. Evaporation is above all when the soil is wet (high water potential), and the air is dry (that is, the relative humidity is low). When the soil dries away at the surface, water rises to the surface to fill the reserves of the evaporated water (Fig. 5). With constant evaporation, the distance that water passes increases, which lowers the water flow rate to the surface in the form of a liquid or steam, the evaporation rate is reduced, and the soil surface remains dry (Fig. 5). Finally, water begins to move to the surface of the soil only in the form of steam, which leads to a very low evaporation rate. Each subsequent fallout of precipitation begins the evaporation cycle again, because The surface of the soil becomes wet again.

In addition to air temperature, other atmospheric effects, such as solar radiation and wind, affect evaporation. Solar radiation gives energy to evaporation, and wind speed affects steam pressure gradient on the soil horizon - the atmosphere. High humidity and low wind speed lead to a smaller pair pressure gradient on the soil horizon - the atmosphere and, thus, lower evaporation rate. As the relative humidity decreases and the wind speed increases, evaporation potential gradually increases. In a windy day, the wet air is constantly replaced by dry air on the surface of the soil, leading to an acceleration of evaporation.

The evaporation of water from the soil passes three stages. Most of all the water is lost in the first stage, and on the subsequent levels of losses decreases. The evaporation in the first stage depends on the environmental conditions (wind speed, temperature, relative humidity and solar energy) and water flow to the surface. The losses are significantly reduced during the second stage, when the amount of water on the surface of the soil decreases. During the third stage, when water moves to the surface in the form of a pair, the speed is very low. The greatest potential to reduce the levels of evaporation lies in the first two stages.

Let's demonstrate how vegetable residues left on the surface of the soil affect the evaporation of water from the soil. Obviously, they will reflect solar energy, cooling the surface of the soil, as well as reflect the wind; Both of these effects will reduce the initial evaporation rate of water (Fig. 6).

Plant residues on the surface of the soil present in the NO-TILL technology significantly reduce the level of evaporation at the first stage. Any material, for example, straw or sawdust, or leaves, or plastic film, detachable on the surface of the soil, will protect the Earth from the effects of rain energy or reduce the level of evaporation. The orientation of plant residues (for the root, laid mechanically or in the form of cover) also affects the rate of evaporation, because Orientation affects aerodynamics and reflecting the ability, which, in turn, affects the balance of solar energy at the surface. An example of the efficiency of the use of plant residues is given in SMIKA scientific work (1983). It measured the loss of water from the soil arising during the 35-day period without precipitation. The losses were 23 mm of uncovered soil and 20 mm with laid residues laid, 19 mm at 75% laid residues and 25% of the residues on the root and 15 mm at 50% of the laid residues and 50% of the residues on the root on the surface.

The number of residues was 4.6 t / ha, and the remains of the root were 0.46 m in height.

The reader should remember that plant residues do not stop evaporation, they delay it. If there is a large amount of time, and the precipitates do not fall out, the soil under the vegetable residues will start to lose the same water as the uncovered soil. Differences will only be that the uncovered soil will lose water quickly, and plant residues will lower the speed with which the water will leave the soil (Fig. 7).

The advantages of slowing the evaporation with the help of plant residues in the NO-TILL system can be demonstrated using the drawing data 7. Suppose it rains per day 0, i.e. And the uncovered soil (the line marked with diamonds) and the soil covered with vegetable residues (the line marked by the squares) is in the same conditions in terms of moisture content. After 3-5 days, very rapid evaporation occurred on uncoated soil, and the surface will be almost air dry. Unlike this, on the soil covered with plant residues, the speed of evaporation was much lower, and it does not make up to 12-14 days after rain falling. Now let's imagine that another rain falls on the seventh day; Because Uncoated soil on the seventh day is already dry, the rain must again moisten the dry soil before saving moisture begins. If this is a very short rain, only the amount of water that has evaporated is filled. In contrast, on the basis, which was covered with plant residues, evaporation was very slow, so the day of the seventh soil under the vegetable residues is still wet (shown in Fig. 6). This means that if the rain falls on the seventh day, he does not need to make a dry soil (it is not), so the water immediately begins to move the soil into the soil, and its accumulation occurs.

Slowing evaporation with the help of plant residues in No-Till systems helps to keep moisture, because The surface of the soil dries slower. However, if the rain is not falling over for a long period, the soil covered with vegetable residues will not save more moisture than uncovered.

The reader should be understood that even if there is a lot of time between the rains and evaporation dries the soil, the plant residues are useful in any case, because They will protect the soil from the energy of the rain drops when the rain goes again.

Demonstration of the effect of soil treatment for moisture evaporation

When the soil is mechanically processed, wet soil opens on the surface. This means that the rapid evaporation begins immediately after processing (Fig. 8). Obviously, if mechanical processing is used to combat weeds, it leads to moisture spending, because Constantly exposes wet soil to quick evaporation on the surface. In contrast, the NO-TILL technology, which uses the control of weeds using herbicides, does not lead to evaporation, because Impact on the soil does not turn out. The soil remains weting on the surface, and, therefore, the next rain will not re-enhance the dry soil, but will penetrate into the soil and accumulate for future use.

conclusions

The key to effectively catching water is favorable conditions on the soil surface so that water can immediately enter the soil, as well as those (conditions) that give enough time for infiltration. The most important principle to achieve the entry of water into the soil is to protect the surface from the energy of the rain drops. The NO-TILL system provides the coating of growing cultures and vegetable residues. The coating absorbs the energy of the droplets, protects the soil units and increases the size of Macoproport. At the same time, this coating slows down the outflow, thereby increasing the accumulation of water in the soil for use by subsequent culture. To preserve the maximum number of accumulated moisture, you must minimize evaporation. NO-TILL reduces evaporation, because With this technology, plant residues remain on the surface, which reduce the temperature of the soil and raise the wind over the soil. Water use by weeds - moisture spending, which could be available for cultivated plants. Mechanical processing usually instantly stops the removal of water weeds, however, it opens the humid soil to the atmosphere, which leads to an increase in the losses as a result of evaporation. When using the NO-TILL system, weed control is carried out using herbicides, which prevents the harmful effect on the soil compared with machining, while water accumulates in the soil. This is especially important in countries such as Ukraine, where the bulk of precipitation falls in the summer.