The laws of agriculture are nothing more than the expression of the laws of nature, manifested as a result of human activities in the cultivation of crops. They reveal the connection of plants with environmental conditions, and also determine the development of agriculture, which should be carried out in strict accordance with these laws. The basic laws of agriculture include the following.
The law of equivalence and irreplaceability of plant life factors.
The law was first expressed by V.R. Williams says: “All factors of plant life are absolutely equivalent and irreplaceable.” According to him, for the normal functioning of the plant organism, an influx of all factors of plant life (terrestrial and cosmic) must be ensured. The manifestation of this law is absolute and relative. The absolute value is expressed in the fact that no matter what factors the plant needs, the absence of any of them leads to a sharp decrease in yield and even death of the plant. For example, no matter how much the moisture content in the soil increases, it cannot compensate for the lack of heat or light in the same way that nitrogen cannot be replaced with phosphorus or potassium.
The law of equivalence and irreplaceability of plant life factors gives a clear idea that there are no main and secondary factors.
The law of minimum was first formulated by J. Liebig. It is stated as follows: “The value of the obtained crop is determined by the growth factor, which is the smallest in relation to the needs of plants.” According to this law, under optimal other conditions, the yield level is determined by the factor that is at a minimum.
This law is clearly depicted in the form of a “Dobenek barrel”, the rivets of which conditionally mean various factors of plant life (Fig. 13). The height of each riveting corresponds to the presence of a certain factor, expressed as a percentage. The dashed line shows the maximum possible crop yield with the optimal presence of all factors. However, the actual yield is determined by the height of the lowest riveting, or the amount of factor that is at a minimum. If you replace this riveting, then the level of the factor will be determined by another riveting, which will be minimal in height, then the third, etc.
The law of minimum, optimum and maximum is formulated by R. Sachs: “The value of the crop is determined by the factor at the minimum. The highest yield is feasible with the optimal presence of the factor. With the minimum and maximum availability of the factor, the crop is impossible. ” Its meaning is that the greatest yield can be obtained with the optimal amount of factor: reducing or increasing it leads to a decrease in yield. This can be clearly seen on the example of any factor (temperature, batteries, humidity, etc.).
Any life process in a plant begins at some minimum temperature, proceeds in the best way at the optimum temperature, slows down, and then completely stops as it increases further.
Fig. 13. Graphic representation of the law of minimum: 1 – possible yield; 2 – actual crop
Therefore, to increase crop yields and more efficient farming, it is necessary not only to take into account factors that are or may be at a minimum, but to carry out activities in such a way that they are always in optimal quantities for plants.
The law of the combined action of plant life factors was established by V.R. Williams. According to this law, to obtain high crop yields, the simultaneous presence and influx of all plant life factors in the optimal ratio is necessary. From this law, important provisions for the practice of agriculture follow. High efficiency in agriculture cannot be achieved by one strong agronomic technique or even by several separate methods. High and sustainable crop yields are achievable only with the implementation of the whole range of agrotechnical measures and in the optimal time.
The law of return was also formulated by J. Liebig. Its essence is as follows: “The main principle of agriculture is that the soil gets back everything that was taken from it.” It is well known that the crop is created from material components under the influence of plant life factors, a certain part of it is due to substances obtained by plants from the soil, as a medium of growth and a mediator of plants in providing them with these factors.
With the systematic alienation of the crop from the field and without returning the nutrients and energy used by the crop, soil fertility is lost. If the removal of substances and energy is compensated and occurs with a certain degree of excess, then the soil not only preserves fertility, but also increases it.
According to the law of return, if the balance of assimilated nutrients in the soil is disturbed as a result of their losses, or as a result of removal from the crop, it must be restored by applying appropriate fertilizers.
Compliance with the law of return is of great importance not only to preserve and increase soil fertility, but also to increase crop yields. By regulating the removal and entry into the soil of nutrients and other factors, it is also possible to regulate the quality of the products obtained (protein content in grain, starch in potatoes, sugar in root crops, etc.).
The law of return is the scientific basis for the reproduction of soil fertility, a partial case of the manifestation of the universal law of conservation of substances and energy.