From the magazine: No. 2 2015
Category: Specialist consultations
Andrey Kalinin, Doctor of Technical Sciences
At the present stage, the intensive development of potato farms is unthinkable without the use of rich foreign experience accumulated by colleagues from Europe. Most of the elements of mechanized technologies promoted by leading potato-producing countries have found their application in the fields of almost every domestic potato grower. To a large extent, the transition to such technologies using the latest developments in mechanization means has made it possible to increase the overall level of potato production, reduce labor costs and improve the quality of the resulting products. However, despite noticeable positive changes, our producers often find themselves hostage to a number of circumstances (unfavorable weather conditions, deteriorating soil conditions, etc.), which do not allow them to achieve average European indicators in potato production. This review presents the results of studies of the dynamics of soil conditions in the development zone of the potato root system using intensive mechanized technologies to understand the causes of the problems faced by most domestic potato growers.
The soil hardness (an analogue of its density), that is, the resistance of the soil when a plunger with a conical tip is introduced into it, was taken as the basis for assessing the soil condition. The soil resistance values were measured simultaneously with the determination of the tip penetration depth. This indicator reflects the ability of the potato root system to penetrate deep into the soil layer (it is known that the potato root system can penetrate to a depth of 130 cm) to more fully unlock the potential of plants and increase their resistance to adverse weather conditions.
Unhindered development of the potato root system is possible if the soil hardness does not exceed 1,0 MPa, however, the spread of the root system deeper into the soil horizon occurs at higher values of this indicator, but with less intensity. The range of hardness values of 1,1-2,5 MPa is taken as a zone of medium compaction, when increased force is required for the penetration of roots between soil elements and the plant spends more energy on this work. Soil hardness in the range of 2,6-4,5 MPa is taken as a zone of strong compaction, when the development of the root system is significantly hampered, but is still possible. At the same time, the plant spends even more energy on root development, reducing the development potential of the tubers of the new crop. The degree of soil compaction with hardness values above 4,5 MPa is taken to be a zone of over-compaction, in which the spread of the root system becomes completely impossible. Symbols of compaction zones are presented in Fig. 1 for subsequent visual assessment of their distribution during potato cultivation.
Studies of the dynamics of soil conditions were carried out on soddy-podzolic soils of light mechanical composition, the most favorable for potato production. When cultivating potatoes, the farm uses generally accepted European technology, which minimizes the number of passes of agricultural machines to reduce the mechanical impact on the soil from tillage units and planting machines. For pre-planting treatment, a combined cultivator Thorit 10/6 KUA from Lemken was used, potatoes were planted with a GL 36T planter from Grimme, single inter-row tillage was carried out with a passive ridge-forming cultivator GH 6. The use of other implements that can change the composition and structure of the soil, the cultivation technology used Didn't include potatoes. Therefore, the condition of the soil was a derivative of the impact of the above machines. Measurements were taken: in the center of the ridge at the location of the seed tubers/potato nests, along the planter's track and along the tractor's track across the entire width of the planting unit. A total of 100 measurements were made (every meter of the distance traveled), which allows us to talk about the real picture of changes in soil state parameters with a high degree of statistical reliability. The level of the daytime surface of the field before the start of spring field work was taken as the zero mark. Soil hardness measurements were carried out after pre-sowing treatment, after planting potatoes (both operations were carried out on the same day), after passing the ridge former (14 days after planting) and before harvesting potatoes (90 days after ridge formation). Thus, the research made it possible to see the dynamics of changes in soil condition after each technological operation, as well as to evaluate the results of the aftereffect of each machine used in potato cultivation technology. The results of soil hardness measurements are presented in Figures 2-5.
Figure 2 shows the distribution of soil hardness along the working width of the tillage unit. From this figure it is clear that after preplanting treatment, the zone of normal compaction in areas not compacted by undercarriage systems is noted at a depth of up to 25 cm, the zone of average compaction is located at a depth of 25 to 35 cm, and below this mark the compaction takes on values indicating noticeable difficulties for penetration of the root system. Increased values of soil hardness along the trail of running systems of tillage units are observed below the 10 cm mark, that is, the depth of preplanting treatment. These data show the importance of using wide-cut implements for pre-planting tillage in order to minimize the compaction area with running systems, as well as the need to perform high-quality soil preparation in one pass of the unit.
To study the impact of the planting unit on changes in soil conditions, soil hardness measurements were carried out immediately after the passage of the planter. The distribution of compaction zones after this technological operation is shown in Fig. 3. Data analysis showed that the coulter group of the planting unit does not contribute to the deterioration of the soil condition at the point of contact with the soil, therefore, in the center of the ridge, at the location of the seed tubers, the distribution of compaction zones in depth remained unchanged compared to the condition of the soil after pre-planting treatment.
Following the tracks of the tractor wheels, the zone of medium compaction is marked directly from the soil surface, however, in the lower layers, the location of the boundary of the high compaction zone remained without significant changes in depth. Significant soil compaction is caused by the impact of the running systems of the planting unit. Along the track of the planter wheels, the zone of high compaction begins at a depth of 25 cm, and at around 50 cm the degree of compaction reaches critical values (penetration of the potato root system is impossible at such indicators). This impact on the soil of the running systems of the planting unit is caused by a significant load on them, especially when the bins for seeds and fertilizers are fully loaded. This figure gives an understanding of the need to use wider tires with an increased diameter on planters in order to reduce the compacting effect on the soil.
In Fig. Figure 4 shows the distribution of compaction zones after the passage of a passive cultivator for inter-row cultivation of potato plantings, equipped with a spring-loaded ridge-forming plate. Measurements of soil condition parameters showed that after performing this operation in the central part of the ridges, in the place of formation of tubers of the new crop and the development of the main mass of the potato root system, there is practically no zone of normal compaction (only the top layer at the top of the ridge no more than 5 cm thick). Tubers of the new crop are forced to develop under conditions of medium compaction; at a depth of 15 cm to 55 cm there is a zone of high compaction, which is difficult for the potato root system to penetrate, and above 55 cm there is a zone of over-compaction where the root system is not able to penetrate. After additional impact of tractor wheels on the soil, the upper boundary of the high compaction zone was already marked at a depth of 25 cm, which indicates a deterioration in the conditions for the development of the potato root system in the tractor's wake. In this place, the layer with an average level of compaction decreased by about 10 cm. The position of the soil compaction zones formed by the running system of the planting unit remained practically unchanged. Analysis of the data obtained showed that, basically, the deterioration of potato development conditions is associated with the use of a ridge-forming plate, which compacts the soil by three-dimensional compression in the longitudinal-vertical plane. In this regard, when using machines for inter-row tillage with a continuous ridge-forming slab, it is necessary to adjust its inclination angle in such a way as to minimize soil compaction by the upper shelf of the slab.
The result of the influence of a complex of machines for cultivating potatoes using intensive technology on the formation of conditions for the development of the root system of this crop is presented in Fig. 5. Measurements were taken before the start of harvesting. Data analysis showed that the condition of the soil formed by the ridge-forming cultivator deteriorated significantly due to the natural shrinkage of the ridges within three months after the passage of this unit. The tubers of the new crop were forced to develop under conditions of high and medium compaction, and at a depth of more than 25 cm, an overcompaction zone was observed everywhere. The presence of overcompaction close to the soil surface not only inhibits the development and functioning of the potato root system, but also significantly impedes the penetration of moisture into the lower layers during precipitation or watering. All these factors lead to a decrease in potato yields and deterioration of harvesting conditions, especially in years with excessive precipitation in the autumn.
Based on the presented materials on the dynamics of soil conditions, when cultivating potatoes from the beginning of field work until the end of the growing season, we can conclude that it is necessary to more carefully configure soil-cultivating units, the correct choice of types of machines and their configuration, taking into account the soil-climatic and economic conditions of production of this crop . The complex of machines must necessarily include loosening systems (to a depth of at least 20-25 cm) to prevent over-compaction of the soil in the areas where the bulk of the potato root system is located and the formation of tubers of the new crop.