Sergey Banadysev, Doctor of Agricultural Sciences, Doka Genetic Technologies LLC
Crop rotation is important to minimize problems caused by the accumulation of infection in the soil, but cannot completely remove them even after an 8-year hiatus with the return of potatoes to a specific field. The use of green manure has a comprehensive positive effect on the farming system. Biofumigation properties at the same time enhance the overall effectiveness of sideration.
Its effective inclusion in short crop rotations is an economical agricultural method for the successful cultivation of quality potatoes.
The industrial production of potatoes is associated with intensive tillage, multiple passes of heavy machinery through the fields and long periods of uncovered soil. The consequence of this is the spraying of soil particles, overconsolidation, destruction of the natural structure of the soil, accelerated mineralization of organic matter. At the same time, let's not forget that the amount of plant residues left by potatoes is relatively small, the humus content after potatoes decreases. In the soil, on plant residues, most diseases and pests of potatoes persist for a long time, an increase in the infestation of fields with resistant weeds occurs. Some rotary crops share pests with potatoes. Summing up, it can be noted that a reduction in the duration of crop rotation in farms specializing in potato cultivation leads to a deterioration in the soil conditions for the formation of the crop, and with short rotations, the costs of fertilizers, water and pesticides can be higher, and the yield - lower.
Only annual cereals (wheat, rye, barley, oats, triticale, corn, ryegrass) do not have common phytopathogenic problems with potatoes.
Soy and rapeseed are susceptible to rhizoctonia and white mold. A lot of cultivated and weedy species of plants suffer from verticillosis. Nematodes and insects have alternative hosts and preserve populations well in those years when potatoes are not grown. On pastures, perennial crops of clover and cereals
grasses create good conditions for the propagation of wireworms, and this option of crop rotation should be avoided if damage to potatoes was noted. These are isolated examples, and in general phytopathological problems have different, often mutually exclusive ways to overcome them using crop rotation (Table 1).
There are no universal solutions, but knowledge of biology and differences of each pathogen allows us to find rational options for overcoming specific situations arising from the high concentration of potatoes in the structure of sown areas.
Effective crop rotation schemes, well-selected predecessors provide an increase in yields, an improvement in agrophysical, chemical and biological properties, maintenance and even an increase in soil fertility, optimization of water consumption, a reduction in the cost of combating weeds, pests and diseases, a decrease in the need for mineral fertilizers, in the first place - nitrogen, uniform distribution of peak loads during the season of field work, the possibility of widespread use of minimal tillage, stabilization of the crop production economy.
Such a complex effect is easier to obtain in perennial crop rotations of crops for various purposes, not only cereals, but also fodder. The harsh economic realities do not allow most enterprises to divert a lot of time and money to the long-term cultivation of other crop rotation crops and livestock.
Given this significant circumstance, we will consider the possibility of short crop rotations (no more than two years off in returning potatoes to the field) to achieve the listed goals in the context of the priority of solving potato problems.
We are not talking about multiplying the fertility of the soil when growing potatoes. The results of many years of scientific research unequivocally testify: no volumes of crop residues and long periods of growing herbs are not enough to maintain a constant humus content, even if the potato occupies only one field in an eight-field crop rotation. There is nothing to talk about short rotations. But these same experiments proved that the annual intensive cultivation of perennial grasses gives a better increase in organic matter in the soil compared to the non-intensive one for many years (Lukin, 2009, Nikonchik P.I., 2012). For a deficit-free humus balance, at least 10 t / ha of organic fertilizers must be applied annually or an equivalent rate periodically. If the enterprise does not have organic matter, then the plowing of green fertilizers provides a similar effect, i.e. all biomass specially cultivated for this sideral crops.
Green fertilizer is, first of all, an important source of organic matter and nutrients, “manure grown on arable land”, which is not inferior in terms of fertilizer value to litter manure. Green bean crops replenish the reserves of biological nitrogen in the soil, convert the mineral nitrogen of the soil and fertilizers into an organic form that is environmentally friendly to the environment. Green fertilizer increases the utilization of mineral nitrogen, preventing its environmentally hazardous accumulation in the soil. Green fertilizer increases the biological activity of the soil, optimizing living conditions for soil biota and reducing the phytopathogenic soil background. Sideration reduces weediness of crops and soil and helps to reduce the pesticidal load on agrocenoses. Green fertilizer increases the fertilizer value of straw and other organic fertilizers.
In principle, any plants can be scented. The list of cultivated plants that can be used for main and intermediate crops in the portfolio of leading selection and seed companies includes more than 30 items, starting from the usual winter rye and ending with such exotics as Abyssinian guisotia.
Table 2. Biomass of green manure crops (Rusakova I.V., 2017)
There are attempts to theoretically substantiate the plowing of even weeds (you don't need to sow anything at all, just wait a couple of months from spring and that's it - the wonderful weeds are ready). Objectively, the biomass of leguminous plants has the highest value; the mass of cereal and cruciferous plant species is reliably inferior to them. This table clearly shows the advantage of leguminous green manure (Table 2).
The general biological assessment of crops grown in the same crop rotation with potatoes is determined not only by the quantity and quality of organic matter, but also by the ability of the biomass to provide phytosanitary, i.e. wellness action. We are talking about the recently discovered ability of the unique biochemical compounds of certain plant species to inhibit, suppress the infectious principles of diseases, weeds and pests. The term “biofumigation” was first used to describe the effects of crop rotation with cruciferous crops and green fertilizer of cruciferous crops on soil-borne pests (Matthiessen and Kirkegaard, 2006). The term implies the possibility of achieving the effect of fumigation of the soil using plants, and not chemistry. Chemical fumigants in Russia are allowed to be used only for the disinfection of premises, grain, lumber, etc. And in European countries, the USA, Canada, Australia, chemical fumigation of soils is carried out in large quantities, in which the norms of 400-500 kg / ha of such "reputable" preparations, for example, metam-sodium and chloropicrin, are officially used.
To date, world science has accumulated a huge array of data on the effect of a wide variety of plants in the aftermath on the size and quality of the potato crop.
For example, in Poland, an effective suppression of several types of nematodes with the help of green mass or extracts from marigolds, as well as winter wikis was revealed. But most often the fumigation efficiency of cruciferous crops is noted. Rapeseed, mustard, radish contain biologically active chemicals called glucosinolates. In the soil, glucosinolates of roots, stems and leaves of green fertilizers break down into isothiocyanates, which kill or suppress some diseases, nematodes and weeds. Over the past 12 years, scientists from the US Department of Agriculture conducted more than 70 studies to study the effect of various rotations on diseases transmitted by potato soil. Although the results varied from year to year and from field to field, cruciferous crops generally reduced potato diseases (such as rhizoctonia, scab and verticillosis) and also significantly improved potato yields. The best phytoncide effect is possessed by oil radish, then Sarepta mustard, then white mustard and rapeseed, i.e. the effectiveness of crops is different. In Germany, special nematode-resistant varieties of oil radish have been created to suppress free and gall nematodes.
Yellow sweet clover (Melilotus officinalis Desr.) And white (Melilotus albus Desr.) Have active biochemical compounds - traditionally biennial leguminous herbaceous plants, but an annual variety is also distinguished, which is very valuable. Organic and mineral substances released into the soil by sweet clover consist of amino acids, compounds of phosphorus, potassium, sulfur, calcium and other chemical elements. Under the influence of the root system of the sweet clover, hardly soluble compounds dissolve in the soil, they transform into forms of nutrients assimilable for plants. The introduction of melilot into crop rotation reduces soil infestation with nematodes and wireworms. The cause of the death of pests and pathogens is dicoumarin, a poisonous substance formed from coumarin during the decomposition of the root and crop residues of sweet clover. Different varieties of yellow and white sweet clover practically do not differ in the coumarin content in plants. Sorghum-Sudanese hybrid and Sudanese grass are effective against rootworm nematodes. These crops release durrin into the soil, which decomposes into hydrogen cyanide. Annual lupine (alkaloid and fodder) is the main green manure crop for sod-podzolic soils.
Green manure varieties of lupine release alkaloids into the soil - quinolizidine derivatives with bacteriostatic, antiviral and herbicidal effects. At the same time, alkaloids can increase the germination and germination energy of seeds, the productivity of various crops by stimulating metabolic processes in plants, reduce the accumulation of nitrates, and they also have an anti-mutagenic effect. Alkaloids, as already noted, can be used as protective substances against plant diseases. It has been shown that they can rapidly degrade in the environment. According to Gross R. Wink M., only 0,1-2,0% of spartein remains in the soil 20 days after application. The antibacterial and antifungal activity of the alkaloid extract of Lupinus angustifolius plants against standard strains of the following bacteria was studied: Escherichia coli, Pseudomonos aeruginosa, Bacillus subtilis and Staphylococcus aureus, as well as against fungi such as Candida albicans and C. krusei. The alkaloid extract showed significant activity against Bacillus subtilis, Staphylococcus aureus and Pseudomonos aeruginosa.
Years of production experiments carried out in the USA and Canada under the guidance of the chief specialist in potato biofumigation - Professor Larkin - have confirmed the high potential of using crucifers in crop rotation as a precursor and green fertilizer for the fight against soil-borne diseases. For the most part, biofumigation through the production of toxic metabolites is a putative mechanism, but effects mediated by soil microbial communities are also important. A number of studies indicate that rapeseed was grown as a cash crop and not all biomass was released into the soil. This proved that the beneficial effects of rapeseed were not related to the biofumigation effects of the incorporated green biomass, but were simply the result of growing another plant species. Green fertilization of rapeseed and white mustard provided a greater reduction in the incidence of rhizoctonia than mustard crops with much higher glucosinolate levels, indicating that biofumigation products were not the main mechanism of action. In general, the role of green fertilizer is lower than the value of crop rotation. More diverse cropping systems lead to an increase in the biomass of soil microorganisms. Crop rotation is the main source of the formation of a full-fledged structure of microbial communities. Each rotational crop contributes to the formation of unique microbial characteristics and can affect the structure and function of microbial communities. The addition of green manure does not necessarily reduce pathogen populations or survival, but increases the population of pathogen-antagonistic microorganisms. Barley and cruciferous rotations consistently had higher bacterial populations and microbial activity than most other rotations, while continuous potatoes (no rotations) resulted in the largest reduction in microbial activity. The combination of intermediate winter rye with rapeseed results in a 25-41% reduction in black scab and common scab relative to a continuous potato crop rotation and by 2137% relative to a standard barley / clover crop rotation. These data are consistent with the concept that higher microbial activity and diversity contribute to better suppression of infection.
However, the effect of the very best predecessors is often not only positive. It turned out that red clover is associated with an increased level of rhizoctonia. Phacelia, for example, suppresses gall nematodes, but is the host plant of nematodes from the genus Trichodorus, which carry the rattle virus. And this virus, in turn, causes symptoms of glandular spotting of tubers. Mustard can cause glandular spotting. And any crop rotation has its own limitations or even negative properties that you need to know. It is appropriate to give a thorough assessment of German researchers regarding the effect of cultivated crop plants on the occurring nematode species and physiological disturbances (Table 3).
We characterize biofumigation crops, the seeds of which can be used in the main and intermediate crops on the territory of the Russian Federation.
1. Sudanese grass and sorghum-ripper, soil former, biofumigator. Sorghum-Sudan Hybrid (SSH) is a hybrid of sorghum and Sudan grass (Sudanggrass). Both species are independently used as green manure, but the hybrid has the advantage of drought and frost resistance. Sorghum bring a huge amount of organic matter into the soil during seeding. These tall, fast-growing, thermophilic annuals choke off weeds, inhibit some nematodes, and penetrate deep into the soil. SSG is the best green manure after harvesting row crops and legumes, as it consumes a lot of nitrogen. It has an aggressive root system, which is a soil aerator, mowing strengthens and branches the root of the Sudanese grass 5-8 times. Stem thickness reaches 4 cm in diameter, height - up to 3 meters.
SSG roots secrete a special allelopathic substance - sorgoleone. It is, in fact, a herbicide that begins to be released as early as the fifth day after germination. The substances of sorghum have the most severe effect on the rope-grass, crab-grass, barnyard, green bristle-grass, squid, and ragweed. It also strongly affects cultivated plants, so it is necessary to maintain the interval between plowing Sudanese grass and planting crops. Sowing Sudanese sorghum in place of the harvested crop is a great way to disrupt the life cycle of many diseases, nematodes and other pests. Due to the huge biomass and subsoil root system, Sudanese sorghum restores the fertility of the depleted and compacted soil in a year. It is the best green manure for draining clay, moist soils on which heavy equipment has been working. The mowed green mass can be used for mulching in other fields, for forage and silage. One cutting per season is optimal. Biomass decomposes for a long time, it cannot be left without plowing. Suppression of nematodes is possible only when plowing fresh green mass that has not reached the tube stage. Sorghum has its own pests, some hybrid varieties are not suitable for livestock feed, as they contain hydrocyanic acid.
2. Crucifer green manure satisfy all the requirements for green manure: they grow quickly, have a rich juicy biomass and a huge network of small roots, suppress weeds, fungi, wireworms and nematodes, scab. Some cruciferous plants, for example, daikon, have a root that can pass through the plow sole much more effectively than other siderates.
Mustard is ideal for fixing the nitrogen left over after harvest as it quickly builds up greens. The suppression and control of weeds by cruciferous green manures is due to the rapid growth and "closing of the dome", that is, the high covering ability of the soil. Not the least role is played by the allelopathic influence of decomposing residues plowed up in autumn. Mustard and oil radish interfere with the development of shepherd's purse, mari, bristle grass, prutnik, barnyard grass, squid, etc. Crops can be sown to legumes, i.e. when they are already rooted, it is not worth sowing in the mixture - cruciferous plants overtake other plants and inhibit their development. Seed consumption - 10-30 kg / ha. Embedding of cruciferous green manures can be carried out at any stage of the growing season, but the optimal time is the beginning-middle of flowering, during this period the plant reaches its maximum biomass.
The biomass started in late autumn begins to release nitrogen in early spring, i.e. just in time for landing.
Cabbage species need additional nitrogen and sulfur; with their help, essential oils-fungicides and glucosinolate are synthesized. Mineral fertilizers are well applied precisely under green manure, as they return accumulated in chelate form. They accumulate phosphorus well, make it more accessible with the help of root secretions. In terms of carbon content and decomposition rate, cruciferous plants occupy an intermediate position between cereals and legumes.
The main problem of cabbage green fertilizers is the danger of damage and even complete destruction of seedlings by a cruciferous flea. In addition, when using cruciferous plants, the seeds should not be allowed to ripen, as this forms a huge stock of unwanted weeds for the entire crop rotation. And once again it is necessary to emphasize that the species and varieties of cruciferous crops have many biological and technological differences and are far from equal in terms of biofumigation properties. In the first place - oil-bearing radish (nematodoresistant varieties), in the second - yellow or Sarepta mustard. Unfortunately, agrarian science has not carried out an assessment of the fumigation properties of cruciferous varieties of domestic breeding, and German special varieties are not officially available, since they are not included in the Russian register.
3. Sweet clover - biennial, less often, an annual plant with a height of up to 2-2,5 m in culture with an unbroken stalk, one of the most valuable sideral crops.
Unlike most other leguminous species, it is very plastic and forms a large green mass. During cultivation, it accumulates from 100 to 300 kg of nitrogen per hectare.
In terms of the rate of decomposition of organic residues, due to the narrow ratio of carbon and nitrogen (about 20), sweet clover has no equal among legumes. Its role is great in regulating the balance of organic matter, activating biological processes in the soil, in optimizing agrophysical properties, and especially on heavy loamy and clayey soils. If, when plowing 60 t / ha of manure, the permeability of the soil increases 1,5 times, then when plowing 20 tons of green mass of sweet clover - 2 times. Drainage, aeration, structure, physicochemical properties are improved and the subsurface horizon is generally cultivated. Melilot has a powerful deeply penetrating root system, due to which hard-to-reach compounds of phosphorus, calcium, potassium and other elements are partially transferred to the upper layers. This not only increases the content of readily available food, but also contributes to some deoxidation of the soil due to an increase in the bases in the soil-absorbing complex.
Melilot green manure steam improves food, water-air regimes and disinfects the soil from harmful pathogens due to increased microbiological activity of saprophytic microflora. The sideral mass of sweet clover, containing coumarin, which turns into decumarin during rotting, significantly reduces the number of wireworms, nematodes and corneidae. In addition, sweet clover is a "trap" for aphids that carry potato viruses. Therefore, green manure fallow from yellow melilot is especially valuable in farms specializing in potato production. For example, LLC Agrofirma Slava Potato uses the following scheme: yellow sweet clover - winter wheat - potatoes - spring cereals with over-sowing of sweet clover. At the same time, against the background of drought, sweet clover can critically reduce the moisture reserves in the soil. 4. Lupine - yellow, white, blue (narrow-leaved) and other annual species. Lupine blue narrow-leaved - one of the best green manures for sandy and sandy loam soils, gives 30-40 t / ha of green mass plus 10-15 tons of roots, totaling up to 50-65 t / ha of organic matter, which is not inferior to the main species in terms of fertilizer value manure. In addition to nitrogen, the green and root mass of lupins is rich in phosphorus, potassium, calcium, trace elements and in such a ratio that is necessary for the normal growth and development of major crops. And what is very valuable - these nutrients are in the organic matter that is plowed into the soil.
Therefore, they are not washed out of the soil, as is often the case with mineral fertilizers.
In areas where lupine grows well, it should be preferred as a more valuable crop. Alternatively, the green mass can be harvested for feed, and the crop residues will be a valuable fertilizer. Good results are also obtained when it is sown at the end of May after rye, mown for green fodder. By the fall, it gains a significant mass, and it is cut down at a high cut (15-20 cm) for ensiling, and the stubble is plowed under the potatoes. As a result, the yield of potatoes increases by 3-5 t / ha. As studies of the Novozybkovsk Experimental Station have shown, potatoes use nitrogen from the stubble-root residues of lupine better than winter rye and spring cereals. For fumigation, the best suited varieties of narrow-leaved lupine, the name of which contains the words "siderat, green manure". This implies an increased content of alkaloids. Lupine, along with perennial grasses, clover, alfalfa, belongs to the category of humus-forming agents. As an example of the use of lupine, we give the crop rotation of the SPK "Dmitrievy Gory" of the Vladimir region: 1 - lupine; 2 - grain winter crops; 3 - potatoes; 4 - lupine; 5 - potatoes.
Along with the advantages, the annual lupins also have relative disadvantages. They accumulate much less nitrogen compared to perennial ones, cannot improve the soil structure, since their root system is too small. The next disadvantage of annual legumes is their slow growth at the beginning of the growing season and sensitivity to weed contamination. In addition, in comparison with other siderates, legume seeds are significantly more expensive per hectare.
In general, the phytosanitary role of green fertilizers is to increase the biological activity of the soil and the active development of saprophytic soil microflora, the suppression of pathogens and a number of pests. When plowing green manure, the quality improves and the yield of potatoes increases, storage losses decrease, and the taste of the product improves. The combined use of siderates is even more effective. In Germany, in recent years, multicomponent sideral mixtures have become widely used.
The agroclimatic resources of most potato-producing regions of the Russian Federation are quite favorable for growing crop crops and using them as siderates.
After harvesting winter and early spring crops, the fields remain unoccupied for more than 70 days, and after annual crops for green fodder - up to 80-90 days. Under favorable conditions, the sum of effective temperatures for this period is 800-1000 ° C, or 30-40% of the agro-climatic resources of the entire warm period of the year. Siderata can be cultivated for a whole season and get two harvests, for example, winter rye + oil radish, Sudanese grass, mustard, buckwheat, lupine. An equal effect will be given by the cultivation of barley for grain and stubble green manure.
Summary: Crop rotation is important for minimizing the problems caused by the accumulation of infection in the soil, but cannot completely remove them. The use of green manure has a comprehensive positive effect on the agricultural system (adding organic matter, erosion control, weed control, improving soil structure, increasing its fertility, increasing agricultural productivity). Biofumigation properties at the same time enhance the overall effectiveness of sideration. Soil improvement with the help of green fertilizer of cruciferous crops, lupine, Sudan grass and clover has been proven.
The inclusion of effective sideration in short crop rotations is an economical agricultural method for the successful cultivation of quality potatoes. Any green man culture has its own natural niche, advantages and disadvantages, but you can always find rational solutions. The choice of the optimal sideration option is made on the basis of taking into account all the essential circumstances of a particular enterprise: soil, climate, phytopathology, economics, and specialization. Cultivation of green manure cultures must be carried out at a high organizational and technological level, otherwise the result will be insufficient or even negative.