Instructions for determining the weediness of fields. Methods for counting weeds
The most important condition for effective control of characteristic types of juvenile weeds on field lands is the correct alternation of crops in crop rotation. The reason is that wintering and early spring weeds, as already indicated, can most easily be destroyed in fields growing under late agricultural plants, and stubble weeds (early and late spring) can be destroyed most easily in areas occupied by row crops and early harvested crops.
In the fields of early ripening crops, one of the most decisive means of combating undergrowth is the autumn agrotechnical complex. After clearing the area from crops, the main part of the weed seeds (70-90% of their reserve in the arable layer) is on the soil surface. It is enough to destroy them, and the weediness of the field will decrease by four or more times. In the 30s Stubble burning was used for this purpose. In fields infested with bindweed, pickleweed, mouse grass and other weeds, which have time to ripen and dry before burning the stubble, 60-80% of their seed germs burn and lose their germination. Seeds located on plants die completely, while those lying on the soil surface die by about half. Ripe and dried seeds of bindweed, Velcro, and field grass burn especially well on the ground. Mouse seeds are the most persistent.
The death of seed buds during stubble burning with the specified botanical composition leads to a significant reduction in crop infestation next year. This is evidenced by the experiments of the Research Institute of Agriculture of the South-East in 1931-1932. in the North Caucasus in the educational and experimental grain state farm No. 2. Here, on the site where stubble burning was carried out in 1931, the infestation of mouse and bindweed was lower than in the control by 99%, weed - by 95%, and white pigweed - 93%, ironweed - 86% and field mustard - 71%. Overall weed infestation decreased by 87%.
If there are green (succulent) weeds in the stubble, such as acorn grass, pigweed and the like, and accompanying ones - thistle and others, burning has a lesser effect. Particularly bad results occur in years with rainy autumns and when stubble burning is delayed; in this case, the stubble plants begin to grow rapidly, and their stems and leaves contain a lot of moisture.
Currently, stubble burning is carried out using fire cultivators. It has become widespread in agricultural production in Central Asia. At the end of the summer of 1965 in the Saratov region, a fire cultivator was successfully used at the Leninsky Put fattening state farm near Saratov. As a result, in 1966, in the burned area of barley crops, on average, 1 sq. m there were 50 young and 21 root shoot weeds, while on the unburnt area there were 86 and 22, respectively. The yield for the plots turned out to be 19.2 and 14.3 centners per hectare.
Now research institutions are looking for chemicals that could kill or stimulate germination of seeds lying on the surface of the soil and on weed plants in the summer-autumn period. The former are called sterilizing herbicides, the latter - stimulating herbicides. In particular, in Japan, the drug NCS(CH2)nSCN was proposed to stimulate the germination of weed seeds during this period.
On lands infested with stubble, after harvesting early ripening crops, the bases of the shoots (“stumps”) of these crops remain in the stubble. weeds, as well as individual specimens of them, for one reason or another, lagging behind in their development. Not shaded by crops, they grow strongly, especially in rainy weather, and produce a huge number of seeds (in some cases up to 20 thousand or more per square meter).
Reapers cannot grow back from their roots. Therefore, in order to prevent the growth and abundant fruiting of these weeds in the stubble, they must be destroyed as quickly as possible after harvesting the crops. To do this, it is enough to carry out stubble peeling or early plowing of plowed land. The earlier the stubble treatment is carried out, the shorter the period during which the stubble plants form seeds, the less of the latter are formed and plowed into the soil (both fallen weeds and together with the plants).
How important early stubble cultivation is (hulling stubble or plowing plowed land) is shown by the experience of the Rassvet collective farm in the Samoilovsky district of the Saratov region. On one of the fields of this farm, in the area where the plowed land was plowed on August 13, an average of 1 sq. m 155 weed seeds were plowed, on August 23 - 1999 pieces, on September 2 - 2238 and on September 12 - 2052.
To prevent the formation of weed seeds in the stubble, it is currently recommended to begin peeling or early plowing of the plowed land simultaneously with harvesting the crops and complete no later than 1-2 weeks. Instead of hulling or early plowing of plowed land, to destroy broadleaf stubble crops, you can spray the stubble with herbicides at the same time as mechanical tillage. 2,4-D preparations are used against most weeds.
It is believed that the main purpose of stubble peeling in the fight against young plants is to cause the germination of their seeds located in the surface layer of the soil. In the conditions of the arid Volga region, due to the rapid drying of the plowed layer, this goal is not achieved when peeling stubble. But stubble peeling is an extremely powerful means of removing seed germs from dormancy. In one of the experiments of the Research Institute of Agricultural Sciences of the South-East, the seeds of amaranth and gray mouse, collected in September from the surface of the soil before peeling the stubble, when germinated in room conditions had zero germination; those collected after peeling with disc tools sprouted by 92% in the first weed and by 67% in the second.
To ensure the germination of weed seeds that have come out of dormancy as a result of peeling or some other event (spraying stubble with stimulating herbicides), they must be embedded in the soil to a depth where there are always sufficient reserves of moisture and air, including in autumn. at optimal temperatures. Similar conditions on chernozem and chestnut soils are usually created in the lower horizons of the arable layer.
Before plowing the plowed land, the main amount of weed seeds (75-95%) is concentrated in a layer of 0-10 cm. Therefore, in order to embed them deeper into the soil, it is enough to cut off this layer and throw it to the bottom of the furrow. This is achieved by plowing plowed land with plows with skimmers. Plowing with plows without skimmers distributes weed seeds more or less evenly throughout the entire thickness of the arable layer (Fig. 32).
As has already been shown, weeds germinate most fully in the deep layers and most poorly in the surface; shoots are formed only from the upper horizons, and only in the spring. Since plowing plowed land with plows with skimmers embeds the bulk of the seeds into the deep layers of the soil, with such basic treatment, significantly more weeds germinate, and much fewer seedlings appear than when plowing with plows without skimmers. This leads to the fact that in areas plowed using the first method, the contamination of the grass stand with above-ground parts of weeds, and the soil with their seeds, is less than with the second method. This is confirmed by observations on collective and state farms.
Production experiments have shown that stubble peeling in combination with plowing plowed land with plows with skimmers for many years ensures more complete germination of young plants (in autumn and spring) than fall plowing alone without preliminary peeling. The reason is that in the first case, under the influence of peeling, weed seeds come out of dormancy better than in the second. But there are years when peeling does not produce a noticeable increase in the percentage of weed germination.
In one of the studies in the fields of the Saratov experimental production farm of the Research Institute of Agriculture of the South-East, in a plot with stubble peeling and plowing of plowland, bindweed buckwheat germinated by 88%, without peeling - by 74%, white pigweed and quinoa - by 92 and 59%, respectively. common acorn - by 91 and 55%. In other years, the efficiency of peeling was lower, and, finally, in the remaining years, no positive results were obtained from this agricultural technique.
In conclusion, it should be noted that autumn plowing in the fight against young plants gives significantly better results compared to spring plowing. The difference in their effectiveness is expressed in the fact that during spring plowing, due to its greater looseness, weeds sprout more abundantly and therefore clog the crops more than in plowed land.
From all of the above it follows that on lands with a young type of weed from under early harvested crops, in order to sharply reduce the seed productivity of weeds during the stubble period and cause the germination of as many of their seed buds as possible in the soil (with a minimum of seedlings), it is necessary to carry out stubble stubble peeling (as much as possible early dates) and plowing plowed land with plows with skimmers. Fields under late agricultural plants are raised under the plow land immediately after they are cleared by plows with skimmers.
In years with dry autumn, plowing with plows with skimmers is not feasible. Instead, the main tillage is often carried out with flat-cutting subsoilers. In this case, the weed seeds remain on the soil surface, which the next year in rainy weather leads to severe weeding of the crops. To prevent this, herbicides should be applied to fields treated with flat cutters in the fall in the spring or summer as soon as weeds appear.
One of the most decisive means for clearing the soil of the seeds of young plants is steam treatment of the soil, more precisely, properly processed black steam. All other types of vapors give significantly worse results. In black fallow at the Balashov experimental station, in the Saratov experimental production farm of the Research Institute of Agriculture of the South-East, in a number of collective and state farms, wild oats germinated by 99-100%, in early (plowed before May 20-25) - by 78-85%, in on average (until June 20 - by 38-83% and late until July 20) - by 10%. Other weeds germinate just as well. Thus, in the Saratov experimental production farm, a pair of mice germinated in black by 92%, acorn grass - by 96-99%, and bindweed - by 88-95%.
Such results do not always occur, but only in years when the soil plowed in the fall emerges from winter in a fairly loose state. If due to heavy autumn rains or for some other reason it becomes very compacted (swimming), after ripening it must be loosened to the full depth of plowing. Otherwise, due to lack of air in the arable layer, weeds will not germinate well.
In the Saratov experimental production farm, with early spring plowing of compacted black fallow, soil contamination with weed germs before sowing winter crops decreased by 52%, with deep loosening at the same time with a cultivator - by 43%, and with surface tillage - only by 5%. Similar results were obtained in other similar cases.
On lands infested with early spring weeds, the best results are obtained by deep loosening of compacted black fallow in late April - early May, and in areas with late weeds - in the second half of May. In particular, on the Progress collective farm of the Samoilovsky district of the Saratov region, early loosening of a heavily overgrown area with rakes to 15-18 cm ensured the germination of 99% of wild oat seeds, with plows without moldboards to the same depth - 98% and with conventional cultivators at 5-6 cm - only 78%. On the Elizavetinskoe state farm in the same region, on a field infested with gray and green mice, when plowing black fallow 20 cm deep with plows without moldboards, these weeds sprouted by 77% at a later date, and without plowing - only by 9%.
Seedlings of juveniles in pairs are destroyed using surface treatments. After each cultivation, especially deep cultivation, the field should be rolled. This ensures that the soil retains moisture and increases the germination of weeds. When plowing black fallow with plows with skimmers, young plants, as in similarly treated plowed land, germinate mainly in the deep layers without the formation of seedlings.
It is also possible to successfully control young weeds in the system of pre-sowing treatment of plowed land. For early spring crops, this system consists of moisture closure and early spring cultivation. Both methods have only indirect significance in the fight against juveniles as measures to ensure favorable conditions for good growth cultivated plants. As a result of their use, weeds are more strongly suppressed by crops.
In the conditions of the arid Volga region, spring young weeds cannot usually be destroyed directly by pre-sowing treatment methods for early crops. The reason is that these weeds form seedlings after early crops are sown. Waiting for full seedlings to appear with the expectation of cutting them with a cultivator and only then sowing is dangerous. You can trim the weeds, but due to late sowing the crops will not produce a harvest. Only in some years with a cold and long spring do early spring weeds begin to sprout 1-2 days before sowing or in the first days of it. These seedlings can be destroyed by pre-sowing cultivation.
Pre-sowing treatment for late spring crops is a much more effective measure to combat young plants, especially wintering and early spring crops. Wild hemp, field mustard, white pigweed, wild radish and other early spring and wintering weeds germinate and form seedlings starting from the last days of April and most often until mid-May. Late weeds, depending on spring conditions, sprout from mid-May and throughout the summer. At the fifth department of the state farm named after. Lenin (Samoilovsky district) 99% of field mustard seedlings appeared before May 20, and in the Saratov experimental production farm by the same time - 95% of wild hemp.
Late crops in the arid Volga region, depending on the conditions of the year, are sown from mid-May to early June, that is, when early spring and wintering weeds practically stop forming seedlings. As a result of pre-sowing cultivation, which destroys all seedlings of these weeds, the crops of late crops are free of them. This reduces the cost of labor and money for weeding, ensures high yields of agricultural crops and prevents the shedding of these weeds while still standing.
The importance of pre-sowing treatment for late crops is not limited to ensuring the cleanliness of crops from wintering and early spring weeds. In the Volga region, these weeds not only form seedlings, but also germinate in their main part, mainly in May. At the fifth department of the state farm named after. By May 18, 98% of the field mustard from the reserve of its seeds in the soil had sprouted through the plowed winter of Lenin, and 93% of wild hemp had sprouted in the Saratov experimental production farm. Thus, before sowing late, it is possible to achieve almost complete cleansing soil from many types of early spring weeds. Only white pigweed, quinoa and some other weeds, in which not all seed germs emerge from dormancy by spring, germinate in slightly smaller quantities, but still more than half.
To ensure mass germination of early spring weeds in the pre-sowing period, it is only necessary to carry out a good system of autumn tillage and timely cover harrowing in the spring, and in case of strong soil compaction, in addition, deep early spring cultivation. The latter ensures that a sufficient amount of air penetrates deep into the soil, which causes more complete germination of weed seeds. At the fifth department of the state farm named after. Lenin, with deep plow cultivation, field mustard sprouted by 98%, and with shallow cultivation - by 77%. The main part of the seedlings of this weed formed before sowing millet and were destroyed by pre-sowing treatment.
The success of combating young weeds largely depends on the condition of crops. If the crops sprouted quickly and quickly, are dense enough and grow quickly, the weeds very soon find themselves under their canopy, begin to wither and even die. In this regard, in the fight against weeds, all methods of advanced agricultural technology for cultivating agricultural plants are important, since they create conditions for suppressing weeds by crops. Among them, timely sowing dates, slightly increased seeding rates, high soil tillage and sowing standards (absence of flaws and sifting), etc. play an important role. For example, in one of the experiments of the Research Institute of Agriculture of the South-East at the Ershov experimental station with irrigated spring wheat, at a sowing rate of this crop of 2.5 million grains per hectare, on each square meter there were 302 weed shoots by the time the crop was eared, and 154 by economic ripeness, at the norm and sowing 4.5 million grains - 182 and 109, respectively.
Autumn tillage ensures the germination of a certain number of weed seed germs (the best variants are larger ones and the worst ones are smaller ones). As a result, soil contamination is reduced. This success must be consolidated, which can be achieved by measures that prevent the formation of new seeds on sprouted and growing weeds or at least to some extent reduce their seed productivity.
In clean fallow, seedlings of all subgroups of young plants are destroyed by cultivation; before sowing late crops, early spring and partially late weeds are destroyed by pre-sowing treatments; directly in the stem of agricultural plants, crops are taken care of (harrowing, treatment of row spacing, manual and chemical weeding).
Harrowing as a means of combating undergrowth is used in fields sown with corn, sunflowers, peas, china, potatoes and many other crops, the sprouts and seedlings of which are quite resistant to this agrotechnical measure. The harrow best destroys small-seeded weeds that emerge only from the top four to six centimeter layer and form weak shoots with small roots. These include white pigweed, quinoa, acorn grass, mousegrass, bindweed, pikulnik and a number of others. The weaker the seedlings and shoots of a weed, the more completely the crops are cleared of it. Harrowing is carried out when the weeds are in the “white thread” (seedling) and newly emerged shoots phases.
At the Elizavetinskoe state farm, harrowing sunflowers within the specified time period ensured the destruction of 89% of green mouse shoots and 82% of blue grass, 77% of pikulnik, 76% of bindweed and 85% of other weeds. The total death of all weeds together was 83%. The wild oats were practically unharmed. In the first two weeds, the roots penetrated to a depth of 2-3 cm during the emergence of seedlings, in the other two - somewhat deeper. Most of the wild oats emerged from a depth exceeding the depth of the harrow teeth. This explains the different resistance to harrowing of these weeds.
The rotary harrow destroys seedlings of small-seeded young plants in agricultural crops quite well. Experiments in the fields of the Research Institute of Agriculture of the South-East, carried out on crops of Sudanese grass, showed that this tool is inferior to the tooth harrow only to a small extent. If the rotary harrow destroyed 81% of the total number of weeds, then the tooth harrow destroyed 93%. The greater effectiveness of both tools in the described experiment was due to the fact that acorn grass and mice predominated in the weed crops.
When processing the row spacing of wide-row, dotted and square-clustered crops, 85-90% of young plants are pruned. Only those weeds that, together with cultivated plants, are in rows and nests (in protective zones) do not die. To eradicate them, weeding harrows or needle discs are installed on cultivators. Each harrow (Fig. 33) must follow its own row of cultivated plants, covering the entire width of the protective zone. The needle discs are arranged in pairs. One pair processes the protective zone to the right of the row, and the other to the left (Fig. 34).
How well weeding harrows work can be seen from the practice of the Saratov experimental production farm. Here, when processing corn with cultivators with weeding harrows, buckwheat seedlings were destroyed by 75%, chicken millet and mice - by 67%, acorn grass - by 29%, and all weeds together - by 55%. In the interrows, weeds were completely cut off by the paws of the cultivators.
Cultivations should be carried out in the early stages of weeds, when they are easy to prune and rows of cultivated plants are clearly visible. The timely implementation of the first inter-row treatment is especially important. It must be done as soon as the rows of crops are identified. A delay of at least a few days leads to the field becoming heavily overgrown with weeds. Cultivated plants end up under their canopy, and cultivation becomes impossible. In addition, the weeds overgrow and are poorly trimmed by the working parts of the machines. In particular, when the mouse takes root, that is, forms secondary (nodal) roots, it is very difficult to trim it not only with a cultivator, but even with a hoe.
Good results in destroying young plants in crops are achieved using chemicals. Of these weeds, winter and spring crops (rye, wheat, barley and oats) are clogged primarily with dicotyledonous species. To kill them, use sodium salt 2,4-D and 2M-4X (at full germination of crops - up to 1.5 kg, at tillering - up to 2 kg), the same chemicals with the addition of 0.5 kg of OP- 7 or 3-5 kg of nitrogen fertilizers (0.7 and 1.5 kg per 1 ha, respectively), amine salt 2,4-D (0.8-1 kg per 1 ha, and only during tillering), 2 esters, 4-D (0.3-0.4 kg, and also only during tillering). Weeds must be in the phase of full germination or beginning to shoot.
Early spring grains with alfalfa undersowing are treated with 2,4-DM in a dose of 2-2.5 kg, and with clover - 2-3 kg active substance per hectare. To destroy dicotyledonous young plants in millet crops, sodium salts 2,4-D and 2M-4X (0.5-0.7 and 1-1.5 kg, respectively), amine salt 2,4-D (0.3-0 .5 and 0.7-0.9 kg) and 2,4-D esters (0.3-0.4 kg per 1 ha). To kill not only dicotyledons, but also cereal young plants, propazine is added at a dose of 3 kg before pre-sowing cultivation. On peas, prometrin (1.5-2.5 kg of active substance per 1 ha) is applied before pre-sowing cultivation against dicotyledonous and cereal young plants.
Herbicides also give good results in row crops. In corn and sorghum, 2,4-D preparations are used against dicotyledonous young plants during their mass emergence. If there are no seedlings of cultivated plants yet, sodium salt is taken at a dose of 2 kg per 1 ha (on light soils no more than 1.5 kg), with the phase of corn and sorghum having 3-5 leaves - 0.4-0.8 kg of active substances per hectare. Amine salt and esters are used in both periods in dosages reduced by 1.5 times.
In permanent areas of corn and sorghum, simazine and atrazine can be used to clear the crops of cereals and dicotyledons. They are applied for pre-sowing cultivation in doses of 4-5 kg per 1 ha for the first herbicide and 2-3 kg for the second. On washed away soils, the dosage of these pesticides is reduced by approximately 1.5 times.
On sugar and table beets, in order to ensure the purity of their crops from cereals and dicotyledons, eptam is added before pre-sowing cultivation (3-4 kg per 1 ha); for sunflower - treflan (2-2.5 kg) or prometrin (2-3 kg per 1 ha). If the row crops have already sprouted, then chemical weeding with ground-based herbicides using tractor machines is most advantageously carried out simultaneously with inter-row cultivation, hanging sprayers on cultivators for this purpose.
Chemical control of juveniles is very beneficial. It ensures the clearing of agricultural crops from them and increasing the productivity of the latter. At the Solyansky state farm in the Saratov region, when using amine salt 2,4-D, the infestation of corn crops with young plants decreased significantly, and the silage yield increased by 46.4 c (24% ). At the Bezenchuk experimental station (Kuibyshev region), sodium salt 2,4-D in millet crops killed 28% of young plants on average over three years, the same herbicide mixed with ammonium sulfate - 56% and butyl ether 2,4-D - 50% . Weeds from other biological groups were also destroyed to a certain extent. As a result, the yield increased in the first case by 2.8 centners, in the second by 3.9 centners and in the third by 5.1 centners per hectare. In the Saratov experimental production farm of the Research Institute of Agriculture of the South-East, in sunflower crops, prometrin destroyed 49% of cereals and dicotyledonous young plants. In accordance with this, the crop seed yield increased by 23 and 33%. The average increase in grain yield as a result of the use of herbicides in the Volga region for spring wheat is expressed at 2.4 centners, and for barley and oats - at 2.5 centners per 1 ha. Chemicals are also beneficial from an economic point of view. The net profit per 1 hectare from their use on millet on average over a number of years is roundedly equal to 34 rubles, peas - 15 rubles, spring wheat - 11 rubles, barley - 10 rubles, oats - 4 rubles.
It is important to control young plants when harvesting crops. Weeds begin to ripen and fall off somewhat earlier than the crops of cultivated plants. As a result, some of their seeds enter the soil, and the other ends up in the grain. Harvesting of crops should be carried out in such a way that, along with the harvest, as many seed germs of weeds as possible are removed from the field and thereby reduce their entry into the soil.
In order to prevent weeds from shedding in grass crops for hay, they must be mowed when weeds from cereals begin to spike, and when weeds from dicotyledons begin to bloom. Around the same time, cultivated grasses bloom and begin to spike. When harvesting during flowering and heading, the highest hay yield is obtained with its highest quality. This means that the requirements for harvesting time both from the point of view of combating young weeds and in order to obtain the highest yield at its best quality basically the same. Thus, on the Elizavetinskoye state farm, when mowing the vetch-oat mixture, when the first crop was blooming and the second was heading, the weeds had not yet fallen off. Meanwhile, out of 235.6 million seeds located in the arable layer per hectare, 2.1 million, or 0.9%, sprouted, and died after germination in the seedling phase before the formation of seedlings, 94.6 million, or 40 .2%. Thus, soil contamination decreased by 41.1%.
In grain crops, weeds always end up in the soil in one form or another. They fall off on the root before the harvesting machine passes, when the header and reel hit the plants, and also remain on the weeds below the grain cut. A significant part of the seed germs of weeds ends up in the machine. At the Elizavetinskoye state farm, when harvesting spring wheat by direct combining before the machine passed, 0.7% of the total weed seeds fell off, 22.2% were lost as a result of impact from the working parts of the machine, 39.4% remained in the stubble and entered the combine bunker 37.7%.
The degree of shedding of weeds before the machine passes depends on the timing of harvesting. On the Elizavetinskoye state farm, when harvesting spring wheat in the phase of full ripeness before the combine passed, only 0.7% of weed seeds fell off, but when harvesting after 2 weeks - 72%. When mowing bread into a windrow until waxy ripeness, shedding of weeds can be reduced to almost zero. Consequently, crops that are heavily infested with young plants must be harvested at wax ripeness (in a separate way), and first of all. Since many young weeds are very juicy, but dry well in the windrow, this sharply reduces the cost of labor and money and improves the quality of grain products when they are processed on the threshing floor.
Clogging of fields due to weed seeds left in the stubble depends on the cutting height of the harvested crops (Fig. 35). An important conclusion follows from this - crop harvesting should be carried out at the lowest possible cut. If at the same time the weeds remain in the stubble, it must be mowed with a hay mower and quickly removed from the field.
In order to prevent the dispersal of weeds, monitors and other similar machines threshing on the header, as well as combines, the latter, if necessary, are equipped with grain catchers. During direct combining, as well as when collecting windrows with a combine, the entire cut mass, along with weeds, enters the thresher. After threshing, one part of the weed seeds goes into the bunker, the other into a screening box (into a bag), the third, together with straw and chaff, into the stacker, and the fourth is sifted into the slot of the grain conveyor.
The distribution of weed seeds in a combine harvester depends on the composition weeds on the fields. Small-seeded weeds (white pigweed, quinoa, acorn grass and others) largely go into the screening box, large-seeded weeds (wild oats) - into the grain bin, light ones (convolvulus buckwheat and others) - into the straw and chaff.
At the Elizavetinskoe state farm, when harvesting small-seeded winter wheat, 83.5% of the white pigweed fell into the screening box; slightly larger seeds - mice - by 69.2% in the weed bin and by 30.6% in straw with chaff; light-seeded - bindweed buckwheat - 74.7% together with straw and chaff - into the straw collector.
In order to prevent the entry of young weeds into the soil when collecting windrows and direct combining, combines must necessarily work with stackers. It is necessary to hang bags in their screening boxes (if any), and install grain catchers in all places where it is possible to sift weed seeds from the machine onto the field surface. It is better to use enlarged stackers, as this results in less weed loss.
To obtain effective results in the fight against the vast majority of young weeds, it is enough to plow the plowed land with plows with skimmers at a depth of 20-22 and even 16-18 cm, but in this case the accompanying root shoot weeds will multiply and increase the weediness of the field. To prevent this, the main fall tillage of fields with early weeds should be carried out with plows with skimmers to a depth of 24-25 cm. Single-occurring root shoots at such a plowing depth will be greatly suppressed. When lifting short-term deposits, such treatment will ensure the destruction of accompanying taproot perennials.
In the rows of gardens, vineyards and berry fields, the fight against seedlings is carried out in the same way as in black fallow. As for tree trunk circles and other similar places, weeds in them are usually destroyed manually, which requires a lot of effort and money. But you can also use chemicals in gardening.
In apple, cherry and plum plantations, as well as vineyards and berry gardens (raspberries, currants, gooseberries), when spraying young weeds before emergence, simazine and atrazine (3-4 kg per 1 ha) give good results. They kill both dicotyledonous and cereal annual weeds. Both herbicides, after being sprayed, are incorporated into the soil.
In hayfields, pastures and other uncultivated lands, the main task of combating undergrowth is to prevent their seeds from shedding. For this purpose, mowing and grazing of grasses is carried out when the weeds have not yet been inseminated (preferably no later than their flowering). Production experience has shown that in this case, in a few years, almost all tall young plants from the Apiaceae and Asteraceae families disappear from hayfields and pastures. The poorly eaten plants remaining on pastures after grazing are systematically mowed down. In cases where the pasture is clogged with plants that are poorly eaten by cattle and well eaten by sheep and goats, instead of mowing after grazing the first animals, it is recommended to graze the second.
On wheatgrass, grass pastures and hayfields, as well as in areas occupied by other forage plants, in which the regeneration organs are located deep in the soil, good results against young weeds are achieved by burning the grass remaining from last year. Burning is done early in the spring. Weed seeds located on the soil surface, as well as on plants, die in this case. In cereal grass stands, herbicides (such as 2,4-D and 2M-4X) can also be used to control young plants.
In order to make the right decision on the advisability of weed control, it is necessary to have information about the actual (crop) and potential (soil) weed infestation. Current weed infestation
Quantitative (instrumental) methods are based on recording weeds using various tools: frames, scales, measuring rulers, standards, etc. They are labor-intensive in their implementation and are used mainly in research work.
Number. the number of plant individuals (stems) per unit area (1 m2). A = a/ns = a/S, a is the number of plant individuals (stems): n is the number of counting or test sites; s - size of the counting area, m 2, S - total counting area, m 2. determined by direct counting them on test sites, allocated using a frame of known size
The number of weeds is determined for each species. QUANTITATIVE-SPECIES method. Taking into account all species as a whole does not provide grounds for developing differentiated measures to combat weeds. The most convenient are rectangular frames with a width to length ratio of 1:1 to 1:3.
The minimum size of a test site for recording young weeds in most cases should not be less than 0.25 m2, for perennial weeds, if their density is small and does not exceed 2-3 pcs/m2 - no less than 1 m2. 50 cm 100 cm
Mass The mass of all above-ground plant organs is expressed in grams per unit area (1 m2). It is characterized by three quantities: the mass of living plants (weight of raw plants, biomass), their absolutely dry mass, the mass of plants in an air-dry state
Model sample method (L. G. Ramensky). In sowing, 100-300 specimens of the population of each species are randomly selected, trying to cover plants of all different age groups. Based on the mass of these plants and their known average number, the mass of individuals of a given species per unit area is determined.
Parallel strip or triple pad method. During the period of mass emergence of weeds, permanent counting areas are allocated so that within each of them the infestation is as uniform as possible. Then, during the first count (it is planned to carry out three), to determine the number and mass of weeds, they are selected by removing them from the first third of the site. At the next period, such a census is carried out on the next third part of the site adjacent to the previous one.
Method of conjugate areas (A. M. Tulikov). Plant samples are taken near stationary quantitative survey sites. The 1 m St trial plot for the next counting period must be located in a new place, but not closer than 1 m both from the previous counting sites from which plants were removed, and from the stationary site. For this purpose, the location of such moving sites for each accounting period is recorded on a diagram relative to the stationary sites.
Volume Filling and coverage of the aerial parts of all plants of an agrophytocenosis or a population of weed species in the air space in the soil layer of the atmosphere. Characterizes the completeness of plants’ use of their habitat by above-ground organs
The above-ground parts of plants removed from a certain area are placed in one cylinder, and then it is filled to the top mark with water from the second cylinder. The amount of water remaining in the second cylinder gives the desired volume of plants.
Projective cover is the proportion of soil surface area occupied by the horizontal projection of above-ground parts of plants, expressed as a percentage. characterizes both the numerical abundance and the mass of above-ground organs of the community as a whole or its individual species. The amount of projective cover serves as an indicator of light use and shade tolerance of plants, their competitiveness
Method of L. G. Ramensky. A frame of a certain size is placed on the sowing. Then, looking vertically down at a limited area, they mentally shift the projections of the aboveground organs of the weeds to one side of the area and determine by eye the proportion of the area covered by them.
Occurrence As a rule, many types of weeds grow in the crops under study, which often leads to the need to determine the frequency of occurrence of a particular species in a particular field community. Occurrence --- the frequency of presence of a given species on sample plots, expressed as a percentage, in relation to their total number: where R is the occurrence of a given species, %; t is the number of sample sites where a given species occurs; n is the total number of sample sites taken for research.
Layered distribution of aboveground organs of weeds above the soil level in comparison with the height of the cultivated plant.
Method of phytocenotic criteria (A. M. Tulikov). When determining the tiered structure of field communities, the phytocenotic characteristics of the plants composing them are taken into account: the height of cultivated plants and their impact on the environment, biological characteristics, ecological response and the minimum amount of projective weed cover
A. I. Maltsev’s eye-numerical method. The method is based on assessing the abundance of weeds by their relative abundance in comparison with the density of the grain crop stem. This method is not used in crops of other crops (row crops, perennial grasses, etc.): the resulting relative values of the abundance of weeds in the fields are not comparable with each other due to the many times different densities of cultivated plants in them.
A. I. Maltsev’s eye method for determining tier I - weeds of the upper tier that outgrow a given cultivated plant and rise above it with their tops (sow thistle, thistle, broom, etc.); II - weeds of the middle tier, extending from the top level of sowing to the middle of the height of cultivated plants (cornflower, chamomile, pigweed, cockle, chaff, etc.); III - weeds of the lower tier, growing at the very surface of the soil and not exceeding half the height of the crop in sowing (violet, chickweed, shepherd's purse, forget-me-not, etc.).
Potential contamination - reserves of weed seeds and organs contained in the soil vegetative propagation perennials. Stocks of weed seeds in the arable layer have increased by 40 - 45% in recent years.
1 - selection of soil samples Soil samples to determine the content of weed seeds in them are taken using drills of the Kalentyev, Shevelev or other design. Samples are taken from at least 6-10 fixed locations, evenly distributed over the area of the field (plot). At the selected location, the drill is immersed vertically into the soil to the required depth. Samples are usually taken by soil layers: 0 - 10, 10 - 20 cm, etc. The selected sample is placed in a bag or box, labeled, delivered to the laboratory, where it is brought to an air-dry state and stored in this form until analysis.
Small sample method. Developed at the Department of Agriculture and Experimental Methodology of the Moscow Agricultural Academy by Professor B. A. Dospehov. When taking conventional samples using a drill or digging, you have to work with a large amount of soil, which dramatically increases the labor intensity of the analyzes performed. At least 10-20 individual samples of about 0.3-0.5 kg each are taken for each horizon separately throughout the survey area or field experimental plot. These samples are combined, one mixed sample weighing 250-300 g is prepared from them and brought to an air-dry state. Then two average samples of 100 g each are selected from it, which are then worked with.
2. Removing the silt fraction from the soil sample. Method of I. N. Shevelev. An average soil sample taken to remove the silt fraction is weighed and then placed on a wicker sieve with square holes measuring 0.25 mm, having a side at least 5-7 cm high. right hand The sieve with the soil sample is placed in a wide tank filled 3/4 with water so that the water reaches the middle of its side. With your left hand, without pressing on the sieve, gently rub the lumps of soil. At the same time, the sieve is either removed from the water or immersed again, which speeds up the removal of silt particles. The sandy residue on the sieve is completely washed in another tank or under a tap until the cloudiness of the flowing water stops. Removal of the silt fraction is significantly accelerated by washing the sample in running water.
3. Isolation of weed seeds from the mineral residue of the washed sample. Method of I. N. Shevelev. This method is based on differences in density. Prepare a 70% solution of zinc chloride (1.96 g/cm3) or a saturated solution of potash (1.56 g/cm3). The density of the mineral part of the soil varies from 2.3 to 4.0 g/cm 3, and the density of weed seeds and organic plant residues ranges from 0.3 to 1.4 g/cm 3. In a beaker or laboratory porcelain mug with a volume of 500- 750 ml is poured into 2/3 of the heavy liquid and the washed remainder of the sample is transferred. Heavier mineral soil particles settle to the bottom, while lighter weed seeds and organic matter float to the surface.
The dry mixture of seeds and organic residues is transferred to a collapsible board and separated into types with a spatula, counted and weighed.
2. Germination of weed seeds contained in the soil without washing samples (biological method). Comparative evaluation of 2 methods
Information about potential weeds allows you to: Strategically plan crop protection against weeds. Prepare in advance the necessary preparations to protect the crop Plan for the need to use soil preparations Selectively approach each specific field with an individual protection program Example. With a high (over 150 seedlings per m 2 expected) degree of infestation with cereal annual weeds (broom) and species sensitive to Dual, it is necessary to use soil herbicides, Dual Gold 1.6 -2.0 l/ha
How to find out about potential contamination with vegetative reproduction organs? Potential contamination by vegetative propagation organs is determined by viewing (sifting) soil from excavations measuring 0.25 x 0.25 m. Selected nodules, rhizomes, and bulbs are weighed by species. Information on the depth and size of weeds is used when developing control measures.
Objectives 1. Study of agrophytocenoses in order to identify the dynamics of their development, species composition and quantitative abundance (Stationary survey cannot and should not be the object of production activities of the farm). 2. Development of a system of measures and assessment of its effectiveness in the fight against the most common, harmful and quarantine weeds as (basic or comprehensive survey). 3. Study of the survey results for the purpose of promptly using various methods of weed control during the initial period of the crop growing season (operational survey).
The main (continuous) survey is carried out throughout the entire territory of the farm, not only the cultivated areas of crop rotations and fields, other types of agricultural land (fallow lands, pastures, meadows, fruit plantations, etc.), but also non-agricultural lands (borders, roadsides, forest belts, areas near livestock farms, economic and residential buildings, banks of reservoirs, etc.) during the period of massive presence of the entire floristic composition of weeds using the quantitative-species method once every 3-5 years to compile maps of crop weediness in order to plan control measures with weeds.
Time for the main survey In grain and flax crops, the maximum species richness coincides with the period 2-3 weeks before harvesting. In fields of perennial grasses, the largest number of weed species can be observed several days before cutting. In row crops, the moment shortly after the plants close between the rows and their growth in height abruptly stops, coinciding in most of them with the end of flowering or the formation of generative organs. If necessary, these terms are clarified by the agronomic service of the district or regional agriculture department.
Technique for inspecting crops for weeds On the day preceding the inspection, the direction of the route is outlined, which should cover the area under study as completely as possible. The route must have a general direction along the field. On a narrow and long field it consists of at least two, and on compact fields - at least three or four straight or broken passes copying each other. It is advisable to plan the general direction of the movement route so that, if possible, it runs across the main tillage and necessarily covers all changes in relief elements.
Along the entire length of the route, a certain number of stops (stations) are marked on the diagram, depending on the size of the field. In fields or individual areas of up to 50 hectares, at least 9-10 stations are allocated, in fields from 50 to 100 hectares - 15-16, and in fields over 100 hectares - for every subsequent 50 hectares, another 1-2 stations are added. The chosen route, the number of passes adopted in it, the order of movement along them and the number of stations planned on them should be adhered to in subsequent years. Compliance with these conditions is especially important when monitoring weeds.
During the main survey, weeds are taken into account by direct counting of their individuals (quantitative-species method). Having reached the station designated along the aisle, the examiner places a 50 x 50 cm (0.25 m2) counting frame in front of the toe. In the area of the frame, the number of weeds for each type is counted and the results are entered into the columns of the primary accounting sheet
Operational examination is carried out on a separate field 3-4 days before extermination measures are carried out using visual methods in order to clarify the species and quantitative composition of weeds for selecting a herbicide and determining the dose of the drug.
Principle of operation Stimulation of light emission from leaves Receiver laser Laser radiation causes fluorescence of chlorophyll in the leaves Light from the laser is reflected by the leaves at a different frequency (fluorescence) The amount of reflected light determines the nitrogen content in the leaves
Obtaining the NDVI index using "Green. Seeker" in barley crops during the tillering phase before herbicide application
NDVI indicator depending on the number of weeds pcs/m 2 Counting plots Passes of the unit across the field 1 2 3 4 5 6 Index with NDVI Number of weeds NDVI index Number of weeds NDVI index Number of weeds Index 1 0, 30 40 0. 34 24 0. 30 52 0. 23 16 0. 33 16 2 0. 28 16 0. 24 40 0. 26 40 0. 41 16 0. 26 3 0. 47 116 0. 20 16 0. 32 56 0. 22 4 4 0. 30 24 0. 28 12 0. 25 16 0. 19 5 0. 27 52 0. 30 12 0. 32 36 6 0. 20 52 0. 56 28 0. 26 7 0. 23 40 0. 51 16 8 0. 25 72 0. 33 36 7 8 Number of weeds NDV Index I Number of weeds 0. 33 28 0. 37 12 0. 26 16 16 0. 29 76 0. 35 32 0 , 29 56 0, 29 4 0, 23 16 0, 38 12 0, 28 16 4 0, 21 12 0, 20 16 0, 35 32 0, 29 44 0, 20 12 0, 27 12 0, 39 8 0, 37 10 0, 35 24 28 0, 15 68 0, 54 40 0, 46 8 0, 33 92 0, 54 12 0 0, 27 84 0, 51 36 0, 53 40 0, 34 12 0, 26 12 0, 23 20 0, 31 60 0, 31 24 0, 44 64 0, 28 32 0, 33 20 0, 28 12 ND VI Note: Bold font sowing by autopilot, normal font by marker Correlation coefficient between the number of weeds and NDVI in barley crops amounted to - 0.32
aerial photo map of the phytosanitary condition of the field The found levels of harmfulness made it possible to identify areas in the field where crop treatment is required and where such treatment should not be carried out. As a result, it was found that treatment needs to be carried out only on 35-40% of the field area, while 50% of insecticides can be saved.
The phytocenotic threshold of harmfulness (FPT) is the abundance of weeds at which they do not cause harm to crops.
The critical (statistical) threshold of harmfulness (CPT) is an abundance of weeds that causes statistically unreliable yield losses.
The economic threshold of harmfulness (EPT) is the minimum number of weeds, the complete destruction of which ensures an increase in yield that pays for the costs of extermination measures and harvesting of additional products. yield increase ≥ 5 -7% of actual yield.
The threshold of economic feasibility of weed control (TECB) is such an abundance of weeds, the complete destruction of which ensures the profitability of the system of extermination measures ≥ 25 -40%.
Threshold of environmental harmfulness (TEH) is the amount of additional harvest that pays for all the costs necessary to restore the ecological situation of the agrophytocenosis within one agricultural year to its original state.
Methods for taking into account the degree of weediness in fields and soil
When intensive farming and designing new crop rotations, it is necessary to take into account the degree of weediness in the fields and soil. The successful completion of this work depends on the systematic examination of agricultural plots and the preparation of special maps of weed infestation. There are two methods for accounting for soil contamination: visual and quantitative-weight.
With the eye method, the field is walked along the boundaries and diagonals and the degree of contamination is determined by eye, using a four-point system. This is the simplest and most superficial accounting method.
Four-point system
1 point – weeds found in crops in single units;
2 points – weeds are few in number, but not isolated;
3 points – weeds growing in crops in large numbers, but not exceeding the number of cultivated plants;
4 points – weeds that are quantitatively dominant over cultivated plants.
A more accurate result is shown by the quantitative-weight method. In this case, frames measuring 1 m 2 are placed along the diagonal of the field every 50-100 m. Plants are removed from these areas, then the number of weeds is counted and their weight is determined. In this case, it is advisable to know the species composition of the weed. Perennial and annual plants are counted and weighed separately. In Group perennial plants Separately select rhizome and root shoot weeds, which are considered the most malicious and difficult to remove field weeds. To eradicate them, special control measures are usually used.
Based on the data obtained, a map of the degree of weediness of the fields is drawn up. On it, annual plants are marked with yellow paint or dotted shading, rhizomatous perennial weeds with green or horizontal shading, root shoots with red or vertical shading. Some areas of the plan are marked symbols the prevailing groups of weeds here and indicate their average number per 1 m 3. In addition, the number of other weeds found there is indicated.
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Depending on the purpose, there are various methods for determining the actual contamination of crops. If this information is needed to make an objective decision about the advisability of preventive and protective measures, records are carried out using the visual method. If the goal is a detailed study of the number and species composition of weeds, weed dynamics, the influence of plant protection systems, etc., then quantitative and quantitative-weight accounting methods are used.
In production conditions, the actual weediness of crops is determined by route surveys annually at the time when all the main types of weeds appear. In particular, in grain crops the main examination is carried out in the heading phase, in row crops - within their growing season. To draw up specific plans for the use of herbicides in the post-emergence period, weed surveys are carried out in the spring after the mass emergence of their shoots.
On each crop rotation field or part thereof with an area of up to 50 hectares, at least 10, from 50 to 100 hectares - 15, over 100 hectares - 20 registration areas with an area of 2-3 m2 (for recording perennial weeds) and 0.25 - 1 m are allocated 2 (with an overwhelming number of young weeds).
Visual accounting method:
The simplest accounting method is eye-based, which is used on large areas. It allows you to determine the prevalence of weeds in each field and their botanical composition. The weediness of the field is assessed on a point scale. The most commonly used seven-point scale is soil coverage by weeds:
0—no weeds;
1 - weeds occur singly, the degree of coverage is close to 0.1-3 weeds per 10 m2;
2 - degree of coverage up to 5%, - 3-5 weeds per 1 m2;
3 - 5-20%, - 5-15 weeds per 1 m2, Cultivated plants dominate over weeds;
4 - 20-50% - 20-30 weeds per 1 m 2, Cultivated plants still dominate the weeds;
5 - 50-70%, the number of weeds is equal to or more quantity cultivated plants, culture under threat;
6 - 75-100%, complete clogging, weeds significantly predominate over cultivated plants.
The visual method involves constant observation during the growing season, since during it changes occur in the species composition of weeds: in the summer the growing season ends and some spring and wintering ones disappear, perennials appear in the fall, and late spring ones finish the growing season.
Quantitative accounting method:
The quantitative method for determining the weediness of crops is based on counting the number of cultivated plants and weeds on the survey sites. In this case, use frames of appropriate sizes. The frames are placed in such a way that one of the lines of the culture is its diagonal.
After counting the number of weeds in the frames, their average number per frame and per 1 m2 is determined, a percentage of the number of cultivated plants, which is taken as 100%. The degree of infestation of crops is determined using the appropriate scale.
The accounting results are compared with the economic thresholds of harmfulness of the main weeds and a decision is made on the application of protective measures.
Quantitative-weight accounting method:
The most detailed method for determining the weediness of crops is quantitative-weight. It is used in stationary fields, where work is being done to improve the protection of agricultural crops from a complex of harmful organisms, incl. and from weeds. Weed surveys are carried out simultaneously with other pests on the same survey sites at appropriate times. At the same time, the number of weeds by type and their total number are counted, their height, development phase and biomass are determined. To determine the latter, all weeds are pulled out on the site, the roots are cut off and weighed, dried to an air-dry state and weighed again.
Determining the type of contamination
An important characteristic of crop weediness is the type of weediness (the ratio of weeds of different biological groups).
The most common types of contamination are:
a) one-year-old cereals - bristle grass and cock's millet, winter and wintering cereals predominate;
b) one-year family - wild radish, field mustard, three-ribs, and blue cornflower predominate;
c) perennial rhizomatous - creeping wheatgrass and horsetail predominate.
d) mixed type - there are representatives of different biological types and groups of weeds. The last type is the most typical for all soil and climatic zones of Russia.
Familiarize yourself with soil sampling techniques to determine potential soil contamination.
Prepare equipment: a cylinder for sampling soil, gauze bags for washing seeds, a magnifying glass for determining the type of weed.
Fill out the table according to Appendix 6.
Familiarize yourself with the methodology for determining potential soil contamination calculations.
Take soil samples along the route suggested by the teacher. Place each sample collected in a gauze bag. Label each bag (Appendix 7).
Wash the soil samples under running water until the water runs clear. Dry the weed seeds remaining in the gauze bags.
Using the proposed method, make calculations and fill out Table 13 in your notebook.
2. 2. Accounting for weediness of crops and drawing up a map of weediness of fields
To successfully combat weeds, it is necessary to determine the weediness of each field separately. In agricultural practice, a distinction is usually made between systematic and operational surveys.
Systematic the survey is carried out on all lands. But due to the labor-intensive nature of this work, it is usually carried out once every 2–3 years. The time for a systematic (continuous) survey is chosen so as to most fully cover the entire species composition and quantitative abundance of weeds in the surveyed area. Continuous research materials are used to develop comprehensive weed control measures.
Operational the survey is carried out annually. There are several methods for operational accounting of contamination: visual, quantitative and quantitative-weight. These counts must be carried out twice during the growing season.
Complete information about the presence of the species composition of weeds in the field can only be obtained through observations throughout the entire growing season. In production conditions, it is difficult to keep a constant record of weeds, so choose the moment when you can get a complete description of the main and most harmful weeds present in the field.
The first time - the count is carried out during the mass flowering of weeds from the cabbage family (radish, rapeseed);
The second time - the count is carried out during the flowering of weeds from the aster family (yellow sow thistle, pink sow thistle). At this time, plants are discovered that were in the germination phase during the first count, for example, bindweed, creeping wheatgrass, etc. To establish the infestation of colza, the count should be done in the spring.
2.2.1. Eye-based method for accounting for field weeds
This method is based on the Maltsev scale with some amendments. It has 4 gradations, which indicate an assessment of the occurrence of a weed when inspecting a field or area:
1 point– weeds are found sporadically, in the total mass of crops weeds do not exceed 10%;
2 points– weeds are more common than sporadically and account for 15–20% of the total mass;
3 points– the crops are heavily weeded, but the weeds do not choke out the cultivated plants; weeds make up about 30%;
4 points– weeds choke out cultivated plants; they make up about 40% of the total mass.
When scoring the occurrence of weeds, it must be borne in mind that a flowering weed is noticeable better than others and provides, as it were, the main background for the field being surveyed. Weeds that are not blooming at this time do not create the impression of weediness. This indicates the need to carefully inspect areas and evaluate weeds on a specified scale.
