Green fertilizers (green manure) – fresh plant matter, plowed into the soil to enrich it with organic matter and nutrients.
Siderats – plants grown as a green fertilizer.
Sideration – a method of enriching the soil with green fertilizers.
Green fertilizers have the same effect on soil properties, crop yield and quality of crops as litter manure.
- Mineral fertilizers
- Microfertilizers
- Complex fertilizers
- Organic fertilizers
Scientific basis for the use of green fertilizers
1. Green fertilizer is a source of organic matter and nitrogen in the soil. When the green mass of green manure is plowed 35-40 tons/ha, 150-200 kg of nitrogen enters the soil, which is equivalent to 30-40 tons of manure. The coefficient of nitrogen use of green fertilizer in the first year is 2 times higher than that of manure. Legume green manure enriches the arable layer with available phosphorus, potassium and other elements. For example, on light soils in Wubern (UK) annual plowing sideratov for 7 years increased the content of organic matter by 10%, at Rotamsted experimental station application of green fertilizer for 30 years has accumulated organic matter in the soil 35 tons / ha. In Bavaria, Germany, the application of green fertilizer on a loamy soil for 25 years increased the humus content from 2.2-2.3% to 2.8%, while the application of only mineral fertilizer reduced the humus content to 1.9%.
Green fertilizer affects the fractional composition of humus. For example, in long-term experiments on sod-medium-podzolic medium-loam soil, green mass of lupine increased the content of humic acids by 20-30%, the absolute and relative content of fulvic acids decreased. Under Central Asian conditions on typical sierozem soils intermediate crops for green fertilization together with alfalfa in cotton-alfalfa crop rotations improved the humus balance, contributed to mobilization and accumulation of phosphorus available for plants from low-soluble phosphates.
2. Green fertilizer improves agrochemical, physico-chemical and physical properties of soil: excessive soil acidity is neutralized, the amount of absorbed bases increases, hydrolytic acidity and content of mobile aluminum decrease, and the cohesiveness of sandy and sandy loam soils increases.
On gray forest medium-loamy soil of the Northern Trans-Ural Region, plowing of green manure leads to the decrease of the soil volumetric weight of the 10 cm layer by 0,07-0,11 g/cm3, in the layer 10-20 cm – by 0,06-0,12 g/cm3. According to the Don Zone Research Institute of Agriculture, in terms of volume weight reduction, green manure is equivalent to 20-30 tons of manure per 1 hectare. In Dagestan green fertilizers in terracing slopes for 4 years on the average reduced the volume weight in the layer 40 cm by 9,5%, the content of humus in the arable layer has increased by 0,54-0,71%.
3. At the expense of increasing humus content and improving agrochemical and agrophysical properties of soil biological activity of soil increases, soil and above-soil air is enriched with carbon dioxide, air nutrition of plants is improved, activity of soil microflora is activated. The number of microorganisms in the 30-cm layer from plowing the green manure increases by 1.5-2 times compared with control, in combination with mineral fertilizers – 2-3 times.
Plowing of buckwheat stubble for green fertilizer on sod-podzolic medium loamy loamy soils of the Moscow region with a mass of 20-30 t/ha has increased the biological activity of the soil and the content of nitrate nitrogen as a result of intensive mineralization of organic matter.
Positive effect of sowing rape, mustard, rye, barley, Turkmen vetch under winter conditions was obtained in Uzbekistan. Sown in September-October, by the beginning of April they accumulate more than 25-40 t/ha of aboveground green mass, and plowing such an amount of organic matter improves soil properties, activates microbiological activity, increases the content of nitrates, saprophytic microorganisms and actinomycetes. All this contributes to improvement of soil phytosanitary condition, including wilt control, so winter sowing of intercrops in growing cotton, first of all in wilt-infested fields, is recommended.
According to field experiments of Timiryazev Agricultural Academy, the use of green fertilizers in pure form and in combination with straw leads to changes in the species composition of spore-forming bacteria: the proportion of bacilli using mineral nitrogen of soil increases, which is an indicator of intensive decomposition of organic material.
4. Green fertilizer – a link of intensive farming, which performs the function of protecting the environment from pollution. With the development of chemization of agriculture, increasing use of mineral fertilizers, losses of biogenic elements as a result of washout from the surface, migration to the deep soil layers, and increased denitrification are increasing. Moreover, the more arable land is not occupied by vegetation, the greater these losses. Intermediate siderats, especially perennial lupine vegetating in autumn and spring between crops of crop rotation, prevent losses of nutrients, protect against the processes of water and wind erosion, thus being elements of soil-protective farming system.
Fallow crops are used in the irrigated areas of Central Asia, in the humid subtropics of the Caucasus and Transcaucasia.
5. Green fertilizer performs a phytosanitary role. For example, plowed plant mass of perennial lupine reduces the defeat of potato tubers with scab, which is especially important when growing seed potatoes. In experiments of the Research Institute of Agriculture and Livestock of the western regions of Ukraine, on the plots where lupine was ploughed in years with high precipitation, the proportion of affected tubers was 1-2%, while on the plots without lupine – 7-8%.
Phytopathogenic fungi causing root rot cause great harm to crops. Plant residues and seeds are carriers of root rot infection. The faster the decomposition of organic residues in the soil, the faster the fungus is brought out of its dormant state and the soil is free of infection. Root syderats increase the number of actinomycetes, which are antagonists of the root rot pathogen, as well as saprophytic microflora that accelerate the mineralization of plant residues.
Systematic scientifically proven use of green fertilizer in conjunction with other agronomic techniques contributes to the profitability of agricultural production. Especially high efficiency from green fertilizers is noted on light sandy soils with poor agrochemical, physical and chemical, biological and water properties. In areas of the Central Non-Black Soil Zone the share of light soils is about 20% of arable land, in some regions, for example, Bryansk and Vladimir – up to 50-60%.
Chemical composition
According to various sources, 1 t of crude weight of legume siderats contains on average:
- in lupin – 210 kg of dry matter; 4.5 kg N; 1.3 kg P2O5; 1.8 kg K2O; 5.0 kg CaO;
- in melilot – 220 kg of dry matter; 7.7 kg of N; 0.5 kg of P2O5; 2.0 kg of K2O; 10.0 kg of CaO;
- in seradella – 210 kg of dry matter; 6.2 kg N; 2.2 kg P2O5; 5.5 kg K2O;
- in esparcet – 200 kg of dry matter; 6.2 kg N; 1.2 kg P2O5; 3.2 kg K2O.
Compared with the chemical composition of mixed manure of dense storage, 1 t of which contains 5 kg N, 2.5 kg P2O5 and 6 kg K2O, legume siderats are richer in nitrogen, poorer in phosphorus and potassium. Mixtures of legumes with cereals, as well as non-legume siderates, are also poorer in nitrogen.
Decomposition processes of green fertilizers in the soil are faster than other organic fertilizers containing slowly decomposing substances.
Application of siderates
A distinction is made between independent and compacted (mixed) crops of siderats.
In the case of independent sowing, the field is occupied with legumes from spring throughout the growing season. It can be plowed both under winter crops and spring crops. Green fertilizer occupies an independent field of the crop rotation.
The practice of Russian agriculture shows that as the soil is cultivated and specialized crop rotations are introduced, it is advisable to introduce intermediate green fertilizer, without disturbing the rotation of crops in crop rotations. The use of green fallows (independent green fertilizer) is more suitable for uncultivated, poor in organic matter soils. Therefore, the practice of using pure fallows in the Non-Chernozem zone is not an agronomic progressive technique. In this zone sideral fallows are more effective. To accelerate the cultivation of podzolic soils green fertilization is combined with the application of manure, compost and mineral fertilizers.
Compacted (mixed) crops can be solid, when part of the field is entirely occupied by green manure, and striped with a strip or row alternation of the main crop and the green manure. For example, green manure planted in between the rows of orchards and berry or row crops, across slopes for anti-erosion purposes.
Depending on the time (before or after harvesting the main crop) a distinction is made between under-seeded, that is sown under the main crop, and intermediate (stubble), that is sown after the harvest of one crop and before sowing the other. This green fertilizer includes stubble crops, autumn and winter crops. The latter are sown in September-October and plowed in spring, they are used in the irrigated areas of Central Asia, in the humid subtropics of the Caucasus and Transcaucasus.
Stubble intermediate green manure is sown after harvesting early spring crops, such as barley, and plowed under the autumn plowing. For this purpose, harvesting is carried out quickly and sowing of plants for green fertilizer is carried out after soil preparation. In this case the green manure has time to accumulate a considerable mass.
Lawn grass seeders are also used for sowing to the main crop, for example, melilot is sown in spring to the cereal crop, after harvesting which until the onset of cold donuts have time to accumulate sufficient mass.
Techniques for the use of green manure: full, hay and herbage green fertilizers.
In full green fertilization, the whole mass of the green manure is plowed in place.
Green fertilizer for mowing is grown in the non-rotation field, then transported to the crop rotation fields and plowed. Suitable for this is perennial lupine, the advantage of which is also that it matures to seed even in the conditions of the northern areas of the Non-Black Soil zone.
After-mowing fertilizer is plowed after removing the mowed or eaten by cattle mass of the grown stubble and root residues of green manure. It is used on crops of sod-podzolic soil, especially light granulometric composition. Used in Siberia and the Far East. Winter and fodder peas, chinam and melilot are sown in the irrigated areas of Turkmenistan, Tajikistan, Uzbekistan, Transcaucasia, Kyrgyzstan, Kazakhstan as a after-mowing siderat.
The main areas of application of green manure are poor in organic matter with unfavorable properties of soils of different zones that require cultivation. They are also used when there is a lack of organic fertilizers.
Green fertilizer is widely used in many countries around the world. Almost everywhere intermediate crops are used as a green fertilizer, independent – only on depleted soils and in areas away from livestock farms.
Stand-alone green fertilizer is also used on the plots that came out of the clearance of wood and shrub vegetation during the development of new lands and enlargement of the arable land.
Under intensive agriculture in Belarus and Non-Black Soil zone of Russia perennial lupine is the key green manure. It grows on poor uncultivated soils. When it is used for tilling of soils without violating the scheme of alternation of crops, 30-50 t/ha is plowed at a time. When 3-fold plowing in 8-field crop rotation provides the average annual input of plant matter not less than 14-19 t/ha, 10-field – 11-15 t/ha.
Green manure has a good effect on potatoes planted after winter rye with perennial lupine as an intercrop.
Normally perennial lupine is sown under winter rye. After harvesting, lupine grows until late fall. In spring, vegetation begins just after the snow melts. Before plowing the green manure for potatoes in spring, lupine has time to grow up to 20 tons/ha of green mass, and with root residues, 30-50 tons/ha. After green fertilizer in the rotation can be placed also buckwheat, corn or sunflowers for silage, vetch-oat mixture for green fodder.
Green fertilizer can be used in a zone of sufficient moisture on all soils, as well as in terms of irrigated agriculture, such as in the Volga region, Central Asia and the subtropics of Transcaucasia, the climatic conditions which contribute to rapid accumulation of organic matter. In the Volga region, Rostov Oblast, Krasnodar and Stavropol Krais and other regions of irrigated agriculture, it is advisable to use stubble and sub-sowing siderats.
In the central regions of the Non-Black Soil Region after harvesting winter and early spring cereal crops, fields may remain unoccupied for more than 60 days with the total of active temperatures of 800-1000 °C, which amounts to 30-40% of agroclimatic resources of the warm period of the year. Also, there is a reserve of such resources in the spring period before sowing of late spring crops. This amount of precipitation and heat is enough for cultivation of sub-sowing and stubble crops. This can be done to the south of the line St. Petersburg – Tver – Ivanovo – N. Novgorod – Kazan – Ufa.
In the Non-Black Soil zone, narrow-leaved (alkaloid) annual lupine, fodder annual (low alkaloid) and perennial (alkaloid) lupine are used as a greenhouse crop. Due to the introduction of fodder lupine into the culture, bilateral use of green manure is practiced:
- green mass of fodder lupine is harvested for silage, and stubble and root residues are plowed under winter crops;
- fodder lupine is grown for grain; straw and root residues are plowed into the soil;
- green mass is mowed at the beginning of budding or flowering and used for fodder.
The field is left uncultivated to allow the grass to grow. If the weather is good, the lupine regrows, and the regrowth of grass is ploughed in as green fertilizer. This method allows you to collect 20-30 t/ha of green mass for silage and 10-15 t/ha of mass after its re-growth for green fertilizer.
Syderates
Leguminous crops such as lupine, seradella, melilot, vetch, chinna, sainfoin, astragalus, peas, pelushka, lentils, clover, alfalfa are used as green manure. Mixtures of legume and cereal grasses or intermediate (insertion) non-legume crops are used less frequently: mustard, bittercress, rape, buckwheat, winter rye, phacelia.
The use of legumes for sideration is due to their ability to enrich the soil with nitrogen, due to nitrogen fixation.
Lupins
Lupins annual and perennial with different content of alkaloids are the most common green manure for acidic soils of the Non-Black Soil zone of European and Asian parts of Russia. Alkaloid lupine is used only as a fertilizer, alkaloid-free – above-ground mass for cattle feed, crop and root residues as a after-mowing fertilizer. All lupins have the ability to assimilate phosphorus hard-to-reach phosphate soil and phosphate and bone meal, improve phosphorus nutrition of subsequent crops of the crop rotation. Lupins can also symbiotically fix atmospheric molecular nitrogen, thus improving nitrogen balance in agrocenoses even on poor sandy and sandy loam soils.
Lupins grow well on acidic soils; very acidic soils require liming, sometimes annual lupins do not tolerate liming, perennial lupins only at the beginning of vegetation. One of the reasons of oppression of lupines on very acidic soils after liming is deterioration of phosphorus nutrition: lime prevents uptake of hard-to-removal phosphates. Therefore, lime and phosphate meal are applied to lupins in layers: lime – deep under plowing with skimmers; phosphate meal – under pre-sowing tillage.
Layered application of lime and phosphate meal in combination with potash fertilizers under lupine is an effective method of soil cultivation.
Annual alkaloid lupins – narrow-leaved blue and yellow – grow in independent and mixed crops, plowed as a complete fertilizer in the period of maximum nitrogen accumulation, ie during the formation of shiny beans on the main stem. On seeded fallow lands, the green manure is crushed with discs and plowed at least 2-3 weeks before sowing winter crops. Before sowing winter crops, the field is rolled over so that the soil settles and does not expose the tillering node. With the development of fodder (alkaloid-free) lupins, the cultivation areas of alkaloid lupins remained only in the northern regions of Vologda, Kostroma, partly Smolensk, Vladimir, and Nizhny Novgorod.
Annual fodder lupins are more valuable in combined use, being an additional protein feed for animals and at the same time a after-mowing siderat. They are effective as green fodder and stubble after-mowing fertilizer after harvesting winter rye for green fodder.
Overground mass of fodder lupins in a combined use is mowed in the phase of budding or flowering at a high (8-20 cm) cut, which provides fodder quality with good re-growth of the herbage.
Thanks to its cold-resistance, perennial lupine matures everywhere, up to Arkhangelsk, with a high reproduction rate. It blossoms and forms seeds in the second year, and reaches its maximum green mass in the 3rd-4th year without fertilizers.
In crop rotations, lupines are sown in siderat fallow or under winter rye cover. Also use under-winter seeding as an intermediate crop in the link seeded fallow, winter rye with under-winter seeding of perennial lupine, potatoes.
On very poor soils, in order to improve the state of cultivation perennial lupine is sown in the output fields, wastelands, in intercrops of fruit and berry nurseries, orchards and berry gardens, forest nurseries and on the slopes of ravines. Lupine is left on such plots for 6-8 years and is used as a mowing green fertilizer in nearby fields, berry and orchard nurseries, and in orchard bedding circles.
Melilot
Melilot is annual and biennial, white and yellow, and white is more productive and yellow ripens earlier. This crop grows well on calcium-rich neutral soils. On calcareous sod-podzolic soils, melilot is more productive than annual and perennial lupine. Due to their powerful root system, they are very drought-resistant and cold-resistant. They are valuable as complete and fallow plants even when their above-ground mass is underdeveloped.
Also used as animal feed. Its high coumarin content decreases its fodder quality, but there are varieties which do not contain coumarin.
One-year and biennial varieties are used for complex use; on fields with a big slope, a biennial is more suitable. Forms of application of under-sowing and independent sowing:
- mowing at the beginning of flowering for fodder and hay fertilization;
- green mass of the first mowing is used to fertilize other fields (mowing fertilizer), the second – for fodder, after-mowing – for fodder or after-mowing fertilizer;
- green mass of the first mowing – for fodder, the second mowing – for mowing fertilizer, after-mowing – for fodder or fertilizer;
- self-sowing as a fallow-occupying crop with plowing for fertilizer under winter crops.
Seradella (Ornithopus)
Seradella (Ornithopus) is an annual moisture-loving legume grass, prefer light slightly acidic (pH 5.0-5.5) soils, can use hard-soluble phosphates and phosphate meal. On sandy and sandy loam soils it responds well to potassium and magnesium fertilizers. On moisture-enriched soils is more effective as an under-seeded crop under the cover of spring and winter (spring) cereal crops. The earlier the cover crop is harvested, the higher the productivity of seradella. Cultivation of seradella on fields which are weed-free, sufficiently moist and early harvested is also effective.
Self-sustained or inserted (intermediate) seradella crops are used as full, mowing and after-mowing fertilizer, more effective a complex application: for cattle feed (mowing or after-mowing) and green fertilizer (mowing, after-mowing or root and stubble residues).
Using stubble residue as green fertilizer
Stubble residue (stubble and roots) is an item of income in the balance of organic matter, is a type of after-mowing green fertilizer.
The quantity and quality of post-harvest residues depend on the biological characteristics of crops, within one species – on the variety, productivity, soil and climatic conditions. Possible amounts of post-harvest (stubble) residues vary (in t/ha dry matter): Annual lupins 0.5-1.5 t/ha, perennial lupins 2.0-3.0 t/ha, clover 3.0-7.0 t/ha, alfalfa 4.0-9.0 t/ha, peas 1.5-3.0 t/ha, winter rye and wheat 2.2-6.5 t/ha, barley 2.0-4.5 t/ha, corn 1.5-6, 0 t/ha, potatoes 0.8-1.2 t/ha, sugar beets 1.0-1.5 t/ha, rye for green fodder 1.0-2.0 t/ha, winter mustard 0.5-1.5 t/ha, mustard 0.4-1.0 t/ha, perennial cereal grasses 5.0-11.0 t/ha.
In terms of reduction of stubble and root residues, crops are arranged in the following sequence: perennial cereals – cereals-legumes – leguminous grasses – corn – winter cereals – spring crops – winter green forage – sugar and fodder beets – potatoes – stand-in (intermediate) crops.
Nitrogen balance due to symbiotic nitrogen fixation is influenced only by legumes and leguminous crops in pure and mixed crops. Nitrogen content in the roots of legume crops reaches 2.0-2.5%, in non-legume crops – no more than 0.5-1.0% on a dry weight. Therefore, post-harvest residues of perennial alfalfa in terms of dry matter and nitrogen content are equivalent to 40 t/ha of manure, clover and clover-timothy grass mixture – 20-25 t/ha.
Cereal perennial grasses take first place by mass of stubble and root residues, but due to low nitrogen content (0.5-0.7%) their C:N ratio is wider than that of legumes. Therefore, when mineralizing residues, microorganisms immobilize forms of soil and fertilizer nitrogen in the same way as when plowing straw for fertilizer.
The amount and quality of post-harvest residues entering the soil is regulated by the structure of cropping areas and intermediate crops, which is taken into account when determining the needs and locations of organic fertilizers in the agrocenosis.
Effectiveness of green fertilizers
The effectiveness of green fertilizers depends on the type, productivity and method of use of green manure. The more and better quality green mass of green manure plowed for fertilizer, the higher is the effect and aftereffect.
The rate of decomposition of green fertilizers depend on the granulometric composition and moisture content of the soil, the phase of plant development at the time of plowing, embedding depth. With an increase in the depth of embedding, age of green manure and the content of clay particles in the granulometric composition mineralization of green fertilizers slows down. Adding small rates of manure, poultry manure, fecal matter and other components rich in microorganisms to green manure during plowing accelerates the rate of mineralization.
Providing a favorable environmental reaction and optimal nutrient regime is a factor in increasing the effectiveness of crops and methods of application of green fertilizers.
Legume siderats due to symbiosis with nodule bacteria are able to satisfy their own and partially following cultures, the need for nitrogen. Methods to increase the nitrogen-fixing ability of legume crops are inoculation of seeds with active races of nodule bacteria and treatment with molybdenum fertilizers (20-25 g Mo per hectare seed rate).
The nodule bacteria are specific and can actively interact only with a particular type of legume crops. The strains of nodule bacteria differ in virulence, i.e. the ability to penetrate the root and form nodules, and activity, i.e. the ability to assimilate molecular nitrogen of the atmosphere. Bacterial preparations for legume seed treatment include nitragin and rhizotorfin, which are specific for each crop and contain virulent and active bacterial strains.
For a hectare norm of seeds, 500 g of the preparation is used, and only the part of seeds which is applied on the same day is treated. Inoculation can be combined with molybdenum fertilizer treatment by dissolving fertilizer and bacterial preparation in one portion of water. However, it cannot be combined with seed dressing, which should be carried out 3-4 weeks before sowing, it can also be combined with treatment with molybdenum fertilizer.
Increase in rye grain yield from lupine green fertilizer is 0.42 t/ha on sandy soils, on sandy loam – 0.47 t/ha, on loam – 0.77 t/ha (the average of 36 experiments). Green fertilizers show high efficiency on other crops, on light soils, their effect is noted for a number of years.
Sources
Agrochemistry. Textbook / V.G. Mineev, V.G. Sychev, G.P. Gamzikov et al. – M.: Publishing house of the All-Russian Scientific Research Institute named after D.N. Pryanishnikov, 2017. – 854 с.
Yagodin B.A., Zhukov Y.P., Kobzarenko V.I. Agrochemistry/Under ed. B.A. Yagodin. – M.: Kolos, 2002. – 584 p.: ill.