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Part III, continued: 

Biotic Substances of the Soil

  It can be seen from the above data that small doses of organic substances,present in processed compost or manure, are needed for the improvement of the growthof plants.

  The question arises which of these organic substances are the activatorsof plant growth.

  It was said above that the organic part of the soil consists of amultitude of complex compounds with specific and nonspecific proportion. The majorityof these compounds are related to humic acids.

  Beside the humic acids many other substances were found in the organicpart of the soil. They include substances with biocatalytic properties, Among theseare enzymes, vitamins, auxins, certain amino acids and other biotic substances.

  Bottomley (1914-1920), Mockeridge (1924), Voelcker (1915), Clark (1935),Saeger (1925), and others, have assumed that the activating effect of humus fertilizers,processing manure and different composts with and without bacteria, in conditionedby special substances present in them, the so-called "auximones."

  Their action is similar to that of the yeast bios. The analysis ofpeat infected with bacteria showed the presence of purine bases. The latter werealso found in the cells of Azotobacter. This was the reason for Mockeridge'sconclusion that the activating compound of composts and Azotobacter to oneand the same substance.

  It wax shown in later studies that the action of humus is caused byspecial substances produced by microbes (Nath, 1932, McCarrison, 1924, And others).

  Anstead (1935) proposed that these substances be called phytamins.According to him the phytamins are formed by microorganisms only. Upon entering theplants they are transformed into vitamins. The latter entering with food into thebody of animals and human beings are subjected to certain transformations and areconverted into hormones. Hormones and vitamins are excreted from the animal bodywith urine or excrements, find their way into the soil or manure, And are there transformedby microorganisms into phytamins.

  In such a way, according to Anstead, phytamins, vitamins and hormonesare products of one and the same substance.

  Analogous views were hold by Daineko (1939). He assumed that thereis no difference between the animal hormones and vitamins, and that they are interlinked.

  The link between plant and animal biocatalysts is stressed by manyinventigators. However, there are no grounds for speaking of any cycle of these substancesin nature.

  Lochhead and Chase (1943) attempted to elucidate the nature of theactivating substance of humus. They prepared extracts from soil humus and subjectedit to various procedures, such as extraction with organic solvents, absorption withcarbon, and other absorbents followed by elution. The experiments showed that theash of humus and composts had no effect whatsoever on the growth of plants and microorganism,Of 63 microbial cultures, only one grew in the presence of ash obtained from composts.The extracts obtained from composts and humus of the soil, however, had a positiveeffect on their growth. The acetone extract was the one most effective, In its presence26 cultures grew well, 26 cultures adequately, and only 11 cultures did not grow.Alcohol and ether extracts also gave good results, Filtrates and eluates from charcoal,each gave a small effect, their effect was larger if they were combined.

  Allison and Hoover (1936) noted a positive effect of humic acids onthe growth and activity of root-nodule bacteria. They have discovered the presencein humin of a special substance which they called "Factor R" or "Coenzyme."

  Robinson and Endington (1946) found a biotic substance in soils "fluorin."This substance, according to them, is absorbed in considerable amounts by plants.

  Parker-Rodes (1940) found auxins in the soil. The quantity of auxinsvaried according to the soil properties. In manure-fertilized soils the amount ofauxins was 0. 200 µ g/ kg and in poor, nonfertilized soils only 0.06 g/ kg ofsoil. These substances are found in lesser amounts (0.09-0.106 µ g/ kg) in soilsunder mineral fertilizers. The soil is enriched in auxins in the course of composting.Sterilized soil contained 0.042 µ g auxins per kg of soil and after 6 days incubationin a glass house, under favorable temperature and humidity conditions, they increasedto 0.146 µ g/ kg of soil.

  Williams, Stewart, Kejes and Anderson (1942) found larger quantitiesof auxins in soils than did Parker-Rodes. According to their data, the A-horizonof fertile soils contains up to 175 µ g auxins per kg of soil, Nonfertile soilscontain 40-60 µ g auxins per kg of soil. In horizon B auxins were not detected.

  Hamense (1946) by the use of improved methods of analysis found 100times more auxins in soils than did previous workers. According to his data the auxincontent was 160-450 µ g per kg of soil (Schmidt, 1951, and Hamense, 1946).

  Stewart and Anderson (1942) had shown that the amount of auxins infertile soils is entirely sufficient for the stimulation of plant growth. Hamense(1946) found in different soils 0.16-0.045 µ g equivalents of ß-indoleaceticacid in 1 g of dry soil. The auxin content increases after the application of organicfertilizers and then falls below the initial level and afterward rises again to thenormal level, characteristic of the given soil. According to the author's observations,chemically pure preparations of auxins are not preserved in the soil for long periods.

  According to Matskov (1954), chemical preparations of 2. 4-dichlorophenoxyaceticacid are preserved in the soil for the duration of a whole winter (5-6 months). Anothergrowth stimulant--heteroauxin (ß-indoleacetic acid) is not preserved in thesoil that long.

  Auxins were also detected in the soil by Roberts I. and Roberts E.(1939) and some other investigators.

  Beside auxins, soils also contain many other biotic substances suchas vitamins, biotin, nicotinic acid, pantothenic acid, folic acid, amino acids, variousgrowth factors R, Z, X, and others, These substances have been found in the followingquantities:

Thiamine 0.29-1.93 µ g Roulte and Schopfer, 1950; Schopfer, 1943
Riboflaven 9.0-980 µ g Schmidt and Starkey, 1951; Carpenter, 1943
Biotin 23.0-62.0 µ g Roulet and Schopfer, 1950
Vitamin B6 amounts not indicated  
Vitamin B12 0.2-1.5 µ g Robbins, Hervey and Stebbing, 1951, 1952
Inositol amounts not indicated  
Nicotinic acid amounts not indicated Roulet, 1948
Para-aminobenzoic acid amounts not indicated Roulet, 1948
Pantothenic acid amounts not indicated Roulet, 1948
Folic acid amounts not indicated Roulet, 1948
Factor X amounts not indicated Lochhead and Texton, 1950
Unknown factor amounts not indicated Lochhead and Texton, 1950

  Apart from complete vitamin molecules, molecule fractions are encounteredin nature which have the same effect on some organisms as the whole molecules, forexample, the pyrimidine, thiazole and others (Lilly and Leonian, 1939).

  We have found vitamins in different soils; as a rule, they were inlarger quantities in places where the microbiological processes were more intense.Thus, they appear in chernozems in larger amounts than in podsol soils (Table 37).

Table 37
Vitamin and bacterial content of various soils

Soils

Riboflavin
µ g/100 gm

Thiamine
µ g/100 gm

Biotin
µ g/100 gm

Bacteria
millions/gram

Chernozem (Moldavian SSR)

98.0

4.5

45.0

1,500

Podsol
(Moscow Oblast')

5.0

1.2

25.0

0.5

  Cultivated soils contain more vitamins than virgin soils.

  The vitamin content of the soil is qualified not only by the extentof cultivation but also by the nature of the vegetative cover. Plants which favorabundant growth of microorganisms, as a rule, assimilate more biotic substances inthe soil. In the serozems of Central Asia the highest concentrations of biotic substanceswere found under 2-3-year-old lucerne, their concentration was lower under cottonand very little was found in virgin soils (Table 38).

Table 38
Vitamin and microbe content of the soils of Central Asia, under various plants

Soil

Thiamine
µ g/100 gm

Biotin
µ g/100 gm

Microorganisms
millions/gram

Virgin soil, the valley of the river Vakhsh

1.5

10.0

0.5

Virgin soil

0

+

0.1

Cultivated soil (2 year-old lucerne)

6.5

38.0

4,500

Cultivated soil (cotton long under cultivation)

3.0

18.0

1,500

  According to Shavlovskii (1954, 1955), soil under potatoes contains0.5 µ g/kg biotin, and soil under clover--l.3 µ g/kg. In the Lvov Oblast'in serozem forest soils and podsol chernozem the author obtained the data shown inTable 39.

Table 39
Vitamin content of soils under various plants, in µ g/kg

Soils

Biotin

Riboflavin

Nicotinic acid

Serozem forest, under wheat

0.3

4.0

100.0

The same, under grasses

0.7

7.0

230.0

Podsol chernozem, under wheat

0.8

10.0

280.0

The same, under grasses

1.5

14.0

350.6

  In soil adjoining the root system there are more biotic substancesthan outside the rhizosphere. In one kg of soil from the rhizosphere of wheat grownin fertilized fields of the Experimental Station of Dolgoprudnoe (Moscow Oblast')we found per 100 g soil 10 µ g of thiamine, 150 µ g riboflavin, 35 µg biotin; outside the rhizosphere, 1.2 µ g thiamine, 25 µ g riboflavin,3 µ g biotin; in the rhizosphere of tobacco, 10-15 µ g thiamine, and outsidethe root zone 1.5-4.0 µ g per 100 g of soil.

  According to Shavlovskii, the amount of vitamins in the rhizosphereof buckwheat is twice as high as that outside the root zone. On the 20th day of growthhe found:

.

in the rhizosphere,
µ g / kg

outside the rootzone
µ g / kg

Nicotinic acid

600

260

Biotin

2

0.5

Vitamin B6

8

--

  Higher concentrations of vitamins in the rhizosphere were noted byRoulet (1954). The amount of biotic substances in the upper layer of the soil ishigher than in the lower layers. The highest concentrations are found in the upperlayer (0-20 cm) (Table 40).

Table 40
The distribution of vitamins in soil layers (µ g/kg)

Soil

Layer, cm

Thiamine

Biotin

Podsol of Moscow Oblast under 2 year clover

0-20

2.3

14

 

20-30

0

3.0

 

50-70

1.9

8.0

 

80-100

0

0

Serozem of Vakhsh Valley under 3 year lucerne

0-20

5.6

42

.

30-40

1.8

14

 

45-60

2.4

21

 

70-90

1.1

4.2

  In some soils a small increase in the concentration of biotic substancesis noted at a depth of 60-70 cm.

  Some other investigators have noted the decrease in concentrationof vitamins in deep layers of the soil. Roulet and Schopfer (1950) give the followingdata on the distribution of vitamins according to, layers (per 100 g of soil):

layer, cm

thiamine, µ g

biotin, µ g

10

1.93

62

20

0.86

39

30

0.62

27

50

0.29

23

  These authors found thiamine and biotin even at a depth of 2.0 to8.5 m.

  Lilly and Leonian (1939) found considerable quantities of thiamineand biotin, as well as vitamin B1 and its components thiazole and pyrimidine,in the soil. They were concentrated in the upper layer of the soil. At a depth of60 cm they were not detected. West and Wilson (1938, 1939) found thiamine and biotinin the root zone of tobacco and flax.

  According to Schmidt and Starkey (1951), riboflavin can be found inthe soil in varying amounts, according to soil fertility, vegetative cover, etc.In soils under forests the authors found 500 µ g of riboflavin and in soilsunder plow and in fertile soils about 10 µ g per 100 g of soil.

  After the application to the soil of organic fertilizers such as straw,grass or sugar, the amount of riboflavin increased. The more organic substances applied,the higher was the concentration of riboflavin in the soil. For example, after applicationof grass 15%*, about200 µ g riboflavin were found; if the amount of grass addedwas 10% 120 µ g riboflavin were found, in the presence of grass of 5% only 60µ g riboflavin was found. The amounts of riboflavin are given per 100 g of soil(Figure 62). *[The 15% refers to the grass, It is not clear what the percentage refersto.]

 

Figure 62. The formation of riboflavin in the soil, in the presence of various quantities of organic substances (lucerne grass):

1--15%; 3--5%

 

  By the end of the growth period, in August-October, more vitaminsare found in the soil than in the spring. The amount of riboflavin found in springwas 80-300 µ g, in autumn it reached 600-980 µ g per 100 g of soil.

  Roulet (1954) found that the amount of biotin in the upper layer ofa botanical garden increases in the autumn and decreases in winter and in spring.

  According to this author, forest and marshy soils contain even morevitamins than garden or meadow soils.

  The amount of biotic substances in the soil constantly changes, accordingto external conditions such as temperature, humidity, season, etc.

  The vitamins are preserved in the soil for various periods of time,the length of which also depends upon soil and climatic conditions. According toStewart and Anderson (1942), growth-stimulating substances can persist in dry soilfor 3-4 years, According to Schmidt and Starkey, 50% riboflavin can be detected infresh soil after 3 days, pantothenic acid is completely decomposed in one day.

  Some amino acids can be listed among the growth factors of lower andhigher plants. Plants synthesize these amino acids in the same way they synthesizevitamins, but, nevertheless, the addition of small doses of amino acids has a positiveeffect on the growth of plants.

  Nielsen and Hartelius (1938) tested amino compounds, Six of them--ß-alanine,asparagine, aspartic acid, glutamic acid, lysine and arginine markedly enhanced thegrowth of lower organisms; ß--alanine had the greatest effect. Five µ gof ß-alanine per 50 ml of medium was sufficient to enhance the growth and increasethe yield by 66% dry weight. The maximal stimulation was found at the concentrationof 1:100,000. Arginine acts at a dilution of 1:20,000 and lysine at a dilution of1:4,000. Glutamine exerts a positive effect on the growth of organisms in a doseof 1:1,000. Substances in such doses can be considered as sources of nutrition. Otheramino acids such as asparagine and others act at even higher concentrations and cannotbe regarded as growth factors but as nutrients.

  The amount of amino acids in soils varies; it depends upon the propertiesof the latter and upon climatic conditions. The more fertile the soil, the more aminoacids it contains. The concentration of amino acids is determined by the rate oftheir influx into the soil and by the length of time of their preservation.

  This list does not include all the biotic substances of the soil.It should be assumed that the soil, the same as other natural substrates, containsmany other substances unknown to us, which act as biocatalysts, enhancing the metabolismof organisms.

  Lochhead and Texton (1940, 1950, 1952) detected activating substancesin the soil which were of an unknown nature and could not be replaced by any of theknown growth factors. 

The origin of the biotic substances of soil

  All the diverse biotic substances have their origin in the metabolicactivity of plants and microbes.

  Formation of biotic substances by the plants. It was mentioned abovethat, during their lifetime, the roots of many plants excrete substances which stimulatethe growth of organisms, For example, the seeds of broomrape germinate, only in thevicinity of roots of sunflower, flax, corn, soy and some other plants, The root excrementsof these plants activate the growth of broomrape sprouts. The activating factor isthermostable and is, not decomposed on boiling and prolonged drying (Bartsinakii,1935; Beilin, 1941).

  According to Golubinskii (1950), morning glory stimulates the germinationof melon seeds. Pollen grains of angiosperms mutually stimulate each other on germinationby excreting activating substances (Golubinskii, 1946).

  Timonin (1941) found thiamine and biotin in the root secretions offlax. According to him, these vitamins secreted by the roots, considerably promotethe growth and proliferation of microorganisms in the rhizosphere.

  West (1939) found thiamine and bios substances in root secretionsof flax and tobacco.

  Meshkov (1952) found biotin and thiamine in root secretions of cornand peas. According to him, the more of these substances are secreted, the more intenseis the growth of the plants. Corn secretes more biotin, and peas more thiamine. Theroot excretions contain vitamins in the following amounts per g dry weight of theplants: corn--0.5402 µ g of thiamine and 0.2308 µ g of biotin; peas--0.6634µ g of thiamine and 0.2658 µ g biotin.

  According to our observations, peas, wheat, and corn secrete morebiotic substances in their early growth period than in the period of fruiting (Table41).

Table 41
The presence of vitamins in root secretions of various plants
(µ g per ml of nutrient solution)

Plants

After 10 days growth: Thiamine

After 10 days growth: Biotin

After 45 days growth: Thiamine

After 45 days growth: Biotin

Wheat

0.1

0.6

0

0.1

Corn

0.2

0.5

0

0

Peas

0.5

1.5

0.1

0.7

  Plants grown in aerated solutions secrete more biotic substances thanthose grown in poorly aerated solutions. For example, wheat grown with good aerationsecreted 0.21 µ g thiamine, and wheat grown in the presence of small amountsof oxygen secreted 0.11 µ g thiamine. The respective amounts of biotin secretedwere 0.8 and 0.6 µ g (per cm3 of medium).

  There are indications in the literature that germinating seeds ofvarious plants secrete small amounts of vitamins into the medium (Meisel, 1950; Schopfer,1943).

  Biotic compounds can find their way into the soil together with decomposingresidues. It is known that plants contain considerable amounts of various compoundswhich can stimulate the growth and development of organisms. For example, accordingto Burcholder and others (1944), the following amounts of thiamine are present inthe tissues of: soya 47-61 x 10-7; barley 28-51.8 x 10-7; corn17.6-31.2 x 10-7 (in mols per kg dry weight). The aerial parts containmore thiamine than the roots: in the leaves of corn were observed 17.6-30. 2 x 10-7;and in the roots--4.06-9.78 x 10-7 mols per 1 kg of dry mass.

  Auxins, vitamins of the B-group, bios, vitamins, D, K, C, H and P,pantothenic acid, paraaminobenzoic acid, nicotinic acid, purine derivatives and varioushormones, etc, have been found in plants (Zeding, 1955; Ovcharov, 1955, and others.

  Many biotic substances are excreted in the feces of animals and humanbeings. For example, human beings excrete daily in urine 60 µ g of thiamine,600 µ g riboflavin, 626 µ g inositol and large quantities of pantothenicacid, as well as other compounds (Meisel, 1950). Vitamins of the B-group, pantothenicacid, nicotinic acid, folic acid, and other substances are found in the faces ofhuman beings and animals. The investigations show that these substances are synthesizedby the microflora of the intestines (Perets, Gryazno and Agibalova, 1948; Nepomnyashchaya,1950; Najjar and others, 1943-1950; Perets, 1955), The vitamins and other substancesenter the soil with manure. According to Bonner and others (1938), 1kg of manurecontains 130 µ g thiamine. Riboflavin, pantothenic acid, nicotinic acid, andother activating substances are present in manure. Sauerland (1948) found considerableamounts of substances of the bios type in manure, feces and urine of cattle, Thequantities of these substances fluctuate with the seasons. The largest amounts beingfound in summer, less in winter. The amount of growth factors in manure and animalfeces also varies according to the quality of the fodder.

  All these substances accidentally find their way into the soil, andon the whole they constitute only a small traction of the total amount of bioticsubstances in the soil. The microorganisms are the main factor in the enrichmentof the soil with these substances. 





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