ISSN 1313 - 8820Volume 7, Number 4

December 2015

2015

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Genetics and Breeding

Atanas Atanasov (Bulgaria)Nikolay Tsenov (Bulgaria)Max Rothschild (USA)Ihsan Soysal (Turkey)Horia Grosu (Romania)Bojin Bojinov (Bulgaria)Stoicho Metodiev (Bulgaria)

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Product Quality and Safety

Marin Kabakchiev (Bulgaria)Stefan Denev (Bulgaria)Vasil Atanasov (Bulgaria)

English Editor

Yanka Ivanova (Bulgaria)

2015

ISSN 1313 - 8820 Volume 7, Number 4December 2015

Phosphorus fractions in alluvial meadow soil after long-term organic-mineral fertilization

S. Todorova*, K. Trendafilov, M. Almaliev

Department of Agro-chemistry and Soil Science, Faculty of Agronomy, Agricultural University, 12 Mendeleev, 4000 Plovdiv, Bulgaria

Abstract. The aim of our study was to investigate phosphorus fractions, their content and distribution in alluvial meadow soil after continuous fertilization. Our research was focused on a long-term field experiment with different variants of fertilization set in 1959 in the Experimental field of Agricultural University of Plovdiv. Since 2006 the fertilization has been discontinued. In 2011, we collected soil samples from two depths (0 – 30 and 30 – 40 cm) and from the following variants: variant 1 (control, without fertilization), variant 2 (N P K ), variant 3 (N P K + 6t/da manure), variant 4 (N P K ). The studied soil is characterized by 50 30 20 25 15 0 50 0 20

relatively good natural phosphate regime. The amount of available phosphates determined by the Egner-Rheem method is high – average 16.76% of the total phosphorus. Over 50% of the mineral phosphates in the soil are in available (in varying degree) form. Relatively high is the amount of organic phosphates, which during the mineralization can also be involved in the plant nutrition. The amount of available phosphates (according to Egner-Rheem) is determined to the highest degree by the total phosphorus in soil, which in turn is highly correlated with the content of hardly soluble calcium phosphates.

Keywords: alluvial meadow soils, phosphorus fractions

AGRICULTURAL SCIENCE AND TECHNOLOGY, VOL. 7, No 4, pp , 2015431 - 435

Introduction reaction is slightly alkaline (pH(H O) – 7.7 – 8.0). The same authors 22+ 2+found high amount of exchangeable bases (Ca + Mg – 20 – 30

meq/100 g soil) in the soil sorption complex.In soil phosphorus is in the form of inorganic and organic The aim of our study is to determine soil phosphorus forms after compounds. Plant roots and mycorrhizal hyphae absorb soil solution

- 2- different regimes of fertilizations.P as orthophosphate ions in either the H PO or HPO form, 2 4 4

depending on soil pH. The dominant solution inorganic P below pH 2-7.2 is the monovalent ion, while HPO dominates at pH values 4

between 7.2 and 12.1. Plant uptake of the divalent ion has been Material and methodsshown to be slower than the monovalent ion (Cresser et al.1993). However, these ions can be adsorbed on the surface or absorbed The object of our study is alluvial meadow soil (Mollic fluvisol, into the solid particles of the soil and then become unavailable for FAO 2006) on which in 1959 a long-term field experiment was set plants. with different variants of fertilization in the Experimental field of

Organic soil phosphorus represents, on average, one-half of Agricultural University of Plovdiv. Since 2006 the fertilization has the total soil P and varies between 15 and 80% in most soils been discontinued. In the spring of 2011, we collected soil samples (Stevenson, 1986). The amount of soil organic P depends on soil from two depths (0–30 and 30–40 cm, from the second and fifth field organic matter content, therefore it tends to be high in the surface and from the following variants: variant 1 (control without horizon and decreases with soil depth. Soil organic P compounds fertilization), variant 2 (N P K ), variant 3 (N P K + 6 t/da 50 30 20 25 15 0

are synthesized by soil microorganisms as esters of manure), variant 4 (N P K ).50 0 20

orthophosphoric acid (Anderson, 1980). The most stable and To determine phosphorus forms, soil samples were analyzed abundant compounds are inositol phosphates which make up 10 to according to the method for fractionation of soil phosphates by 50% of the total soil organic P. Nikolov (1985). This method allows avoiding or highly reducing

Phosphorus is an element with very complex behavior in the some disadvantages of fractionation of inorganic phosphorus in soil, which is determined by its ability to enter into chemical and calcareous soils according to the original methodology of Chang and sorption reactions with soil colloids and mono and polyvalent ions of Jackson (1957). In this modification first are extracted the easily and metals. In a short period of time, these transformations are moderately soluble phosphates – with malic acid and then – determined by the biochemical processes associated with the phosphates associated with soil carbonates by acetate buffer. After formation and decomposition of soil organic matter. In longer term, removal of these forms and CaCO , extraction with NH F and NaOH 3 4

however, the behavior of phosphorus in soil is determined by the + H SO , is applied as in the original method. The preliminary 2 4geochemical transformations specific to soil type (Wandruszka, extraction of easy and moderately soluble phosphates before 2006). As a result of these metamorphoses the applied assimilable application of fluoride extraction makes it possible to eliminate the phosphorus becomes over time less available for plants. positive error due to their dilution in the extract with NH F, noted by 4In other researches concerning the studied soil (Todorova et al.,

Kaila A. 1961. On the other hand, the extraction of phosphorus 2012) it was found that the soil is silty loam according to the

associated with CaCO and removing from the system the 3International Texture Classification, and light to medium clay carbonates allows avoiding the negative error in fluoride extraction, according to the classification developed by Kachinskii (1965). resulting from the precipitation of phosphorus and fluorine on the Despite the small amount of total carbonates (2 – 3%), the soil surface of calcium carbonate found by a number of authors

431

* e-mail: stefi_k.todorova@abv.bg

432

(Garbuchev, 1978; Nejkova-Bocheva, 1978; Williams et al., 1967). available phosphorus to ensure the normal phosphorus diet for most Then dithionite reduction is applied in the presence of sodium of the crops is 5 mgP/100g soil. The amount of this mostly available acetate with which only reductively soluble phosphorus bounded for plants fraction represents from 0.70 to 3.65% of total phosphorus with the iron is extracted, and phosphorus bound to aluminum does in the soil.not pass into the extract, which is determined in the dithionite-citrate The content of moderately soluble phosphates extracted from extraction, applied in the original method. the soil with malic acid is a little higher – 0.49 to 3.51 mgP/100g.

The amount of available phosphates by Egner-Rheem (GOST These phosphates, which play a significant role in the nutrition of 26209-91), organic phosphorus Metha et al. (1954) and total plants, comprise from 1.04 to 7.72% of total phosphorus.phosphorus in the soil after combustion with 60% HClO (Bray and The main part of mineral phosphorus in the studied soil is 4

presented by fractions of phosphates associated with CaCO – Kurtz, 1945) were also determined. In the extracts for determining 3

fractions of inorganic phosphates, available phosphates by Egner- average 6.00 mgP/100g (14.22% of total phosphorus) and hardly Rheem and organic phosphates, phosphorus was determined with soluble calcium phosphates – average 10.98 mgP/100g (26.18% of ascorbic acid reducer by the method of Murphy-Riley (Murphy and total phosphorus). The reason for this distribution of phosphorus Riley, 1962) and total phosphorus was determined by the forms in the soil lies in its genesis. Applied during fertilization, molybdate-vanadate method (Agrochemical methods for soil monocalcium phosphate from the superphosphate reacts with the investigation, 1975). carbonate soils and at lower concentrations of phosphorus at soil

solution, phosphate anions are mainly adsorbed on the surface of CaCO , while at higher concentrations along with the adsorption, 3

precipitation of dicalcium phosphate takes place, octacalcium Results and discussion phosphate and, in some cases it is possible to form harder soluble calcium phosphates such as apatite (Nikolov, 1985; Cole et al., The results for the amount and composition of the forms of 1953).phosphate compounds in the studied alluvial-meadow soil are

Reductively soluble iron phosphates are formed under presented in Tables 1 and 2. We searched correlations between the conditions of poor aeration, excessive compaction of the profile as a content of available phosphates determined by Egner-Rheem and result of high content physical clay, and during gleization of soils i.e. fractions of phosphorus determined by the method of Nikolov (1985) in soils where reduction processes dominate. Since such conditions organic phosphorus and total phosphorus. Data show that the are not observed in the studied soil, then the content of this fraction is content of easily soluble phosphates is not high and varies from 0.31 low – 0.92 – 1.66 mgP/100g, which is an average of 2.98% of the to 1.66 mgP/100g soil, which by itself is not enough to meet the total phosphorus.requirements of plants. It is considered that the minimum amount of

Table1. Content of mineralforms of phosphorus, organic phosphorus and total phosphorus, mgP/100 g soil

Varia

nts

1

2

3

4

1

2

3

4

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

Fie

ldF

ifth

Sec

ond

Dep

th

0.31

0.33

0.91

0.72

1.66

1.03

1.26

1.12

0.82

0.79

3.33

3.04

1.49

0.95

0.81

0.72

Eas

ily s

olub

le Р

0.52

0.49

2.27

2.09

3.51

3.33

2.64

2.95

2.49

2.84

5.63

5.23

3.04

2.61

2.16

1.93

Mod

erat

ely

solu

ble

Р

Fractions

5.32

5.54

6.59

5.86

6.66

5.03

3.98

3.25

5.33

5.91

9.72

8.58

7.95

6.00

5.26

5.08

Pho

spho

rus

asso

ciat

ed

with

CaC

O3

2.25

2.11

2.46

2.05

2.17

1.83

1.81

1.65

1.88

1.77

3.33

3.04

2.79

2.13

1.78

1.46

Har

dly

solu

ble

Al -

Р

3.61

3.89

2.86

2.44

2.13

1.91

2.49

2.38

2.92

2.39

4.35

3.63

3.16

2.49

2.17

1.99

Har

dly

solu

ble

Fe

- Р

0.98

1.06

1.05

1.15

1.08

1.13

1.46

1.62

0.92

1.21

1.38

1.66

1.24

1.44

1.29

1.31

Red

uctiv

ely

solu

ble

Fe

- Р

0.89

0.96

0.77

0.70

0.64

0.74

0.76

0.75

0.71

0.89

0.69

0.70

0.71

0.64

0.78

0.66

Occ

lude

dA

l - Р

0.92

0.89

0.94

0.89

0.91

0.89

0.94

0.86

0.91

1.01

0.96

1.03

0.93

0.72

0.98

0.91

Occ

lude

dF

e -

Р

9.96

10.68

12.39

11.96

11.36

10.42

9.66

10.06

9.02

9.98

12.28

11.19

13.69

11.95

10.84

10.23

Har

dly

solu

ble

Ca

- Р

11.75

12.10

9.84

11.03

12.21

11.98

13.80

11.87

8.53

6.55

8.33

6.55

6.07

5.79

6.27

5.48

Org

anic

Р

24.76

25.95

30.24

27.86

30.12

26.31

25.00

24.64

25.00

26.79

41.67

38.10

35.00

28.93

26.07

24.29

Min

eral

Р

39.46

46.91

42.73

48.00

45.46

47.64

48.55

45.82

38.73

37.64

52.37

45.82

41.46

34.91

32.82

33.82

Tota

l Р

2.95

8.86

2.65

9.11

3.13

9.35

9.75

9.31

5.20

4.30

2.37

1.17

0.39

0.19

0.48

4.05

Inso

lubl

e re

sidu

e

7.02

6.46

8.48

7.38

12.70

9.38

6.54

6.14

4.93

4.84

10.08

8.93

9.82

7.40

3.18

2.71

Ava

ilabl

e ph

osph

orus

by

Egn

er-R

heem

433

The low content of hardly soluble phosphates bounded to Al and The indicated high positive correlation between available Fe is reasonable, respectively 2.16 mgP/100g and 2.80 mgP/100g. phosphates (according to Egner-Rheem) and the fraction of hardly The blocking of phosphorus in these soils does not take place by way soluble Al-P (Figure 1), may have resulted from slightly alkaline of its binding with iron and aluminum oxides and hydroxides, as their reaction of the medium in which the solubility of these phosphates is amount and activity in these soils are small because of slightly increased to some extent. It must be noted that the amount of these expressed processes of destruction of silicate minerals and the phosphates is low. The fraction of hardly soluble Al-P constitutes absence of the process of acidification. In confirmation to this is the about 5% of total phosphorus, which leads us to believe that in our fact that in most variants, in both depths iron phosphates case, these phosphates are actually not essential for the predominate over aluminum. phosphorus nutrition of plants.

Table2. Percentage of phosphorus fractions of the total phosphorus in soil (as % of Р total)Va

riant

s

1

2

3

4

1

2

3

4

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

0-30cm

30-40cm

Fie

ldF

ifth

Sec

ond

Dep

th

0.79

0.70

2.13

1.50

3.65

2.16

2.60

2.44

2.12

2.10

6.36

6.63

3.59

2.72

2.47

2.13

Eas

ily s

olub

le Р

1.32

1.04

5.31

4.35

7.72

6.99

5.44

6.44

6.43

7.55

10.75

11.4

17.3

37.4

86.5

85.71

Mod

erat

ely

solu

ble

Р

Fractions

13.48

11.81

15.42

12.21

14.65

10.56

8.20

7.09

13.76

15.70

18.56

18.73

19.18

17.19

16.03

15.02

Pho

spho

rus

asso

ciat

ed

with

CaC

O3

5.70

4.50

5.76

4.27

4.77

3.84

3.73

3.60

4.85

4.70

6.36

6.63

6.73

6.10

5.42

4.32

Har

dly

solu

ble

Al -

Р

9.15

8.29

6.69

5.08

4.69

4.01

5.13

5.19

7.54

6.35

8.31

7.92

7.62

7.13

6.61

5.88

Har

dly

solu

ble

Fe

- Р

2.48

2.26

2.46

2.40

2.38

2.37

3.01

3.54

2.38

3.21

2.64

3.62

2.99

4.12

3.93

3.87

Red

uctiv

ely

solu

ble

Fe

- Р

2.26

2.05

1.80

1.46

1.41

1.55

1.57

1.64

1.83

2.36

1.32

1.53

1.71

1.83

2.38

1.95

Occ

lude

dA

l - Р

2.33

1.90

2.20

1.85

2.00

1.87

1.94

1.88

2.35

2.68

1.83

2.25

2.24

2.06

2.99

2.69

Occ

lude

dF

e -

Р

25.24

22.77

29.00

24.92

24.99

21.87

19.90

21.96

23.29

26.51

23.45

24.42

33.02

34.23

33.03

30.25H

ardl

y so

lubl

e C

a -

Р

62.75

55.32

70.77

58.04

66.26

55.23

51.49

53.78

64.55

71.17

79.57

83.15

84.42

82.87

79.43

71.82

Min

eral

Р

29.78

25.79

23.03

22.98

26.86

25.15

28.42

25.91

22.03

17.40

15.91

14.29

14.64

16.60

19.10

16.19

Org

anic

Р

7.48

18.89

6.20

18.98

6.89

19.63

20.08

20.32

13.42

11.43

4.52

2.56

0.94

0.53

1.46

11.99

Inso

lubl

e re

sidu

e

17.79

13.77

19.85

15.38

27.94

19.69

13.47

13.40

12.73

12.86

19.25

19.49

23.69

21.20

9.69

8.01

Iby

Egn

er-R

heem

avai

labl

e ph

osph

orus

2.50

P-CaCo3

Figure2. Linear regression between phosphorus associated with CaCO and Egner-Rheem phosphates 3

with intervals of variation

Egn

er-R

heem

4.00 6.00 8.00 10.00

5.00

7.50

10.00

12.50

y=1.86+0.9*x

1.00

2.50

Hardly soluble Al-PFigure1. Linear regression between hardly soluble Al-P and Egner-Rheem phosphates with intervals of variation

Egn

er-R

heem

1.50 2.00 2.50 3.00 3.50

5.00

7.50

10.00

12.50

y=0.12+3.3*x

434

In accordance with the small absolute amount of the hardly correlation between available phosphates (according to Egner-soluble aluminum and iron phosphates, the relative amount of their Rheem) and organically bounded phosphorus (Figure 3). Despite occluded forms is low, respectively 1.79 and 2.19% of the total the high degree of mineralization of soil organic matter, only a small phosphorus, and again the forms bounded with iron predominate. part of organically bounded phosphorus is susceptible to This confirms the statement that in the studied soil there are no decomposition and is involved in the plant nutrition.reduction processes related to dissolution and deposition of sheaths The insoluble residue of soil phosphorus represents single of iron hydroxides during wetter periods of the year and primary apatite crystals included in other (larger) unweathered consequently the formation of occluded forms of phosphorus. aluminosilicate minerals, phosphorus replacing the silicon in the

From the mineral phosphorus compounds with the highest crystal lattice of silicate minerals and some phosphate minerals availability for plants are characterized phosphates of alkali and insoluble in the reagents for fractionation. The amount of this fraction alkaline earth metals, except for calcium phosphates such as apatite in different variants included in our study varies widely – from 0.53 to (hardly soluble Ca-P). The reason for Ca-phosphates (fraction of 20,08% of total phosphorus. From an agrochemical point of view, CaCO -P) to be the best potential food for plants, lies in their good this insoluble residue cannot be considered as a reserve for plants 3

nutrition.solubility and in the fact that along with phosphorus plants also The strongest correlation was found between available absorb calcium from these compounds. The great importance of this

phosphates determined by the Egner-Rheem method on one hand, fraction of mineral phosphates is confirmed by the established high and total phosphorus and hardly soluble Ca-P, on the other side correlation between available according to Egner-Rheem (Figures 4 and 5). The amount of available phosphates (according to phosphates and phosphates associated with CaCO (Figure 2).3

Egner-Rheem) is determined to the greatest extent by the total It is considered that Fe and Al phosphates can also play a phosphorus in soil which in turn is highly correlated with the content certain role in plant nutrition, especially hardly soluble Al-P and Fe-P.

Unlike calcium, however, these ions are not absorbed by the plants so intensively and in many cases are toxic, especially Al.

In total, inorganic phosphate compounds are from 51.49 to 84.42% of total phosphorus, while organic phosphates are from 14.29 to 29.78%. The course of the curve of organically bounded phosphorus down the soil profile, for most of the variants, is similar to the course of soil organic matter, which speaks about close relationship between organic carbon and organic phosphorus. According to Hinov et al. (1967), about 20% of organic phosphorus is bounded to the high-molecular fractions of humic acids and is not susceptible to hydrolysis. This is a residue that cannot be referred to as reserve phosphorus for plants. The remaining 80% of the organic phosphates assign to relatively easily hydrolysable components of soil organic matter, and it is assumed that it can be a potential phosphoric food for plants during the mineralization of humic acids. Compared to control variants there is a tendency for reducing the amount of organic phosphates in variants with prior mineral and organic-mineral fertilization. Application of fertilizers in these variants created more favorable conditions for microbiological activity and thus stimulated the mineralization of soil organic matter.

The results of regression analysis showed a weak positive

2.50

Organic PFigure3. Linear regression between organic phosphorus and Egner-Rheem phosphates with intervals of variation

Egn

er-R

heem

4.00 6.00 8.00 14.00

5.00

7.50

10.00

12.50

y=4.57+0.29*x

10.00 12.00 30.00

2.50

Total PFigure4. Linear regression between total phosphorus and Egner-Rheem phosphates with intervals of variation

Egn

er-R

heem

35.00 40.00 45.50 50.00 55.00

5.00

7.50

10.00

12.50

y=4.85+0.28*x

2.50

Hardly soluble Ca-PFigure5. Linear regression between hardly soluble Ca-P and Egner-Rheem phosphates with intervals of variation

Egn

er-R

heem

9.00 11.00 12.00 14.00

5.00

7.50

10.00

12.50

y=-6+1.21*x

10.00 13.00

435

of hardly soluble Ca-P. Under conditions of neutral to slightly alkaline FAO, 2006. World Reference base for Soil Resources, Rome, Italy, medium (as in our case), hardly soluble Ca-P retain their inertness pp. 131.and to the greatest extent determine the reserves of total Garbuchev I, 1978. Adjusting the phosphate regime of the main phosphorus in soil, so a strong correlation between available soils in Bulgaria. Zemizdat Press, Sofia, (Bg).phosphates and hardly soluble phosphates of Ca is reported. GOST 26209 - 91 – Soils. Determination of available forms of

phosphorus and potassium according Egner-Rheem method (DL-Method) (Ru).Hinov G, Ganev S and Hadjigencheva M, 1967. Behavior of Conclusionphosphorus from humic acids during their acid hydrolysis. Symposium Phosphorus, Sofia-Belgrade (Ru).In relation to the above mentioned, it can be concluded that the Kachinskii NA, 1965. Soil Physics, Vysshaya Shkola, Moskow, 1 studied soil is characterized with relatively good natural phosphate (Ru).regime. This is confirmed by the high amount of available Kaila A, 1961. Fertilizer phosphorus in some Finnish soils. The phosphates according to the Egner-Rheem method – average Journal of the Scientific Agricultural Society of Finland, 33, 133-139.16.76% of the total phosphorus is in assimilable for the plants form. Metha NC, Going JO and CA Black, 1954. Determination of Considering all fractions that could potentially be involved in plant organic phosphorus in soils – Extraction method. Soil Science nutrition, it can be seen that over 50% of mineral phosphates are in Society of America Proceedings, 18, 443-449.available (to varying degree) form. This assumption is Murphy J and Riley JP, 1962. A modified single solution method for complemented by the relatively high amount of organic phosphates, the determination of phosphate in natural waters. Analytica Chimica which during the mineralization can also take part in phosphorus Acta, 27, 31-36.nutrition.Nejkova-Bocheva E, 1978. New aspects of phosphate regime of the soils and possibilities for prediction of phosphorus fertilization. Thesis for PhD, Sofia, (Bg).ReferencesNikolov N, 1985. Advanced methods for control and regulation of phosphorus in soils. Thesis for PhD, Sofia, (Bg).

Agrochemical methods for soil investigation, 1975. Moscow, Stevenson FJ, 1986. Cycles of soil; Carbon, nitrogen, phosphorus,

Press „Nauka” (Ru).sulfur, micronutrients. John Wiley and Sons, New York, NY.

Anderson G, 1980. Assessing organic phosphorus in soils. p. Todorova S, Simeonova N, Trendafilov K and Valcheva V, 2012.

411–431. In F.E. Khasawneh et al. (ed.) The role of phosphorus in Change of some chemical properties of alluvial-meadow soil (Mollic

agriculture. ASA, Madison, WI.fluvisols) after long term fertilization. Agricultural Science and

Bray RH and Kurtz LT, 1945. Determination of total, organic and Technology, 4, 285-287.

available forms of phosphorus in soils. Soil Sciences, 59, 39-45.Wandruszka RV, 2006. Phosphorus retention in calcareous soils

Chang SC and Jackson ML, 1957. Fractionation of soil and the effect of organic matter on its mobility. Geochemical

phosphorus. Soil Sciences, 84, 133-144.Transactions, 7, 6.

Cole CV, Olsen SR and Scott CO, 1953. The nature of phosphate Williams JDH, Syers JK and Walker TW, 1967. Fractionation of

sorption by calcium carbonate. Soil Science Society of America Soil Inorganic Phosphate by a Modification of Chang and Jackson`s

Proceedings, 17, 352-356.Procedure. Soil Science Society of America Proceedings, 31, 736-

Cresser MS, Killham K and Edwards T, 1993. Soil Chemistry and 739.

its applications. Cambridge University Press, Cambridge, UK.

Review

Genetics and Breeding

Nutrition and Physiology

Production Systems

Effect of feeding program for first two months after birth of female calves on growth, development and first lactation performanceG. Ganchev, E. Yavuz, N. Todorov

Involvement of the transcriptional variants of histone H3.3 in the development and heat stress response of Arabidopsis thalianaM. Naydenov*, B. Georgieva, V. Baev, G. Yahubyan

Study of factors affecting sporophytic development of isolated durum wheat microsporesV. Bozhanova, Hlorst Lörz

Screening Pisum sp. accessions for resistance to Pseudomonas syringae pv. pisiM. Koleva, I. Kiryakov

Investigation on the parthenogenetic response of sunflower lines and hybridsM. Drumeva, P. Yankov

Hybridization between cultivated sunflower and wild annual species Helianthus petiolaris Nutt.D. Valkova, G. Georgiev, N. Nenova, V. Encheva, J. Encheva

Ethological and haematological indices in yearling sheep fed various dietary nitrogen sources I. Varlyakov, V. Radev, Т. Slavov, R. Mihaylov

Phosphorus fractions in alluvial meadow soil after long-term organic-mineral fertilizationS. Todorova, K. Trendafilov, M. Almaliev

Energy productivity, fertilization rate and profitability of wheat production after various predecessors I. Energy productivity of wheatZ. Uhr, E. Vasileva

Influence of mineral nitrogen and organic fertilization on the productivity of grain sorghumS. Enchev, G. Kikindonov

Influence of the farm construction, farm regimen and season on the comfort indices of dairy cowsD. Dimov, Ch. Miteva, Zh. Gergovska

Effect of the way of pre-sowing soil tillage for wheat on the development of its rootsP. Yankov, M. Drumeva, D. Plamenov

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Occurrence of grapevine leafroll-associated virus complex in the Republic of Macedonia E. Kostadinovska, S. Mitrev, I. Karov

Influence of sowing and fertilization rates on the yield and plant health of einkorn wheat (Triticum Monococcum L.)V. Maneva, D. Atanasova, T. Nedelcheva, M. Stoyanova, V. Stoyanova

Effect of stocking density on growth intensity and feed conversion of common carp (Cyprinus caprio L.), reared in a superintensive systemS. Stoyanova, Y. Staykov

Monitoring of fungal diseases of lavenderK. Vasileva

Nitrogen mineralization potential of alluvial meadow soil after long-term fertilizationV. Valcheva, K. Trendafilov, M. Almaliev

Changes in the leaf gas exchange of common winter wheat depending on the date of application of a set of herbicides Z. Petrova, Z. Zlatev

Leaves area characteristics of Betonica bulgarica Degen et Neiĉ., during vegetation1 2 1 1 1M. Gerdzhikova *, N. Grozeva , D. Pavlov , G. Panayotova , M. Todorova

Design and development of a device for measuring vacuum-pulsation parameters of milking unitG. Dineva, V. Vlashev, L. Tsanov

Agriculture and Environment

Short communications

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Instruction for authors

Preparation of papersPapers shall be submitted at the editorial office typed on standard typing pages (A4, 30 lines per page, 62 characters per line). The editors recommend up to 15 pages for full research paper ( including abstract references, tables, figures and other appendices)The manuscript should be structured as follows: Title, Names of authors and affiliation address, Abstract, List of keywords, Introduction, Material and methods,Results, Discussion, Conclusion, Acknowledgements (if any), References, Tables, Figures.The title needs to be as concise and informative about the nature of research. It should be written with small letter /bold, 14/ without any abbreviations. Names and affiliation of authorsThe names of the authors should be presented from the initials of first names followed by the family names. The complete address and name of the institution should be stated next. The affiliation of authors are designated by different signs. For the author who is going to be corresponding by the editorial board and readers, an E-mail address and telephone number should be presented as footnote on the first page. Corresponding author is indicated with *.Abstract should be not more than 350 words. It should be clearly stated what new findings have been made in the course of research. Abbreviations and references to authors are inadmissible in the summary. It should be understandable without having read the paper and should be in one paragraph. Keywords: Up to maximum of 5 keywords should be selected not repeating the title but giving the essence of study. The introduction must answer the following questions: What is known and what is new on the studied issue? What necessitated the research problem, described in the paper? What is your hypothesis and goal ?Material and methods: The objects of research, organization of experiments, chemical analyses, statistical and other methods and conditions applied for the experiments should be described in detail. A criterion of sufficient information is to be possible for others to repeat the experi-ment in order to verify results.Results are presented in understandable

tables and figures, accompanied by the statistical parameters needed for the evaluation. Data from tables and figures should not be repeated in the text.Tables should be as simple and as few as possible. Each table should have its own explanatory title and to be typed on a separate page. They should be outside the main body of the text and an indication should be given where it should be inserted.Figures should be sharp with good contrast and rendition. Graphic materials should be preferred. Photographs to be appropriate for printing. Illustrations are supplied in colour as an exception after special agreement with the editorial board and possible payment of extra costs. The figures are to be each in a single file and their location should be given within the text. Discussion: The objective of this section is to indicate the scientific significance of the study. By comparing the results and conclusions of other scientists the contribution of the study for expanding or modifying existing knowledge is pointed out clearly and convincingly to the reader.Conclusion: The most important conse- quences for the science and practice resulting from the conducted research should be summarized in a few sentences. The conclusions shouldn't be numbered and no new paragraphs be used. Contributions are the core of conclusions. References:In the text, references should be cited as follows: single author: Sandberg (2002); two authors: Andersson and Georges (2004); more than two authors: Andersson et al.(2003). When several references are cited simultaneously, they should be ranked by chronological order e.g.: (Sandberg, 2002; Andersson et al., 2003; Andersson and Georges, 2004).References are arranged alphabetically by the name of the first author. If an author is cited more than once, first his individual publications are given ranked by year, then come publications with one co-author, two co-authors, etc. The names of authors, article and journal titles in the Cyrillic or alphabet different from Latin, should be transliterated into Latin and article titles should be translated into English. The original language of articles and books translated into English is indicated in parenthesis after the bibliographic reference (Bulgarian = Bg, Russian = Ru, Serbian = Sr, if in the Cyrillic, Mongolian =

Мо, Greek = Gr, Georgian = Geor., Japanese = Jа, Chinese = Ch, Arabic = Аr, etc.)The following order in the reference list is recommended:Journal articles: Author(s) surname and initials, year. Title. Full title of the journal, volume, pages. Example:Simm G, Lewis RM, Grundy B and Dingwall WS, 2002. Responses to selection for lean growth in sheep. Animal Science, 74, 39-50Books: Author(s) surname and initials, year. Title. Edition, name of publisher, place of publication. Example: Oldenbroek JK, 1999. Genebanks and the conservation of farm animal genetic resources, Second edition. DLO Institute for Animal Science and Heal th, Netherlands.Book chapter or conference proceedings: Author(s) surname and initials, year. Title. In: Title of the book or of the proceedings followed by the editor(s), volume, pages. Name of publisher, place of publication. Example: Mauff G, Pulverer G, Operkuch W, Hummel K and Hidden C, 1995. C3-variants and diverse phenotypes of unconverted and converted C3. In: Provides of the Biological Fluids (ed. H. Peters), vol. 22, 143-165, Pergamon Press. Oxford, UK.Todorov N and Mitev J, 1995. Effect of level of feeding during dry period, and body condition score on reproductive perfor-

thmance in dairy cows,IX International Conference on Production Diseases in Farm Animals, September 11–14, Berlin, Germany.Thesis:Hristova D, 2013. Investigation on genetic diversity in local sheep breeds using DNA markers. Thesis for PhD, Trakia University, Stara Zagora, Bulgaria, (Bg).

The Editorial Board of the Journal is not responsible for incorrect quotes of reference sources and the relevant violations of copyrights.

Animal welfareStudies performed on experimental animals should be carried out according to internationally recognized guidelines for animal welfare. That should be clearly described in the respective section “Material and methods”.

Volume 7, Number 4December 2015

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