181
SUMARY OF PHD THESIS
The research for the PhD thesis „Research on the influence of soil tillage system
on Agropyron repens (sin. Elymus repens) and Cirsium arvense crop weed growth” was
organized during the 2009-2011 period, in Cluj Napoca, within the Fruit Growing
Research and Development Station.
The research focuses on finding the influence of four methods of soil tillage on
weed growth in general, with special reference on Agropyron repens and Cirsium
arvense.
Establishing the interaction between the method of soil tillage and the weed
growth was approached starting with the fact that the presence of a species, either
Agropyron repens or Cirsium arvense, interacts with the other weed species, thus the
knowledge of total weed growth and its flower composition seems more illustrating.
The presence of the two species that the thesis referred to is directly related to the
cultivation technology in a crop rotation, specific corn-soybean-wheat crop rotation.
The results included in the thesis focuses on finding the percent in which the two
weed species are found in general weed growth.
The objectives of research are as follows:
1. Establishing the influence of soil tillage method on weed growth in corn crop;
2. Establishing the influence of soil tillage method on weed growth in soybean crop;
3. Establishing the influence of soil tillage method on weed growth in wheat crop;
4. Determining the evolution of weed growth under the influence of a soil tillage
system during the three years corn-soybean-wheat crop rotation;
5. Establishing the influence of weed growth of couch grass on corn, soybean and
wheat crop production;
6. Establishing the influence of weed growth of couch grass on corn, soybean and
wheat crop production;
182
7. Establishing the influence of weed growth of creeping thistle on corn, soybean and
wheat crop production;
The four methods of soil tillage, expressed in experimental factors and the
herbicides used during research were:
Factor A – Method of soil tillage
a1. The conventional system, worked with plough;
a2. The unconventional chisel tillage system;
a3. The unconventional paraplow tillage system;
a4. The direct sowing system
Factor B – The herbicides used
The herbicides used were differentiated depending on the cultivated plant.
The influence of the method of soil tillage on weed growth of Agropyron repens
and Cirsium arvense was tested during a three years crop rotation: corn (2009), soybean
(2010), autumn wheat (2011).
The cultivation technology for every crop culture was zone specific, only the
method of soil tillage and the use of herbicides making the difference.
The hybrid variety used in corn crop was Turda 200 variety, in soybean crop was
Triumf and in autumn wheat crop was Arieşan variety.
The influence of soil tillage system on weed growth with Agropyron repens and
Cirsium arvense was concluded through observations on total weed growth, and special
reference on the percent of these two species in general weed growth, depending on the
method for soil tillage.
Agropyron repens and Cirsium arvense weed growth was tracked down through
the number of plants per square meter and the regeneration capacity of the two species on
the field worked differently with conventional or unconventional systems.
183
Because the percent of the two species in general weed growth was low, a separate
influence of those on crop production could not be expressed, being necessary an
estimation of total weed growth.
In wheat crop the effect of soil tillage on weed growth was observed without
herbicide differentiation. The reason for this choice in wheat crop was the uniformity of
weed species identified in every soil tillage variant, no significant changes being noticed
regarding the number of species and the dicotyledonated / monocotyledonated weed ratio
that would impose herbicidal differentiation.
The field setup of corn, soybean and wheat crops is reproduced in the next
experimental field schemes. For wheat crop only two herbicides were used.
Experimental field scheme for corn crop, 2009
b1 b2 b3 b4 b5 b6 b1 b2 b3 b4 b5 b6 b1 b2 b3 b4 b5 b6
a1
a2
a3
a4
R1 R2 R3
Experimental field scheme for soybean crop, 2010
b1 b2 b3 b4 b5 b6 b1 b2 b3 b4 b5 b6 b1 b2 b3 b4 b5 b6
a1
a2
a3
a4
R1 R2 R3
184
Experimental field scheme for wheat crop, 2011
b1 b2 b1 b2 b1 b2
a1
a2
a3
a4
R1 R2 R3
Experimental conditions and experimental field features are characterized by:
from pedological point of view, the experimental field is an aluvisol-calcaric type on
gravels with a loamy clay texture in the first 40 cm and clay loam texture over 60cm.
Morphologically, the soil identified in the experimental field has the following
succession of horizons: Ap – A/C – Cka, which ensures an useful edafic volume of more
than 50 cm. Within this volume, the roots are present in the first 40 cm, being only
sporadically identified in 40-52 cm horizons and none at depths bigger than 52 cm. Its
worth mentioned that in the first 50 cm no other restricting elements were identified, like
gravel or gleic horizons or salted horizons that would limit the root system development
and implicitly, the development of plants forming the crop rotation structure.
Biological activity within the experimental field soil is in normal limits,
cervotocines and coprolites being identified in the fertile horizon of 0-40 cm depth. The
internal drainage system of soil is good even if at 60-70 cm an excess of clay is
registered; we assume that this excess do not give gleization processes because of the
20% sand presence, which favors the drainage of water excess.
Compaction degree of soil is in normal range, with values of apparent density
between 1,20 and 1,30 g/cm3.
185
The total porosity of soil is 54,0%, which ensures the minimal limit of aeration.
The compaction degree of soil in 0-10 cm depth emphasizes a very good soil
looseness, which favors in the first stage the weed seeds to reach the minimal
germination depth of 3-4 cm, but during vegetation period, in 5-6 cm depth some lack of
water problems rise, following the water evaporation and drainage towards higher depths.
This aspect was observed also at corn crop emergence, when appeared some non-
uniformities related to sowing depth.
As a conclusion, in what concerns the physical features of soil, these are in favor
of growth and development of plants used in the experiments (corn, soybean, autumn
wheat) and are not restrictive for soil tillage systems use, even if the clay content of soil ,
around 41%, is limited.
The above ascertainments are necessary for fundament the effects of soil tillage
both on weed growth and on crop production that may be registered in the experimental
field, then in extensions plots and normal culture.
The chemical features of soil in experimental field are related to soil texture,
respectively to treatments applied in pre-emergent crop, before starting the experiments.
The soil reaction (water pH) is weak alkaline on entire soil profile, with a
moderate content of calcium carbonate, having 8,5 – 9,7% in the first 40 cm, then an
increase to 14% in the 65-75 cm horizon, and then a decrease to a moderate value of
9,4%.
The humus content is medium at surface and low in depth, but traces were
identified until 100 cm, owed to a biological activity in sol, related either to a physical
displacement or a soil micro fauna’s activity.
The nitrogen content is moderate in the first 40 cm, as well as the phosphorous
content, aspect taken into consideration in the crop fertilization within the crop rotation.
186
The potassium content is high, over passing 360 ppm in the first 20 cm, 360 ppm
in 20-40 cm depth and 200 ppm at depths higher than 60 cm.
As a conclusion, the chemical features of soil do not limit the growth and
development of plants in experimental crop rotation.
The soil quality, synthetically expressed in the bonitation chart, correlated to
bonitation of relief conditions and to climatic resources, ensures framing the
experimental filed soil in class 2 of quality, with 73 bonitation points, good favorability
for corn crop, followed by wheat and soybean crop.
The soil influences both production and weed growth degree, Agropyron repens (
sin. Elymus repens) and Cirsium arvense species included.
The influence factors of soil, presented by bonitation chart, are humus reserve,
medium to high, higher useful edafic volume and ground water depth, which in case of
Cirsium arvense species have significant influence.
The bonitation conditions confirm that no atypical factors, like excess of humidity,
flood ability, pseudo-gleization, are involved in influencing the weed growth in crop
cultures, in different ways depending on climatic conditions of the experimental years.
187
ANALYTICAL DATA OF SOIL PROFILE
Horizons Ap Ao Cka Cgo Depth (cm) 5-12 25-36 67-75 103-110 Coarse sand % 3,88 4,37 0,39 0,39 Fine sand % 23,25 22,7 13,92 19,38 Dust I % 12,25 14,99 12,78 11,58 Dust II % 18,61 16,82 24,63 19,41 Clay 0,002mm % 41,98 41,12 48,28 49,24 Texture interpretation Lut
argiloasa Lut
argiloasa Argilo lutoasa
Argilo lutoasa
Scheleton % - - - - Hygroscopicity % - - - - Apparent density g/cm3 1,20-1,30 1,30-1,35 - - Total porosity % 54,0 53,8 - - Interpretation Mare Mare - - pH 8,34 8,22 8,38 8,32 Interpretation Slab
alcalin Slab
alcalin Slab alcalin Slab alcalin
Carbonates CaCO3 % 8,5 9,7 14,0 9,4 Interpretation Moderat
carbonatat Moderat
carbonatat Puternic
carbonatat Moderat
carbonatat Humus % 2,15 2,00 1,27 1,24 Interpretation Mijlociu Slab slab Slab N total % 0,169 0,164 0,116 0,113 Interpretation Moderat moderat slab Slab P205 mobile ppm 34 26 6 6 Interpretation Mijlocie mijlocie Foarte
slaba Foarte slaba
K20 mobile ppm 384 364 206 206 Interpretation Foarte bun Foarte bun Foarte bun Foarte bun SB me - - - - AH me - - - - T me - - - - V % - - - - Interpretation - - - - Other observations - - - -
188
FIŞA DE BONITARE
PENTRU STABILIREA CLASEI DE CALITATE A TERENULUI SITUAT ÎN
CÂMPUL EXPERIMENTAL Nr. ind.
Denumire indicator Cod ind.
Limite de încadrare
Coeficienţi de bonitare ARABIL
GR PB SO 3C T.m.a.(val.corectate)
08,5 8,1-9,0 1 0,9 0,9
4C P.m.a.(val.corectate)
0,650 601-700 0,9 1 0,9
14 Gleizare
00 Negleizat 1 1 1
15 Pseudogleizare
00 Nepseudogleizat 1 1 1
16/17 Salinizare/Alcalizare
00 Nesalinizat 1 1 1
23a Textura (0-20cm)
50 33-45 1 1 1
33 Panta
01 Sub 2% 1 1 1
38 Alunecãri
00 Absente 1 1 1
39 Adâncimea apei freatice
03,5 3,01-5,00 0,9 1 0,9
40 Inundabilitate
0 Neinundabil 1 1 1
44 Porozitatea totalã
+15 39-43 0,9 0,9 0,9
61 Conţinutul de CaCO3
10 8-12 1 1 1
63 Reacţia solului
8,1 7,9-8,4 1 1 1
133 Volumul edafic util
0,88 76-100 1 1 1
144 Rezerva de humus
180 161-200 1 1 1
181 Exces de umiditate
00 Fara exces de umiditate
1 1 1
Produsul coeficienţilor de bonitare
0,73 0,81 0,66
Nota de bonitare
73 81 66
Nota medie de bonitare
73
Clasa de calitate a- II-a
* GR - grâu, PB - porumb, SO - soia
189
Form climatic point of view, the experimental years 2009, 2010, 2011 are
characterized by average temperatures of 11,2 (2009), 12,6 (2010) and 11,7 (2011- July)
and precipitations with values ranging from 756,6 (2009), 710,9 (2010) and 314,4
(2011- July).
Thermal regime during experimental period 2009-2010-2011(July) in Cluj-Napoca
Temperatures (ºC)
Month Annual
average I II III IV V VI VII VIII IX X XI XII
Average 2009 1,9 2,4 4,1 13,7 18,9 19,1 21,1 18,3 14,6 12,8 5,9 2,1 11,2
Average 2010 -0,9 7,0 7,8 12,2 17,5 22,7 23,7 24,1 17,3 10,0 9,8 1,1 12,6
Average 2011 -1,5 -5,2 9,1 14,3 19,1 22,8 23,8 - - - - - 11,7
Normal over 105 years
-4,5 -2,3 3,2 9,1 14,3 17,5 19,3 18,3 14,3 9,1 3,3 -1,6 8,3
± 2009 deviation 2,6 0,1 0,9 4,6 4,6 1,6 1,8 0,0 0,3 3,7 2,6 0,5 2,9
± 2010 deviation 3,6 4,7 4,6 3,1 3,2 5,2 4,4 5,8 3 0,9 6,5 0,5 4,3
± 2011 deviation 3 2,9 5,9 5,2 4,8 5,3 4,5 - - - - - 3,4
Source: USAMV Meteorological Station, Cluj-Napoca
Rain regime during experimental period 2009 -2010 -2011(July) in Cluj-Napoca
Precipitations (mm)
Month Annual Sum
I II III IV V VI VII VIII IX X XI XII
Average 2009 19,8 27,3 26,4 29,8 105,7 64,2 116,3 113,2 119,4 75,4 39,7 19,4 756,6
Average 2010 4,0 14,4 15,6 47,2 105,3 183 121 57 63,2 28 27,8 44,4 710,9
Average 2011 23,4 1,8 7,8 39,0 67,2 80,4 94,8 - - - - - 314,4
Normal over 105 years
26,2 24,5 29,4 47,0 76,3 90,4 82,2 69,3 43,6 41,5 30,9 29,5 590,8
± 2009 deviation
-6,4 2,8 3,0 -17,2 29,4 26,2 34,1 43,9 75,8 33,9 8,8 -10,1
165,8
± 2010 deviation
- 22,2
10,1 13,8 0,2 29 92,6 38,8 12,3 19,6 - 13,5
- 3,1 14,9 120,1
± 2011 deviation
-2,8 22,7 21,6 8 9,1 10 -12,6 - - - - - -276,4
190
Results obtained
The results obtained during research period and included in the thesis attempt to
answer to research objectives.
Following is synthetically presented the influence of soil tillage systems and
chemical treatment system for every crop in rotation, with reference to general weed
growth and Agropyron repens and Cirsium arvense species percent.
The special reference for the two species is made because of their specific
breeding particularities, behavior towards the method for soil tillage and the weather
course.
CORN
The results concerning the corn crop weed growth and corn production validates
the direct influence of soil tillage and of herbicides, depending on the variant used.
The analysis of weed growth degree confirms the occurrence of a diversified weed
growing, made of 20 weed species pertaining to 4 groups, annual and perennial
monocotyledonated, annual and perennial dicotyledonated.
The first analysis of registered data on weed number per m2 emphasizes the fact
that the plough working system is able to reduce the degree of weed growth more than
the other experimental systems applied.
Chisel and paraplow working systems induce an increase in weed growth,
compared to the ploughed witness, with 31% for chisel and 22% for paraplow.
The direct sowing in stubble contributes to an increase in weed growth by 48%
compared to ploughed witness and by 17% compared to chisel and paraplow working
variants.
191
Considering the higher number of weeds per m2 observed even in the young
vegetation phase of corn, we assume that none of the 4 working systems of soil is able to
solve the problem of weed control in corn crop on soils with features similar to those in
the experiment and normal climatic conditions. If in the first step we estimated the
number of weeds/m2, in the next steps we observed the appearance of other weeds, the
first ones being very well developed, practically compromising the crop from
economically point of view.
A second significant element concerning the weed growth, after the number of
weeds/m2, is the flower composition of weed species. The results showed a higher
percent of dicotyledonated weeds compared to monocotyledonated ones, in all systems
for soil tillage, with slightly differences between them. Thus, in ploughed variant, the
dicotyledonated species (59) represents 184,37% compared to monocotyledonated
species (32); for chisel variant, the dicotyledonated species represents 164,44% compared
to monocotyledonated ones and for paraplow variant the percent is 177,59 compared to
monocotyledonated. For the direct sowing variant the dicotyledonated species represents
159,61% compared to monocotyledonated.
The third significant element is the high percent of annual weeds compared to
perennial ones, in all working variants for soil tillage, thus annual weeds being 3-4 times
more per surface unit compared to perennial ones.
Because the thesis focuses on the relationship between two perennial weed
species, Agropyron repens and Cirsium arvense, with the method for soil tillage, we can
observe that by comparison to the witness variant (ploughed), the other 3 working
systems showed a higher number of Agropyron repens (with 3 to 5 plants), and Cirsium
arvense (with 3 plants).
As for the percent of these 2 weed species, couch grass and creeping thistle, no
significant differences appear between the unconventional systems and direct sowing,
with one observation: paraplow system has a better control of couch grass than chisel
192
system, for Cirsium arvense no differences being noticed. The reason for this observation
is the fact that the paraplow, as well as the plough, cuts part of the root system of couch
grass, diminishing the vigor of the plants and their early start in vegetation.
15 days after the corn crop sprouting in the variant were no work has done for crop
maintenance and no herbicide was used, the total number of weeds / m2 was 91 for
ploughed variant, 104 for chisel variant, 111 for paraplow variant ad 135 for direct
sowing variant.
The influence of soil tillage system on weed growth in corn crop depending (2009)
Soil working
system
Total number of weeds (no/sqm)
Total
from
which:
Monocotyledonated Dicotyledonated
Total
from
which:
perennial
annual
Total
from
which:
perennial
annual
a1:plough 91 32 7 25 59 10 49
a2:chisel 104 45 11 34 74 15 59
a3:paraplow 111 40 9 31 71 12 59
a4:direct
sowing
135 52 12 40 83 14 69
Weed growth is significantly influenced by the interaction between the soil
working system and the herbicides used.
The analysis of data referring to chemical control variants confirms a maximum
value for weed growth in variant 6, no herbicide used, were the weed control was covered
only by soil tillage.
The minimal weed growth was identified in variant 2, were the number of weeds
was 23 plants/ m2, followed by variant 4, and were the number of weeds per m2 was 26.
for variants b1 and b4, intermediary values of 37 plants/m2 were registered.
193
Considering the variant 6, no herbicide used, as a witness, by pre-emergent
herbicide treatment with Guardian (2l/ha) or post-emergent treatment on stubble with
Roundup (4l/ha), the weed growth is reduced by 65,75%, having the same flower
composition with the one identified in experimental field.
By completing the total herbicide treatment with a post-emergent one with
Ceredin Super 40, 1l/ha dosage (b2), the weed growth is reduced by 78,71%, the effect of
post-emergent treatment being 12,96%.
The same beneficial effect of reducing the weed growth is observed for post-
emergent chemical treatment with Ceradin, and for pre-emergent treatment with
Guardian, but in this case, the Ceradin effect is only 10,18%.
As for the total chemical treatment with Roundup, compared with pre-emergent
chemical treatment with Guardian, the control effect is the same, at least in what concern
the total number of weeds /m2 determined 15 days after treatment.
By comparing the weed growth reduction in all variants were herbicides were used
with the soil tillage effect, it can be stated that the plowing, as basic tillage, is not able to
ensure weed control, the alternatives being pre-emergent herbicide treatments (that
controls the monocotyledonated perennial and even annual weeds) completed with post-
emergent treatments for dicotyledonated weeds control.
In what concern the two species, Agropyron repens and Cirsium arvense, the
solution is total chemical control with Roundup and even pre-emergent with Guardian.
Cirsium arvense specie is harder to control, being identified in higher numbers in all
treatment variants, pre-emergent, pre-emergent and post-emergent or only post-emergent.
The herbicide treatment system influenced both the number of species and the
ratio between different weed groups.
The highest number of species, 11, was registered in no herbicide variant and the
minimal number in variant 4, with both pre-emergent and post-emergent treatment.
194
In what concerns the ratio monocotyledonated / dicotyledonated weeds, it is in
favor of dicotyledonated ones in variants b1, b3, b6, were only pre-emergent or no-
treatment was applied.
For the variants were only post-emergent treatments were applied (b5), the
dicotyledonated weeds were significantly reduced, also in the variant when Ceradin
Super (1l/ha) was applied on an agro fond with total Roundup chemical control in spring.
The structure of weed growth degree with respect to monocotyledonated and
dicotyledonated weeds is in favor of dicotyledonated and especially of annual
dicotyledonated.
The degree and structure of weed growth are elements forming the base of weed
control system and of choice patterns between pre-emergent and post-emergent treatment
or the combination of the two. The answer to this technical problem is given by the
economical efficiency, established at the end for every control system used.
Taking into consideration variant 6 (no herbicidal treatment applied) as witness
variant, in all other 5 control systems the weed growth degree is reduced; this means that
for paraplow variant is a confirmation that any soil tillage has an influence on weed
growth especially when accompanied by chemical control ways.
The number of weed plants identified in the field in chemical treatment variants is
highest for variant 5, when only post-emergent treatment with Ceredin 1 l/ha was applied.
The big number of weed plants is motivated by the lack of control over
monocotyledonated species, which in this variant is virtually equal to dicotyledonated
species, and by the fact that Ceredin doesn’t fully control all species, for instance
Santhium strumarium, Poligonum persicaria and Atriplex patula being identified in
relatively high number per m2.
The lowest number of weed plants was identified in variant 4, when pre-emergent
Guardian 2 l/ha and post-emergent Ceredin 1 l/ha were used.
195
For variants 2 and 3 were identified virtually an equal number of weed plants per
m2.
When related to Agropyron repens and Cirsium arvense species, the differentiated
treatments confirm the effect on reducing the number of plants / m2 from 11 to 2, in the
case of Agropyron repens, and from 10 to 3-4 plants /m2 in the case of Cirsium arvense.
In the case of paraplow tillage also, total herbicidal treatment with Roundup do not
totally reduce the 2 species.
The fact that the 2 species are still present in the field, even if in a smaller number,
it is explained also by the deeper placing of root system in soil and by the fact that no
furrow turning up occurs and the root system is not subjected to more stress factors, like
frost in the winter and excessive heat during summer.
The weed growth in direct sowing variant is maintained at highest level from all
experimental plots, with a significant percent of annual monocotyledonated and
dicotyledonated weeds. Chemical treatments influence also in these plots the weed
growth degree.
The highest weed growth appears in variant b6, being identified 128 weed plants /
m2, compared to the lowest value of 57 weed plants/m2.
The weed control degree range between 46,1 – 55,47% in variants where a total
herbicidal treatment with Roundup took place and post-emergent with Ceredin 1 l/ha.
The effect of Ceredin is around 9,37%, when annual dicotyledonated weeds are
dominant.
For pre-emergent chemical treatment with Guardian and post-emergent with
Ceredin, weed control degree ranges between 42,19 – 54,69%, smaller in comparison to
Roundup variant. The effect of Ceredin in this variant is 12,50%. The analysis of these
data shows that when using a pre-emergent chemical treatment, Roundup is preferred
196
over Guardian, the control degree being 46,1% for the first herbicide and 42,19% for the
second.
Ceredin herbicide is more effective in variant that uses Guardian, probably due to
remaining dicotyledonated weeds, for which ensures a better control.
When used alone, like in variant b5, Ceredin herbicide achieve a 45,54% weed
control, lower than the total herbicide control with Roundup.
The decrease of weed growth degree because of soil tillage and herbicides is
exemplified also by the crop productions in corn culture.
The analysis of production yields emphasizes crop productions ranging between
4355 – 6356 kg/ ha corn grain, regardless the soil tillage system.
By comparing the crop yields, we observe the highest value of 6356 kg/ ha for
plough tillage system at 28030 cm depth. The explanation is assigned to the positive
effects that the plowing has on water conservation in soil, weed control and enhancing
the microorganisms activity through a better heating of soil during first stage of
vegetation; this favors the better starting in vegetation in the ploughed variant compared
to the other variants. The better start of corn plants in this variant is maintained during the
vegetation period, the plants forming earliest breeding organs (panicle and silk), and at
maturity the water content was lowest.
The soil tillage systems with chisel (a2) and paraplow (a3) registered production at
80-84% of the witness variant (ploughed) value. The 20% difference in minus for chisel
variant and 16% for paraplow variant is related firstly to the higher weed growth degree
registered in this two soil tillage systems. To this is added the less favorable interaction
with fertilizers and the reduction of soil compaction degree, compared to the field where
soil was mobilized by plowing.
197
In variant 4 (a4) only 68% of the witness variant (ploughed) crop yield is
achieved, which raise the question over the economical efficiency of this system for the
corn crop in Cluj Napoca conditions.
Synthetically, considering the ploughed tillage system as witness variant, all the
other 3 systems (a2, a3 and a4) gave crop yields between 4355 and 5082 kg /ha, with
very significant negative differences, with limits between 984 and 1274 for paraplow and
chisel, respectively 2001 kg /ha for direct sowing.
Interaction herbicide – soil tillage – crop yield can be synthetically expressed as
follows:
- for ploughed variant (a1) the best option is pre-emergent herbicide treatment with
Guardian, which gives crop yields benefits of 19%, followed by option with
Guardian and Ceredin, with crop yield benefits of 15%.
- The variant with only post-emergent treatment is not viable, even for ploughed
soil because the presence of annual and perennial monocotyledonated weeds
diminishes the crop yield to 89% of the crop yield of witness variant treated with
Roundup 4 l/ha.
- For chisel and paraplow variants, any of the herbicide treatments applied in b2, b3
and b4 variants is an alternative in comparison to witness treated with Roundup 4
l/ha, the crop benefits for b2 variant ranging between 8 and 11% over a2 and a3
agro fond, and for b3 variant ranging between 2 and 8% over an a2 and a3 agro
fond. Guardian 2 l/ha and Ceredin 1l/ha treatments gave the highest crop benefits,
ranging between 17 and 19% compared to witness variant treated with Roundup 4
l/ha.
- In the plots worked with chisel and paraplow, the only post-emergent Ceredin 1
l/ha treatment is not a solution because the crop production is only 92-95% of the
witness variant treated with Roundup 4 l/ha.
198
SOYBEAN
The soil tillage systems with plough (a1), chisel (a2), paraplow (a3) and direct
sowing (a4) influence the weed growth degree, namely the number of species, the
monocotyledonated/dicotyledonated ratio, and the annual or perennial character of
weeds.
The influence is greater on the weed growth degree and less on number of species.
In general, the species are the same both for annual and perennial monocotyledonated,
the differences being noticed in regard with annual dicotyledonated species. In what
concerns the monocotyledonated/dicotyledonated ratio, the dicotyledonated species have
a higher percent in all soil tillage variants.
A particular element is the presence of Agropyron repens and Cirsium arvense
species, their frequency being higher in chisel, paraplow and direct sowing variants
compared to ploughed variant. This is a significant aspect coming from our observations;
it seems that working the field with the three variants leads to a weed growth of the two
species, for instance in case of couch grass was registered a significant increase from 4 to
20 weed plants in a short period of time, approximately 2 weeks after sowing the soybean
culture.
Synthetically, the weed growth in soybean crop depending on soil tillage system is
confirmed by a variation of weeds number / m2 from 94 (in variant worked with plough)
to 157 (in direct sowing variant). Based on the registered data, we can estimate an
increase by 30,85% of weed growth in paraplow variant, respectively by 138,29% in
chisel variant, compared to variant 1, plough worked soil. The 31-38% increase in the
unconventional variants paraplow and chisel is significant and imposes a change of weed
control strategy, due to the pronounced early start of weed growth which will have an
influence on soybean crop production.
199
The degree of weed growth reaches 167,02% in case of direct sowing variant,
which is in accordance to the specialty literature data, which mentioned a higher weed
growth in direct sowing variants.
Synthetically, in what concerns the degree of weed growth in soybean crop related
to soil tillage system, it can be concluded that the plowing ensures the best weed growth
prevention, with only 94 weed plants/m2 compared to the paraplow variants, where weed
growth increase by 30%, in chisel by 38% and in direct sowing variants by 67%.
The soil tillage system influences the total weed growth but also the
monocotyledonated/dicotyledonated ratio, in all variants the dicotyledonated weeds being
dominant, with a 60% compared to monocotyledonated weeds. Consequently, the weed
control strategies have to comprise, in a mandatory manner, dicotyledonated weed
control herbicides because regardless the soil tillage system, this weed group is dominant.
In relation to annual or perennial character of species, the annual ones have a higher share
compared to perennial species.
The Agropyron repens and Cirsium arvense species grow significantly in chisel
and paraplow working variants, 15-17 plants/ m2 compared to 4 plants in ploughed
variants. In the case of direct sowing variant, Agropyron repens specie grow to be 5 times
more present compared to ploughed variant, and this after a short period of time after
starting the culture.
The Cirsium arvense specie is increasing its number of plants in unconventional
variants, reaching to 19 plants / m2 compared to 12 in ploughed variant.
It can be stated that the soil tillage system influences both the total degree of weed
growth in soybean crop and the frequency of dicotyledonated species in spite of the
monocotyledonated ones, respectively increase of weed growth of Agropyron repens and
Cirsium arvense perennial species in all ploughed variants.
200
The total degree of weed growth related to chemical treatment variants and soil
tillage systems is presented in the Figure below, confirming that the weed growth is
lowest on the ploughed field regardless the chemical treatment variant, and is highest for
direct sowing variant.
The chisel and paraplow tillage systems behave similarly in all chemical treatment
variants, with differences from a treatment to another, but always the weed growth is
higher on the plough field and lower on direct sowing field.
- a1 - a2 - a3 - a4
Gradul de îmburuienare în funcţie de lucrarea solului şi erbicidele folosite
Lucrarea solului Varianta de erbicidare
b1 b2 b3 b4 b5 b6
Arat a1 37 18 32 38 32 109
Cizel a2 65 55 64 57 57 132
Paraplow a3 68 56 66 62 60 134
Semănat direct a4 73 64 72 78 79 157
0
20
40
60
80
100
120
140
160
b1 b2 b3 b4 b5 b6
The soil tillage systems and the herbicides used have influenced the weed growth
of the culture and consequently, the crop yields obtained in the culture year.
The soil tillage systems in variants a1-a4, ploughed, worked with chisel, paraplow
and direct sowing, ensure soybean crop productions ranging between 2025 kg/ ha for
direct sowing variant and 2499 kg/ ha for ploughed variant; the other variants ensure crop
productions between 2167 – 2278 kg/ ha.
201
Compared to witness variant a1, the other working variants of soil allowed
soybean productions of only 81-89%, the differences being very significant negative,
meaning that can be achieved over 2000 kg/ha productions if soil is worked with
paraplow, chisel or direct sowing, but with a minus in crop production of 10,9 to 13,3 %
when using chisel or paraplow, respectively 18,9% when direct sowing is applied in
stubble.
WHEAT
The influence of soil tillage system on weed growth emphasize a different degree
in weed growth depending on tillage system; thus, compared to witness variant with
plough, where 85 plants/mp were identified, in chisel and paraplow working systems the
number of weed plants range between 104-105, meaning an increase with 22-24%. In the
case of direct sowing, the weed growth degree is the highest, reaching 141 plants/mp,
meaning an increase with 65,88%.
The weed growth emphasizes also the percent in which Agropyron repens and
Cirsium arvense appear depending on the soil tillage system; thus, for Agropyron repens,
from plough system to chisel and paraplow, the weed growth degree increase with 37%,
and with 50% in the case of direct sowing.
In the case of Cirsium arvense specie, passing from the classical system to
unconventional system means an increase in appearance with 36% for chisel and
paraplow, and over 100% in case of direct sowing in stubble.
Following a chemical treatment with Icedin Super 1 l/ha, the weed percent reduces
significantly for dicotyledonated species, but annual and perennial monocotyledonated
remain unchanged. In case of perennial dicotyledonated species, a decrease was observed
right after chemical treatment and an increase before harvesting, due to weed breeding
regeneration system. At harvest time, the degree of weed growth is different depending
202
on the tillage system, with 27% higher for unconventional variants (paraplow and chisel)
and with 82,7% for direct sowing.
Synthetically, the degree of weed growth depending on tillage system, identified
before harvest time is maintained also at the harvest time.
The wheat production in 2011 confirms the efficiency of unconventional systems
in soil tillage as cultivation technology.
The level of productions ranged between 4067 kg/ha for direct sowing variant and
4632 kg/ha in case of ploughed variant.
The variance analysis emphasizes that in culture year 2011, the unconventional
systems variants registered decreases in crop production with 8-10% for paraplow and
chisel variants, compared to ploughed variant.
The direct sowing variant permitted a minus of 12,2%, meaning approximately
565 kg/ha of wheat.