THESES OF DOCTORAL (PhD) DISSERTATION

15 Pages·2009·0.23 MB·English

Theses of Varga Zoltán’s doctoral (PhD) dissertation 1
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THESES OF DOCTORAL (PhD)
DISSERTATION

UNIVERSITY OF VESZPRÉM
GEORGIKON FACULTY OF AGRICULTURE
MULTIDISCIPLINAR SCIENCES OF AGRICULTURE
DOCTORAL SCHOOL

Dissertation advisor:
DR. VARGA-HASZONITS ZOLTÁN
DSc

EFFECT OF METEOROLOGICAL FACTORS ON MAIZE
PRODUCTION

Written by

VARGA ZOLTÁN

Veszprém
2001
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1. Introduction and aim

Due to an increasing demand for food all over the world, there has been a boost
in agrometeorological research activities in recent years. The global warming caused by
the continuously rising carbon dioxide content of air also requires detailed analysis. The
consequences of a possible climate change may be alarming even for countries having
highly developed agricultural production systems. For these reasons, we examined the
role of climate as a natural resource in agricultural production and the effect of
meteorological factors on the growth, development and productivity of plants.
This problem can be examined either by global circulation models used for
analyzing the consequences of only one given type of climate change or by determining
the relationship between the variability of climate and plants, the latter being a more
appropriate method of analysis. In this case, reactions of plants to a wide range of
climatic effects can be simulated, which greatly helps decision-making. Therefore, we
decided to use the latter method in our research on maize.
Maize is one of our major field crops. It has the second largest production area
in Hungary, which clearly indicates the primary importance of this crop. For this reason,
the research into the effect of meteorological factors on maize production should cover
the whole country.
Crops are grown under given climatic conditions and the yearly variability of
meteorological factors has an effect on plants. That is the reason why meteorological
conditions of maize’s growing season were studied and the effect of humidity and
thermal elements on the development, growth and productivity of this important fodder
plant was analyzed and modeled. The research was based on several decades long data
series and the climate-growth relationship was examined by field studies.
The results of this research help agriculture to adapt to meteorological
conditions. Moreover, variability, change or extreme effects of climate can thus be
considered as risk factors. Therefore, the effect of climate on the growth, development
and productivity of maize was modeled on the basis of an agroclimatological database

built at our department and a field study designed and realized by us.
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2. Materials and methods

When examining the problem, both basic methods of agrometeorological
research were used:
(1) an agroclimatological database built up at our Department was analyzed, and
(2) field studies were carried out in Mosonmagyaróvár between 1997 and 1999.
Thus a lot of several decades long meteorological and phenological data-series were
gathered. Mathematical statistics methods and computer softwares were used for the
analyses.
Meteorological variability of growing season was studied on the basis of the
period of 1951-90. The measurements were organized by the Hungarian Meteorological
Service. Every county was represented by data of a single meteorological station. These
stations are as follows: Győr, Szombathely, Zalaegerszeg, Kaposvár, Pápa, Tatabánya,
Martonvásár, Iregszemcse, Pécs, Kecskemét, Budapest (Pestszentlőrinc), Szolnok,
Szeged, Békéscsaba, Debrecen, Nyíregyháza, Miskolc, Kompolt és Balassagyarmat.
A monthly sum or average value of meteorological elements was used because
they characterize well the variability of climate in time and space. Not only the months
of the growing season, but also the rest of the year was analyzed. Yearly variability was
illustrated by these monthly values which showed the period of the year appropriate for
growing the plant. In terms of temperature, the period of >10°C coincides with the
growing season of maize.
Calculated and measured daily meteorological values can also be found in the
database. They are used for calculating values regarding different periods when
studying climate-development relationship. The measurements were organized by the
Hungarian Meteorological Service. The database also includes phenological data for the
period of 1960-85. Phenological stations are as follows. Early maturity group of hybrids
(FAO 300): Abaújszántó, Debrecen, Iregszemcse, Kompolt, Székkutas, Szombathely,
Tordas, mid-early maturity group of hybrids (FAO 400): Debrecen, Iregszemcse,
Kaposvár, Karcag, Mátételke, Székkutas, Szombathely, Szarvas, Tordas. These
measurements were organized by the National Institute for Breed Quality Control.
When examining the effect of meteorological factors on development of maize,
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phenological and meteorological stations were paired as follows: Abaújszántó-Miskolc,
Debrecen-Debrecen, Iregszemcse-Iregszemcse, Kaposvár-Kaposvár, Karcag-Szolnok,
Kompolt-Kompolt, Mátételke-Kecskemét, Szarvas-Szarvas, Székkutas-Szeged,
Szombathely-Szombathely, Tordas-Martonvásár.
Regression was calculated between meteorological elements and development.
First the date of phenological events was determined in numerical form (1st January is
1st, 31st December is 365th or 366th). The duration of phenological stages (in days) can
be calculated as follows:

n=F -F (1)
k (k-1)

wn=Fk−F(k−n) here F is the date of a certain phenological event and F is the date of the following
(k-1) k
phenological event. Then the effect of meteorological factors on the duration of a
phenological stage can be studied:

n=f(m1,m2,...,mk) n=f(m ,m ,…,m ) (2)
1 2 k

where m , m ,…,m are values of meteorological elements.
1 2 k
It is a well-known fact that meteorological factors strongly influence crop
yields. Therefore, agricultural and related sciences (for example agrometeorology) have
an important task to determine and quantify this effect. This study was based on the 45
years long data series of our agroclimatological database. The meteorological data used
were measured by the Hungarian Meteorological Service, and the yield data were taken
from the records of the Hungarian Central Statistical Office. The data of the above-
mentioned representative meteorological stations and yearly average yields of counties
were paired.

First we separated the agrotechnical and meteorological components by means
of a suitably chosen trend function (Varga-Haszonits, 1992) [5]. Comparing the two
groups of components, we may state that they differ from each other in time variability.
In the case of non-meteorological components, the variability is mainly caused by
human activity (using intensive varieties and new technological methods). These
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changes occur gradually because of their dependence on human, social activities, thus
tendencies of yearly variability can be calculated by means of trend functions.
Meteorological conditions can significantly change from year to year so their
effects on plants may also indicate considerable variability in time. These fluctuations
occur around “technological level” (values calculated by means of trend functions).
Good fitting was the most important when trend functions were chosen.
Separation of agrotechnical and meteorological components enabled us to
determine the complex meteorological effect. The fluctuations in plant attributes, such
as yield, are the aggregated effect of technological and meteorological components. The
question is whether technological and meteorological effects add up (additive character)
or multiply (multiplicative character). The latter was found to be the case for maize. The
yearly variations in anomalies of trend ratios were calculated for the period of 1951-95.
Values above 0 mean a favorable complex meterorological effect.
The following equation can be used for studying the effect of single
meteorological elements:

Y /Y = f(m , m ,…,m ) (3)
(t) o(t) 1 2 k

where m , m ,…,m are values of meteorological elements.
1 2 k
Radiation efficiency and water use of maize were also analyzed. Radiation
efficiency is the ratio of the energy used (by plants) and the available,
photosynthetically active radiation. Water use is the ratio of precipitation or
evapotranspiration during growing season and the amount of biomass produced.
The connection between meteorological factors and life phenomena or
productivity of plants can be examined easily if data for the whole growing season are
taken into consideration. During growing season, plants go through different stages of
development. In the course of these stages, the effects of meteorological components are
different. Several investigations have pointed out that the sensitivity of crops to
meteorological factors is different in different developmental phases. That is the reason
why the growing season used to be divided into shorter stages. Longer calendar stages
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(e.g., months) or any period of time that is of interest in terms of climate-plant
relationship can be applied. All the four methods were illustrated in the dissertation.
During the field studies, both meteorological and phenological data were
collected. Plant characteristics (leaf area, height and biomass) and soil moisture contents
were measured in every 10 days and the data of a meteorological station situated right
next to the field were also used. Comparative studies were performed of methods for
determining soil moisture as well as of relation between tendency of soil temperature
under bare soil and under covered soil. Actually, we did not quit performing the field
studies in 1999, and this enabled us to check the validity of our results on the basis of
the data of year 2000. In the field studies, hybrids of the early (FAO 300) and mid-early
(FAO 400) groups were used that are the most frequently grown hybrids in Hungary.
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3. Results

Radiation, temperature, and moisture are essential meteorological factors for
plants. Therefore, the variability of these factors (altogether 10 elements) was examined
during the growing season of maize. The humidity elements were found to be more
variable than the thermal ones, so these might have played an important role in variation
in yields. Humidity elements are limited during July and August, that is the critical
period for maize and it can largely reduce yields. The results of our studies, based on
data from the period of 1951-90, can be compared to results of similar studies analyzing
different intervals. The differences can be informative about climate variability or
change.
Figure 1. Effects of soil moisture and soil temperature on change of leaf area

The data of field studies were used to examine the temporal trend of growth
characteristics of maize. The effect of thermal time (effective degree days) on height,
leaf area and biomass of maize was modeled. Validity of results was checked on the
basis of data of 2000. The model describes the connection between thermal time and
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height very precisely, whereas the relationship of thermal time and leaf area gave a less
accurate result. In conclusion, these models are suitable for describing meteorological
effect on growth. The relationship between meteorological elements and growth was
also analyzed. First the effect of one single meteorological element was examined, so
the most important ones could be selected and the effect of several elements on growth
characteristics could be determined. Higher correlation coefficients were presented
when the effect of moisture content of soil under 40 cm (where the mass of root can be
found) and temperature (instead of sunshine duration) were determined (Figure 1). A
model describing the effect of global radiation and temperature on the amount of
biomass was built up. Variation in biomass can be determined quite well by means of
these factors.
160
140
120
s)
y
da 100
n (
o
ati 80
dur y = 1,8845x-1,0589
e 60
g R= 0,9802
a
St
40
20
0
0 0,05 0,1 0,15 0,2 0,25 0,3 0,35 0,4 0,45 0,5
Photothermal index

Figure 2. Effect of photothermal index on development of maize during the whole
growing season in Hungary

On the basis of decade-long data-series, statistics was compiled on
phenological events and phase duration of the early and mid-early hybrids. Generally,
the growing season of mid-early hybrids lasted 10 days longer than that of early hybrids
did, however, both intervals fitted well in the period with a mean temperature of over
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10°C. Three stages were separated during the growing season: sowing-emergence,
emergence-silking and silking-ripening. The relationship between meteorological
elements and development was examined during these stages. The effect of thermal
elements was greater than the effect of humidity elements. Among humidity elements,
potential evapotranspiration, which is strongly determined by thermal elements, gave
better results. Indices including temperature and radiation (photothermal index and
radiothermal index) had a very pronounced effect on the development of maize. The
results were very much alike in the case of the various stations, therefore all the data
were unified and a model describing the effect of photothermal index on development
for all stages was created (Figure 2).
On the basis of 45-year long data-series, a climate-yield model was built up.
First the meteorological and agrotechnical effects were separated and a complex
meteorological effect was calculated. Meteorologically favorable and unfavorable years
were determined then. The role of water use and radiation efficiency in achieving higher
yields was also analyzed.
1.6
1.4
1.2
o 1
ati
r
d 0.8
n
e
Tr 0.6
y = -0,0835x2 + 0,3151x + 0,7729
R = 0,5364
0.4
0.2
0
1.00 1.50 2.00 2.50 3.00 3.50 4.00
Aridity index
Figure 3. Effect of humidity on yield in Győr-Moson-Sopron County during 1951-95
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The effect of one or more meteorological elements on the productivity of
maize was analyzed. Nonlinear statistical methods were used. Intervals (months) critical
for yield were separated and the meteorological requirements of maize were determined
during these periods. Temperatures in August and moisture levels during July and
August largely affect the yields in Hungary. In addition, temperatures in springtime also
have an effect on productivity in some counties. The climatic requirements of maize and
the effect of extreme humidity values on yield were quantified (Figure 3). Figure 3
shows that aridity indices (i.e., the ratio of potential evapotranspiration and precipitation
of growing season) below 2.8 do not reduce yields. An aridity index of above 3.3
reduces yields at least by 10% and values above 4.0 result in a loss of more than 30%.
The results of this study clarify the relationship between maize and climate,
and enable the extensive use of meteorological information in maize production. The
effect of climate on the quality of yield needs to be studied further.