THESES OF DOCTORAL (PhD) DISSERTATION

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1 1 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

2 2 Theses of Varga Zoltán s doctoral (PhD) dissertation 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.

3 3 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 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 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 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,

4 n = F k F (k n ) n = f ( m 1,m 2,...,m k ) 4 Theses of Varga Zoltán s doctoral (PhD) dissertation 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 (1 st January is 1 st, 31 st December is 365 th or 366 th ). The duration of phenological stages (in days) can be calculated as follows: n=f k -F (k-1) (1) where F (k-1) is the date of a certain phenological event and F k is the date of the following phenological event. Then the effect of meteorological factors on the duration of a phenological stage can be studied: n=f(m 1,m 2,,m k ) (2) where m 1, m 2,,m k are values of meteorological elements. 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 abovementioned 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

5 5 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 Values above 0 mean a favorable complex meterorological effect. The following equation can be used for studying the effect of single meteorological elements: Y (t) /Y o(t) = f(m 1, m 2,,m k ) (3) where m 1, m 2,,m k are values of meteorological elements. 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

6 6 Theses of Varga Zoltán s doctoral (PhD) dissertation (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 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.

7 7 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 , 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 The model describes the connection between thermal time and

8 8 Theses of Varga Zoltán s doctoral (PhD) dissertation 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 Stage duration (days) y = 1,8845x -1,0589 R= 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

9 9 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 Trend ratio y = -0,0835x 2 + 0,3151x + 0,7729 R = 0, Aridity index Figure 3. Effect of humidity on yield in Győr-Moson-Sopron County during

10 10 Theses of Varga Zoltán s doctoral (PhD) dissertation 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.

11 11 4. Theses 1. The variability of meteorological elements during the growing season of maize in Hungary was calculated on the basis of data from The results of this research, based on a relatively huge database, can be compared to results of similar studies analyzing different intervals. The differences can be informative about climate variability or change. 2. On the basis of field studies, the effect of thermal time on growth characteristics of maize was examined in the case of two hybrids representing the main maturity groups grown in Hungary. A model describing the effect of global radiation and temperature on the amount of biomass was built up. 3. Non-linear relationship between one or more meteorological elements and development was modeled during different phenological stages of maize on the basis of decade-long data-series. Using all available phenological data, a model describing the effect of photothermal index (that contains both temperature and radiation) on development was created for all stages. 4. On the basis of a 45-year long data-series, a climate-yield model was built up. The use of such a long data-series is unusual in agrometeorology. First the meteorological and agrotechnical effects were separated and a complex meteorological effect was calculated, then 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. The role of water use and radiation efficiency in achieving higher yields was also analyzed.

12 12 Theses of Varga Zoltán s doctoral (PhD) dissertation 5. Theoretical and practical use of research In accordance with the suggestion of the World Meteorological Organization, meteorological conditions and variability of elements during the growing season of maize were studied on the basis of four decades long data series. It was necessary to analyze such a long period of time because climate determines both the kinds of crops to be grown in a given region and the time suitable for growing these crops. It is important to know the meteorological conditions of the entire country because different meteorological conditions prevail in different regions. It also contributes to the efficient utilization of this natural resource. A prosperous plant production system should be adaptable to environmental conditions. The productivity of an agricultural ecosystem mainly depends on the supply of its energy requirements (energy of solar radiation and supplementary energy). For realizing this, it is important to increase the utilization of solar radiation, thereby decreasing the quantity of supplementary energy needed for increasing crop production. To reach this goal, agricultural production should be adjusted to the environmental conditions, which requires a profound knowledge of plant-environment relationship. A plant production system is considered to be welladapted if it has a structure of production that optimally utilizes ecological conditions in the case of a given specific input. This requires the knowledge of laws of agricultural ecosystems and the methods of their application. Further progress can be made if any changes in the functioning of the system are forecast precisely. This enables the improvement of conditions necessary for reaching higher productivity. Variability is a fundamental characteristic of climate. Therefore, this year-toyear variability has various economic consequences: it can increase or reduce costs. Radiation, temperature, and moisture are essential meteorological factors for plants, that is the reason why the effect of one or more of these elements on maize were examined and modeled. Extreme values of variability can be considered as risk factors because they may result in yield losses. In the case of maize, drought is the most dangerous extreme effect, but extremely high humidity conditions can also be harmful. Threshold values of

13 13 humidity and their effect on yield were determined and they can be used for economical analyses.

14 14 Theses of Varga Zoltán s doctoral (PhD) dissertation 6. Publications Printed materials (books and journal articles): 1. VARGA-HASZONITS Z. - VARGA Z. - SCHMIDT R. - LANTOS ZS. (1997): The effect of climatic conditions on maize production. Acta Agronomica Óváriensis 39 (1-2), VARGA-HASZONITS Z. - VARGA Z. - LANTOS ZS. - KAJDI F. - VÁMOS O. (1998a): A kukorica vízellátottsági viszonyainak éghajlati elemzése 110 éves adatsorok alapján. Acta Agronomica Óváriensis 40 (1), VARGA-HASZONITS Z. - VARGA Z. - LANTOS ZS. - KAJDI F. - VÁMOS O. (1998b): A meteorológiai tényezők szerepe a kukorica termésstabilitásának alakukásában. Acta Agronomica Óváriensis 40 (1), VARGA-HASZONITS Z. - VARGA Z. (1998): A meteorológiai tényezők hatása a kukorica fenofázisainak tartamára. Növénytermelés 47 (5), VARGA-HASZONITS Z. VARGA Z. (1999): Agroklimatológia (Éghajlat és növénytermesztés). Egyetemi jegyzet. Mosonmagyaróvár. 6. VARGA-HASZONITS Z. - VARGA Z.- LANTOS ZS.- VÁMOS O. (1999a): Hazánk hőmérsékleti és csapadékviszonyainak elemzése 110 évi adatsorok alapján. Acta Agronomica Óváriensis 41 (1), VARGA-HASZONITS Z. - VARGA Z. - LANTOS ZS. - SCHMIDT R. - VÁMOS O. (1999b): A fontosabb gazdasági növények sugárzáshasznosítása. Növénytermelés 48 (2), VARGA Z. (1999): A kukorica (Zea mays L.) vegetációs periódusa alatti meteorológiai viszonyok összehasonlító vizsgálata. Acta Agronomica Óváriensis 41 (1), VARGA-HASZONITS Z. - VARGA Z. - VÁMOS O. - LANTOS ZS. - SCHMIDT R. - BUSSAY A. (2000a): Az közötti időszak termikus jellemzőinek agroklimatológiai elemzése. Acta Agronomica Óváriensis 42 (2), VARGA-HASZONITS Z. - VÁMOS O. - VARGA Z. - LANTOS ZS. - SCHMIDT R. - BUSSAY A. (2000b): Az közötti időszak nedvességi jellemzőinek agroklimatológiai elemzése. Acta Agronomica Óváriensis 42 (2),

15 VARGA Z. - VARGA-HASZONITS Z. - LANTOS ZS. (2001): A kukorica hőmérsékleti és nedvességi igényének meghatározása a terméshozamokra gyakorolt hatás alapján. Növénytermelés (accepted for publication). Dissertations: 1. VARGA Z. (1996): Az éghajlati változékonyság hatása a kukorica termesztésére. Szakdolgozat, Mosonmagyaróvár. Published lectures: 1. VARGA Z. (1997a): A nedvességi tényezők hatása a kukorica terméshozamaira. Egyetemi Meteorológiai Füzetek. Budapest. No VARGA Z. (1997b): The effect of climatic conditions on the maize production. Egyetemi Meteorológia Füzetek. Budapest. No VARGA Z. (1998): The effect of climatic conditons on maize production. ICA Summer School on Agricultural Challenges and EU Enlargement Mosonmagyaróvár VARGA-HASZONITS Z. VARGA Z: (2000): Az agrometeorológia alpvető irányzatai és várható jövőbeli alakulásuk. Magyar Meteorológiai Társaság XXVIII. Vándorgyűlése. Sopron, Published in CD.