Papers by Valentin S KAZANDJIEV
SGEM International Multidisciplinary Scientific GeoConference� EXPO Proceedings
The last decade has been characterized by an increased frequency of climatic anomalies and their ... more The last decade has been characterized by an increased frequency of climatic anomalies and their amplitude. These anomalies affect the productivity of crops and orchards, which is directly dependent on agro-meteorological conditions. The registered tendencies to change the hydrothermal conditions in the different regions of the country sometimes are a risk factor for their productivity, especially in the initial phenological stages of the development of the fruit trees. Bud dormancy on the fruit trees from the temperate zones is a phase of development that occurs annually and enables trees to survive cold winters. To estimate the chill requirements of orchards, besides temperature data, three chronological dates must be defined: the chill accumulation start date, the deep dormancy breaking date, and the date of eco dormancy end. This study aims to assess the thermal conditions in the initial stages of development of some stone fruit plants grown in Bulgaria. There were analyzed the ...
Challenges in Agro-Climate and Ecosystem
Bulgaria is located in an area with insufficient humidification and is characterized by periods o... more Bulgaria is located in an area with insufficient humidification and is characterized by periods of the drought of varying duration and intensity. From the last 15 to 20 years, the limiting factor in agro-meteorological conditions was the drought. Agro-meteorological drought consists of the depletion of available soil water reserves in the root zone. Ultimately, the results of droughts affect the size of yields and the quality of production. The consequences of this extreme condition from a meteorological and agro-meteorological point-of-view phenomenon can be mitigated only by expanding the irrigated areas. The aim of this work was to present the tendencies in the change of the potential evapotranspiration during the studied period 1986–2015 as a result of the climate changes and also the tendencies of the conditions for occurrence of agricultural drought in the future, and also to propose an approach where using certain indicators controls the process of accumulation and consumptio...
Journal of Balkan Ecology, 2018
COST Action …
During the past decades, in connection with the development of computers, many new software tools... more During the past decades, in connection with the development of computers, many new software tools were developed to be used for agricultural research as well as for decision making. For example, crop and whole farm system modelling, pest and disease warning models/algorithms, models for irrigation scheduling or agroclimatic indices can help farmers significantly in decision-making for crop management options and related farm technologies. In research, models can be used to simulate and analyse the complex interactions in the soil-plant-atmosphere system for example in the important field of climate change impacts on agricultural production. All these modelled systems and their interactions include however many different kind of uncertainties and limitations, such as trends in technology and human activities, models representation of reality, lack of knowledge on system responses or lack of calibration data. Much research was done worldwide in the field of model development, model improvements or model comparisons. Also in Europe in many countries significant work was done in this field. The aims of Working group 1 of COST734 is a review and assessment of agroclimatic indices and simulation models relevant for various European agricultural activities. The results of an Europeanwide survey are presented in this study. It includes an overview of most used agrometeorological indices and process oriented models for operational and scientific applications, an analysis of the limitations for applications and an overview of spatial applications in combination with GIS and remote sensing in Europe.
Bulgarian Journal of Agricultural Science, 1995
Agriculture
Serious economic damages in many regions of the world were caused by the changes in agroclimatic ... more Serious economic damages in many regions of the world were caused by the changes in agroclimatic resources during the last 2–3 decades. The Balkan Peninsula is much affected by the temperatures rising, changes in the distribution of precipitation, and the increasing frequency of extreme events—basically, droughts and frosts. Bulgarian agriculture is developed under various agrometeorological conditions. The climate of the country is characterized by the atmosphere and soil moisture deficit in the time of active crop vegetation and yield formation. The aim of this research is to assess the changes in agrometeorological conditions for the growth of the main grain crops and the possibilities for reaction through agro-technologies. Furthermore, the features of contemporary varieties and hybrids of spring and autumn cereals will be taken into account. The next important factor is the specific requirements for hydro-thermal conditions at different phenological phases of agricultural crop ...
In this article are present the results of remote sensing investigations in optical and near infr... more In this article are present the results of remote sensing investigations in optical and near infrared range waves (NIR) for different soil types in Bulgaria. Through using the measured data for Spectral Reflectance Coefficients (SRC) we estimate Spectral Brightness Indexes (SBI). By the application of correlation analysis we investigate the most sensitive to soil moisture brightness indexes and their combinations. Regression model for soil moisture approximation in 0-5 cm layer by SBI utilization is obtained. The fluctuation of soil moisture for dark (tchernozem) and light (gray) soils is observed. Relations between soil moisture in 0-5 cm and 0-50 cm, 0-100 cm layers and their estimation are determined
From an agricultural point of view Bulgaria has insuffi cient and uncertain water resources. For ... more From an agricultural point of view Bulgaria has insuffi cient and uncertain water resources. For the last decades, the potential vegetation period temperature sums submit to a positive tendency and the rainfall sums – to a negative one almost all over the country. Th is is evidence for the current drought processes determined by the global climate change. Th e increasing atmospheric drought impacts negatively water content in soil, especially that one available for plants. Th e paper deals with the impact of the contemporary climate changes upon the available soil water under winter wheat- one of the most important of our country crops for the food balance. Th e data processed have been gathered from 24 sites and refer to six soil types all over the agricultural territory. Th ey cover the period of the “contemporary climate ” (1961-2000). Actualized zoning of the soil water resources and maps of the changes in the availability of soil water have been elaborated. Th e results obtaine...
Agriculture and Food, Sep 18, 2021
IOP Conference Series: Materials Science and Engineering, 2021
Introduction. The condition of the vegetation cover can be traced from Space. Aim of the research... more Introduction. The condition of the vegetation cover can be traced from Space. Aim of the research. To assess the condition of the vegetation cover in Bulgaria during the last twenty years – its distribution over the country, its change in connection with the typical climatic changes, its seasonal change. Material and methods. The vegetation index NDVI according to NASA data was used to analyze the condition of the vegetation cover in Bulgaria for the years 2000-2020. The methods used were: seasonal data decomposition, t-test, GIS methods for spatial representation of data, Fourier analysis. Conclusions. 1. During the summer months the vegetation in the eastern parts of the territory of Bulgaria is noticeably weaker than in the western parts. The influencing factors-drought and frequent fires are probably related to global warming. 2. For the territory of Bulgaria there is a seasonal rotation of the horizontal gradient of the vegetation index in a counterclockwise direction-from east...
14th SGEM GeoConference on WATER RESOURCES. FOREST, MARINE AND OCEAN ECOSYSTEMS, 2014
During the last decade climate variability and anomalies become more evident and their impact is ... more During the last decade climate variability and anomalies become more evident and their impact is more expressive. Appearances are different - sudden changes in weather conditions transitional seasons are becoming shorter with fuzzy borders, dry spells and droughts in combination with forest and field fires. Simultaneously, there are torrential rains accompanied by devastating floods that caused significant damage to agriculture. These anomalies affect on the conditions for grow of crops because 90% of the yields depend from weather conditions. The winter wheat has a long vegetation period. Development of wheat crops depends of different combinations from state of basic meteorological elements. Main purpose of this paper is to assess the agro-climatic conditions in major grain producing regions of Bulgaria to the use of agroclimatic potential of each. This investigation covers the period 1981-2010, and refers to occupied territories with winter wheat and barley. Data were analyzed for fundamental values of weather elements - maximum, minimum and average daily air temperature (°C), rainfall sum (mm). An assessment of agro-meteorological conditions during critical phases of crop values on the main weather elements - sowing winter conditions, water saving, tillering, stem elongation, earing and milk ripening. It is traced as the dynamics of the main meteorological elements and their complex effects on growth and development of crops from the calculation of some indices characterizing hydrothermal conditions.
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Papers by Valentin S KAZANDJIEV