Wpływ ekstremalnych warunków klimatycznych na względną zależność "plon - ewapotranspiracja"

The relative relationships "yield - evapotranspiration" were used long time ago. The well known linear relationship yi = 1 - ky (1 - ei), where yi is relative yield, ky - yield response factor and ei - relative evapotranspiration was proposed. It's usually assumed that ky is constant for a given crop and climatic conditions. It was found, however, that ky for late variety of maize H 708 varied through the study years (1984-1990) in the Plovdiv region ( South Bulgaria , altitude 150 m). During the dry years it was significantly higher than in the medium and humid years. The range of ky for maize in this location was 1.12-1.90, the average value being 1.50. The climate in the Sofia region (the experimental field of Chelopechene, altitude 550 m) is comparatively more humid. The two regions approximately outlined the boundaries of the appropriate economical conditions for grain maize production. The experiments in the Sofia region were carried out in the years 1994-2000. The seven years results for mean variety maize showed that the relationships "yield - evapotranspiration" and, respectively, ky varied at these climatic conditions too. The highest ky value was 1.41 for the driest year (2000) and the lowest value - 1.05 for the most wet years (1995, 1999). The value of ky for average years was 1.21. The yield response factor ky is of more significance when the relative evapotranspiration is less than 0.7-0.8. Thus, the extreme or the average values of ky could be used for the corresponding climatic regions. The relationships between ky and relative yield were established without considering irrigation.W pracy przedstawiono wyniki badań nad plonami i ewapotranspiracją dwóch mieszańców kukurydzy. Badania te prowadzono w różnych okresach siedmioletnich w dwóch odmiennych klimatycznie regionach Bułgarii. Analizowane regiony wyznaczają granice obszarów opłacalnej uprawy kukurydzy na ziarno w tych warunkach klimatycznych. Przedstawiono analizę wartości wskaźnika ky w latach suchych, średnich i mokrych. Wykazano wyraźne zależności korelacyjne między plonami a ewapotranspiracją, potwierdzone bardzo wysokimi wartościami współczynników determinacji R2. Wartości ewapotranspiracji aktualnej ETa i potencjalnej ETm wyznaczono na podstawie zaleceń FAO. Badania udowodniły, że wartość ewapotranspiracji może ulec istotnej zmianie w wyniku ewentualnej zmiany klimatu. Już obecnie obserwuje się w Bułgarii wzrost temperatury i zmniejszenie opadów atmosferycznych, co może mieć duży wpływ na plonowanie roślin uprawnych

Impact of extreme climate years on relative "yield -evapotranspiration" relationships

Abstract: The relative relationships "yield -evapotranspiration" were used long time ago. The well known linear relationship yi = 1 -ky (1 -ei), where yi is relative yield, ky -yield response factor and ei -relative evapotranspiration was proposed. It's usually assumed that ky is constant for a given crop and climatic conditions. It was found, however, that ky for late variety of maize H 708 varied through the study years (1984)(1985)(1986)(1987)(1988)(1989)(1990) in the Plovdiv region (South Bulgaria, altitude 150 m). During the dry years it was significantly higher than in the medium and humid years. The range of ky for maize in this location was 1.12-1.90, the average value being 1.50. The climate in the Sofia region (the experimental field of Chelopechene, altitude 550 m) is comparatively more humid. The two regions approximately outlined the boundaries of the appropriate economical conditions for grain maize production. The experiments in the Sofia region were carried out in the years 1994-2000. The seven years results for mean variety maize showed that the relationships "yield -evapotranspiration" and, respectively, ky varied at these climatic conditions too. The highest ky value was 1.41 for the driest year (2000) and the lowest value -1.05 for the most wet years (1995, 1999). The value of ky for average years was 1.21. The yield response factor ky is of more significance when the relative evapotranspiration is less than 0.7-0.8. Thus, the extreme or the average values of ky could be used for the corresponding climatic regions. The relationships between ky and relative yield were established without considering irrigation

Durabilité agro-environnementale d'un système d'irrigation à la raie hétérogène sous différents contextes agro-régionaux

International audienceThe aim of this paper is to evaluate the impact of distribution uniformity on environment and productivity under furrow irrigation in different agrolandscapes in Europe and propose geographically oriented irrigation options. Various situations in free drained furrow plots in France and Bulgaria are analysed by field observations and modelling. Unlike studies based on a single furrow observation, these analyses take in to account global uniformity that is experienced by plant due to irrigation water distribution (downfield and transversal) when more then 30-40 simultaneously irrigated furrows are considered. FURMOD (Popova, 1990; Popova et al, 1996) and SOFIP (Maihol, 2001; Maihol et al., 2003) models are calibrated and validated with data from field observation. Then they are used to estimate deep percolation and runoff losses provoked by any specific irrigation practices. FURMOD is a model allowing the evaluation of water distribution, deep percolation and runoff losses depending on application time and depth, soil infiltration parameters, water deficit in the root zone when lateral nonuniformity of the advance process is taken into account. The estimated water application depths (WAD) are therefore inputs of a crop model for evaluating the impact of WAD heterogeneity on crop production and nitrogen leaching. SOFIP is a simulation model allowing analysing the impact of a furrow irrigation practice on the risks of deep percolation and crop productivity. Taking into account different sources of variability (discharge inlet, infiltration parameters) at the plot scale, the prediction capability of SOFIP aims at the improvement of the furrow irrigation systems management and design. These two different approaches are compared in terms of robustness and convenience of use. The role of irrigation practice in increasing the efficiency of the use of land and water resources in the different regions is defined. It is concluded that the maintenance of environmental and productivity stability requires better distribution uniformity and land preparation in case of high irrigation requirements. Strategies of furrow irrigation development may consist of different regional techniques for improving global distribution uniformity in the irrigation plot in order to produce maximum yield and reduce deep percolation and runoff. It is recommended to reduce furrows permeability by every furrow or every other furrow compaction before first flow, improve uniformity of stream advance by applying lower inflow rates and diminish runoff by closed-end furrows rather free draining furrows for in Tarascon, South France. Improved lateral uniformity of streams advance could both save irrigation water and mitigate environmental hazards in Sofia region, Bulgaria. It could be achieved by reducing variability of inflow at the furrows head, frequent application scheduling, surge irrigation respectively in advance and recession phase