Probability Of Frost Research Articles

Four decades in the vineyard: the impact of climate change on grapevine phenology and wine quality in northern Italy

The wine sector, among the most profitable agricultural segments, has been markedly affected by the ongoing climate change impacts, such as warmer climate conditions with higher frequency of extreme temperatures and a trend of decreasing precipitation. All this results in higher evaporative demand and therefore higher occurrence of water stress events leading to advancement of temperature-sensitive phenological stages (e.g., budburst and ripening). Such negative effects eventually affect berry development and quality, especially in historically valuable viticultural areas, forcing winegrowers to work within a compressed harvest period to maintain wine typicity. In this work we examined the relationship between environmental variables (air and soil temperature, relative humidity, precipitation, and solar radiation), phenology, berry, and wine quality for the two varieties (Chardonnay and Teroldego) in Trentino Alto-Adige/South Tyrol (Italy) over 36 years. Huglin Index (a bioclimatic heat index), growing degree days (measure of heat accumulation), and overall mean temperature showed linear increase (p < 0.001) in the last years, while no variations were recorded for precipitations. Despite no major effects being observed for phenological interval lengths, the onset of most of the phenological stages for both varieties had significantly (p < 0.001) advanced. However, i) early budburst pushed the budburst-flowering interphase by -1.2 days every two years toward putative colder periods with increased late frost probability and potential slower phenological progression towards flowering, and ii) early veraison shifted the veraison-ripening interphase by 0.25 day per year into warmer periods that oppositely impose faster phenological advancement. Hence, a substantial equilibrium in the seasonal growing length over years was maintained. Potential carry-over effects from the previous season were observed, particularly associated with heat requirements to unlock early phenological events, raising additional concerns on the additive effects of climate change to viticulture. Generally, white wine quality increased (p < 0.05) over the years, while red and sparkling wines remained unaffected. This was putatively related to accurate harvest date decision-making dictated by berry quality parameters: sugar-to-acidity ratio for Chardonnay and bunch sanitary status for Teroldego. Overall, this work provides evidence of the dynamics involved in climate change, and, to our knowledge, its overlooked effects on viticulture, thus providing new insights that can contribute to further developing adaptive strategies.

Changing Climatic Conditions in Czechia Require Adaptation Measures in Agriculture

Changes in climatic conditions increase risks associated with crop production in certain regions. Early detection of these changes enables the implementation of suitable adaptation measures in the local area, thereby stabilising agricultural production. Our analysis shows a significant shift in climatic conditions in Czechia between 1961 and 2020. We examined the changes in observed temperature conditions, precipitation distribution, drought occurrences, and frost incidents at a high resolution (0.5 × 0.5 km). The outputs show a significant increase in air temperatures and drought occurrence. Temperature totals above 5 °C in 1991–2020 were 15% higher than in 1961–1990. Furthermore, the relative change in totals above 10 °C was 26% after 1991. Over the last 30 years, drought incidence was four times more frequent than in 1961–1990, particularly in spring. In contrast, no significant changes in the distribution of precipitation occurred, and there was a slight decrease in the probability of frost during the growing season. Ongoing climate change brings warmer and drier conditions to higher-altitude regions in Czechia. Assessing climatic conditions on a global scale is less precise for relatively small and topographically diverse countries like Czechia due to coarse resolution. Therefore, a high-resolution analysis is more appropriate for these countries.

TECHNICAL PROPOSAL FOR MODIFICATION OF MAIZE SOWING DATE IN THE FUERTE-MAYO REGION, SONORA, MEXICO

Maize is the second most important crop in southern Sonora, Mexico, so it is an asset for the economy of the region, and it is highly relevant for the fall-winter crop pattern. The Fuerte-Mayo region is conducive for maize high grain yield potential; however, farmers used to establish the crop in a period of high frost occurrence. Therefore, the objective of this work was adjust the sowing date in order to optimize grain yield per hectare and escape the frost and heat risks. Experiments were established in the Fuerte-Mayo region which is located in the southwestern part of Sonora, during the crop season 2016-2017. Five commercial fields sown on different dates and in different areas of the region were selected for a follow up of the different phenological stages. Climatic information was taken close to the crop, by placing digital sensors within three of the fields; also, temperature data was taken from the automated weather stations from Module 01 and Zapata which belong to the weather network of the National Water Commission (CONAGUA), from October to June during the years 2015 to 2017, in order to identify months with high probability of frost and heat risks. Based on the temperature recorded by the digital sensors and the development of maize in those fields, three climatic zones were detected for avoiding the possible frost and heat risks: from November 15 to December 15 for early hybrids in a cold zone (central and northwest of the region), intermediate hybrids in the intermediate zone (central and east), and late hybrids in the warm zone (southeast and west). From November 15 to 30 for intermediate hybrids in the cold zone, and late hybrids in the intermediate zone, and from November 15 to December 31 for early hybrids in the intermediate and warm zones, and intermediate hybrids in the warm zone.

МЕТОДИ ТА ПЕРСПЕКТИВИ СЕЛЕКЦІЇ ЦУКРОВОЇ КУКУРУДЗИ АДАПТОВАНОЇ ДО УМОВ ЦЕНТРАЛЬНОГО ЛІСОСТЕПУ УКРАЇНИ

The aim of the research is selection and genetic improvement of the source material of maize silica and sugar subspecies by methods of classical selection and experimental mutagenesis and synthesis on their basis of high-yielding, adaptive hybrids capable of stably realizing their yield potential in different growing conditions. Research methodology. Field experiments were conducted at the Cherkasy State Agricultural Research Station NSC "IZ NAAN", located in the central Forest-Steppe of Ukraine (Smila) during 2020-2021. The period of action of active temperatures (above 10 ° С) begins on April 20–28 and lasts 155–180 days. The probability of frost to -3 ° C during the sowing of corn (III decade of April and the first decade of May) is 10 and 5 %, respectively, and during ripening (September – first half of October) from 1 to 30 %. Sowing of the experimental material was carried out in the third decade of April in early May. During the growing season, phenological observations were made, during flowering the plants self-pollinated under parchment insulators, crossbreeding, evaluation and selection of the best samples were performed. Common field, laboratory and statistical research methods were used. Research results. Based on the morphobiological characteristics and assessment of the set of features of the samples of the sugar corn collection, the length of the period from emergence to flowering to 75 % of the panicles was determined, early-maturing samples were selected. When studying the genetic variability of the characteristics of the performance of inbred lines such as weight and length of the head, the number of rows of grains revealed the best lines, the average of which differs significantly from the standard. Based on genetic analysis of performance traits, it has been shown that the selection of starting material by cob weight and length may be most effective, as under favorable conditions these traits are controlled by additive genes, while other traits play a crucial role. Conclusions. The frequency of the obtained more productive self-pollinated lines on the original hybrid material with a significant excess of control indicators for such elements of productivity as cob weight, length and number of rows of grains is 7.19 ± 1.36 %. Selection based on "number of rows of grains" is effective, the best multi-row lines are selected based on genetic sources from Australia. As a result of the analysis of the sugar content in the grains, samples with a sugar content of 8.6% in the top sugar and 5.8 % in the white corn were selected. The coefficient of inheritance of quantitative traits, such as cob weight, length, number of rows of grains, number of grains in a row, is 0.71–0.93, which indicates the possibility of successful selection of these traits. All studied numbers exceed the hybrid standard by cob weight and number of rows of grains. Numbers 269, 272 and 276 and 277 were significantly better in terms of yield, with yields of 15.7–19.8 t/ha.

Frost Risk and Rural Insurance in Brazil

Abstract In developing countries, such as Brazil, farmers are susceptible to extreme events.The Brazilian federal government created insurance programs to mitigate extreme event effects, such as frost, called “Programa de Subvenção ao Prêmio do Seguro Rural”. Frost is an atmospheric phenomenon that causes damage to plants due to low temperatures that exceed their resistance to freezing. This paper seeks to verify the risk level of frost in Brazil, connecting this information with farmers, who contracted Rural Insurance to protect themselves from this extreme event. To reduce possible biases in calculating the frost probability, this study uses two climatological databases. The majority of the Brazilian territory has very low probabilities of this phenomenon occurring. In the databases used to verify the probability of a temperature below 2 °C, the data proposed by Sheffield paper, show that, in part of the Brazilian territory, there is less chance of frost than Xavier's data. Regardless of the database used, in Brazil, there are farmers who contract frost insurance in areas where the risks are close to zero.

The study of frost occurrence and risk analysis in Indo-Gangetic Plains of India during recent decades

Frost, an important meteorological extreme event has discernible impacts on agricultural crops specifically in Indo-Gangetic plains. The information on time of occurrence of frost and its frequency can help in reducing the risks and avoidable losses due to frost. The study investigated the occurrence of frost indices viz., onset, cessation and frost-free duration at nine locations in six States in Gangetic Plains of India during November to March (151 Days) using daily minimum temperature from 1980 to 2015. The multiple risk levels (90%, 70% and 50%) were used to determine the occurrence of frost probability for all frost indices. Trends in the frost indices were analyzed using the non- parametric Mann-Kendall test. The results showed the onset of frost mostly in December and January, whereas cessation of frost was observed during January to March with variations in date of onset and cessation from one location to another. The mean value of frost duration varied between 42 days at Amritsar to 2 days at Delhi during past 36 years. Number of frost days showed negative trends reflecting reduction in duration of frost. The rate of decrease in frost duration ranges from 0.5 day to 1.5 days per decade depending on the location. Trends for onset, cessation and frost-free duration were inconsistent at different stations.

Experimental Evaluation of Multiple Frost Heaving Parameters for Preflawed Granite in Beizhan Iron Mining, Xinjiang, China

Ice-driven mechanical weathering in cold regions is considered a main factor impacting the stability of rock mass. In this work, the response surface method (RSM) was employed to evaluate and optimize the multiple frost heaving parameters to seek the maximum frost heaving force (FHF), in combination with experimental modeling based on a specially designed frost heaving force measurement system. Three kinds of rocks were prepared with parallel flaws in it having different flaw width, length, and cementation type, and these factors were used to fit an optimal response of the maximum FHF. The experimental results reveal five distinguished stages from the frost heaving force curve, and they are inoculation stage, explosive stage, decline to steady stage, recovery stage, and sudden drop stage. The sensitivity analysis reveals the influential order of the considered factors to peak FHF, which is the rock lithology, flaw width, flaw cement type, and flaw length. For low-porosity hard rock, increasing flaw width, flaw length, and flaw cement strength can improve the probability of frost heaving failure. It is suggested that rock lithology determines the water migration ability and influences the water-ice phase transformation a lot.

Modelling phenology to probe for trade-offs between frost and heat risk in lentil and faba bean

Extreme temperatures at critical developmental phases reduce grain yield. Combinations of sowing date and cultivar that favour faster development reduce the likelihood of heat stress but increase the risk of frost at critical phases. Current models are unable to predict pulse yield in response to frost and heat, hence our focus on phenology. Our aim was to model phenological variation with sowing date and cultivar for lentil and faba bean against the climatic patterns of frost and heat in 45 Australian locations that spanned 29 °S-41 °S, 11−340 m.a.s.l., and 1−423 km to the coast.For both crops, modelled mean and standard deviation of time to flowering were close to actuals and mean prediction error was below 5%. Comparison of actual and modelled time to flowering returned: r = 0.89 (n = 121, P < 0.0001) and modelling efficiency = 0.73 for lentil, and r = 0.96 (n = 123, P < 0.0001) and modelling efficiency = 0.84 for faba bean.The critical period for yield determination was assumed to span from flowering to 200 °Cd after flowering. Curves fitted to the time-course of frost (< 0 °C) and heat (> 34 °C) probabilities between 1957 and 2018 were used to estimate the date of 10 % frost probability and the date of 30 % heat probability as the boundaries of a frost-heat risk window for the critical period. Out of the 45 locations, 12 were frost-free but with risk of heat, 7 were heat-free but with risk of frost, 3 were frost- and heat-free, and 23 featured a window defined by both frost and heat boundaries. Frost variables discriminated locations more strongly than heat variables. Geographical patterns in thermal regimes emerged that were associated with latitude, altitude and continentality.Realised warming between 1957 and 2018 advanced the time to 200 °Cd after flowering and shortened the critical period in most locations, particularly in early-sown crops. Comparisons of the probability curves of frost and heat between 1957–1985 and 1986–2018 showed, with few exceptions, an asymmetry between delayed late frost (up to 44 d) and earlier heat onset (up to 11 d), with a narrowing of the frost-heat risk window from 46 to 90 d for the period 1957–1985 to 34–64 d for 1986–2018.We identified a dominant role of frost as (i) the main discriminating factor among geographically distinct locations, (ii) the main source of variation of the frost-heat window, and (iii) a putatively increased risk factor with climate change. Adaptation to frost in the critical period for yield is important for pulses despite warming trends. Increased frost tolerance can directly improve yield and indirectly contribute to reduce risk of heat and drought later in the season.

Probability of Spring Frosts, Not Growing Degree-Days, Drives Onset of Spruce Bud Burst in Plantations at the Boreal-Temperate Forest Ecotone.

Climate warming-driven early leaf-out is expected to increase forest productivity but concurrently increases leaf exposure to spring frosts, which could reduce forests' net productivity. We hypothesized that due to their damaging effect on buds, spring frosts exert a stronger control on bud phenology than do growing degree-days. We monitored bud flush phenology of three white spruce seed sources (one local seed source from the boreal mixedwood forest and two seed sources from the temperate forest), one black spruce seed source originating from the boreal mixedwood forest and four nonlocal Norway spruce seed sources in 2016 and 2017 in two plantations located on both sides of the temperate-boreal mixedwood forest ecotone in eastern Canada (Quebec). We aimed to determine inter- and intraspecies variations in bud break timing and sensitivity to air temperature and photoperiod. We expected that bud break timing for boreal species and seed sources would be better synchronized with the decrease in frost probability than for nonlocal species and seed sources. We used mixed binomial regressions and AICc model selection to determine the best environmental variables predicting each transition from one stage of bud phenology to the next. At both plantation sites, white spruce bud flush began and ended earlier compared to black and Norway spruce. Buds of all spruce species were sensitive to frost probability for early phenological stages, whereas growing degree-days controlled the remaining stages. Photoperiod sensitivity was higher for white spruce compared to black and Norway spruce and reached its maximum in the temperate forest. At intraspecies level, the two southern white spruce seed sources opened their buds earlier than the local source and were more sensitive to photoperiod, which increased their exposure to spring frosts. Onset of spruce bud flush is driven by spring frosts and photoperiod, but once started, bud phenology responds to temperature. The high photoperiod sensitivity in white spruces could counterbalance climate warming and limit future premature leaf-out, whereas the low photoperiod sensitivity in black spruce should not restrain leaf-out advancement with climate warming. Our results call for adapting the temperature-driven hypotheses of ecophysiological models predicting leaf-out to include spring frost probability.

Genetic association with high-resolution climate data reveals selection footprints in the genomes of barley landraces across the Iberian Peninsula.

Landraces are local populations of crop plants adapted to a particular environment. Extant landraces are surviving genetic archives, keeping signatures of the selection processes experienced by them until settling in their current niches. This study intends to establish relationships between genetic diversity of barley (Hordeum vulgare L.) landraces collected in Spain and the climate of their collection sites. A high‐resolution climatic data set (5 × 5 km spatial, 1‐day temporal grid) was computed from over 2,000 temperature and 7,000 precipitation stations across peninsular Spain. This data set, spanning the period 1981–2010, was used to derive agroclimatic variables meaningful for cereal production at the collection sites of 135 barley landraces. Variables summarize temperature, precipitation, evapotranspiration, potential vernalization and frost probability at different times of the year and time scales (season and month). SNP genotyping of the landraces was carried out combining Illumina Infinium assays and genotyping‐by‐sequencing, yielding 9,920 biallelic markers (7,479 with position on the barley reference genome). The association of these SNPs with agroclimatic variables was analysed at two levels of genetic diversity, with and without taking into account population structure. The whole data sets and analysis pipelines are documented and available at https://eead-csic-compbio.github.io/barley-agroclimatic-association. We found differential adaptation of the germplasm groups identified to be dominated by reactions to cold temperature and late‐season frost occurrence, as well as to water availability. Several significant associations pointing at specific adaptations to agroclimatic features related to temperature and water availability were observed, and candidate genes underlying some of the main regions are proposed.

The effect of winter length on duration of dormancy and survival of specialized herbivorous Rhagoletis fruit flies from high elevation environments with acyclic climatic variability.

Dormancy can be defined as a state of suppressed development allowing insects to cope with adverse conditions and plant phenology. Among specialized herbivorous insects exploiting seasonal resources, diapause frequently evolves as a strategy to adjust to predictable plant seasonal cycles. To cope with acyclic and unpredictable climatic events, it has been found for some insects that a proportion of the population undergoes prolonged dormancy. We compared the response of three species in the Rhagoletis cingulata species group exploiting plants differing in fruiting phenology from environments varying in frequency and timing of acyclic climatic catastrophic events (frost during flowering and fruit set) and varying also in the time of the onset of the rainy season. Small proportions (10 months), and large proportions of pupae died without emerging as adults. The number of days elapsed from the end of artificial winter and adult eclosion was longer for R. cingulata exploiting late fruiting Prunus serotina in Northeastern Mexico than for flies recovered from earlier fruiting plants in the central Altiplano. Rhagoletis turpiniae and northeastern R. cingulata pupae suffered high proportions of parasitism. Large proportions of R. cingulata from central Mexico engaging in prolonged dormancy may be explained by the fact that flowering and fruit set for its host, P. serotina var capuli, driven by the timing of maximum precipitation, matches a period of highest probability of frost often resulting in large areas with fruitless trees at unpredictable time intervals. As a consequence of differences in host plant fruiting phenology, central and northeastern Mexican R. cingulata were found to be allochronically isolated. Prolonged dormancy may have resulted in escape from parasitism.

Effect of over tree cooling irrigation on ‘Bosc’ pear orchards microclimate

Irrigation in some countries is a horticultural practice mainly used only to supply water. At the same time the use of microsprinklers have a powerful infl uence on the changes of temperature in orchards. When the air’s temperature is high (about 20 °C or higher) the evaporative cooling irrigation signifi cantly decreases the plants’ surface temperature and air temperature. The cooling effect is stronger when the air is dryer. By using cooling irrigation regularly, canopy temperature can be decreased so that the beginning of blooming can be delayed. Also if the blooming is early and frost probability is high, serious damages can happen in orchards. The benefi cial effect of cooling irrigation is the temperature reduction and frost protection. In March 2010, one month earlier than the expected blooming an irrigation system was established to produce anti-frost treatment and regulate the micro-climate of a Bosc pear orchard which belongs to the University of Debrecen (Hungary). The objective of sprinklers was to cool the air by increasing water evaporation and relative humidity. The position of the micro-sprinklers was planned in three levels (around the tree trunks, a few cm near to the soil surface, in the crown region and above the crown, a half meter higher). The results showed that the water sprayed in the orchard by micro-jets infl uenced decisively the temperature of the plantation. At higher temperatures (around 20 °C), the drop of temperature may attain 5–7 °C. A low relative humidity of the air may increase the relative effect. When water was applied at intervals of 15 minutes for ten times a day from 8 am to 18 pm, the air, fl owers and bud’s surface temperature could be kept low. At certain days when the temperature was higher than 10 °C, irrigation was used at night time in similar 15 minutes intervals, from 18 pm and 6 am. The beginning of bloom could be delayed for more than ten days. The Bosc pear variety blooming dynamics was characterized by a logistic curve in the treated as well as in the control plot. In the treated plot, the curve was steeper than in the control one in spite of the equal temperatures measured in the plots. Under Hungarian climatic conditions, the method was successfully used to delay blooming dates. The main result was the diminution of the frost damage in the spring that assured pears yields.

Xylem vessel traits predict the leaf phenology of native and non‐native understorey species of temperate deciduous forests

Summary Non‐native understorey woody species have been shown to extend leaf display and inhabit vacant phenological niches in early spring and late autumn when growing with native counterparts in temperate deciduous forests across the world. Despite the potential competitive advantages, extended leaf duration also subjects non‐native species to possible hydraulic risks associated with maintaining leaves during periods of increased frost probability. It remains unclear how non‐native species are able to maintain xylem function within this context. Leaf phenology in temperate deciduous trees has been shown to be a function of xylem anatomy, with earlier bud break associated with smaller xylem vessels due to the presumed resistance of smaller vessels to freezing‐induced cavitation. We examined relationships between leaf phenology and xylem vessel traits across 82 native and non‐native understorey deciduous woody species common to eastern U.S. deciduous forests. We hypothesized that non‐native species possess xylem vessel traits associated with maximum hydraulic safety during frost‐prone spring and autumn leaf display without compromising rapid growth rate. Larger metaxylem vessels in non‐native species were associated with both faster spring growth and delayed autumn leaf fall compared to native species. Non‐native species also had smaller latewood vessel diameter, latewood vessel area percentage and a higher proportion of solitary vessels in the entire secondary xylem cross section compared to natives, potentially increasing their resistance to freezing‐ and/or drought‐induced cavitation in autumn, thus allowing for delayed autumn leaf fall. Native and non‐native species exhibited similar dates of spring bud break and leaf emergence, consistent with similar xylem vessel size and vessel area percentage within metaxylem and earlywood. Within both groups, species with earlier bud and leaf emergence had a higher total percentage of vessel area within metaxylem and earlywood. This suggests understorey species need sufficient water to support their early spring growth at the risk of freezing‐induced cavitation. Our study suggests xylem vessel properties, along with cross‐sectional spatial xylem vessel distribution, reflect the capacity of non‐native plants to thrive in a new environment and deepen our understanding of the physiological mechanisms of successful invasions of non‐native understorey woody plant species.

AGROCLIMATIC RISK ASSESSMENT BY SPRING FROST DAMAGE OF OVIDIOPOLSKYI AND LANKA GRAPE VARIETIES

Purpose. The aim is to assess the degree of risk of damage to the grapes of different varieties of spring frost using the developed model, the conditional probability of frost. Methodology. The initial information was compiled observations in the Odessa region in the thermal regime in the spring and autumn periods in five agrometeorological stations (Odessa, Bolhrad, Ishmael, Serb and Sarata) in wine-growing zone. Calculations were made for table varieties and wine grapes – Ovidiopolskii and Lanka. To determine the risk of frost damage to grapes used the method of conditional probabilities. Finding. Termination date of spring frosts observed much earlier onset dates vegetative phases of grapes, in some circumstances, freezing in the active layer can be up to very dangerous levels. Results. In the course of this work it was found that over the past decade, the timing of phenological phases grapes shifted to a later time. Such changes are observed both for dining and for wine grapes with varying degrees of ripening period. For the entire period of time periods offensive phase «Start Sap» and «bud» has shifted almost a decade. Nevertheless, despite the fact that according to the temperature in the meteorological hut (at 2 m) the risk of damage to grapes in the spring varies from 8 to 15% in the layer of air 50 cm from the soil surface can be observed risks of damage from 40 to 95 %.

The effects of frost conditions on forest management based on the example of the July 1996 period at Hala Izerska in the Izera Mountains

Abstract This paper presents the characteristics of a frost episode that occurred July, 20-23, 1996 in the centre of the Izera Mountains and its effects on forest management. Source data consisted of air temperature measurements originating from the author’s own and archival databases of the Institute of Meteorology and Water Management (IMGW), Voivodeship Inspectorate of Environmental Protection (WIOŚ), University of Wrocław (UWr) and the Bureau of Forest Management and Geodesy in Brzeg (BULiGL). The intensity, time of occurrence and effects of this particular episode were extreme. The estimated probability of frost in the centre of the mountain dale Hala Izerska in July at a temperature of -5.5°C two meters above ground level is 2.4%. Therefore, it can be stated that such a sharp decline of Tmin in the middle of the growing season can occur in this area once every 40-50 years. Strong, nocturnal decreases of Tmin below 0°C during the growing season occur in the Izera Mountains almost every year, causing significant damage to silviculture. The interior of the Izera Mountains, represented by mountain dale Hala Izerska, is one of the coldest or even the coldest site in Poland in terms of absolute minimums of air temperature during the growing season. In the mountain areas, knowledge of the impact of climate, such as thermal factors, on tree stands enables silviculture work to be optimised, ultimately allowing funding to be rationalised. The distinct climatic conditions of mountain basins and valleys, slopes and plateaus located at similar altitudes need to be considered.

Frost resistance is associated with development of sour cherry (Prunus cerasus L.) generative buds

Spring frost is a limiting factor for yield and its stability in sour cherry. Shoots of sour cherry (Prunus cerasus L.) 7 cultivars were artificially frozen at −4°C for 30 min at the Department of Orchard plant Genetics and biotechnology of institute of Horticulture, lithuanian research Centre for agriculture and Forestry. Dynamics of phenological phases was observed and probability of spring frost was evaluated. Cultivars were divided into two groups according to resistance to spring frost at different phenological phases. the first group consisted of plants that were most sensitive to frost in the fruit germ phonological phase. the second group consisted of the cultivars which were mostly sensitive in full bloom phase. It was established that resistance of sour cherry cultivars to spring frost is a combination of several biological components. Sour cherry resistance to spring frost depends on the level of development of generative buds during spring frost; stability of bearing depends also on the duration of most susceptible phenological phases and spring frost probability during these phases. plants of ‘Orkolija’ cultivar were the most injured at −4°C in full bloom phase as compared to other phonological phases and differed significantly compared to other cultivars studied. Stable bearing occurs in the sour cherry cultivars with short phenophases in which generative organs are most vulnerable to frost, and these phases occur when the probability of spring frost is low. key words: phenological phase, Prunus cerasus, spring frost.

A simple agroclimatic index to delineate suitable growing areas for rainfed maize production in the Free State Province of South Africa

The risk associated with climate and its variability over the Free State Province of South Africa is the major determining factor for agricultural productivity and has a major impact on food security in that region. In this study, suitability of planting a rainfed maize crop in the province was investigated using an agroclimatic index. The index is formulated from the combination of frost probability over the growing period, non-exceedence probability of onset of rains and agricultural drought index. The Poone AgroClimatic Suitability Index (PACSI) was introduced to integrate the major climate hazards affecting maize production in the Free State. The index was further used to delineate suitable areas across the Free State for planting a maize variety requiring 1420 growing degree days (heat units) to maturity. The resulting maps show areas of high maize production suitability over the Thabo Mofutsanyane district from mid-October to early November. Areas over Fezile Dabi and northern parts of the Lejweleputswa district also showed high suitability of maize especially from mid-November to the end of December. The western and southern Xhariep district is not suited for planting maize while other marginal dryland maize production areas include western Motheo, southwestern Lejweleputswa and most parts of the central and eastern Xhariep districts. Comparison of the index with maize yields and crop model outputs shows a good agreement in most stations and areas respectively and thus, PACSI can be used to delineate areas suitable for planting maize in the Free State Province of South Africa.

Surface atmospheric circulation patterns and associated minimum temperatures in the Maipo and Casablanca valleys, central Chile

This paper analyzes the influence of circulation anomalies on the magnitude of minimum air temperature (Tmin) at a daily scale in two important agricultural valleys of Chile (Maipo and Casablanca) during the period 2001–2007. A statistical classification of synoptic fields was performed, resulting in eight circulation patterns (CPs, 84 % of explained variance). The corresponding anomalies of Tmin (ATmin) of each CP were analyzed in order to understand their synoptic-scale forcing mechanisms. Results showed a direct association between ATmin and the synoptic structure. The average weakening in sea level pressure (SLP) yields positive ATmin, while negative ATmin is associated with a strengthening in SLP. In the latter case, it was also found that a synoptic structure (10.2 % of frequency) corresponding to a migratory high-pressure system passing eastward across the Andes led to the lowest ATmin and a higher probability of frost in both valleys (22 % on average) in winter and springtime.

MICROCLIMATE MODIFICATION IN PEAR PLANTATION BY USING COOLING IRRIGATION

Irrigation in some countries is a horticultural practice mainly used only to supply water. At the same time the use of micro-sprinklers have a powerful influence on the changes of temperature in orchards. When the air temperature is high (~20°C or higher) evaporative cooling from irrigation significantly decreases the plant surface temperature and air temperature. The cooling effect is stronger when the air is dryer. By using cooling irrigation regularly, canopy temperature can be decreased so that the beginning of bloom can be delayed. Also if the bloom is early and frost probability is high, serious damages can happen in orchards. The beneficial effect of cooling irrigation is the temperature reduction and frost protection. In March 2010, one month before expected bloom, an irrigation system was established to produce anti-frost treatment and regulate the micro-climate of a ‘Bosc’ pear orchard which belongs to the University of Debrecen (Hungary). The objective of sprinklers was to cool the air by increasing water evaporation and relative humidity. The position of the micro-sprinklers was planned in three levels (around the tree trunks, a few cm near to the soil surface, in the crown region and above the crown, 0.5 m higher). The results showed that the water sprayed in the orchard by micro-jets influenced the temperature decisively. At higher temperatures (~20°C), temperature reduction may attain 5-7°C. Low relative humidity of the air may increase the relative effect. When water was applied at intervals of 15 min ten times per day from 8:00 to 18:00, the air, flower and bud surface temperatures could be kept low. When the temperature was higher than 10°C, irrigation was used at night in similar 15-min intervals, from 18:00 to 6:00. The beginning of bloom could be delayed for more than ten days. ‘Bosc’ pear blooming dynamics were characterized by a logistic curve in the treated as well as in the control plot. In the treated plot, the curve was steeper than in the control in spite of the equal temperatures measured in the plots. Under Hungarian climatic conditions, the method was successfully used to delay bloom dates. The main result was the diminution of the frost damage in the spring that assured pear yields.

Potential for growing Arabica coffee in the extreme south of Brazil in a warmer world

Agriculture appears to be one of the human activities most vulnerable to climatic changes due to its large dependence on environmental conditions. However, the diversity of Brazilian environmental conditions could be of great advantage to adapting this sector to new climatic conditions, which should be assessed as in this study on shifting Arabica coffee cultivation to the extreme south of the country. The methodology applied is the same the one used to define climatic risks in current productive regions of Brazil and their vulnerability to climatic change predicted by IPCC reports. The basic climatic parameters applied were frost probability and annual average temperature, since annual water deficit did not prove to be a restricting factor for Arabica coffee cultivation in the study area. The climatic conditions suitable for coffee production are: annual average temperature between 18°C and 22°C, annual water deficit less than 100 mm and frost probability (risk of lowest annual temperature less than 1°C) less than 25%. An area is said to have “low climatic risks” for coffee production when these three climatic conditions are met. Current climatic conditions were used and simulations of four temperature increases between 1°C and 4°C were also performed. The results indicated a substantial increase in the size of low climatic risks areas for the production of Arabica coffee in the extreme south of Brazil, mainly for mean temperature increases of 3°C in the study area in relation to present conditions. Increases of 2°C and 4°C were also favorable, but not as good as those obtained for 3°C. It should be underscored that areas with low climatic risks will be able to be found mainly in the extreme south of the study region, the border with Uruguay and North of Argentina.