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The effect of water-stress on the mineral nutrition of fruit plantations
187-192Views:83Besides agro-techniques the climatic conditions play an important role in agricultural production. Weather extremes are
significant hazards to many horticultural regions all over the word. It has a profound influence on the growth, development and yields of a
crop, incidence of pests and diseases, water needs and fertilizer requirements in terms of differences in nutrient mobilization due to water
stresses. Nowadays, the weather extremes cause more and more problems and significant hazards to many horticultural regions in Hungary.
The aim of this study is to explore the problems of nutrient uptake followed from climatic anomalies and response it. In this study
we focus on water supply problems (water-stress).
Reviewing the effects and nutrient disorders caused by climatic anomalies, the following statements can be taken:
· Nutrient demand of trees can be supplied only under even worse conditions.
· The most effective weapon against damage of climatic anomalies is preventative action.
· Proper choice of cultivars, species and cultivation should provide further possibilities to avoid and moderate the effects of
climatic anomalies.
· Fruit growing technologies especially nutrition should be corrected and adjusted to the climatic events as modifier factors.
· The role of foliar spraying, mulching and fertigation/irrigation is increasing continuously.
· Urgent task of the near future is to correct and adjust the tested technologies of fruit growing according to these climatic events as
modifier factors.
Optimal nutrient supply of trees decreases the sensitivity for unexpected climatic events. To solve these problems supplementary, foliar
fertilization is recommended, which adjusted to phonological phases of trees. Moreover, mulching is regarded as an excellent water saving
method. -
Efficiency of Fertilization in Sustainable Wheat Production
59-64Views:94In sustainable (wheat) production plant nutrition supply and fertilization play decisive roles among the agrotechnical elements, because of their direct and indirect effects on other agronomical factors.
In long-term experiments, we studied the roles of agroecological, genetic-biological and agrotechnical factors in the nutrient supply, fertilization and its efficiency in wheat production under continental climatic conditions (eastern part of Hungary, Trans-Tisza) on chernozem soil. Our results have proved that there are different (positive and negative) interactions among ecological, biological, and agrotechnical elements of wheat production. These interaction effects could modify the nutrient demand, fertilizer (mainly nitrogen) response of wheat varieties and efficiency of fertilization in wheat production.
The optimum N-doses (+PK) of wheat varieties varied from 60 kg ha-1 (+PK) to 120 kg ha-1 (+PK) depending on cropyears, agrotechnical elements and genotypes. The winter wheat varieties could be classified into 4 groups according to their fertilizer demand, natural and fertilizer utilization, fertilizer response and yield capacity.
Appropriate fertilization (mainly N) of wheat could affect both the quantity and quality of the yield. By using optimum N (+PK) fertilizer doses, we could manifest genetically- coded baking quality traits of winter wheat varieties and reduce quality fluctuation caused by ecological and other management factors. The efficiency of fertilization on different baking quality parameters (wet-gluten, valorigraph index etc) were variety specific (the changes depended on genotypes).
Our long-term experiments proved that appropriate fertilization provides optimum yield, good yield stability and excellent yield quality in sustainable wheat production. We could this get better agronomic and economic fertilization efficiency with less harmful environmental effects. -
Causes of floods and flood protection in Subcarpathia
72-75Views:90Subcarpathia is one of the richest regions in surface waters in the Ukraine. Due to its geographical, relief and climatic conditions, it belongs to the active precipitation zone, where great floods frequently occur. As a result of many years of observation, it can be concluded that the interactions of many natural factors can lead to various floods in the catchment area of the river Tisza. These are mostly hydro-meteorological factors, which can lead to great floods with the characteristics of the formed flow. Human activity also significantly influences the occurance of floods: clearing, which can accelerate the process of the runoff, ploughing in the catchment area, which can lead to erosion and the utilisation of areas endangered by floods for various economic sectors.
A series of questions arose in recent years regarding the formation of floods: what could be the causes of floods and what actions need to be made to prevent them. The evaluation of floods made us conclude that passive protection by using dams does not always ensure protection against floods as these were constructed in different times for different water levels. Many factors can affect the whole process which cannot be foreseen, therefore the development of new solutions and new technologies is necessary in flood protection. -
Effect and interaction of crop management factors and crop year on the yield of maize (Zea mays L.)
31-41Views:186The aim of this study was to determine the combination of treatment levels of crop management factors which can optimize and sustain maize yield under varying climatic conditions. The effect of winter wheat forecrop, three tillage systems (Mouldboard-MT, Strip-ST, Ripper-RT), two planting densities (60,000 & 80,000 plants ha-1), three fertilizer levels (N0-control, N80, N160 kg ha-1) with four replications in irrigated and non-irrigated treatments were evaluated over a five year period, 2015–2019. The obtained results revealed that growing season rainfall positively correlated with yield, whereas, temperature negatively correlated with yield. Impact of adverse weather on yield was less severe in biculture, irrigated plots, at lower planting density (60,000), lower fertilizer rate (N80) and in RT and ST, compared to MT. In years with favorable rainfall, yields of MT and RT were significantly (P<0.05) higher than ST. However, in a less favorable year, such as 2015, with 299 mm growing season rainfall and the lowest July rainfall (59% below mean) there was no significant difference (P>0.05) in yield among the three tillage treatments. Higher planting density (80,000), and fertilization rate (N160) in tandem with MT are treatments combination conducive for high yield under favorable climatic conditions, whereas, in years with low rainfall and high temperatures, RT and ST offer alternative to MT for optimum yield with 60,000 plants ha-1 and N80 treatment level. Crop year effect accounted for 20.7% of yield variance, fertilization 35.8%, forecrop 12.8%, plant density 3.4%, tillage 1.2% and irrigation <1%. It is conclusive that with proper selection of the appropriate levels of agrotechnological inputs the adverse effect of weather on yield can be mitigated.
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The impact of climatic factors on the relative chlorophyll content and yield of a maize hybrid in a long-term experiment
71-77Views:193The impact of the climatic factors of crop year on the relative chlorophyll content of maize was examined for three years. The examinations were carried out on the Látókép Experiment Site of the University of Debrecen on calcareous chernozem soil in a small-plot, non-irrigated long-term field experiment with strip plot design. In addition to a non-fertilised (control) treatment, nitrogen (N) fertiliser doses were applied as base and top dressing. The 60 and 120 kg N ha-1 base dressing doses were followed by two top dressing doses at the V6 and V12 phenophases.
Averaged over the different fertiliser treatments, SPAD readings increased in all three years as the growing season progressed. The highes SPAD value increase was observed in the average crop year (2017) at the V12 phenophase (11.8), which further increased at the R1 phenophas, by 3,7. No significant Spad value difference was observed between the average (2017) and the dry year (2018) at the V6 growth phase. However, in the wet crop year (2016), the V690 treatment provided the statistically highest relative chlorophyll content (46.8). At the V12 phenophase, the base dressing dose of 120 kg N ha-1+30 kg N ha-1 (V6150) showed to be successful in two years (2016 and 2018), while in 2017, the base dressing dose of A60 was successful. The impact of crop year on relative chlorophyll content can be clearly shown at the R1 growth stage. In all three years, the significantly highest relative chlorophyll content could be achieved at different nutrient levels: A60 in 2016, V6150 in 2017 and V690.
In a wet year (2016), higher yield could be achieved as a result of the 60 kg N ha-1 base dressing and 30 kg N ha-1 at the V6 growth stage (V690) as top dressing in comparison with 2017 and 2018, when higher fertiliser dose (120 kg N ha-1 base dressing and 30 kg N ha-1top dressing at the V6 growth stage) was needed to achieve a significant yield surplus.
Altogether, averaged over the different treatments, the highest yield (12.48 t ha-1) was observed in the wet year, when the relative chlorophyll content was also the highest (50.6).
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Changes of chemical composition and nutritive values of Reed Canary Grass (Phalaroides arundinacea) in first growth
37-42Views:94Change in chemical composition and nutritive value of Reed Canary Grass (Phalaroides arundinacea) were investigated in springtime in 2004-2006. The nutritive value of Reed Canary Grass was observed between the end of April and the middle of June relating to the following parameters: crude protein, crude fibre, crude fat, ash, N-free extract, net-energy growth, net-energy maintenance, Metabolizable Protein Energy dependent,
Metabolizable Protein N-dependent.
It was also analysed whether a relationship between the climatic factors affecting the growing period as well the chemical composition of grasses and the annual weather were looked for. For the estimation of weather conditions the climate index was calculated. A correlation can be detected between the change of parameters of nutritive value and the quality of the current year. Between 2004 and 2006, the result of the analysis of nutritive value indicated a significant difference with respect to each chemical composition at the rate of P<0.01 depending on the time when the samples were taken. According to the outlined data it can be stated that the change of the value of crude protein and ash show decreasing endency agreeing the research literature. In parallel with the change of nutritive value, the amount of crude fibre and N-free extract increased. However, the value of Net-Energy maintenance revealed an alteration only in the first half of the observed period. The same alteration tendency can be detected
in the Net-Energy growth. -
Challenges – the impact of climate change on the nutritional management of Hungarian orchards
323-334Views:211The agricultural sector is increasingly exposed to both environmental and economic risks due to the phenomena of climate change and climate variability. Fruit growth and productivity are adversely affected by nature’s wrath in the form of various abiotic stress factors. Climate change and extreme climatic events are predicted to increase in intensity, frequency, and geographic extent as a consequence of global climate change. It is no doubt that frequency of unexpected climatic events and their growing rate result in an increasing amount of problems for fruit growers globally. Today, climate change impacts are the most serious problems for Hungarian fruit growers as well. It can be stated that the nutrient demand of fruit trees can be supplied only under even worse conditions.
Therefore, it is so important to know and apply adaptation and mitigation strategies in horticulture to improve fruit quality and yield. In the last ten years, at the Faculty of Agricultural and Food Sciences and Environmental Management at University of Debrecen expanded studies have been made to prove the importance of groundcover management in horticultural applications. In this mini review paper, is presented, how the university's researches contributed to the expansion of knowledge of preservation of soil moisture and what advice we can provide for fruit growers to face the challenges of climate change.
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Comparison of major population parameters of Brown hare (Lepus europaeus, Pallas 1758) in two hunting fields of the Great Hungarian Plain
69-74Views:133Hungarian stock of game is not only part of our national treasure but also one of our domestic products and economic income. Not indifferent therefore the number and the state of health of our wildlife. Population decline of the Brown hare (Lepus europaeus, Pallas 1758) (one of our most important small game in Hungary) takes a long time. Demographic parameters of Brown hare was examined, particularly the factors affecting the decline of the species in Hungary. We took samples from typical habitats where the Brown hare could be found in relatively high density in our country. The article reports data of reproductive characteristics, diseases, parasites of Brown hare and other factors such as climatic and anthropogenic which could influence of the population dynamics. We mention sample collection and processing methods eg: population size estimates, examination of reproductive organs, the sex ratio and the age structure as well as the individual condition based on data of domestic and foreign authors and our partial results.
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Investigation of the Resistance Against the Fusarium solani at Different Pea Varieties and Combinations of Breeding
157-160Views:32The Fusarium species are soil and polyphage parasits, and the rate of damage, caused by them, highly depend on interactions between climatic and edaphic factors and also on sensitivity of cultivars. Even though about 70-80 percent of the widely grown green peas cultivars is resistant to Fusarium oxysporum f. sp. pisi 1. race, the rate of Fusarium infections and severity of symptoms increased in the latest years. It is supposed that another Fusarium sp. the Fusarium solani has been spreading. The most exact way to study the cultivars in a provoking garden established in natural environment, where the pathogen is artificially enriched to a level, at which the cultivars can be distinguished according to their susceptibility. In the provoking garden the reaction against to Fusarium of our breeding lines and our registered cultivars and cultivars existed on the National List (including cultivars with well-known susceptibility as standards) are examined year by year. In our experiments we could found two green peas cultivars to be resistant to Fusarium solani (Early sweet (13,36%) and Lora (16,9%)) The breeding lines Margit and 8607/75-3-2 proved to be the most susceptible to Fusarium solani (94,4% and 73,1% infected plants, respectively).
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Interaction of yield stability and year in major agricultural crops
41-46Views:84The effect of hydro-meteorological extremities on plant cultivation is the result of the correlation of many factors. These may increase or decrease the effects of hydro-meteorological extremes. The degree of this variance depends on the professionality of treatments, on the quality of the applied technique and technology and also on the soil’s water management characteristics.
The water management characteristics of Hungary’s arable land are mainly unfavorable or medium. In the past two decades the conditions of originally good soils, from a water management aspect, have significantly deteriorated in the critical 0-60 cm soil layer. This is mainly due to unprofessional land use, a lack of deepening cultivation and neglected organic cultivation. At the same time, hydro-meteorological extremities occur more frequently and the sensibility of plant cultivation has increased.
The sensibility of plant cultivation is type and location specific, yet, it also effects both the quality and quantity of the result.
The stability analysis, which covered the period of four decades and incorporated 6-7 agro-ecological areas proves and highlights the following:
• Winter wheat only reacted to extensive cultivation and unfavorable environmental conditions to a small degree. On the other hand, the effect of hydro-meteorological extremities increases.
• The stability analysis of maize, which is sensitive to cultivation technology and the location of cultivation, proved just the opposite. Good soil and adequate technology significantly reduces the effect of any particular year.
• From the years examined, the most favorable proved to be the one with average precipitation. Maize reacted to both extremities in a similar way. Winter wheat reacted to more precipitation with less yield.
• The yield quality of winter wheat was negatively effected by drought. The negative effect of precipitation is limited to the period of ripening and harvest, so the likelihood of such an effect is not significant.
• The yield of sunflower – due to pests – significantly reduces in years with high precipitation, while a difference between dry and average years cannot be pinpointed out. The oil content in both dry years and in years with high precipitation is evident, compared to years with average precipitation.
• The root yield of sugar beet is reduced by drought while the sugar content depends on soil characteristics and climatic extremities. A difference could also be noted by location, whether in Western Hungary and on the Great Plain. Great sugar content can be achieved in years with high precipitation in Western Hungary, while the same result occurred with average precipitation on the Great Plain. Drought did not have a positive effect on sugar content in either location. -
Agronomic bases of precision barley production
217-220Views:90To ascertain the importance of individual preciosion factors in achieving yield and quality of malting barley, we established a multifactor
experiment at the research station of the Slovak University of Agriculture in Nitra in 2009 and 2010. Four variants of fertilization, 2 ways of soil cultivation and four varieties 'Bojos’, 'Kangoo’, 'Marthe’ and 'Xanadu’ were observed. From the quality indicators the nitrogen content (%) was observed. The results were statistically analyzed by using a multifactor analysis of variance by using Statistica 8, the program Statgraphics. The difference between years was statistically significant (1.87 t ha-1) in favour of 2010. The difference was also significant between the varieties 'Bojos’ and ’Kangoo’(1.07 t ha-1), respectively. 'Martha’ and 'Xanadu’ as well as 'Kangoo’ (0.56 resp. 0.33 t ha-1). Conventional soil cultivation in
comparison with a minimalization technology, demonstrated a tatistically insignificant increase of yield. Significant differences were obtained between the variants of fertilization. Treatment by using Condit (b-var.) showed a very positive impact in climatic favorable year (2010) with a yield result of 7.42 t ha-1. In comparison with an untreated control, the difference in yield was 0.89 t ha-1. A significant increase of yield was achieved by using the combination of solid fertilizer with foliar fertilizer (LAV + Hakofyt, var.c) 0.47 t ha-1. The crude protein content was statistically influenced by a variety and year. In 2009, the crude protein content was above average (12.38%). Significantly lower attributes were achieved in 2010 (9.90%). From the studied/observed varieties the lowest crude protein content was showed by a variety 'Kangoo’ (1.68%). -
Results of fast neutron induced mutations in M1 and M2 generations of sorghum (Sorghum bicolour)
49-54Views:78Due to climatic barriers, the genetic variability of Sorghum varieties decreases away from the gene centre, therefore hybrids cultivated in Hungary are restricted to a relatively limited genetic basis. This limited genetic basis results in a lower rate of genetic improvement, so the genetic basis of cytoplasm factors are to be extended. We enhanced the diversity of primary materials by fast neutron treatment. As a result of this treatment we detected sterile, deformed specimens with double panicles in the stock treated with a dose of 12.5 Gy in the M1 generation. Agronomically useful
specimens were found in the stock treated with 10 Gy and 7.5 Gy doses, where the leaf area index (LAI) and Harvest- index gave higher values than those of the control group. In the stock treated with 5 Gy dose, variations were less significant. In the reseeded M2 generation we detected albino specimens with extreme chlorophyll defects in the 10 Gy Zádor stock. -
Examination of the Effect of Cropyear on the Yield Potential and Yield Stability of Winter Wheat Varieties
62-67Views:100Variety selection is one of the most important, determinative elements of sustainable winter wheat production. Yield potential, and yield stability are the most important elements in the variety selection of winter wheat, but baking quality parameters play an important role, too.
Several winter wheat varieties were tested for yield and yield stability on chernozem soil in the Hajdúság (in the eastern part of Hungary), in the 2001-2002-2003-2004 cropyears. The management factors were the same for all cropyears. 15 varieties in early the maturity group, 14 varieties in the middle maturity group and 4 varieties in the late maturity group were tested in the above mentioned cropyears. The climatic conditions were average in 2001, dry in 2002, extremely dry in 2003, and very favourable in 2004.
We obtained 5298-6183 kgha-1 yield from early maturity varieties, 5683-6495 kgha-1 from middle, 5694-6031 kgha-1 from late ones in the average of four years. The cropyears had strong influence on the yields, even on chernozem soil, and were characterized by excellent water – and nutrient – husbandry. Averaging of cropyears and genotypes, we obtained 6984 kgha-1 in 2001 (average cropyear), 5452 kgha-1 in 2002 (dry cropyear), 3120 kgha-1 in 2003 (extremely dry cropyear) and 8400 kgha-1 in 2004 (optimum cropyear), respectively. The yield differences between the minimum and maximum yields were 885 kgha-1 in early varieties, 812 kgha-1 in middle and 337 kgha-1 in late maturity varieties, respectively. The varieties characterized by high yield potential and the varieties characterized by good yield stability were different, so in variety selection we have to take both genetic traits into consideration. There were positive, significant correlations among the yields of winter wheat varieties (early, middle, late), the temperature of spring months. (March-April), and the rainfall of spring months (March-April) (R2=0,703**-0,768** and R2=0,681**-0,749**, respectively). We found a high negative correlation between the temperature of early summer months (May-June) and the yields of wheat varieties (R2= -0,856**- -0,918**).
According to the results of our experiment, it is very important to harmonize yield potential and yield stability in the variety selection of winter wheat. -
Stevia (Stevia rebaudiana B.) yield in the case of different production technologies
71-77Views:185Stevia rebaudiana B. offers a natural alternative of sweetening, potential health promotion plant, and our country shows increased interest about cultivation in Hungary in addition to the neighboring European countries. The agricultural production system installation necessary
understanding of the needs of the plant, as well as exploring the agronomic potential. Field experiments were conducted in 2015 with the aim to highlight some of the technological production parameters and correlations between them. We have reviewed the most important agronomic factors, the spacing (50×50 cm and 33×33 cm), ground covering (agro-cloth covered and uncovered/ control), their vegetative growth (first-,second-order branch), herb yield and quality in effect.
Based on empirical evidence, that the Hungarian climates also have the opportunity of 3 cuttings during a growing season, besides of early planting, optimal climatic conditions (in October didn’t reduce the daily minimum temperature below 0 °C, after cuttings the maximum interval values remain below 40 °C), and adequate water supply and crop protection facility. The 33×33 cm spacing evaporates more than 50×50 cm spacing, because of the dense population, the continuous canopy less able to breathe, so there are serious chances to the pathogen colonization.
Based on the results of our research to the wider 50×50 cm spacing favorable appreciate the stevia optimal progress in terms of qualitative and quantitative parameters of the yield. The stevia yields produced in the Northern Great Plains field cultivation can produce similar results as stevia crop yields in warmer climates, where the primary crops. Our research experience suggest that there is a viable domestic stevia cultivation, developing the necessary technology is still growing further investigation justifies. -
Preparatory studies for modelling production on protected grasslands
64-69Views:145There is a mutual dependence between nature conservation activity and agriculture in Hungary, as the management of the protected areas cannot be achieved without ecological farming methods. Moreover, viable economic activity can be only imagined through the harmonization of agricultural and nature conservation interests. From a nature conservation point of view, grass management systems play the greatest role in domestic agricultural systems. Yet, due to the prohibition of certain management methods and the spatial and temporal restraints on grazing, nature conservation activities have priority on protected grasslands. While nature conservation activity is still of prominent importance, it is not equally suitable for the economical management of protected grasslands per se. With our examinations, we would like to emphasize the common interests of these mutually dependent activities and to promote bilateral cooperation. Our aim is to model the production of grass on the great pastureland of Hajdúbagos. Potential grass production levels are easily calculable with a computer model based on data collected through a series of test harvests, as well as by factoring in changing climatic factors and by simulating the effects of grazing animal species and stocks. This model is not only useful for determining the optimal number of the grazing animal stock and grazing method, and therefore the most suitable management strategy, but it also supports local farmers to be able to plan their activities. In this way, both nature conservation and economic aims can be easily harmonized, which would be an important factor for the sustainable development of rural areas.
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Seed biology and possibility of improvement of seed germination capacity on Virginia mallow (Sida hermaphrodita L. Rusby)
71-76Views:136Sida hermephrodita or Virginia mallow is a perspective perennial herb in the Malvaceae family able to yield a biomass crop through the last two decades. Additionally, the plants have a lot of uses and benefits for instance it can use as a fodder crop, honey crop, ornamental plant in public gardens. It has favourable features like fast growing and resistance against the disease and climatic fluctuations, etc. Sida is in the beginning phase of domestication therefore it has a serious disadvantage: the low and slow germination as a big part of wild plants. Due to the expressly low germination percent the need of seed showing of driller is should tenfold, 200 thousand seeds/acre instead of 10–20 thousand what is not available and expensive Therefore practical purposes of our research of seed physiology was to increase the seed germination percent in a available, basically wild Sida population. In the first stage of our experiments we examined two factors relating to seed germination percent and seed germination power during our research: the influence of hot water treatment and the effect of exogenous or endogenous infection of seed. However, in our germination tests, utilizing scarified seeds with hot water (65 oC, 80 oC, 90 oC), from 29,3% to 46% germinated from those samples which were collected from the population of Sida hermaphrodita in Debrecen. The average germination for all season was 5–10% without treatment and rinsed using hot water up to almost 50%. When physically scarified used, the oldest seeds showed the best germination (46%) after the hot water operation in spite of the previous studies. We discovered that apparently there are close relationship between the seed fresh weight or water uptake capability and the percentage of infection. Following these recognition we modified our technique,in such a way that we fractionated the seeds based on their fresh weight/or relative density before we carried out the treatment. When we filtered the floating seeds on the surface of water, the hot water treatment was performed considerably better on the sunk seeds after separation. Therefore, by this special priming process we were able to reach 80% germination capacity of Virgina mallow seeds under laboratory conditions (26 oC without illumination).
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The Effect of Year and Irrigation on the Yield Quantity and Quality of the Potato
12-16Views:90In Hungary, the growing area of potato area reduced dramatically in the last few decades, additionally we are lagging behind the Western European countries as regards yields and the competitiveness of production is further decreased by the great alternation in yields from year to year, the unpredictable market conditions, bad consumption habits and many times unfortunately the lack of quality products.
The ecological and climatic conditions of Hungary are not everywhere suitable for potato, in the area of Debrecen the amount of rainfall was lower, and the monthly average temperature was higher than the requirement of potato in its growing season in 2002 and 2003.
The experiment was carried out at the experimental site of the University of Debrecen, Farm and Regional Research Institute, at Látókép. In our experiment we examined the yield and some quality parameters of 8 and 9 medium-early varieties in large parcels in 2002 and 2003 respectively. Out of the examined varieties 3 are of Dutch, and 6 are of Hungarian breeding.
The experiment was set up on 49.5 m2 parcels on calcareous chernozem soil after winter wheat as a forecrop in both years. The 9 varieties were examined in 4 repetitions in randomized blocks, out of which two repetitions were irrigated, and two were non-irrigated.
We examined the yields of the varieties, the distribution of tubers according to size and their percentages, and the changes in specific parameters of quality and inner content due to irrigation. We studied the dry matter content, the starch content, the under-water mass, the amount of reducing sugars, the colour index of frying and the element contents of tubers.
Summing up, it can be stated that among the agrotechnical year effect, variety and irrigation factors have considerable impact on potato yield quality and quantity. On the basis of our results, it can be stated that in potato production variety should be chosen in accordance with the aim of production and technology should be adapted to that specific variety. -
Examination of drought stress of two genotype maize hybrids with different fertilization
53-57Views:110In the growing season of 2019, we analysed stress resulting from climatic factors on maize hybrids of different genotypes, with the aim of gaining a better understanding of the physiological responses of each hybrid, which might support the elaboration of a cost-effective irrigation plan.
Our experiments were carried out at the Látókép Experimental Station of the University of Debrecen on calcareous chernozem soil in a small-plot long-term field trial with strip plot design. In the scope of the experiment, N-fertilizer doses were applied as basic fertilizer and top-dressing in addition to the non-fertilized (control) treatment. The 60 and 120 kg N/ha doses applied as basic fertilizers in the spring were followed by top-dressing in the V6 phenophase with a +30 kg N/ha dose. Measurements were carried out with the involvement of the Renfor early (FAO 320) and Fornad (FAO 420) late maturity hybrids-
The stomata of the plants became more and more closed with the progression of the phenological phases; their stomatal conductance decreased. However, the hybrids responded differently to environmental stress. In the case of the Renfor hybrid, the highest conductance (669 mmol/m2-s) was recorded in the V12 phenophase with the 150 kg N/ha treatment. The stomata were more open due to the high turgor pressure, allowing plants to evaporate properly. The plant was in its worst physiological condition on 2nd July, at the time of the appearance of the last leaf in the case of the 120 kg N dose (224 mmol/m2-s). The value measured in the V12 phenophase has already shown that the stomata were closing due to the self-regulating system of the plant. It would have been necessary to dispense irrigation water following the measurement. This confirms the finding that water stress can be prevented by measuring stomatal conductance.
In the case of the Fornad hybrid, stomatal conductance was the highest on 12th June (630 mmol/m2-s) in the 90 kg N/ha treatment and it was the lowest (183 mmol/m2-s) in VT (emergence of the last leaf) phenophase in the 60 kg N/ha treatment. In this case, the appropriate time for applying irrigation water would have been early July, when the conditions for the plants were still adequate. Subsequently, the stomata began to close due to a reduction of the water resources available to them.
There was a significant correlation between soil moisture and stomatal conductance, as well as between temperature and stomatal conductance.