In the study of Tomlain (1997) a soil water balance model was applied to evaluate the climate change impacts on the soil water storage in the Hurbanovo locality (Southwestern Slovakia), using the climate change scenarios of Slovakia for the years 2010, 2030, and 2075 by the global circulation models CCCM, GISS and GFD3. These calculations did not take into consideration neither the various soil properties, nor the groundwater table influence on soil water content. In this study, their calculated data were compared with those monitored at the same sites. There were found significant differences between resulting soil water storage of the upper 100 cm soil layer, most probably due to cappilary rise from groundwater at sites 2 and 3. It was shown, that the soil properties and groundwater table depth are importat features strongly influencing soil water content of the upper soil layer; thus the application of the soil water balance equation (Eq. (1)), neglecting the above mentioned factors, could lead to the results far from reality. and V práci Tomlaina (1997) bol aplikovaný bilančný model vodného režimu pôd na ohodnotenie dopadu klimatickej zmeny na vodné zásoby pôdy v lokalite Hurbanovo (juhozápadné Slovensko), použijúc scenáre klimatickej zmeny pre Slovensko pre roky 2010, 2030 a 2075, založené na globálnych cirkulačných modeloch CCCM, GISS a GFD3. V týchto výpočtoch nebol braný do úvahy vplyv vlastností pôdy a hladiny podzemnej vody na vlhkosť pôdy. V práci boli porovnané vypočítané hodnoty zásob vody s monitorovanými v tej istej lokalite. Bol nájdený význačný rozdiel medzi zásobami vody v 100-cm hornej vrstve pôdy najpravdepodobnejšie spôsobený kapilárnym prítokom od hladiny podzemnej vody v monitorovacích miestach 2 a 3. Bolo ukázané, že pôdne vlastnosti a hĺbka hladiny podzemnej vody sú dôležitými faktormi, ktoré silno ovplyvňujú vlhkosť hornej vrstvy pôdy; z toho vyplýva, že aplikácia bilančnej rovnice (rov. (1)), ktorá zanedbáva vyššie uvedené faktory, nedáva reálne výsledky.
Earth’s climate has experienced notable changes during the past 50-70 years when global surface temperature has risen by 0.8°C during the 20th century. This was a consequence of the rise in the concentration of biogenic gases (carbon dioxide, methane, nitrous oxide, chlorofluorocarbons, and ozone) in the atmosphere that contribute, along with water vapor, to the so-called ‘greenhouse effect’. Most of the emissions of greenhouse gases have been, and still are, the product of human activities, namely, the excessive use of fossil energy, deforestations in the humid tropics with associated poor land use-management, and wide-scale degradation of soils under crop cultivation and animal/pasture ecosystems. General Circulation Models predict that atmospheric CO2 concentration will probably reach 700 μmol(CO2) mol-1. This can result in rise of Earth’s temperature from 1.5 to over 5°C by the end of this century. This may instigate 0.60-1.0 m rise in sea level, with impacts on coastal lowlands across continents. Crop modeling predicts significant changes in agricultural ecosystems. The mid- and
high-latitude regions might reap the benefits of warming and CO2 fertilization effects via increasing total production and yield of C3 plants coupled with greater water-use efficiencies. The tropical/subtropical regions will probably suffer the worst impacts of global climate changes. These impacts include wide-scale socioeconomic changes, such as degradation and losses of natural resources, low agricultural production, and lower crop yields, increased risks of hunger, and above all waves of human migration and dislocation. Due to inherent cassava tolerance to heat, water stress, and poor soils, this crop is highly adaptable to warming climate. Such a trait should enhance its role in food security in the tropics and subtropics., M. A. El-Sharkawy., and Obsahuje bibliografii
Almost four decades have passed since the new field of ecosystem simulation sprang into full force as an added tool for a sound research in an ever-advancing scientific front. The enormous advances and new discoveries that recently took place in the field of molecular biology and basic genetics added more effective tools, have strengthened and increased the efficiency of science outputs in various areas, particularly in basic biological sciences. Now, we are entering into a more promising stage in science, i.e. 'post-genomics', where both simulation modelling and molecular biology tools are integral parts of experimental research in agricultural sciences. I briefly review the history of simulation of crop/environment systems in the light of advances in molecular biology, and most importantly the essential role of experimental research in developing and constructing more meaningful and effective models and technologies. Such anticipated technologies are expected to lead into better management of natural resources in relation to crop communities in particular and plant ecosystems in general, that might enhance productivity faster. Emphasis is placed on developing new technologies to improve agricultural productivity under stressful environments and to ensure sustainable economic development. The latter is essential since available natural resources, particularly land and water, are increasingly limiting.
Results of cadmium sorption and desorption, as well as distribution coefficients of cadmium in the soils from the Danubian Lowland and from Veľký Ďur (neighbourhood of the nuclear power plant Jaslovske Bohunice) are presented in this study. It was found that Cd adsorption is high in studied soils already after the one-minute lasting Cd-soil contact. The results obtained show that the highest sorption of cadmium is in the loamy-sand soil from Kalinkovo (99.75 %). Zeolite application was the most effective in the loam soil from Macov. Sorption of cadmium in this soil increased by 1.45%. The presence of zeolite in chosen soil samples influenced Cd desorption, too. In loamy-sand soil from Kalinkovo cadmium desorption decreased by 50 % after zeolite application. Sorption experiments with radionuclides (85Sr and 137Cs) were conducted on brown earth from the site Velľký Ďur. The 137Cs sorption is very high in studied soil. Zeolite is more effective in the case of 85Sr. Desorption of radiostrontium decreased by 50% after zeolite application. and V práci sa prezentujú výsledky sorpcie, desorpcie a hodnoty rozdeľovacieho koeficientu kadmia vo vybraných vzorkách pôd Podunajskej nížiny a hnedozeme z lokality Veľký Ďur. Kadmium je silne sorbované sledovanými pôdami už po 1 minúte trvania kontaktu. Najvyššia sorpcia sa pozorovala u hlinito-piesočnatej pôdy z lokality Kalinkovo, kde pomerné adsorbované množstvo S kadmia bolo 99,75 %. Aplikácia zeolitu sa najviac prejavila u hlinitej pôdy z Macova, kde sa pomerné adsorbované množstvo S kadmia zvýšilo o 1,45 %. Zeolit ovplyvnil aj desorpciu naviazaného kadmia v sledovaných pôdnych vzorkách. Najviac kadmia sa desorbovalo z hlinito-piesočnatej pôdy z Kalinkova a aplikácia zeolitu znížila pomerné desorbované množstvo kadmia na menej ako polovicu. Sorpčné experimenty s rádionuklidmi (85Sr a 137Cs) boli vykonané na hnedozemi z lokality Veľký Ďur. 137Cs je už samotnou pôdou sorbované takmer na 100 % a prítomnosť zeolitu už sorpciu prakticky nezvyšuje. Zeolit zvyšuje sorpciu hlavne u rádiostroncia. Desorpcia stroncia po aplikácii zeolitu sa znížila o 50 %.
The review sums up research conducted at CIAT within a multidiscipline effort revolving around a strategy for developing improved technologies to increase and sustain cassava productivity, as well as conserving natural resources in the various eco-edaphic zones where the crop is grown, with emphasis on stressful environments. Field research has elucidated several physiological plant mechanisms underlying potentially high productivity under favourable hot-humid environments in the tropics. Most notable is cassava inherent high capacity to assimilate carbon in near optimum environments that correlates with both biological productivity and root yield across a wide range of germplasm grown in diverse environments. Cassava leaves possess elevated activities of the C4 phosphoenolpyruvate carboxylase (PEPC) that also correlate with leaf net photosynthetic rate (PN) in field-grown plants, indicating the importance of selection for high PN. Under certain conditions such leaves exhibit an interesting photosynthetic C3-C4 intermediate behaviour which may have important implications in future selection efforts. In addition to leaf PN, yield is correlated with seasonal mean leaf area index (i.e. leaf area duration, LAD). Under prolonged water shortages in seasonally dry and semiarid zones, the crop, once established, tolerates stress and produces reasonably well compared to other food crops (e.g. in semiarid environments with less than 700 mm of annual rain, improved cultivars can yield over 3 t ha-1 oven-dried storage roots). The underlying mechanisms for such tolerance include stomatal sensitivity to atmospheric and edaphic water deficits, coupled with deep rooting capacities that prevent severe leaf dehydration, i.e. stress avoidance mechanisms, and reduced leaf canopy with reasonable photosynthesis over the leaf life span. Another stress-mitigating plant trait is the capacity to recover from stress, once water is available, by forming new leaves with even higher PN, compared to those in nonstressed crops. Under extended stress, reductions are larger in shoot biomass than in storage root, resulting in higher harvest indices. Cassava conserves water by slowly depleting available water from deep soil layers, leading to higher seasonal crop water-use and nutrient-use efficiencies. In dry environments LAD and resistance to pests and diseases are critical for sustainable yields. In semiarid zones the crop survives but requires a second wet cycle to achieve high yields and high dry matter contents in storage roots. Selection and breeding for early bulking and for medium/short-stemmed cultivars is advantageous under semiarid conditions. When grown in cooler zones such and as in tropical high altitudes and in low-land sub-tropics, leaf PN is greatly reduced and growth is slower. Thus, the crop requires longer period for a reasonable productivity. There is a need to select and breed for more cold-tolerant genotypes. Selection of parental materials for tolerance to water stress and infertile soils has resulted in breeding improved germplasm adapted to both favourable and stressful environments.
Acidic herbicide MCPA (4-chloro-2-methylphenoxyacetic acid) is applied to post-emergence control of annual and perennial broad-leaved weeds, mostly in cereals. This study was undertaken with two soils of different properties sampled from two soil horizons to determine the extent of degradation, sorption and desorption of MCPA. These processes are the most important to evaluate the fate of the herbicide in soil and its potential to leach from soil into groundwater. Two soils were used: a calcareous, sandy-loam soil with organic carbon content of 2.486 % (Pararendzina) taken from surface A horizon (the A topsoil) and a calcareous, loamy-sand soil with organic C content of 0.600 % (Fluvisol) sampled from subsurface C horizon (the C subsoil). The extent of degradation, sorption and desorption of MCPA were measured in laboratory batch experiments. Degradation followed first-order kinetics, with the MCPA half-lives of 11 and 24 d for the A topsoil and C subsoil, respectively. Soil organic carbon influenced MCPA degradation. Sorption followed a Freundlich isotherm equation and linear isotherm equation, as well. The distribution coefficient KD was higher in the A topsoil (0.387 l kg-1) than in the C subsoil (0.165 l kg-1), consistent with the higher organic C content of the A soil. The results indicate that MCPA is potentially mobile and might pose a threat to future groundwater quality due to its low sorption, relatively high water solubility and slow degradation in the C subsoil. and MCPA, slabokyslý herbicíd, sa používa postemergentne na ničenie jednoročných a trvalých širokolistých burín, najmä v obilninách. Cieľom tejto práce bolo štúdium degradácie, sorpcie a desorpcie MCPA v dvoch rozdielnych pôdach odobratých z odlišnej hĺbky. Tieto procesy v najväčšej miere ovplyvňujú celkové správanie MCPA v pôdach a determinujú jeho migračný potenciál. Použité pôdy boli: karbonátová, piesčito-hlinitá pôda s obsahom organického uhlíka 2,486 % (pararendzina) odobratá z vrchného A horizontu (pôda A) a karbonátová, hlinito-piesčitá pôda s obsahom organického uhlíka 0,600 % (Fluvizem), so znakmi oglejenia odobratá z C horizontu v hĺbke 2 m (pôda C). Všetky sledované procesy boli realizované v nádobkových experimentoch. Rozklad MCPA vyhovoval rýchlostnej rovnici reakcie prvého poriadku. Rozklad MCPA bol rýchlejší v pôde A so zisteným polčasom rozkladu 11 dní ako v pôde C s polčasom rozkladu 24 dní. Rozklad MCPA súvisel s odlišným obsahom organického uhlíka v týchto dvoch vzorkách pôd. Získané sorpčné izotermy MCPA vyhovovali rovniciam Freundlichovej a lineárnej sorpčnej izotermy. Rozdeľovací koeficient KD MCPA bol vyšší pre pôdu A (0,387 l kg-1) ako pre pôdu C (0,165 l kg-1). Vyššia sorpčná kapacita pôdy A ako pôdy C sa zhodovala s vyšším obsahom organického uhlíka v pôde A. Výsledky tejto práce naznačujú, že MCPA je potenciálne mobilný herbicíd a môže predstavovať veľké riziko pre kvalitu podzemných vôd v dôsledku jeho málo účinnej sorpcie, pomerne vysokej rozpustnosti vo vode a zvýšenej perzistencii v hlbších častiach pôdneho profilu.
This contribution presents a proposal of semiempirical method to estimate vertical profiles of nutrients uptake rate by plant roots, based on results of field measurements of soil - plant - atmosphere continuum (SPAC). The transport of chemicals in porous media can be described by convection-dispersion equation, containing sink term, characterising the solute (nutrients) uptake by roots. To determine this sink term was the aim of presented study. The data - necessary for determination of nutrients uptake rate profiles - during plants ontogenesis were acquired by measurement in the field site with maize canopy, near Trnava locality, South Slovakia. The proposed method of vertical profiles of nutrients uptake calculation is based on the estimated direct proportionality between nutrients uptake rate (nitrogen, phosphorus and potassium) and transpiration intensity during ten days time intervals. Shorter time interval is not recommended to be utilised, because estimation errors are comparable to the changes of estimated values of nutrients concentration in plants. A nutrient uptake rates profiles can be determined using the Eq. (9), knowing water uptake rate profiles and the ratio of transpiration flux and particular nutrient uptake rate. The nutrient uptake rate profile calculated by the proposed method can be incorporated into the convection-dispersion equation and is used to model nutrient transport in the soil, taking into account uptake of particular nutrients by plants, during the vegetation period. Comparison of nitrogen uptake rates estimated from field measurements and those, calculated by the presented method shows significant differences in some cases, but seems to be applicable for mathematical modelling of nutrients uptake by plants. and Príspevok obsahuje návrh poloempirickj metódy výpočtu vertikálneho rozdelenia intenzít odberu rozpustených látok (najdôležitejších živín) porastom poľnohospodárskych plodín. Súbor údajov (chodov intenzít transpirácie počas ontogenézy rastlín a sezónnych chodov obsahu vybraných živín v pôde a v rastlinách), umožňujúcich výpočet, bol získaný z výsledkov komplexných meraní charakteristík systému pôda - rastlina - atmosféra (SPAC) v pôde s porastom kukurice v objekte bývalého Výskumného ústavu kukurice v Trnave. Predpokladajúc platnosť zistenej priamej úmernosti medzi intenzitami odberu živín (dusík, fosfor, draslík) rastlinami z pôdy a intenzitou transpirácie porastu, navrhnutá bola metóda výpočtu vertikálneho rozdelenia intenzít odberu rozpustených látok (najdôležitejších živín) porastom poľnohospodárskych plodín. Jej aplikácia umožňuje určenie odberového člena v rov. (1) a riešením tejto rovnice môžeme vypočítať zmeny koncentrácie vybraných živín v pôde, berúc do úvahy ich odber koreňmi rastlín. Odberový člen možno vypočítať pomocou rov. (9), ak poznáme vertikálne rozdelenie intenzít odberu vody koreňmi rastlín a pomer medzi transpiračným tokom a celkovou intenzitou odberu príslušného iónu porastom v danom časovom intervale. Porovnanie celkových intenzít odberu dusíka porastom kukurice, ktoré bolo určené z výsledkov poľných meraní a intenzít, vypočítaných predloženou metódou síce v niektorých prípadoch ukazuje na značné rozdiely (obr. 4), avšak v prvom priblížení je metóda vhodná na modelovanie pohybu žívín v pôde.
Povodně a sucho se v posledních letech skloňují ve všech pádech. Často se v tomto kontextu zmiňuje potřeba budování přehrad a dalších nákladných děl, která však řeší jen důsledek mnohdy špatné péče o krajinu. Ne každý si totiž uvědomuje, jak důležitou roli hraje v koloběhu vody půda a stav krajiny. Kvalitní a nedegradovaná půda dokáže poutat značné množství vody, čímž reguluje dopady obou klimatických extrémů. Pestrá krajina s přirozenými mokřady a dalšími krajinnými prvky s vodou hospodaří lépe než krajina plná velkých půdních bloků s monokulturami zemědělských plodin a regulovanými vodními toky. and Jiří Hladík, Jan Vopravil, Marek Batysta.
Presented are results of simulations of root water uptake applying a macroscopic model of water transport in Soil - Plant - Atmosphere - Continuum. As a simulation tool is used the software package GLOBAL, based on the solution of the one-dimensional Richards equation. The main objective is to examine the contribution of root extraction functions (sink terms) based on different root morphological parameters to the changes in the soil water content profiles during the vegetation period of three crops. The root extraction functions are estimated using dry mass, length and surface area density distributions of all (total) and the fine roots (< 0.5 mm) of spring barley, winter rye and maize. It was observed that the ''root mass'' extraction curves slightly deviate from the ''length'' and ''surface area'' ones, especially in the topsoil and for the crops with a longer vegetation period. Nevertheless, the resulted differences in the soil water content distributions were small. The role of ''fine roots'' distribution was also examined. Calculating the water storage, it was found that the deviations were within the error of direct measurements. The sensitivity of the models based on the Richard´s equation to the different root extraction functions was found to be low, which reflected in small differences in soil water content distributions. Hence, any of the studied root morphological parameters can be successfully applied for simulations of root uptake at macro scale. and Práca obsahuje výsledky simulácie odberu vody koreňmi rastlín makroskopickým modelom pohybu vody v systéme pôda - rastlina - atmosféra, ak boli funkcie odberu vody koreňovým systémom určené z rozdelení rôznych charakteristík koreňového systému. Použili sme simulačný model GLOBAL, založený na riešení jednorozmerného tvaru rovnice Richardsa. Cieľom práce bolo určiť funkcie odberu vody koreňovým systémom rastlín, s využitím rozdelenia rôznych charakteristík koreňového systému tej istej rastliny a ich vplyv na vlhkostné profily v pôde počas ontogenézy rastlín. Simulácia bola vykonaná pre tri porasty - jarný jačmeň, ozimnú raž a kukuricu. Funkcie odberu vody boli vypočítané z údajov o rozdelení hmotnosti suchých koreňov, ich mernej dĺžky a merného povrchu pre všetky korene a pre ''jemné'' korene (< 0,5 mm v priemere). Ukázalo sa, že funkcie odberu založené na rozdelení hmotnosti koreňov sa nevýrazne odlišovali od tých, ktoré boli vypočítané s použitím ''dĺžky'' a ''povrchu'' koreňov v orničnej vrstve pôdy a pre porasty s dlhším vegeračným obdobím. Aj rozdiely medzi funkciami odberu s využitím rozdelenia rôznych vlastností ''jemných'' a všetkých koreňov boli v medziach presnosti merania. Z toho vyplýva, že ľubovoľný z použitých rozdelení parametrov koreňov (hmotnosť, dĺžka, povrch) môže byť použitý na výpočet odberových funkcií pre simuláciu pohybu vody v systéme PRAT a následnú simuláciu makroskopickými modelmi, založenými na riešení rovnice Richardsa.
We investigated the sorption-desorption behaviour of acid herbicide MCPA (4-chloro-2-methylphenoxy acetic acid) in five soils (denoted as A1-5), three bottom sediments (S1-3) and in two river sediments (L1-2) at two initial concentrations in aqueous solution - C0 = 0.5 and 10 mg L-1. Sorption and desorption of MCPA was measured by a batch equilibrium technique using analytical pure MCPA. There was no significant influence of the initial concentration of MCPA on its equilibrium distribution between soil/sediment and aqueous solution. The difference between distribution coefficient KD at C0 = 0.5 mg L-1 and KD at C0 = 10 mg L-1 was found only in the case of one bottom sediment (S2). Simple regression analysis between KD at C0 = 0.5 and 10 mg L-1 and soil/sediment properties indicated that the most important property which determined the variation in MCPA sorption is organic carbon (r = 0.885** and r = 0.921***, respectively). Similarly, the desorption of MCPA was inversely proportional to organic carbon content of the soils and sediments used (r = -0.821* and r = -0.888**). These observations showed that sorption-desorption behaviour of MCPA in soils and sediments was primarily controlled by organic components of the geosorbents used. Overall, the sorption extent of MCPA in soils and sediments was low (Psorp ≈ 5 - 53 %; KD = 0.131 - 2.827 L kg-1) and desorption extent was relatively high (Pdes ≈ 11 - 52 %), especially in soils and sediments with the lower organic carbon content. The experimental results and calculated values of groundwater ubiquity score GUS and relative leaching potential index RLPI imply that MCPA is very mobile in all soils and has high potential to contaminate groundwater. and Laboratórnymi metódami sme skúmali sorpčno-desorpčné správanie herbicídu MCPA (kyselina 4-chlór2-metyl fenoxyoctová) s kyslým charakterom (pKa = 3,07) v 5 vzorkách pôd (A1-5), v 3 vzorkách dnových sedimentov (S1-3) a v 2 vzorkách riečnych sedimentov (L1-2) pri dvoch koncentráciách vo vodnom roztoku - 0,5 a 10 mg l-1. Počiatočná koncentrácia MCPA vo vodnom roztoku nemala vplyv na jeho rozdelenie medzi pôdu/sediment a vodný roztok, iba v prípade 1 vzorky dnového sedimentu (S2) bol zistený rozdiel v rozdeľovacích koeficientoch KD. Sorbované množstvo MCPA v sledovaných pôdach a sedimentoch priamo úmerne záviselo od celkového obsahu organického uhlíka. Podobne, vodou desorbované (extrahované) množstvo MCPA z pôd a sedimentov vyjadrené v % (Pdes) nepriamo úmerne záviselo od celkového obsahu organického uhlíka. Tieto pozorovania dokumentujú, že sorpčno-desorpčné správanie MCPA v pôdach a sedimentoch je primárne kontrolované organickými zložkami sledovaných geosorbentov. Celkovo bol sorbovaný podiel MCPA v pôdach a sedimentoch nízky (Psorp ≈ 5-53 %; KD = 0,131-2,827 l kg-1) a desorbované množstvo relatívne vysoké (Pdes ≈ 11-52 %), zvlášť v pôdach a sedimentoch s nižším obsahom organického uhlíka. Experimentálne výsledky a vypočítané hodnoty GUS (Groundwater Ubiquity Score) a RLPI (Relative Leaching Potential Index) poukazujú na výraznú pohyblivosť MCPA v pôdach a vysokú tendenciu MCPA preniknúť do podzemných vôd.