’s nitrogen balance (PhD-thesis) Faculty of Bioscience Engineering, UGent
Van Meirvenne M. — Hofman G.: 1989. Spatialvariability of soil nitrate nitrogen after potatoes and its change during winter — Plant and Soil vol
agricultural production is a basic, traditional constituent of the Hungarian economy. An importance question nowadays is how the land can be cultivated and agricultural goods produced under the conditions of sustainable development. From the plant nutrition point of view the establishment of an environment-friendly fertilizer recommendation system is essential if sustainable development is to be achieved. Most experts agree that this type of fertilizer recommendation system is able to fulfil the growing demands of a growing population, while keeping the environment in good condition for the next generations. The experts also agree that fertilizer application could not be replaced widely with organic farming alone. An environmentally friendly fertilizer recommendation system has to be sensitive enough to respond to the effects of different conditions, e.g. great spatial variability of soil characteristics, mosaic-like soil cover, climate, crop rotation practices, soil nutrient supply, etc. There was a dramatic change in Hungarian agriculture at the beginning of the 90s, as the result of which the use of fertilizers decreased sharply for several reasons, e.g. privatization, changes in ownership, withdrawal of state subsidies for mineral fertilizers, drought, etc. Both Hungarian agriculture and the country as a whole is now facing two challenges, i.e. to overcome the economic difficulties and to complete the final phase of preparations to join the EU. Land use change scenarios have proved that the natural endowments of Hungary are suitable for integrating agricultural production with environmental and landscape protection and nature conservation.
Authors:Z. Varga-Haszonits, E. Enzsölné Gerencsér, Z. Lantos, and Z. Varga
The temporal and spatial variability of soil moisture, evapotranspiration and water use were investigated for winter barley. Evaluations were carried out on a database containing meteorological and yield data from 15 stations. The spatial distribution of soil moisture, evapotranspiration and water use efficiency (WUE) was evaluated from 1951 to 2000 and the moisture conditions during the growth period of winter barley were investigated. The water supply was found to be favourable, since the average values of soil moisture remained above the lower limit of favourable water content throughout the growth period, except for September–December and May–June. The actual evapotranspiration tended to be close to the potential evapotranspiration, so the water supplies were favourable throughout the vegetation period. The calculated values of WUE showed an increasing trend from 1960 to 1990, but the lower level of agricultural inputs caused a decline after 1990. The average values of WUE varied between 0.87 and 1.09 g/kg in different counties, with higher values in the northern part of the Great Hungarian Plain. The potential yield of winter barley can be calculated from the maximum value of WUE. Except in the cooler northern and western parts of the country, the potential yield of winter barley, based on the water supply, could exceed 10 t/ha.
Authors:Syahidah A. Muhammad, Russell D. Frew, and Alan R. Hayman
Compound-specific isotope analysis (CSIA) is fast becoming an important tool to provide chemical evidence in a forensic investigation. Attempts to trace environmental oil spills were successful where isotopic values were particularly distinct. However, difficulties arise when a large dataset is analyzed and the isotopic differences between samples are subtle. Thus, this study intends to demonstrate any linkages between diesel fuels in a large number of datasets where subtlety in the isotopic values is accentuated by the near single-point source of origin. Diesel fuels were obtained from various locations in the South Island of New Zealand. Aliquots of these samples were diluted with n-pentane and subsequently analyzed with gas chromatography-isotope ratio mass spectrometry (GC-IRMS) for carbon and hydrogen isotope values. The data obtained were subjected to principal component analysis (PCA) and hierarchical clustering. A wide range of δ13C and δ2H values were determined for the ubiquitous alkane compounds (the greatest values being −4.5‰ and −40‰, respectively). Based on the isotopic character of the alkanes it is suggested that diesel fuels from different locations were distinguishable and that the key components in the differentiation are the δ2H values of the shorter chain-length alkanes. However, while the stable isotope measurements may provide information to classify a sample at a broad scale, much more detailed information is required on the temporal and spatial variability of diesel compositions. The subtle differences of the stable isotope values within the alkanes of different diesel fuels highlighted the power of CSIA as a means of differentiating petroleum products of different origins, even more so when two or more stable isotopes data are combined. This paper shows that CSIA when used in tandem with multivariate statistical methods can provide suitable tools for source apportionment of hydrocarbons by demonstrating a straightforward approach, thus eliminating lengthy analytical processes.
Authors:Róbert Víg, Péter Tamás Nagy, Attila Dobos, and János Nagy
A talaj N-szolgáltató képessége és az elérhető termés – többek között – függ a 0,01 M CaCl2-oldható szerves N-frakció mennyiségétől. Jelen tanulmányban vizsgáltuk, hogy a növényi kondíció és a termés hogyan változik a táblán belül egy heterogén növényállományban, és milyen összefüggésben van a 0,01 M CaCl2-oldható szerves N-frakció mennyiségével.
Egy 10,4 hektáros mintaterületről növénymagasság térképet készítettünk, majd a különböző magasságú állományrészekben több ismétlésben mintavételi pontokat jelöltünk ki. Mintavételi pontonként termés- és talajmintákat vettünk.
A mérési eredmények alapján megállapítottuk, hogy a termés, a levelek SPAD-értéke és a talajban lévő 0,01 M CaCl2-oldható szerves N-frakció mennyisége a növénymagasság növekedésével nőtt, míg a termésben jelentkező heterogenitás csökkent. Megállapítottuk, hogy a növényállomány heterogenitásában szerepet játszhat a 0,01 M CaCl2-oldható szerves N-frakció mennyiségének területi variabilitása is.
A termés becsülhető a 0,01 M CaCl2-oldható szerves N-frakció mennyisége és a termés közötti összefüggést kifejező regressziós egyenletek alapján, viszont a becslés pontossága a különböző kondíciójú állományrészekben eltérő.
Authors:Barbara Simon, E. Michéli, G. E. van Scoyoc, and et al.
The Typic Haplustalfs
soils (Karád and Oltárc) and the Typic Ustochrepts (Gödöllő) are developed on
loess, and on aeolian sand parent material, under forest vegetation, resp. The
Dystric Ustochrepts (Velem) soil formed on metamorphic schist parent material and
had forest vegetation, while the Typic Medisaprists (Zalavár) soil developed on
peat parent material and had marsh vegetation.
Based on this study the spatial variability of surface pH samples
indicate that the TIM sampling procedure should be improved. Ten to thirty
samples must be collected at each site to be able to monitor changes of 0.2 pH
units. If only one sample is taken at each site yearly, spatial difference in
pH or other parameters are likely to obscure differences which may be occurring
over time. The colloidal composition
(organic matter and clay minerals), influenced by parent material, vegetation,
and precipitation, showed a close relationship with the acidity factors, such
as pH, HAC
values. The pH values were the
lowest in the Velem and Oltárc soils where the annual precipitation was the
highest (750-800 mm), and in the Karád soil, where the annual precipitation was
650-700 mm. The Gödöllő soil had the highest pH values, probably due to the
lowest amount of rainfall (550-600 mm) and the disturbance. The Zalavár soil
had fairly high pH throughout the profile probably due to a fluctuating water
table. The HAC
values were the highest in the Velem soil when compared to the other mineral
soils. The pH values were the lowest at
this site. The HAC
values were lower in the
other three forest soils, at the Karád, Oltárc, and Gödöllő sites. The Zalavár
soil had fairly high HAC
values in the H3, H4 and H5 horizons,
probably due to the very high OM content, which provided a lot of H
ions that can dissociate from the exchange sites. The E4/E6 ratios were closely related to the
decomposition or humification rate in the upper and the subsurface horizons
with accumulation of low molecular weight soluble fraction in the deeper
horizon. The mineralogical analysis
showed similar compositions for the soils developed on loess (Karád and
Oltárc), or aeolian sand (Gödöllő), where the major minerals were vermiculite,
mica, kaolinite, and chlorite. A different mineral composition (mica,
vermiculite, clintonite, and kaolinite) was observed for the Velem site, where
the parent material was metamorphic schist. The four mineral soils are forest
soils, with a predominant downward water movement, thus with fairly intensive
leaching process. However, there was a distinct difference among the soils
formed on loess (Karád and Oltárc), or aeolian sand (Gödöllő), and the soil
(Velem) developed on metamorphic schist parent material. The soils at the Karád, Oltárc, and the
Gödöllő sites were less acidified, with higher pH, and lower HAC
values as compared to the Velem soil, even if the
precipitation was very high. The calcareous loess parent material probably
compensated for the higher precipitation and the resulting leaching process at
the Karád and the Oltárc sites. The Gödöllő soil received a very low amount of
precipitation, which resulted in a low degree of weathering, with higher pH,
and lower HAC
, and EAC
values. However, the metamorphic
schist parent material probably contributed to a lower pH and lower buffering
of the developing soil. Based on the
chemical and physical analyses, we concluded that among the soil forming
factors, precipitation and parent material had the greatest influence on the
acidity characteristics of the examined soils. The parent material influenced
the mineralogy of the developing soil, which then influenced the pH, HAC
, and CEC values of the soil. In order to substantiate these
tendencies more samples from a wider array of geological regions are