T. Nemeth, NITROGEN IN HUNGARIAN SOILS - NITROGEN MANAGEMENT RELATION TO GROUNDWATER PROTECTION, Journal of contaminant hydrology, 20(3-4), 1995, pp. 185-208
Citations number
24
Categorie Soggetti
Water Resources","Environmental Sciences","Geosciences, Interdisciplinary
Nitrogen is widely used in agricultural practice in different organic
and inorganic forms to enhance crop productivity. After the growing se
ason, a part of the nitrogen remains in forms sensitive to changes of
the conditions, such as nitrate. In years with above-average precipita
tion a significant amount of nitrate can leave the rooting zone of var
ious crops even when land is cropped annually. Integration of knowledg
e related to environmental conditions of a certain area with the soil,
water and crop management practices helps to prevent the simultaneity
of the unfavourable processes leading to nitrate leaching, thus water
resources may be protected from nitrate pollution of agricultural ori
gin. It is of increasing importance that such an approach be applied i
n the Hungarian crop production. Since the great spatial variability o
f soil-forming factors is clearly reflected by the heterogeneous (some
times mosaic-like) soil cover in Hungary, differentiation of categorie
s within the soil types is strongly needed for agricultural practices.
Basic features of a computerized fertilizer recommendation system dev
eloped in RISSAC to characterize the soil fertility levels in Hungary
are: classification of the soils into a new land-site category system
characterized by 4-digit codes, and also into aggregated land-site gro
ups with regard to the major plant nutrients; and characterization of
the nutrient status of soil by establishing nutrient supply categories
which consider also the fertilizer requirements of the main crops. Si
nce during the last few decades Hungarian farmers have applied more N-
P-K fertilizers than the crops required, and at the same time there wa
s a large increase in other potential pollution sources, harmful side-
effects such as unfavourable changes in the quality of surface and sub
surface water resources were detected. Hence, it was imperative to dev
elop methods to calculate N balances which take into account the amoun
t of N originating from other sources than the applied mineral fertili
zers and also N output via nitrate leaching down the soil profile. Com
parison of the results of several long-term field trials conducted sim
ultaneously at several experimental sites which differed in environmen
tal characteristics such as soil type and climatic conditions was show
n to provide a good basis for a more generalized quantification of the
overall turnover of nitrogen and for calculating improved N balances.
The results indicated that when the rational use of organic manures a
nd N-containing fertilizers is based on the plant's N demand, the nitr
ogen balances are in equilibrium. The amount of N needed to obtain eco
nomically viable yields, while at the same time being in balance with
the requirements of the crops and keeping the environment uncontaminat
ed, varied in long-term trials from 0 to 50 kg ha(-1) yr(-1) on fertil
e soils, 50 to 100 kg ha(-1) yr(-1) on coarse textured soils, while 10
0 to 150 kg ha(-1) yr(-1) in farm field analysis. Residual effects of
nitrate in long-term experiments proved that after proper application
of N fertilizer the amount of the residual nitrogen was low and no nit
rate-N accumulation was detected under the root zone even for coarse t
extured soils.