Soil erosion, soil loss tolerance and sustainability in Hungary

3rd International Conference on Land Degradation and Meeting of the IUSS Subcommission C - Soil and Water Conservation September 17-21, 2001 - Rio de Janeiro - Brazil

Symposium II Presentation: Oral (S2-002)

Soil erosion, soil loss tolerance and sustainability in Hungary CENTERI, Csaba1, PATAKI, Róbert2, and BARCZI, Attila3 1

SzIE-GTI, Dept. of Soil Science and Agricultural Chemistry, 2100-Godollo, Pater K. u. 1., Hungary, TEL: +36-28-522-000/1805, FAX: +36-28-410-804, E-mail: [email protected]; 2Institute of Geodesy, Cartography and Remote Sensing, Budapest, Hungary; 3SzIE- GTI, Dept. of Landscape Ecology, Godollo, Hungary

Introduction Because soil is formed slowly, it is essentially a finite resource. As a result of this relatively recent realisation, the severity of the global erosion problem is gradually becoming widely appreciated. The area of Hungary is 9.3 million hectares. 6.4 million hectares are covered by agricultural land. Estimations show that about 30-40 % of the country’s area is affected by erosion but it might go up to 50 % since 50 % of Hungary’s total area is arable land. Digital version of genetic soil map, land cover map and relief map are available at the scale of 1:100 000 for Hungary’s total area. Our present work describes results of preparing erosion map with the Universal Soil Loss Equation at this scale. The most important of all, how we evaluate soil loss categories. We need to inspect soil loss tolerance (T) values in order to tell decision makers, farmers and environmentalists the rate of soil loss and the state of sustainability. We analyze the affects of tolerance values in connection with sustaining Hungarian soils. Differences between soil formation and permissible soil loss will give us a ratio that worth evaluating sustainability of our agricultural lands. We can tell how well protected our soils are, where do we really need protection and where shall we change arable land to pasture or forest land.

Materials and methods The standard reference for erosion modeling is the Wischmeier-Smith’s Universal Soil Loss Equation (USLE) (Wischmeier and Smith, 1978). New models were developed since 1978 but their hunger for input is so huge that it is almost impossible to prepare any digital version at any scale in Hungary, since either the database is not available or it is very expensive to prepare. This is the reason why we chose USLE for our present work. We used ESRI (Environmental Systems Research Institute, Inc), NT Arc/Info 7.2 under Unix operation system for digital works and calculations, ESRI Arc/View 3.1 under Win98 operation system for presentation. The USLE is an empirical model that uses physical factors to quantify the amount of soil lost per hectare per year. A = Soil Loss (t ha-1 y-1); R = Rainfall Erosion Index (MJ mm ha-1 h-1 y-1 or N h-1), (- our R factor is from Thyll’s isoerodent map (1992)); K = Soil Erodibility Factor (t ha h ha-1 MJ-1 mm-1), (- we used the digital version of the Hungarian Soil Map 1:100 000 (Várallyay, 1985) and the estimation of K factor from Stefanovits (1966)); L = Slope Length (dimensionless), S = Slope Gradient Factor (dimensionless), (-L and S factors are combined to give one topographic factor: the LS factor. We used the modified version of slope length calculation of Hickey - Smith – Jankowski (1994)); C = Cropping Cover Management Factor (dimensionless), (the CORINE Land Cover 100 was the base for C factor evaluation); P = Agricultural Practice Factor (dimensionless) (- It is the ratio of soil loss with a specific support practice to the corresponding loss with upslope-downslope cultivation (Wischmeier and Smith, 1978). Since upslopedownslope cultivation is wide spread in Hungary, and at this scale soil conservation tillage practice did not show up at the map the factor had to be standard (P=1)). Since USLE is not able to calculate sedimentation, wherever the soil types’ properties suggested (Cambisols, Fluvisols (FAO classification)), marshland with forest covers (Hungarian classification) we gave zero K factor to show these soil types as potential sedimentation areas for the erosion map of Hungary. Comparing our map with the earlier, analog map (prepared in the 1960’s) we can see that our estimations for sedimentation cover almost the same areas. We had rainfall simulation studies to calculate soil erodibility that we used for preparing our erosion map (see poster section). Before all we had for K factor is estimations. Outputs show that previous estimations overestimated soil erodibility and in some cases we only had estimations for particle size classes.



Results We prepared the 1:100 000 scale of soil erosion prediction map of Hungary (Map 1.). We have three main soil loss categories on the map: 1. below 2 tons per hectare (according to Hungarian (Stefanovits, 1966) and foreign) estimations, this is the average rate of soil formation, so if the soil loss is below this level we can say agricultural production is sustainable); About soil loss tolerance: In agricultural production permissible soil loss means that agricultural activity gives chance for soil formation and does not reduce soil fertility (Holý, 1982). Hall et. al. (1985) concluded, “An upper limit (to allowable soil loss) of 11 t/ha/year is generally accepted since it approximates the maximum rate of A horizon development under optimum condition” (emphasis added). Larson (1981) proposed a two-level approach to setting T values: a T1 value reflecting on site soil productivity maintenance objectives, T2 value reflecting broader social purposes and off-site concerns, such as water pollution and reservoir sedimentation. The T1 values would be set by scientific experts in soils and agriculture, T2 values would be set by economists, environmental scientists and planners, and public policymakers. This way T2 temporarily might be set higher than T1. 2. Between 2 and 12.5 tons per hectare per year (since USLE offers 5 tons per acre per year maximum level of permissible soil loss that is about 12.5 tons per hectare per year – this limit was established according to economically allowable nutrient loss for USA farmers), however, comparing to soil formation estimates there is need for protection on these areas, so in our case 2 t/ha/y is T1 and 12,5 t/ha/y is T2 value; 3. This category is above 12.5 tons per hectare per year where arable agriculture should not be done or only with strict regulations. Our present map shows arable lands with C factor of 0,25 (winter wheat), so it shows the soil loss in case we plant winter wheat everywhere on arable lands. Analyses show that about 80 percent of the soil surface is in the sustainable zone (taking out water surfaces, settlements, roads, etc.). About 14 % belongs to 2-12,5 t/ha/y zone and 6 % suffers severe erosion. We also had analyses for changing winter wheat to corn, so C factor from 0,25 to 0,5. This small change means about 6 % decrease of sustainable area (below 2 t/ha/y). In case we apply more strict regulation for permissible soil loss (T1) value and push it down from 2 t/ha/y to 1 t/ha/y it means about 13 % growth of endangered area. We can do the same with T2 value, since its estimations vary from 11-15 t/ha/y. It also causes differences in spatial distribution of soil loss categories. It is possible to make estimations with various plants on arable lands and it is also possible to change the forests’ and pastures’ C factor to see what effect does it have on soil loss. We can see how values of different limits affect erosion measures and estimates. Soil loss is very hard to estimate. To reach better results there is need for local measures that are very expensive but necessary. In most cases we have researches, results but very local ones. It is desirable to have more local measures for calculating more proper soil loss. We can use soil erosion maps to outline potentially endangered areas for sediment and high soil loss values. We can outline areas where there is need for soil protection and also can tell the rate of the need for sustainable agricultural production. Therefore, our map is good for regional planning. It shows highly erodible areas, areas potentially affected by sedimentation, need for crop rotation change and land use change.



Map 1. Predicting soil erosion with USLE in Hungary

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