Keywords: soil origin, potassium, K fertilisation strategies, yield gap, CEE countries.
During the last 17 years (i.e. 1988-2004), yields of the main crops (cereals) in the Central-Eastern Europe (CEE) countries have undergone a significant decline. This was basically attributed to changes related to the shift from a planned to a free market economy, which in turn led to a rise of prices of the means of plant production, including fertilisers among other inputs. A study was conducted in selected countries of the CEE which revealed that the decline in crop yields in the last 17 years was strongly related to potassium (K) soil fertility status. For example, referring to the average yields of winter wheat for the period 1988-91, it was found that the quantitative yield decline reached 1.0 t grain per ha. The greatest drop in yield occurred in the period 1990-93, i.e. 3 or 4 years after cessation of high K use. At present, the lower but stable level of yields is a permanent feature of agriculture in Czech Republic, Poland and also in Bulgaria and Romania, but a linear decrease still occurs in Hungary and Slovak Republic.
This study has also revealed that in most CEE countries the original concept of build up and maintenance of soil K reserves remains in force in spite of the growing gap between recommended and applied potassium rate. Therefore new strategies of more sustainable K management are required in order to increase the availability of soil potassium reserves and utilisation coefficients of potassium applied in fertilisers. Two concepts are suggested (i) a refinement of soil K test in relation to the most sensitive crop in the rotation (ii) an enhancement of the accessibility of subsoil K reserves to crop plants.
It was also found that the CEE region is not uniform with respect to soil K supply potential. Poland is naturally poor in potassium resources, due to the different origin of the main soil types. Therefore any kind of K management strategy must take into account the regional or even local (field scale level) soil potential for K supply and the use of crops in the rotation which can exploit soil and fertiliser potassium resources.
Witold Grzebisz, Department of Agricultural Chemistry, Agricultural University, Wojska Polskiego 71F, 60-625 Pozna?, Poland.
Mariusz Fotyma, Institute of Soil Science and Plant Cultivation — State Research Institute, Czartoryskich 8, 21-400 Pu?awy, Poland.
24 pages, 8 figures, 8 tables, 28 references.