Officially published data for the Czech Republic (CR) from 1920 to 2000 and for selected European countries (mostly from 1960 to 2000) were analysed. In the last 40 years, the yield of the five main crops was comparable with European Union (EU) for wheat, barley and rape, but lower for potato and sugar beet. The fastest yield growth was found for flax (2.15% per year), maize and wheat (1.61 and 1.53%), while growth was slower for hops and root crops and slowest for grassland hay (0.22%). The highest yield variation caused by individual years was for wine grapes (32.5%), poppy, edible legumes and flax (18.5-18.3%), while the lowest level of variation was for cereals, i.e. oats, barley, wheat, rye and hay from arable land (9.7-12.0%). For many crops, yield variation decreased over time. The most adaptable crops, whose yield increased most in fertile years, were flax, wheat, edible legumes, maize, rape and barley (regression coefficient of 1.76-1.24), while the lowest level of adaptability was shown by hops, sugar beet, hay from grassland and poppy (0.68-0.14). The higher the level of adaptability the higher the yield growth over the 75 years analysed. The differences in yield of the most commonly grown crops between the EU and the CR can be explained by the different levels of adaptability of the crops in the two regions. Of the five most commonly grown CR crops, wheat was the most adapted crop in 7 of the 10 European countries studied (without regard to other countries), and sugar beet was the least adapted in 6 countries, Within the 10 countries analysed (without regard for the adaptability of the crop in particular countries) wheat, rape and sugar beet were most adaptable in Spain; barley was most adaptable in Italy; and potato was most adaptable in Hungary. The crops in other countries showed more stability across years. Yields of these five crops in the 10 countries were correlated to each other, with only the yield of potato and sugar beet in the former Soviet Union and that of rape in United Kingdom not being influenced by general factors affecting other countries. The higher the yield of sugar beet in a country of the 10 evaluated, the higher was its adaptability in that country (r = 0.717*). Crop diversity in the CR decreased significantly over the period. Each year the percentage of the three most commonly grown crops increased by 0.41% (percentage of the five most commonly grown crops by 0.14%). The percentage of particular cereals on arable land (wheat 23.0%, barley 17.1%, rye 5.1%, oat 5.2%) and their yields were related to their response to fertilisation over the last 40 years. The average temperature increased significantly during the last 50 years, on average by 0.021 degreesC each year, but in the last 10 years by 0.087 degreesC each year. These climate changes were favourable for the most of the commonly grown crops (wheat, barley, rape, sugar beet, rye, maize and legumes), since the crops gave higher yields in warmer years that were accompanied by more hours of sunshine. The other crops were indifferent to climate changes. Fertilisers have been used in the CR to a greater extent since 1946/1947 (22 kg of nutrients per hectare) with maximum usage in 1985/1986 (273 kg ha(-1), including 105 kg N, 86 kg P and 82 kg K). The consumption rate of nutrients increased by 2.91 kg ha(-1) annually from 1918 to 2000, as found by the regression coefficient. One kilogram of nutrients (N + P + K) increased yields of cereals by 6.7-10.1 kg ha(-1) of grain, rape by 5.2, root crops by 26.1-37.8, hops and wine grapes by 2.0-2.6 kg ha(-1). Yield growth due to fertilisation varied from 9.1% (hay from arable land) up to 84.1% (hops) of the entire growth (=100%). The percentage in grain crops (cereals, grain legumes and rape) was 54.3 (maize)-69.8% (barley), and 63.3% on average in the eight crops. It was also similar in root crops, but only 13.4% for wine grape yields. The highest yield growth per 1 kg of nutrients from fertilisers was found in wheat, rape, sugar beet and potato at the level of application of 70-120 kg ha(-1) nutrients. The efficiency of applied nutrients was higher in years with average precipitation than in years with over-average precipitation, and much higher than in dry years. The yield growth for 1 kg nutrients in all grain crops was lowest in years with average temperature, and highest in most of the crops in years with low mean annual temperature. The estimated balance of nitrogen (applied nitrogen in fertilisers minus nitrogen utilised in harvested crops) was negative during 1947-1960, positive during 1970-1990, and slightly negative again from 1995 to 2000. The surplus of applied mineral nitrogen reached in the years of positive balance was 18.5-36.8 kg ha(-1). The impact of the weather was less than the influence of fertilisation. The dynamics of yield in Germany was studied by multiple regression analysis from 1946 to 1999. The annual increase of wheat yield was 50 kg ha(-1), and per kilogram of N-fertiliser by 10 kg ha(-1). The increase per year in the multiple regression was only 73% of the increase in the simple regression. Therefore, 27% of the increase was related to N-fertilisation (and also to other inputs). The corresponding figures were 25% for rye, 30% for rape, 36% for oats, 47% for potato and 66% for flax. No significant influence of N-fertiliser could be found for other crops. It is concluded that those crops exhibiting the highest increase in yield in the CR over the 75 years investigated were also the most adaptable to inter-annual variability in weather, cultivars grown and to cultivation technologies used. The least adapted crop across 10 European countries was sugar beet, for which adaptability was correlated to yield in the particular country. Among the factors studied, the high response to fertilisation was an important factor in the adaptability of particular crops over the 75 years studied. The adaptability of crops to inter-annual variation is therefore a very important trait for consideration by plant breeders. (C) 2003 Elsevier B.V. All rights reserved.
