IPI International Potash Institute
IPI International Potash Institute

Research Findings: e-ifc No. 16, June 2008

Long-term field experiments in Central Europe

Popp, T., IPI Coordinator Central Europe


Long-term field experiments (LTFE) have a long tradition in the countries of Central Europe, the oldest trial in Skierniewice, Poland beginning in 1923. Many other trials were established in the late sixties and early seventies and have been in operation for almost 40 years (Table 1). The exciting part of these trial projects is that the experiments have been set up on very different soil types varying in soil texture and are being carried out under different climatic conditions, with annual precipitation from 425 to 798 mm and an average temperature from 6.5 °C to 12.0 °C.

Table 1. Countries, sites and characteristics of LTFE in Central Europe.
Country No. Site Start Altitude Rain Temp. Soil type Soil texture
  year m above mm °C  
Bulgaria 1 Plovdiv 1959 160 425 12.0 Mollic Fluvisol NA
Czech 1 Chrastava 1977 345 798 7.1 Luvisol loamy sand
  2 Horazďovice 1978 472 573 7.4 Cambisol loamy sand
  3 Jaroměřice 1975 425 535 7.5 Luvisol loamy
  4 Krásné Údolí 1977 645 605 6.1 Cambisol sandy loam
  5 Lednice 1977 172 540 9.2 Chernozem loamy clay
  6 Libějovice 1974 460 606 7.6 Luvisol sandy loam
  7 Lípa 1974 505 632 7.7 Cambisol sandy loam
  8 Pusté Jakartice 1979 290 650 8.0 Luvisol loamy
  9 Sedlec 1972 300 581 8.4 Chernozem loamy
  10 Staňkov 1981 370 511 7.8 Luvisol loamy
  11 Svitavy 1981 460 624 6.5 Luvisol sandy loam
  12 Uherský Ostroh 1972 196 551 9.2 Luvisol loamy
  13 Věrovany 1990 207 563 8.5 Chrenozem loamy
  14 Vysoká 1983 595 655 7.4 Pseudogley loamy
  15 ?atec 1972 247 451 8.3 Chernozem clay loam
Hungary 1 Bicsérd 1967 160 650 10.4 Luvic Phaeosem clay loam
  2 Hajdúböszörmény 1967 124 516 9.5 Luvic Phaeosem clay loam
  3 Iregszemcse 1967 130 623 10.2 Calcaric Phaeosem loamy
  4 Karcag 1967 87 502 10.4 Luvic Phaeosem clay loam
  5 Keszthely 1967 132 600 10.0 Eutric Cambisol loamy
  6 Kompolt 1967 150 533 9.7 Haplic Phaeosem clay loam
  7 Mosonmagyaróvár 1967 122 566 9.7 Calcaric Fluvisol sandy loam
  8 Nagyhörcsök 1967 103 566 9.9 Calcaric Phaeosem loamy
  9 Putnok 1967 160 547 8.7 Ochric Luvisol clay
Poland 1 Balcyny 1986 150 550 7.0 Luvisol silty loam
  2 Skierniewice 1923 128 527 7.9 Haplic Luvisol loamy sand
Romania 1 Livada 1967 120 723 9.3 Eutric Cambisol NA
Slovakia 1 Báhoň 1974 159 534 9.3 Chernozem loamy
  2 Bodorová 1974 485 783 7.1 Cambisol NA
  3 Haniska 1977 200 664 8.4 Luvisol loamy
  4 Jakubovany 1987 385 591 7.5 Luvisol loamy
  5 Veľké Ripňany 1985 172 600 9.3 Luvisol loamy
  6 Vígľaš 1980 340 670 7.7 Gleyic Luvisol NA
Fig 1. Total amounts of fixed potassium and percentage of applied potassium are shown for the studied soils.
Fig 1. Location of LTFE sites in Central Europe.
(click to enlarge)

A very extensive programme of LTFE is established in the Czech Republic with 15 trials (Fig. 1), of which nine trials are set up in the potato growing area and six in the more favourable sugar beet growing area (Table 2). All the trials are supervised by ÚKZÚZ, the Central Institute for Supervising and Testing in Agriculture.

Quite a large programme also exists in Hungary, which started as a national project in 1967 (Table 1). The LTFE comprises nine trial sites, and with two different crop rotations and one maize monoculture 20 NP and NPK treatments with various application rates being covered. Different institutions are managing the various trial sites; unfortunately because of financial problems the results from the trial sites have not been summarized over the past two years.

Following the same tradition as in the Czech Republic, ÚKSÚP is handling the trial programme in Slovakia. The structure is similar to that of the Czech Republic, the only difference being that in Slovakia, three growing areas are distinguished, which includes that of maize as well as potato and sugar beet (Table 2).

Table 2. Crop rotation on LTFE in the Czech and the Slovak Republic
  Czech Republic   Slovakia
Year sugar beet potato   maize and sugar beet potato
1 oats + alfalfa oats + clover   grain maize silage maize
2 Alfalfa clover   winter wheat winter wheat
3 winter wheat winter wheat   spring barley spring barley
4 silage maize early potato   grain maize potato
5 winter wheat winter wheat   spring barley spring barley
6 spring barley spring barley   oats + alfalfa oats + clover
7 sugar beet potato   alfalfa clover
8 spring barley spring barley   winter wheat winter wheat

The oldest LTFE in Skierniewice, Poland (started in 1923) can perhaps be mentioned in the same breath as Rothamsted, UK (1843) and Bad Lauchstädt, Germany (1902). In fact for the Polish LTFE we can talk about three different field research projects, an arbitrary rotation with and without legumes, a crop rotation with five crops (Table 3), and potato and rye monoculture. This year the 85th anniversary was celebrated, and this event honoured by holding an international conference about potassium and magnesium which took place at the beginning of June 2008. A second LTFE in Poland is located in the northern part of the country near the town of Ostroda. Eight different N:P:K-ratios are compared with and without application of farmyard manure.

Table 3. Crop rotation on LTFE in Poland.
Year Balcyny Skierniewice
1 sugar beet potato
2 spring barley spring barley
3 silage maize red clover
4 spring wheat winter wheat
5   rye

We are aware of one LTFE in Bulgaria and 11 trials in Romania, but we have experimental findings from only one site. This is in Livada, where two trials are located. The first deals with nine different application rates of lime in combination with eight nutrient treatments and started in 1961, the second has 5 P x 5 N rates, 4 NP x 4 K rates and 4 NP rates x 4 farmyard manure rates and was first carried out in 1967. The LTFE in Plovdiv, Bulgaria was established in 1959 and has 7 treatments with different NPK application rates (N0P0K0, N500P300K200, N500P0K200, N500P300K0). One trial follows a normal crop rotation (Table 4), the other trial has alfalfa as a monoculture.

Table 4. Crop rotations on LTFE in Romania, Bulgaria and Hungary (note: in Bulgaria and Hungary there are 2 and three typical crop rotations in each LTFE site, marked in the table a-c.)
Year Romania Bulgaria   Hungary
  a b   a b c
1 winter wheat maize alfalfa   winter wheat winter wheat maize
2 maize winter wheat alfalfa   maize maize maize
3 oat Forage peas alfalfa   maize maize maize
4 sunflower spring barley alfalfa   field pea winter wheat maize
5 soybean   maize
6 flax   maize

Results from LTFE

Czech Republic
Almost four full cycles of crop rotations, each comprising eight different crops (one crop per year), have been evaluated over a period from 1972 till 2002. As the different fertilizer treatments did not show a significant effect on yield in the more fertile sugar beet growing area, this data is not shown here. Nevertheless, increasing potassium application rates had an enormous influence on yield development on the more marginal soils of the potato growing area (Fig. 2).

Fig 2. Average yields in the potato growing area of Czech Republic (average of nine sites and eight crops in rotation, 1972-2002).
Fig 2. Average yields in the potato growing area of Czech Republic (average of nine sites and eight crops in rotation, 1972-2002).

The results show that N, P and K contributed approximately to an additional 50 per cent yield over the years. Between K0 and K158 with constant application of 88 and 80 kg N and P2O5, respectively, 108 kg K2O/ha K contributed an additional 10 per cent of yield.

When K application was neglected over a period of 22 years, the K balance was negative at 87.7 kg K2O/ha (Fig. 3). Soil K content dropped from 168 mg/kg soil at the beginning of the field trial to 132 mg/kg soil during 1981-1983 and further to 107 mg/kg soil during 2000-2002. Only with an annual application rate of 158 kg K2O/ha could a positive K balance be achieved and available K in the soil be maintained at almost the same level. This data shows that soil K fertility is maintained only with constant application of potassium.

Fig 3. The comparison of potassium balance and the content of available potassium in soil in experiments in the potato growing area (data is average of nine sites and eight crops in rotation, 1972-2002).
Fig 3. The comparison of potassium balance and the content of available potassium in soil in experiments in the potato growing area (data is average of nine sites and eight crops in rotation, 1972-2002).

The results from four sites (Bicsérd, Iregszemcse, Keszthely, Mosonmagyaróvár) were evaluated for grain maize which was cultivated seven times during the period 1989 till 2001. If we sum up the accumulated yield differences as of the untreated control plot in 1989 we see that omission of all nutrients created a yield loss of 5.57 mt/ha (Fig. 4). If N only was applied, a certain yield increase could be recognised, which resulted in a cumulative yield of 10.18 mt/ha until 2001. The additional application of phosphate did not show much effect during the first years until 1997, but during the last two years the NP treatment gave a 21.7 per cent yield increase as compared to N only. However, balanced fertilization with the addition of 200 kg K2O/ha resulted in an accumulated yield increase of 13.22 mt/ha (Fig. 4).

Fig 4. Additional cumulative yields in a LTFE in maize in Hungary (average of four sites).
Fig 4. Additional cumulative yields in a LTFE in maize in Hungary (average of four sites).

Results of soil K (Table 5) in the four sites show that in two of the sites (Iregszemcse and Keszthely), soil K was decreased during the period 1987- 1999 when K was not applied (control plots), but in all four sites soil K was either maintained or even increased when K was applied at 200 kg K2O/ha.

Table 5. Soil potassium content (AL-K2O, mg/kg) in two treatments and two sampling dates.
Site Control plot   N200P120K200
  1987 1999   1987 1999
Bicsérd 263 268   299 337
Iregszemcse 169 141   238 269
Keszthely 188 144   238 238
Mosonmagyaróvár 95 116   119 145

The LTFE in Skierniewice has produced thousands of results during its duration giving rise to numerous publications. As an example we present some data, which was published by S. Mercik and W. Stępień in Fragmenta Agronomica 2005. These demonstrate the effect of the different nutrient combinations and three cultivations systems on yield of rye, a crop which is extensively grown in Poland. The results clearly show that only with a sustainable fertilizer application of all important nutrients, could the highest yield be achieved (Fig. 5). Monoculture of rye leads to a significant reduction of yield, especially when the application of nutrients was limited. A similar trend but on a higher level can be demonstrated, if the application of farmyard manure and the incorporation of legume crops in the rotation are neglected. The lack of nitrogen was the most important factor limiting yields (-31% to -52%), followed by phosphorus (-17% to -34%) and potassium (-10% to -18%). In conclusion, the 33 LTFE experiments described in Central Europe are well able to demonstrate the various benefits that can be learned only over a relatively long time span of 40 years of repeated cropping systems. These experiments show that with adequate supply of nutrients, that both high yields as well as soil fertility can be maintained as indicated by K balance calculations and soil K levels. The effects of insufficient supply of potassium are hard to detect over an annual cycle, and only LTFE can demonstrate the slow, costly reduction in productivity of crops.

Fig 5. The effect of N, P and K omission as compared to control (full omission) and full NPK application on yields of rye in Skierniewice, Poland (average of six crops, 1976-2004).
Fig 5. The effect of N, P and K omission as compared to control (full omission) and full NPK application on yields of rye in Skierniewice, Poland (average of six crops, 1976-2004).
Note: N, P2O5 and K2O are 90, 30 and 110 kg/ha, respectively. Lime application was given at 2.0 mt/ha every five years for the rotation with FYM and legumes, and at 1.6 mt/ha every four years to the No FYM or legumes, and Monoculture (rye only) rotations.

Further reading

  • Mercik, S. and W. Stępień. 2005. The most important soil properties and yields of plants in 80 years of static fertilizing experiments in Skierniewice. FRAGMENTA AGRONOMICA, (XXII) No. 1 (85), pp. 189-201.
  • Čermák, P. and S. Torma. 2006. Importance of balanced fertilization for sustainable crop production in Czech and Slovak Republic. IPI Annual Report, pp. 41 - 58.
  • Debreczeni, K. 2005. Dauerdüngungsversuche zur Kaliumwirkung (in German). Trial report 2005, 13 p.
Fig 5. The effect of N, P and K omission as compared to control (full omission) and full NPK application on yields of rye in Skierniewice, Poland (average of six crops, 1976-2004).
IPI meeting in Brno, Czech Republic, during the conference on "Plant Nutrition and its Prospects", organized by the Mendel University of Agriculture and Forestry, Brno, Czech Republic, 5-6 September 2007. Photo by T. Popp.

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