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

Long-term field experiments in Central Europe

Popp, T., IPI Coordinator Central Europe

Introduction

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.

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).

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.

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.

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).

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).

Hungary
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).

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.

Poland
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).
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.

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.