The effects of different N, P and K supply levels and their combinations were examined on the quality nutritional values and nutrient yield of an established 2 year old all-grass sward in the 29th year of a long-term fertilization field experiment set up on a calcareous chernozem soil. The soil of the growing site contained around 3% humus, 3-5% CaCO3, 20-22% clay in the ploughed layer and was originally moderately well supplied with available N, K, Mg, Mn and Cu and poorly supplied with P and Zn. The trial included 4Nx4Px4K=64 treatments in 2 replications, giving a total of 128 plots. The fertilizers applied were Ca-ammonium nitrate, superphosphate and potassium chloride. The groundwater table was at a depth of 13-15 m and the area was prone to drought. In 2002, the area had 401 mm precipitation and gave 2 cuts of grass. The 1st year results of the trial were published earlier (Kádár, 2005a, b). The main conclusions can be summarised as follows:
1. The N-responses were decisive for both the hay quality and the hay and nutrient yields. The N-fertilizer increased the crude protein content and diminished the same time the crude fibre, crude ash and total sugar contents in the hay. The P-responses were not significant while the K-fertilization stimulated the crude ash accumulation in both cuts.
2. The hay yield of 2 cuts in 2002 amounted to 1,7 t/ha on the N0P0K0 plots not receiving any fertilizer during the 29 experimental years, while on the maximum N3P3K3 supply levels figured out 8.7 t/ha. The same time here the crude fibre increased from 532 kg/ha to 2876 kg/ha, crude protein from 113 kg/ha to 1100 kg/ha, crude ash from 132 kg/ha to 672 kg/ha, crude fat from 39 kg/ha to 173 kg/ha, while the crude fibre/crude protein ratio dropped from 4.7 to 2.6.
3. After 3 years storing the decisive part of carotine decomposed in the hay and gave as little as 0.9 mg/kg average value. The N-control gave 0.6 mg/kg, the 200 kg/ha/yr N-treatment resulted in 1.3 mg/kg, than the N-excess 300 kg/ha/yr plots showed again significantly less 0.9 mg/kg.
4. The 2nd cut hay had a little yield however, was rich in crude protein and crude ash having 50-70% higher average content compared with the primary hay. The crude fat content was 3-times higher in the 2nd cut hay, while the crude fibre about 20% less. The ratio of crude fibre/crude protein figured as an average 1.9, while in the low-quality primary hay amounted 4.2.
5. The N-fertilization depressed the content of N-free extract and acid detergent fibre (ADF) and enhanced the content of energy dependent protein (MFE), N-dependent metabolic protein (MFN) and nettoenergy (NE) parameters. The P fertilization did not cause any changes, while the K-fertilization decreased the N-free extract and the nettoenergy parameters (NE) and slightly stimulated the neutral detergent fibre (NDF) synthesis in the 2nd cut hay.