Fjölrit RALA - 15.12.2000, Blaðsíða 27

25
Crude protein
Crude protein content was analyzed in samples from 1996 and from three harvest times in
1997 (Tables 24-26). Crude protein content in grass is closely dependent on the rate of diy
matter growth. Another important factor for crude protein content is the utilization of fertilizer
nitrogen and available nitrogen ífom the soil.
As expected, protein content was highest in early spring but decreased during the
growth period. Grass takes up nitrogen when it is available and this is subsequently diluted in
an increasing amount of dry matter (Gillet, 1982). The crude protein content in Upemaviarsuk
was very low on the first harvest date in 1996, which can probably be explained by the fact
that the grass had at that time not taken up all available nitrogen írom the soil or it was still in
the roots. Uptake is dependent on temperature and water flow, and temperature was lower in
Upemaviarsuk than at the other locations.
Nitrogen uptake differs between varieties and locations. Generally the amount of
nitrogen found in the plants was high in relation to the amount of fertilizer used (70-80% on
average). The Poa pratensis varieties gave much less N in the herbage than the other varieties.
The amount of nitrogen found in the plants at Korpa was relatively higher than at the other
locations. This could have been because there was so much nitrogen in the soil from earlier
years. Leguminous plants (Lupinus nootkatensis) had earlier been cultivated in this field.
Table 24. Crude protein content (%) in the yield on different harvest dates in Kollafjorður 1996 and 1997, n=2.
29.5. 12.6. Harvest dates 1996 26.6. 10.7. 24.7 1.8.
Lavang 22.5 14.1 9.2 8.6 7.5
Fylking 20.4 13.9 9.8 9.4 7.6
Seida 19.1 21.8 14.6 10.5 9.2
Vega 21.5 21.7 13.2 8.6 6.7
Engmo 18.8 19.3 11.9 8.3 5.7
Harvest dates 1997
2.6.*) 16.6. 30.6*) 14.7. 30.7.
Lavang 30.0 23.6 14.1 14.2 12.1
Fylking 32.2 25.6 18.5 15.3 11.2
Seida 30.5 24.4 17.5 15.0 13.0
Vega 29.4 21.3 14.5 12.4 10.7
Engmo 32.9 23.6 15.7 14.3 9.7
) Analysed with NIR.