Rlm. Schils, EFFECT OF A SPRING APPLICATION OF NITROGEN ON THE PERFORMANCE OF PERENNIAL RYEGRASS WHITE CLOVER SWARDS AT 2 SITES IN THE NETHERLANDS, Netherlands journal of agricultural science, 45(2), 1997, pp. 263-275
In the Netherlands, the introduction of milk quota and concern about N
losses has led to a lower N application on grassland. Moreover, the p
resent government policy will lead to a further reduction of N applica
tion. These developments have renewed the interest in white clover. Tw
o cutting trails were set up to (i) evaluate the potential performance
of mixed swards in the Netherlands and (ii) to quantify the effect of
spring N on mixed swards. In a five year trial on clay soil five rate
s of N application in spring (0, 25, 50, 75 and 100 kg ha(-1) year(-1)
) were combined with two cutting frequencies (4-5 cuts year(-1) and 6-
7 cuts year(-1)). In a three year trial on sandy soil only the effects
of spring N application (0, 50, and 100 kg ha(-1) year(-1)) were stud
ied. Average annual DM yields were 14.66 and 13.76 t ha(-1) year(-1) f
or the clay and sandy soil, respectively. Spring application of 100 kg
ha(-1) increased the yield in the first cut with 11.1 kg DM per kg ap
plied N. White clover contents decreased with increasing N rate, reduc
ing the DM yield in the remaining cuts on the fertilised treatments. N
evertheless, on an annual basis, 100 kg N ha(-1) increased the yield w
ith 7.4 kg per kg applied N. Annual N yields were not affected by spri
ng N application. Compared to a cutting frequency of 4 to 5 cuts year(
-1) a frequency of 6 to 7 cuts year(-1) increased the white clover con
tent from 36 to 47% and the N yield from 458 to 524 kg ha(-1), but did
not affect the DM yield. It was concluded that spring application of
N can be a practical tool to secure herbage production in spring with
only a short-lived negative effect on white clover content.