Agriculture Reference
In-Depth Information
100
90
80
70
60
50
40
30
20
10
0
0
40
50
75
80
100
120
150
200
Dose of nitrogen (u/ha)
Fig. 5.11.
Relative fibre content as a function of nitrogen fertilization of the sown crop (soil nitrogen content
unknown). Synthesis of the tests undertaken by ITC (2003) (SPC, FNPC) and FDGEDA de l'Aube (1982).
8.43 kg/t DM. The fibre content appears
to be relatively unaffected by nitrogen
levels (Fig. 5.11).
constituent of chlorophyll. A magnesium
deficiency will result in colour loss in the leaves
and the appearance of necrotic lesions.
For the same nitrogen dose and date of
fertilization, hurd and seed yield - and, to a
lesser extent, fibre yield - appear to benefit
from magnesium sulfate fertilization (Fig. 5.15).
It promotes hurd and seed yield when applied
at planting (compared to the 50 cm stage).
However, the opposite is true where fibre con-
tent is concerned.
Sulfur does not appear to affect hurd or
fibre yield and increases seed yield only if added
at planting. These conclusions all require
confirmation by additional research, as this
synopsis is based on only 3 years of tests, but
the deviations observed are relatively small.
Influence of the date of fertilization and
splitting of fertilization on yields
Nitrogen fertilization at planting increases hurd
yield compared to fertilization at the 50 cm
stage (Figs 5.12 and 5.14). By contrast, the
date of fertilization does not appear to affect
fibre content, even when an increase in content
is observed following a late fertilization (Figs
5.13 and 5.14). A late fertilization improves
seed yields much as is seen for cereal crops.
A divided fertilization (X units at planting
and X units at the 50 cm stage) appears to have
no effect on hurd and seed yields when compared
to a dose of 2X units at planting. It also appears
to have no effect on fibre content, even when an
increase in content is observed in individual trials
where a split fertilization is used. Recall that late
fertilization can make fibre processing more dif-
ficult, as the hurds stay green longer.
5.4.5 Potassium fertilization
Potassium fertilization was investigated between
1977 and 1989 at Le Chambre d'Agriculture
de l'Eure. The results indicate:
uptake of potassium by hemp in the order
•
5.4.4
Sulfur and magnesium
fertilization
of 200 kg/ha for a yield of hurds of
10-11 t/ha;
excess potassium is not absorbed;
•
•
hemp is able to draw on potassium held
Sulfur is necessary for the formation of many
plant proteins. It is also a catalytic element that
participates in essential metabolic reactions
including chlorophyll formation.
Sulfur is found in mineral form in the
ground as well as in organic materials. When
mineralized, it forms sulfates. Magnesium is a
deep in the ground when availability in the
tilled layer is inadequate;
potassium fertilization only affects hurd
•
yield in particularly difficult years. Under
such conditions, potassiumsupplementation
can improve growth (Fig. 5.16).
