Agriculture Reference
In-Depth Information
112
110
108
106
104
102
100
98
96
94
92
90
88
111.2
small grains
rape (colza)
105.7
103.9
104.9
field beans
103.2
101.5
100.1
100.0
100.0
96.9
95.9
94.8
regr. for drilling:
y = 107.97 - 0. 66 x
r = 0. 987**
15
20
12
24
36
12
24
48
10
row-spacing in cm
row-spacing in cm
row-spacing in cm
Fig. 8.5
Seed distribution over the area and yield. In all cases, the respective yield for drilling with
12 cm row-spacing is set to 100. Broadcast seeding is done by wing-coulters, which allow a similar
precision in depth control as conventional openers for drilling. The seed-rates per ha are constant.
For details see Heege
1993
or Heege and Billot
1999
8.3
Seeding Depth
A precise control of the seeding depth is important for a uniform emergence and
development of all plants. This is in turn essential for treating all plants of a crop
at the same growth stage with agrochemicals and thus for high yields.
Prerequisites for the germination of seeds are an adequate temperature, enough
water and sufficient oxygen for respiration. The farmer can influence the tempera-
ture only by selecting the best time of the year. Control of water- and oxygen supply
is possible via the seeding depth, which is a means to provide these factors in the
best proportion.
An increase of the seeding depth generally improves the water supply for germi-
nation, since in most cases the water content of a soil rises with the distance from
the surface. But the higher the water content, the lower is the oxygen supply, since
the soil pores are either filled with water or air. A very high seeding depth hence can
put the oxygen supply of seeds at risk.
The energy for the growth of seedlings before assimilation starts can only be
provided by the seeds themselves. Hence, even after germination took place, too
deep planting can result in either in no emergence or in weak plants arriving at the
soil surface.
Thus low or uneven emergence can be the result of either a
lack of water
, a
lack
of oxygen
or a
lack of energy
.
Generally, due to the influence of the weather,
controlling for an adequate supply of water is the main problem.
