SOIL PREPARATION

CHAPTER 3

i

ii

iii

iv

v

5

i Dead vines ii Very poor growth iii Moderate growth iv Normal growth v Moderate growth Zones of vigour

4

3

2

Aerial Growth (kg/vine) 0 1 0 4

8

12

16

20

Distance (m) from centre of dead area

-10

Distance (m) from centre of dead area vs Aerial growth (kg/vine)

-20

-30

1 500 kPa 2 000 kPa

-40

-50

Depth (cm)

-60

-70

-80

FIGURE 3.6: Relationship between performance of a commercial vineyard and soil depth at which a critical penetrometer resistance was encountered (redrawn after Van Huyssteen, 1983). The above-mentioned work of Van Huyssteen (1983) proved that the penetrometer is a most useful tool in assessing soil physical conditions and superior to the bulk density measurements. In measuring the efficiency of soil preparation methods, Van Huyssteen (1983) could e.g. not detect clods with the bulk density measurements, since only one representative position per plot could be handled. Penetrometer measurements are easy and rapid to do and enable the user to easily measure soil strength in 10-15 places per plot. In contrast, bulk density measurements are laborious and time- consuming, a fact that leaves little choice as to the preferred method when the degree, position and extent of compaction has to be determined. However,

SOIL PREPARATION | 41