COVER CROPS in South African Vineyards

COVER CROPS IN SOUTH AFRICAN VINEYARDS

Fertilisation of cover crops The fertilisation of cover crops in a vineyard must be executed within the framework of the fertilisation programme for the grapevines. Previous guidelines for cover-crop fertilisation were based on general guidelines for grass cover crops within a general strategy for grapevines on all soil types. Subsequent research was done over a ten-year period at theARC Infruitec- Nietvoorbij research farm near Lutzville in the Olifants River valley. The aim was to determine the fertiliser needs of both grasses and legumes on a relatively poor, sandy soil.With extremely limited guidelines, it was decided to compare no fertiliser, and double the amount of fertiliser, to the existing norm for cover crops in vineyards. The different treatments are summarised inTable 4.1.The resulting dry- matter production is shown in Figure 4.4.

TABLE 4.1. Fertiliser applications tested in the Olifants River valley. Adapted from Fourie et al (2005).

Just after sowing

At the 2–4- leaf stage

Two weeks after bud-break

Treatment N 1

N 1

P 2

K 3

N 1

N 1

P 2

K 3

Zero

–

–

–

–

–

–

–

Black oats

Standard 14 30 30 Double 28 60 60

28 56

42 84

– 30 – 60

Zero

–

–

–

– – –

– – –

– – –

– – –

Grazing vetch

Standard – 30 30

Double

– 60 60

1 Nitrogen in kilogram per hectare 2 Phosphate in kilogram per hectare 3 Potassium in kilogram per hectare

85