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t
his article is the 15th in a series of articles highlighting a
specific pasture crop species that can play an imperative
role in conservation agriculture (CA) based crop-pasture
rotations. Besides improving the physical, chemical, hydro-
logical and biological properties of the soil, such species, in-
cluding annual or perennial cover crops, can successfully be
used as animal feed.
Livestock production systems are in many ways dependant on
the utilisation of pasture species, in this case as a pasture ley crop
and can therefore become an integral component of CA-based
crop-pasture rotations.
It is imperative to identify a pasture species fulfilling the require-
ments of a dual purpose crop, i.e. for livestock fodder and/or soil
restoration. This article focuses on a root forage crop commonly
used in the winter season as a crop to improve soil conditions and
to provide cover in the winter months of a summer rainfall region.
This annual crop could possibly succeed a perennial grass pasture
prior to planting the next season of grain crops.
Raphanus sativus
(Radish)
Radish (also commonly known as Japanese, forage or tillage rad-
ish) is an annual plant that originates in East Asia and Europe. This
forage crop is well-known in the cooler summer rainfall regions of
South Africa.
The root component of the crop comprises approximately 50% of
the total production, with moisture content as high as 90%. Both the
leaf and root material of this crop can be used as young fresh mate-
rial in winter or carried over to late winter or early spring for fodder.
The most common cultivar is Nooitgedacht, with alternative culti-
vars such as Samurai, Sakurajuma, Star 1650 and 1651 and a soft
leaf cultivar by the name of Sterling.
Agro-ecological distribution
This crop is adapted to the cooler eastern parts of the country;
where rainfall is reasonably reliable during January to April. More
recently, alternative cultivars are being grown in the western parts
of the country as well.
This species is both cold- and drought-resistant, but not toler-
ant of waterlogged conditions. Radishes grow best when planted
early enough to allow six weeks of growth before regular frosts.
Radishes are winter hardy plants and are tolerant of light frosts,
but generally show injury when temperatures drop below the -0°C.
A suitable rainfall for radish production requires a minimum of
650 mm per annum and it proliferates with a good autumn rain.
Management and utilisation
This crop is best established on sand to sandy loam soils that have
a good water holding capacity. Often well-drained clay soils with
good water holding capacity are also suitable. The normal planting
date is January/February, however, in the cooler eastern Highveld
regions, the crop can be planted as early as middle December.
If this crop is planted too early, this species tends to flower prema-
turely, not allowing sufficient root formation to occur. Late plantings
could potentially result in insufficient soil moisture reserves.
When this crop is planted in rows, it is recommended that rows
are planted 90 cm apart with plant interspacing of 35 cm - 50 cm
from each other. However, when planted as a cover crop, denser
seeding rates are used (usually broadcasted) and narrower rows of
maximum 50 cm apart are preferred. The seeding rate of 2 kg/ha
in rows is advised and 4 kg/ha when sown in a broadcast fashion.
A pre-establishment herbicide, for example Treflan, can be used
to control grass and some broad leaved weeds. A product such as
Dual can be used to control weeds that emerge once the crop has
surfaced. Karate pesticide can be used to control cut worms.
Radish reacts well to a good fertilisation of phosphate (P) and potas-
sium (K) before establishment. Fertilisation should initially strive to
obtain at least 20 mg/kg of P and 140 mg/kg of K.
Under dryland conditions 50 kg - 70 kg N/ha are recommend-
ed, whereas irrigated conditions will require two applications of
75 kg N/ha each. Many producers and researchers are experimen-
ting with cover crop mixtures that combine radish with legume
cover crops that fix N (e.g. grazing vetch) and temperate grasses (e.g.
black oats), hence providing more persistent residues.
WAYNE TRUTER,
University of Pretoria,
CHRIS DANNHAUSER,
Grass SA,
HENDRIK SMITH,
Grain SA and
GERRIE TRYTSMAN,
ARC-Animal Production Institute
Integrated crop and pasture-based
livestock production systems
– Part 15
AGRICULTURE
Conservat ion
Series
ON FARM LEVEL
Conservation agriculture
55
June 2015