It is important that each and every planted pasture should be
fertilised for long-term sustainable production. Rhodes grass will
grow in soil with a pHof 6 to 7, but alsogrowswell inhigher pH and
brackish conditions.
The phosphorus (P) content of the soil should be 12 mg/kg -
18 mg/kg before establishment, while the potassium (K) content
should be between 100 mg/kg and 120 mg/kg. It is important to
monitor these fertility levels, especially in thecaseofhayproduction,
whereno recyclingof dung andurineoccur.
An annual application of 60mg/kg to 150 kg/ha pureN (± 200mg/kg
to600kg/haof limestoneammoniumnitrate), dependingon rainfall, is
suggested. Because of high fertiliser prices, the following procedure
canbe followed: In low rainfall areas, apply±30 kgN/ha (±100 kg/ha
of limestone ammonium nitrate), early summer, after the first 50mm
to70mm rain.
After the first cut or grazing cycle, apply 30 kg N/ha again and if
there is enough rain in January, a final application of 30 kgN/ha can
be applied (total 90 kg N/ha) if deemed necessary. In higher rainfall
areas (600mm+) thesamestrategycanbe followed, butwithhigher
application rates (50 kg to 60 kg N/ha or 170 kg/ha to 200 kg/ha
limestone ammoniumnitrate).
Because of Rhodes grass’s inherent palatability, it can be used in a
fodder flow programme for an entire year. Besides being used for
grazing, Rhodes grass makes excellent hay and is regarded a good
foggage (
staandehooi
) option inwinter.
To be employed as a foggage, the grass should be utilised early in
summer asgrazingor hayand thenbe rested frommid-Januaryuntil
the beginning of winter. Fertilisation in January is then of utmost
importance.
Management challenges
If overutilised, Rhodes grass tends to die out at an early stage. It
is speculated that its growth points are situated higher above the
soil level than other grasses and are therefore easily damaged by
short grazing.
A second theory is that the grass stores its energy reserves during
winter in the root crowns as well as the base of the plant (above
soil level) and that short spring grazing can be detrimental. The fact
that a sward of Rhodes grass in the Free State survived for 17 years
because it was only cut for hay and not grazed, might support the
abovementioned theories.
Soil conservation and health benefits
Because of Rhodes grass’s ability to spread by stolons or runners,
it is a good species to be used for erosion control. Rhodes grass
alsohasa further advantage through itsability tocontrolNematodes
(eelworm). Both thesecharacteristicsmake it auseful rotational crop
for tobacco, tomato, potato andpineapple farmers.
Themost important characteristics of Rhodes grass are:
It germinates and establishes faster thanmost other perennial,
sub-tropical grass species.
It produces stolons that cover the soil quickly and prevent
erosion.
It has the ability to control nematodes in the soil and is used for
that reason as a rotational crop for tobacco, tomatoes, potatoes
andpineapples.
It isadapted tobrackishsoilsandeven limitedwaterloggedsoils.
Ifovergrazed, thevigourwilldeclineandcandisappear in three to
five years.
These characteristics make it a very useful and an “all-rounder”
pasture.
Animal production aspects
Research has shown that grazing capacities of up to 2 LSU/ha can
be achieved with a total weight gain of 0,6 kg/LSU/day, with a total
mass of 448 kg/ha. In extremely high rainfall seasons it can be
expected to achieve 23 tons/ha hayproduction.
Thenutritional valueofRhodesgrass ishighlydependent onclimatic
factors, soil fertility and fertilisation. The crude protein content of
younggrowth can vary between 15% - 17%, and canhowever be as
low as 4% if thepasture is verymaturewithold stems.
Grain crop production
After establishing a typical ley crop system using Rhodes grass for
aperiodof around fiveyears, the soil shouldbe sufficiently restored
to cultivate annual grain crops under a CA system. Herbicides kill
the pasture quickly and the pasture residues remain on the soil
surface providing cover that limits erosion, enhance water infiltra-
tion and reduces their rateofmineralisation.
Onceadecision ismade to terminate the ley, all pasturecomponents
should be considered as “weeds” that need to be removed. They
shouldno longer be regarded as a sourceof fodder for livestock.
Depending on the pasture species and situation (e.g. dry or wet
area), the pasture could be killed a season before planting grain
crops toallow thesoil profile tobe replenishedwithwater. Thewater
requirement of the first cropplanned after pasturewill influence the
timingof removal of thepasture. Reliableand timelyseasonal rainfall
forecastsmay assist in this planning.
Following the pasture phase, grain crop yield will be restricted
unless the soil water profile is replenished. After removing the
pasture, weeds in the fallow must be controlled to conserve soil
water to maximise the benefit of the ley. A suitable no-till planter
should be used to plant the grain crops directly into the residues of
the pasture crop, without any other cultivation practice disturbing
the soil. Normal integrated fertiliser (basedon soil fertility levels and
yield targets), weed andpest control practices shouldbe followed.
Conclusion
Rhodes grass is a grass that comes highly recommended. It
is regarded to have many functions within a crop and livestock
production system. Not only does it provide good quality
hay and grazing when it is used as pasture in a ley cropping
system, it serves as a fumigant for soils infested with nematodes
for example.
This grass establishes itself quickly and has the ability to stabilise
degraded and/or vulnerable soils with a high erosion potential,
protecting soils from being destabilised by overgrazing. As with
many pastures, if high quality pasture is required, responsible
fertilisation at appropriate times is essential.
For more information, contact Dr Wayne Truter at
wayne.truter@
up.ac.za
, Prof Chris Dannhauser at
Dr Hendrik Smith at
or Mr Gerrie
Trytsman at
CONSERVATIONAGRICULTURE
51
June 2014
ON FARM LEVEL
Conservationagriculture
