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For indeterminate flowering legume species (flowering is spread
over weeks), it is more difficult to determine the best harvesting
time. Pods should be regularly collected and the proportion of shat-
tered mature and immature seed should be an indication of when to
harvest.
Seed harvesting, cleaning and storage
Seed harvesting can be an intricate process and access to a seed
combine is considered advantageous in ensuring maximum seed
yields, provided the harvested seed crop is rapidly dried in a
seed dryer after harvesting.
Once seeds are harvested the seed needs to be threshed, cleaned,
packed and stored. Seed cleaning is an important operation in the
seed production process and aims to remove husks, diseased, dam-
aged, foreign seed and unwanted material.
Commercial seed producers or seed producing companies in-
vest in huge seed cleaning equipment, but on-farm seed cleaning
can be done by hand or by using basic cleaning equipment. Most
arable pasture and forage species are recognised as orthodox (seeds
can be dried without any damage to low moisture contents with in-
creased longevity); whereas some tropical fodder tree species are
recalcitrant (seeds cannot be dried or cooled below 10oC for tropical
or 0oC for temperate species without damaging the seed).
The seed moisture when harvested is usually higher than that rec-
ommended for storage. To reduce the seed moisture to reduce the
risk of loss in germination and or infestation from between 40% to
70% to between 8% and 12%, seeds need to be dried.
An electronic moisture meter is used to determine seed moisture
and if needed a producer can use a seed testing laboratory to deter-
mine this. Three drying methods are essentially used for seed name-
ly sun/shade drying, natural force air drying or artificial drying. It is
important to take into account that when seed is sun/shade dried, the
seed should be protected from ground moisture.
Legumes have harder seed coats and can thus be exposed to higher
temperatures before seed is damaged. The main advantages of sun/
shade seed drying are that it is ideal for small seed quantities and in-
expensive, however the main disadvantages are weather dependen-
cy, more seed loss due to wind and contamination with other seed.
Natural forced air drying uses the flow of air through seeds placed
on beds made of perforated material, allowing air ventilation, to dry
seeds to the recommended seed moisture content. The main advan-
tages of this method are that it is easily constructed on-farm and that
seed can be turned easily for faster drying whereas the disadvan-
tages are that it is weather dependent and not a suitable method for
humid areas.
Artificial drying uses heated air (35oC - 40oC) or chemical desic-
cants, with or without the dehumidification of dry seed. The main
advantages of this method are that seed can be harvested earlier and
that larger seed quantities can be dried independently of weather
conditions whereas the disadvantages are that the equipment is an
expense and running costs are high. There are guidelines for seed
moisture content for many species (e.g. for Glycine max 9,5% -
11,5%) to ensure optimum storage thereof, however, storage tem-
perature, length of storage and humidity will influence seed moisture
as a result. It is advised that storage bags or bins should be properly
labelled e.g. species name, cultivar and harvest date and mass.
Seed storage facilities should always be kept clean and sanitised,
ensuring cool to cold temperatures. In humid areas, a dehumidifier
should be installed. Seed bags should be packed in such a way that
all bags are easily accessed and that the labels are visible. Where
possible pack seed on wooden pallets. Under ideal conditions seed
can be stored for more than five years without loss in viability.
Conclusion
On-farm production of cover crop seed is a viable option for the ad-
vancement of CA systems in South Africa. However, seed produc-
tion is a complex and intricate process and requires adherence to
fairly strict guidelines.
This illustrates the important function that seed producers and com-
panies play in ensuring good quality seed. It is reiterated that many
cultivars are protected by plant breeders’ rights and this seed can
only be produced under authorisation and strict regulations.
Should producers choose to grow uncertified seed of unregistered
cultivars for their own use it must be noted that in terms of the Plant
Improvement Act, 1976 (Act No. 53 of 1976) that this seed may not
be sold ‘over the fence’ to neighbouring producers or through any
other outlet.
For more information, contact Dr Wayne Truter at wayne.truter@
up.ac.za, Dr Hendrik Smith at or
Mr Gerrie Trytsman at
Literature and websites
African Seed Trade Association:
Directorate Genetic Resources, Seed Testing Services:
docs/geneticresources/seed_testing_services.htm.
Gillera, KE, Witter, E, Corbeels, M, Tittonella, P. 2009. Conservation agriculture and
smallholder farming in Africa: The heretics’ view. Field Crops Research. Volume
114, Issue 1, 1 October 2009, pp. 23 - 34.
Hobbs, PR, Hobbs, K, Sayre, R Gupta. 2008. The role of conservation agriculture in
sustainable agriculture Philos. Trans. Roy. Soc. B, 363 (2008), pp. 543 - 555.
HSU. 1994. Forage Seed Production. ILCA training manual. http://192.156.137.110/
website/html/trainingMat/Seed.pdf.
Lahmar and Triomphe. 2008. Key lessons from international experiences about
conservation agriculture and considerations for its implementation in dry areas.
Stewart, BI, Asfary, AF, Belloum, A, Steiner, K, Friedrich, T. (Eds.), Conservation
agriculture for sustainable land management to improve the livelihood of people in
dry areas , ACSAD & GTZ (2008), pp. 123 - 140.
Organisation for Economic Cooperation and Development (OECD):
oecd.org/tad/code/seeds.htm.
Rockström, J, Kaumbutho, P, Mwalley P, Temesgen M. 2001. Conservation farming
among small-holder farmers in E. Africa: Adapting and adopting innovative land
management options. Conservation agriculture, a worldwide challenge. Proceed-
ings of the First World Congress on Conservation Agriculture, vol. 1: Keynote Con-
tributions, Madrid, Spain, October 1 - 5, 2001 (2001), pp. 363 - 374.
SANSOR South African National Seed Organisation:
Van den Burg, H. 2004. Small-scale seed production with variety improvement of
cereals and pulses.
On-farm cover crop seed production
Seed
FOCUS
Special