Agriculture Reference
In-Depth Information
for many organic growers. Even when using appropriate equipment, cover crop regrowth can
be a serious weed problem, necessitating that remedial weed-management measures be per-
formed to minimise weed-crop competition. Mowing off cover crop regrowth with a f flail
mower, weed whip or scythe, or applying caustic organic materials such as acetic acid have
been effective in some instances in keeping regrowth to an acceptable level (R. Morse unpub-
lished data, 2001-2005).
Establishment of cash crops
Objective
To effectively establish seeds or transplants in high-residue mulch, with minimum disturbance
of surface residue or surface soil.
Recommendations
Normally, a short fallow or waiting period of 2-3 weeks is recommended after killing cover
crops to verify the effectiveness of the kill methods used and allow time for allelochemicals
(natural toxins that interfere with biological processes such as seed germination and plant
growth) to dissipate from killed residues before planting cash crops. After the appropriate
waiting or interim pre-plant period, precision place seeds or transplants using proven no-till
equipment. Commercially available one-pass no-till seeders and transplanters would be the
choice for large-scale organic farms or farmer cooperatives. These one-pass no-till implements
slice the organic mulch, loosen a narrow in-row strip, precision-place fertiliser, and plant with
minimum residue or soil disturbance (Morse 1999).
Limitations
For small-scale farms, both residue management and plant establishment present challenges
because existing available no-till equipment is expensive and small-size (1- or 2-row model)
versions are normally unavailable. Although challenging, small-scale farmers can adopt no-
till practices by using multiple field passes with simplified equipment to slice organic surface
mulch, loosen in-row soil, precision-place organic fertilisers, and plant. Development of
affordable small-scale no-till equipment is underway to facilitate adoption of high-residue no-
till systems by small growers (R. Morse unpublished data, 2005).
Weed suppression
Objective
To reduce weed seedbank using year-round integrated weed management practices; and
minimise early season weed growth (i.e. weed growth during the minimum weed-free period
(MWFP), normally 4-6 weeks after planting).
Recommendation
Use integrated weed management strategies, emphasising permanent soil coverage, diverse
rotations of cover crops and cash crops, and reduced soil disturbance (i.e. employing no-till or,
at most, non-inversion tillage practices). Preventing weed seed production is an important
cultural practice for organic growers, and is considered essential for organic producers who are
exploring no-till systems. Roguing out escaped weeds by hand, using high-residue cultivators
or elevated mowers can prevent weed seed production. Roguing to achieve a no seed threshold
(NST) is highly recommended for many invasive weed species (Norris 1999). Also, using
cultural practices that promote rapid plant growth and canopy closure of cash crops will result
in improved weed suppression (Morse 1999). Recommended cultural practices include:
