Home - Tour BHUOT - Organic No-Till Crop Production
Organic No-Till Crop Production
Organics without cultivation?
Bare soil, whether left exposed by tillage or by herbicide, means potential for wind and water
erosion, nutrient leaching, reduced biological diversity, loss of organic matter, and further
challenges to the sustainability of farming. These downsides of clean tillage were not so much
denied as they were simply accepted as the necessary costs of crop agriculture.
Even to those concerned with conservation, other options were not readily apparent.
It has been taken for granted by many that organic farming, which does not use herbicides, will always need clean cultivation. This assumption has been used disparagingly to characterize organic crop production as erosive and environmentally destructive.
Very little no-till/low-till research has been done under conditions typically found on organic
farms. To achieve a true organic context for a research trial, it is not enough simply to avoid
the use of prohibited fertilizers and pesticides. The fields on which the trial is conducted should
be certified, or be close to certifiable, as organic. In this way, the real-world conditions of an
organic farm—conditions that follow from crop rotation, natural nitrogen cycling, lack of herbicide
carryover, enhanced beneficial populations, and so on—can have their effect on the outcome
of the trial. These factors can make a big difference in how a system performs over time when
a new practice or product is tested.
Two organic no-till systems
Making conservation tillage work in organic systems is, apparently, not easy. Many of the
approaches discussed are clearly not "field ready." More research is definitely needed.
Two different systems using cover crops can be used in organic no-till agriculture:
- killed mulch systems (growing a cover crop and killing it mechanically, or by frost or with heat and drilling or transplanting into the created mulch layer)
- living mulch systems (growing a cover crop that continues to grow while corps are sown or transplanted into the living stand o the cover crop. Here the cover crop will have to be controlled and managed very carefully)
In this area we are trialing killed mulch systems
Killed Mulch Systems
Advances in cover crop research have generated some innovative approaches to conservation
tillage that show great potential for organic conservation tillage. Systems are now evolving
centered on the concept of growing a dense cover crop, killing it, and planting or transplanting
into the residue. The dense biomass provided by the killed cover crop not only protects and
builds the soil, it also provides substantial weed suppression. On a small scale, organic
gardeners have long relied on dense mulches as an alternative to hoeing and cultivation for
weed management. Killed mulch systems are an attempt to capture the benefits of that practice
on a larger scale.
In conventional conservation tillage, herbicides are primary tools for killing cover crops. The
non-chemical alternatives being tried for organic systems include a number of mechanical
implements and weather stress. The mechanical technologies currently being explored include
mowing, undercutting, rolling, and roll-crushing. Thermal technologies using heat include using
gas flames and steam.
The Challenges of Killed Mulches
Most killed mulches do not provide thorough, long-season weed control without some additional
effort. Studies on light penetration done in California found that even the densest of killed
mulches still allowed roughly 20% of sunlight to leak through to the soil surface. This percentage
increases as the mulch layer decomposes and weeds will begin to emerge. Some form of
hoeing, cultivation, or both may be needed later in the season. One strategy that is being
used to improve stands is to shift from direct seeding to the use of transplants. Transplanting
can be done somewhat later than direct seeding, allowing for greater warming of the soil. It
also assures a better stand and allows the crop a more competitive jump on weeds. Transplanting
is somewhat limited, however, as it is not appropriate for all crops.
Based on information from the following Hyperlinks:
http://attra.ncat.org/attra-pub/organicmatters/conservationtillage.html
http://www.newfarm.org/features/0104/no-till/chart.shtml
