LISA as Applied to Vegetable Production Systems
1) Evaluate the suitability of various cover crops and combinations of over crops for use in
tomato production systems for Midwestern conditions.
2) Determine appropriate polyculture combinations of cover crops to take advantage of beneficial
3) Compare weed suppression characteristics of the various cover crops, and evaluate
non-chemical methods of managing cover crops to maximize weed suppression and minimize
4) Measure the impact of diseases and insects on vegetable crops in cover crop systems.
5) Evaluate the performance of tomatoes when planted in a killed cover crop mulch.
6) Conduct economic analyses on the most promising management systems.
7) Disseminate results through extension and outreach.
The mixture selected from the screening (hairy vetch, crimson clover, rye, and barley) provided a
quick ground cover, produced large amounts of above ground biomass and nitrogen, had a C:N
ratio of 22:1 which would limit immobilization of N after cover crop kill, overwintered
consistently, killed easily by mechanical means, and demonstrated weed control potential. An
undercutter, which severs cover crop roots and lays the residue intact on the soil surface, was
designed for use in this study. Cover crops suppressed more weeds when killed with the
undercutter as compared to a flail mower, as the mulch was thicker and longer lasting.
In the systems study, the cover crop mixture produced high amounts of above ground biomass
(9570 kg/ha in Columbus, and 14,290 kg/ha in Fremont) and nitrogen (220 kg/ha in Columbus,
and 360 kg/ha in Fremont). The C:N ratio averaged 22:1. Larger plants and an earlier fruit set
contributed to higher yields for the conventional plots in Fremont. The cover crop mulch
conserved soil moisture and reduced soil maximum temperatures. The mulch suppressed weeds
in this study as well as the herbicides did in the conventional plots. There were no differences in
insect populations between the plots. The no-input system had the highest economic return over
variable costs in Columbus. In Fremont, the conventional system netted much higher returns than
the other systems, attributable to higher yields.
Potential Contributions and Practical Applications:
Using an undercutter to manage cover crops, leaving the residue on the surface as a mulch has
the potential for several important benefits. By keeping the soil covered through the fall, winter,
and spring, soil erosion can be minimized. By having non-legumes in the cover crop mixture,
residual nitrogen in the soil can be conserved over the winter rather than being lost to leaching.
In this experiment, the need for herbicides was completely eliminated, as was the need for
fungicides, which is substantial in tomato production systems. Cover crops can also significantly
reduce the need for added nitrogen. Organic and low-input vegetable growers generally view
weed management as the biggest problem they face, and this system may be at least a partial
answer to their problem.
Farmer Adoption and Direct Impact:
Two of the three cooperators involved in the project will try this system on their own farms in
coming years. One of the farmers has already initiated the system, borrowing the undercutter
from the university. Because of the articles in the farming press about the undercutter, farmers
from all over the country have called or written to get the designs for the implement. Many of the
growers at the various seminars and field days have expressed interest in trying out the system on
their own farms.
Growing mixtures of cover crops vs. single species can enhance many of the benefits of cover
crop use. Experimenting with mixes is highly recommended. Undercutting and leaving the cover
crop residue intact as a surface mulch vs. mowing the residue would be the best way to manage
cover crops for weed control.
Areas needing Additional Study:
There are many other research/demonstration projects which could be initiated from this project.
Many growers have asked how this system would work with other vegetables, especially
pumpkins. Weed control is very difficult in many of these minor crops, and this system has a
great potential for reducing weeds. Optimum dates of planting the cover crop mixture and date of
mechanical kill could be researched in various parts of the country. Determining the specific
contribution with regards to weed control for each of the cover crop species is important.
Determining the optimum management for an organic production system, based on this approach
(that is, how to augment the nitrogen with organic sources for optimum economic yield), will
also require additional research.