Francis, C.A., and M.D. Clegg. 1990. Crop rotations in sustainable
Mallarino, A.P., and E. Ortiz-Torres. 2006. A long-term look at
production systems. In Sustainable Agricultural Systems, ed.
crop rotation effects on corn yield and response to nitrogen fer-
C.A. Edwards, R. Lal, P. Madden, R.H. Miller, and G. House.
tilization. In 2006 Integrated Crop Management Conference,
Ankeny, IA: Soil and Water Conservation Society.
Iowa State University, pp. 209–217.
Hanson, J.D., M.A. Liebig, S.D. Merrill, D.L. Tanaka, J.M. Krupin-
Merrill, S.D., D.L. Tanaka, J.M. Krupinsky, M.A. Liebig, and J.D.
sky, and D.E. Stott. 2007. Dynamic cropping systems: Increas-
Hanson. 2007. Soil water depletion and recharge under ten crop
ing adaptability amid an uncertain future. Agronomy Journal
species and applications to the principles of dynamic cropping
99: 939–943.
systems. Agronomy Journal 99: 931–938.
Gantzer, C.J., S.H. Anderson, A.L. Thompson, and J.R. Brown.
Meyer-Aurich, A., A. Weersink, K. Janovicek, and B. Deen. 2006.
1991. Evaluation of soil loss after 100 years of soil and crop man-
Cost efficient rotation and tillage options to sequester carbon
agement. Agronomy Journal 83: 74–77. This source describes
and mitigate GHG emissions from agriculture in eastern Cana-
the long-term cropping experiment in Missouri.
da. Agriculture, Ecosystems and Environment 117: 119–127.
Grubinger, V.P. 1999. Sustainable Vegetable Production: From
Mohler, C.L., and S.E. Johnson. 2009. Crop Rotation on Organic
Start-Up to Market. Ithaca, NY: Natural Resource and Agricul-
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tural Engineering Service.
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National Research Council. 1989. Alternative Agriculture. Wash-
Long. 1990. Crop rotation and tillage effects on soil organic
ington, DC: National Academy Press. This is the reference for
carbon and nitrogen. Soil Science Society of America Journal
the rotation used on the Thompson farm.
54: 448–452.
Peterson, G.A., and D.G. Westfall. 1990. Sustainable dryland agro-
Karlen, D.L., E.G. Hurley, S.S. Andrews, C.A. Cambardella, D.W.
ecosystems. In Conservation Tillage: Proceedings of the Great
Meek, M.D. Duffy, and A.P. Mallarino. 2006. Crop rotation
Plains Conservation Tillage System Symposium, August 21–23,
effects on soil quality at three northern corn/soybean belt loca-
1990, Bismark, ND. Great Plains Agricultural Council Bulletin
tions. Agronomy Journal 98: 484–495.
No. 131. See this reference for the wheat-corn-millet-fallow rota-
Katsvairo, T.W., D.L. Wright, J.J. Marois, D.L. Hartzog, K.B.
tion under evaluation in Colorado.
Balkcom, P.P. Wiatrak, and J.R. Rich. 2007. Cotton roots, earth-
Rasmussen, P.E., H.P. Collins, and R.W. Smiley. 1989. Long-Term
worms, and infiltration characteristics in sod–peanut–cotton
Management Effects on Soil Productivity and Crop Yield in
cropping systems. Agronomy Journal 99: 390–398.
Semi-Arid Regions of Eastern Oregon. Pendleton, OR: USDA
Krupinsky, M.J., K.L. Bailey, M.P. McMullen, B.D. Gossen, and
Agricultural Research Service and Oregon State University
T.K. Turkington. 2002. Managing plant disease risk in diversi-
Agricultural Experiment Station, Columbia Basin Agricultural
fied cropping systems. Agrononmy Journal 94: 198–209.
Research Center. This describes the Oregon study of sunflowers
as part of a wheat cropping sequence.
Luna, J.M., V.G. Allen, W.L. Daniels, J.F. Fontenot, P.G. Sullivan,
C.A. Lamb, N.D. Stone, D.V. Vaughan, E.S. Hagood, and D.B.
Werner, M.R., and D.L. Dindal. 1990. Effects of conversion to
Taylor. 1991. Low-input crop and livestock systems in the south-
organic agricultural practices on soil biota. American Journal of
eastern United States. In Sustainable Agriculture Research and
Alternative Agriculture 5(1): 24–32.
Education in the Field, pp. 183–205. Proceedings of a confer-
ence, April 3–4, 1990, Board on Agriculture, National Research
Council. Washington, DC: National Academy Press. This is the
reference for the rotation experiment in Virginia.
125
Building SoilS for Better CropS: SuStainaBle Soil ManageMent
a case study
aleX and betsy hitt
grahaM, north Carolina
Alex and Betsy Hitt were forced to reevaluate their farm
“so much competition and diversity” in the soil. They
fertility program in 1990 when a nearby horse stable that
see little or no erosion, despite farming some fields that
had provided them with manure went out of business.
have as much as a 5% slope. Furthermore, they have dis-
The Hitts, who raise 80 to 90 varieties of vegetables
covered that their covers smother and crowd out weeds,
and 160 varieties of cut flowers on their 5-acre farm,
and the timing and spacing variations within their
have created elaborate rotations involving cover crops
rotation have improved weed control. “We either have a
to supply organic matter and nitrogen, lessen erosion,
different crop [from season to season] or we’re planting
and crowd out weeds. “We made a conscious decision
it differently, so we don’t get the same weeds the same
in our rotation design to always use cover crops,” Alex
time every year,” Alex says. “When we went to a longer
Hitt says. “We have to—it’s the primary source for all of
rotation and changed the timing, we noticed it quickly.”
our fertility. If we can, we’ll have two covers on the same
Over time, the Hitts’ rotation scheme has evolved in
piece of ground in the same year.”
Alex and Betsy designed their initial rotation scheme
Their farm stays essentially free of soilborne
to include all their farmed acreage, using the guid-
diseases and pests, which they attribute to “so
ing principle of separating botanical families to break
disease and insect cycles. They intentionally incorpo-
much competition and diversity” in the soil.
rated as many variables as possible into that rotation
They see little or no erosion, despite farming
(cool- and warm-season crops, vegetables and flow-
some fields that have as much as a 5% slope.
ers, heavy and light feeders, deep- and shallow-rooted
plants, etc.). Later, as they came to rely more on cover
crops for organic matter maintenance, the Hitts tweaked
tandem with their production methods. Four different
their rotation to maximize cover crop growth periods.
rotations are now used to maintain or boost soil quality
“We always lean towards [cover] crops that will grow us
in specific parts of their operation (see chart, p. 128). For
the most biomass and fix the most nitrogen,” says Alex.
example, their main field is in a five-year rotation plan,
“These . . . usually . . . mature later and are harder to
while the addition of six movable 16-by-48-foot hoop
turn under and decompose.” Other criteria include ease
houses used for season extension led to the creation of
of establishment, seed cost and availability, and adapt-
a special twelve-year rotation. Areas under large-scale
ability to their climate.
multi-bay high tunnels, as well as fields with flood-prone
The payoffs from the Hitts’ commitment to their
or heavy soils, have their own three-year rotations.
rotation are clear. Their farm stays essentially free of
The Hitts use a consistent approach to manag-
soilborne diseases and pests, which they attribute to
ing cover crops in all of their rotations, regardless of
126
building soils For better CroPs: sustainable soil ManageMent
rotation length. “We have essentially arrived at two
planting, cultivating, irrigating, trellising, etc. There is
winter and two summer combinations of cover crops,”
no need to reset equipment or have different lengths of
each of which always includes a legume and a grass,
row covers if all the beds are the same.”
Alex explains. Typically, they plant rye and hairy vetch
The Hitts are making the most of their efficiency
or sorghum sudan grass and cowpeas prior to late-
gains. In recent years, although they’ve scaled their
planted spring crops, no-tilled summer cash crops, and
production down from 5 to 3 acres, they are realizing
fall-planted cover crops. Oats and crimson clover or
greater profits by continually refining and diversifying a
pearl millet and soybeans precede early-spring-planted
lucrative set of cash crops. In recognition of their inno-
crops and fall-planted cash crops. The Hitts alter these
vation and success, Alex and Betsy received the presti-
combinations if needed to prevent disease buildup. They
gious Patrick Madden Award for Sustainable Agriculture
sometimes “fine-tune” their rotation by inserting an
from USDA’s Sustainable Agriculture Research and
extra planting of a wheat, barley, or triticale cover crop
Education (SARE) program in 2006.
prior to a first tomato planting.
The Hitts are convinced that the complexity built
The Hitts are interested in expanding no-till planting
into their rotations has led to a reduction, rather than
on their farm and trying out cover crops, such as rape
an increase, in their workload. Alex—who has found
and forage radish, that can easily be turned under in
time over the years to volunteer for SARE committees—
spring—because these are followed by an early-spring-
estimates that about ten days of work are required to
seeded rye and hairy vetch cover that is rolled down to
manage the cover crops within his rotations each year. A
create a mulch layer under their no-till summer-planted
week is used in the fall to seed, prepare, and hill 3 acres.
crops. “I am still working on getting the right coulter/
In the spring, covers are mowed weekly as needed, and
beds are turned under or rolled prior to planting. Once
row openers for [no-till] seeding of certain flowers like
cash crops are harvested, rotational units are mowed,
zinnias and also sweet corn,” Alex says.
disked, and seeded with a summer cover crop, all in
The Hitts’ flowers, fresh leafy greens, heirloom toma-
the same day. After eight weeks, this summer cover is
toes, hot and sweet peppers, leeks, and other vegetables
mowed down and disked in preparation for another cash
are popular with area chefs and at farmers’ markets in
or cover crop planting.
nearby Chapel Hill. Their main challenges, Alex says,
The Hitts believe such time is well spent. “There
are twofold: to choose which cover crops should precede
are a billion benefits from cover crops,” Alex says. “We
and follow their diverse set of cash crops, and to deter-
have really active soil—we can see it by the good crops
mine optimal spacing and timing for their cash crops. “If
we grow, and by the problems we don’t have. The whole
cash crops go in and out basically at the same time, this
[farm] is really in balance, and the rotation and cover
makes it easier to choose a cover crop and its following
crops have a lot to do with that.”
cash or cover crop,” he says. “This also makes irrigation,
cultivation, and other jobs more efficient.” Standardizing
—uPdated by aMy kreMen
bed widths and lengths and the spacing used for trans-
plants and direct-seeded crops has made their cash crop
management “essentially automatic when it comes to
127
building soils For better CroPs: sustainable soil ManageMent
aleX and betsy hitt’s rotations
Key: O-CC = oats with crimson clover. R-HV = rye with hairy vetch. SG-CP = sudan grass with cowpeas.
M-SB = millet with soybeans. FP = fall planted.
Main field rotation: 5 years
Year 1. O-CC → spring lettuce followed by summer flowers → R-HV.
Year 2. Peppers (half no-till into rye/hairy vetch) → O-CC.
Year 3. Half hardy flowers/1st summer flowers → SG-CP → O-CC.
Year 4. Spring vegetables followed by summer flowers → overwintered flowers (no cover crop).
Year 5. Overwintered flowers → SG-CP → O-CC.
Rotation for 16-by-48-foot sliding tunnels: 12 years
Year 1. O-CC → tunnel moves over → tomatoes → fall-planted hardy vegetables → tunnel moves off.
Year 2. FP hardy vegetables → M-SB lettuce and late-winter-planted vegetables.
Year 3. Overwintered bulb crops → late-summer lettuce → late-winter-planted vegetables.
Year 4. Late-winter-planted vegetables → tunnel moves off → M-SB → O-CC.
Year 5. O-CC → tunnel moves over → melons, cucumbers → FP hardy vegetables → tunnel moves off.
Year 6. FP hardy vegetables → M-SB → overwintered bulb crops planted → tunnel moves over.
Year 7. Overwintered bulb crops → late-summer lettuce and late-winter-planted vegetables.
Year 8. Late-winter-planted vegetables → tunnel moves off → M-SB → O-CC.
Year 9. O-CC → tunnel moves over → tomatoes → FP hardy vegetables → tunnel moves off.
Year 10. FP hardy vegetables → M-SB → overwintered bulb crops planted → tunnel moves over.
Year 11. Overwintered bulb crops → late-summer lettuce and late-winter-planted vegetables.
Year 12. Late-winter-planted vegetables → tunnel moves off → M-SB → O-CC.
Rotation for heavy and flood-prone soils: 3 years
Year 1. Winter squash into no-till into rye/hairy vetch residue → O-CC.
Year 2. Sweet corn (part no-till) → R-HV
Year 3. Mixed vegetables and flowers, grown using no-till if possible → R-HV.
Rotation for multi-bay tunnels: 3 years
Year 1. Tomatoes half no-till into rye w/ hairy vetch residue → O-CC.
Year 2. Mixed early and mid-season flowers → R-HV.
Year 3. SG-CP → half wheat w/ crimson clover, half rye w/ hairy vetch (prior to tomatoes).
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building soils For better CroPs: sustainable soil ManageMent
