Crop rotation
Crop rotation is a planned system of plant production where crops and surface are defined
for longer period of time. Plant species are sequentially planted in time and space. In organic field crop production, crop rotation is seen as an important phytosanitary measure that
reduces the diseases, pests and weeds. In all field crop production systems, strong crop rotations are applied with a significant share of annual and perennial legumes and their mixtures
with grasses to enrich the soil with nitrogen and provide enough roughage for livestock on
a farm.
Due to its complex and manifold positive effects on soil and yields, crop rotation in organic
production is returning to basic principles in times when agriculture was based on methods
applied in organic farming nowadays. Share of legumes and grasses in such crop rotations
is huge (20-40%), either as setting pastures and meadows on some part of fields, or annual
and perennial legumes. In this type of crop rotation focus is on activating and preservation
of natural fertility of soil, and less on plant nutrition, as opposed to intensive conventional
production.
One of the precondition for successful management of organic crop production
is by introducing cover crops in rotation. Benefits for soil and main crop are manifold: erosion control, increase in organic matter content, management of soil moisture, water quality
protection, weeds and pests control, etc. Planning of such crop rotation is done parallel for
the main and the cover crops.
Soil productivity increases by implementation of wide-row crop rotation without ploughing,
with inclusion of more plant species. Crops that leave on the field less remains (brassicas)
should be sown in combination with grains. Available content of nitrogen for plants can be
increased by rotation of grains or oleaceus plants with legumes and forage crops. Symbiotic
nitrogen from legumes can persist for some time, depending of legumes involved. Pay attention that symbiotic nitrogen fixation in legumes depends on mycorrhiza providing phosphorus, needed for absorption of nitrogen and Rhisobium responsible for nitrogen fixation.
Legumes grow well on biological active soil, creating even better biological soil activity.
After several years of cultivation of perennial fodder crops, soil gets better structure, better
biological activity, organic matter is higher, is enriched with in nitrogen in comparison to
monoculture crops. Legumes with strong and deep root system (alfalfa) in the crop rotation
increase softness of the soil and nitrogen content. Intercropping in crop rotation intensify
agrobiodiversity, leading to better biological diversity in soil. Such soil is more resistant to
drought, extensive utilization, with less tillage and less nutrients.
In comparison to monoculture crops, crops in crop rotation are less damaged by diseases
and pests. Cultivation of the same crop or the crops prone to same disease on the same
place over the years, results in spreading plant diseases and pests and their piling in the soil.
Crop rotation interrupts life cycle of pests.
For example, population of click beetles (Elateridae) reach their peak of ability to damage grains is in the following year, therefore is needed
to grow oat or flax as part of the next year crop rotation. Susceptibility to diseases should be
considered in planning crop rotation. For example, crops prone to same diseases should not
be sown one after another (Table 1), like crops prone to white mold, require 4-5 year crop
rotation period.
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Table 1. Possible crop diseases appearing in crop rotation
Crop
Possibility
of diseases
and its development*
Not to grow after Reason
Barley, wheat
1
2
3
Barley, wheat
Maize
Winter rye
Leaf diseases, Common root rot
Scab
Ergot of rye
Flax 1
1
Sugar beet, peas,
lenticels
Flax
Rhizoctonia root rot
Rhizoctonia root rot
Rye 1 Rye, wheat, barley Ergot
Canolaand
mustard
1
2
Canola, mustard,
beans
Sunflower, soybeans, lenticels
White mold, Rhizoctonia root rot
White mold
Sunflower
1
1
2
Sunflower, soybeans, beans
Canola, field mustard
Lenticels
White mold , black
rust
White mold
White mold
Peas, beans
1
2
2
1
Peas, beans
Sugar beet
Alfalfa, flax, lenticels, beans
Sunflower, lenticels, canola,
field mustard,
beans, mustard
Bacteriosis
Rhizoctonia root rot
Fusarium, Pythium
White mold
*Ranking potential of appearance
of disease and its development: 1-
strong, 2 –moderate, 3 – weak
Pests struggle to find host crops in intercropping systems which lessen problems in some
extent. Establishing habitats for predators and parasitoids with perennial legumes enables
better pest control. Alfalfa attracts many beneficial organisms able to destroy pests in neighboring field. Intercropping of soybeans and corn resulted in lower infection rate.
Crop rotation planning
Crop rotation is one of the most powerful weapons organic farmer has against weeds and in
maintaining soil fertility, thus has high priority in this plant production system. Crop rotation
in organic farming should be diversified as much as possible. Crops with deep root system
(alfalfa) should switch crops with shallow root system (grains) to maintain structure and
drainage. It is desirable to switch legumes (nitrogen fixation) with heavy nitrogen feeders,
crops with bigger root biomass with crops with less, bigger consumers with smaller, etc.
Recommendation is to include cover crops with different characteristics and pasture crop
rotation involving legumes.
Key to good crop rotation is in diversification of rotating crops, belonging to different plant
groups, sown in different time and with different nutritional demands, etc. It is important to
understand principles of crop rotation to be able to adjust it to your farm conditions. Crop
rotation on one successful farm for sure will not work on another, because every farm is
unique. However, successful crop rotation (Scheme 1) can give ideas and models adjustable
to the needs of other farms.
Scheme 1. Example of crop rotation on organic farm without livestock and with alfalfa 2015
Summer Cover crop
Alfalfa
Autumn Alfalfa
2016
Winter
Spring
Summer
Autumn Common millet
2017
Winter
Spring Spelt
Summer
Autumn
Living mulch
2018
Winter
Spring
Common millet
Summer
Autumn Spelt Sunflower
2019
Winter
Spring Оat
Summer Cover crop
Autumn
Mulching + compost
Living mulch, formed partly
from subsoil ploughed alfalfa
Cover crop formed after har- vested true cereal grain
Cultivation and soil
incorporation
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Winter
Spring Sunflower
Summer
Autumn Оat
2021
Winter
Spring
Summer Cover crop
Autumn Alfalfa
Planning of crop rotation requires estimation of following:
• economic value of production,
• importance as feed for livestock,
• role in building organic matter in soil,
• cover crops – soil erosion control,
• rising or depletion of nutrients,
• ability to compete with weeds and their suppression,
• pest tolerance,
• need for human labor in production.
Legumes used as the livestock feed can provide other benefits as well. They can be used as
hay, roughage or for seed production, but they are also contributing to weed and pest control, building nitrogen in soil for succeeding crops, improving soil structure. Buckwheat could
be used for grain production, but is also included in the crop rotation to control weeds, and
is used as the green manure for phosphorus accumulation and food for the bees. Winter rye
is produced for its grains and huge quantities of straw for bedding and compost, and in the
crop rotation control weeds and builds up organic matter in soil.
Example: Five-field crop rotation on organic farm without livestock, is modeled with alfalfa
inclusion (Scheme 1). Alfalfa should be cultivated for two years, which is suitable as total
surface is faster enriched with nitrogen and free from weeds for the next crop. It means that
alfalfa will be in the same field every five years, and meanwhile in the middle of that period,
field is fertilized with farm compost. Alfalfa yield can be up to 52 t ha-1 green biomass, i.e.
12,6 t ha-1 dry matter on annual level. Part of this biomass can be used for compost production to maintain soil fertility on farm. Due to alfalfa seed production which is providing economic sustainability, suggested technology sustains soil fertility in natural and sustainable
way.
Significance of vegetable crop rotation
Vegetable crop rotation has important biological impact: it maintains balance of nitrogen in
soil, stabilizes active matter in the soil, reduces loss of nutrients by runoff water, maintains
microbiological soil activity and reduces weeds and pests. Ground of the vegetable production presents solid vegetable, and if the farm has the possibility, can apply field crops-vegetables and field crops-fodder crops-vegetable crops crop rotation by including green manure,
fodder crops and grain cereals which will help to control diseases, pests (white clover...) and
weeds (spelt, rye, triticale) efficiently. However, if cultivated crops require more nitrogen
(fruit-bearing vegetables, brassicas, potato, squash), then in the crop rotation should be at
least 25% of legumes with vegetation period longer than three months (French bean, lenticels, fava bean, and as a successive crop alfalfa, Crimson clover or clover). In practice, content and size of the crop rotation vary from many factors: whether vegetables will be sold on
the green markets (different species, varieties) or processed on the farm, perhaps vegetables
will be used as a raw material for processing industry, or as a propagation material.
Economic significance of correct implementation of the crop rotation mainly comes from the
negative consequences of vegetable conventional production where crop rotation is lacking.
Vegetables in monoculture and tiredness of soil long-term influence to yield decrease and
directly to the farm income. Poorly planned crop rotation in vegetable production results in
more weeds, due to the wrong selection of species (some crops in vegetation can cover soils
with their biomass), and due to the appearance of rhizome weeds. Therefore, farmer needs
to spend resources to eliminate weeds manually and mechanically. Correct crop rotation in
combination with cover crops reduces labor work, not only in weeding, but also in the inter-row cultivation.
Planning vegetable crop rotation
Crop rotation is usually planned for several years (3-7). In planning successive plant production and in selection of crops, farmer complies crop rotation with available farm resources.
It is important to rationally use soil resources, to fertilize vegetables with products of natural
origin (taking into consideration plants’ needs). Sowing and harvesting as labor intensive activities should be well planned to comply with other work on the farm. Production in greenhouses is especially demanding as it adds costs for heating as well.
It is essential to cultivate cash crops with market demand and which producer knows how
to grow (has enough experience and knowledge). For selected crops, producer has to have
appropriate machinery and equipment and to fully respect times of plant propagation, planting, harvesting, washing, sorting, packing, etc. Farm should have enough workers and labor
costs need to be calculated in the farm income. If everything above is applied, farmer can
expect profit.
Every producer plans crop rotation in compliance to the agro ecological conditions, soil parameters, irrigation possibility and set production goals. Though it may seem otherwise, to
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make a good crop rotation plan is not easy. Producer plans crops sequencing in time and
space and periods when soil rests. Moreover, producer needs to select species, resistant
variety, fertilizers, adequate soil preparation, set deadline for sowing and planting, harvesting, etc. In order to make proper crop rotation, one should know which crops were grown
previously and on which fields. Farmer divides production field in the several plots and in the
Field book plans future crop production.
Vegetables are divided into several categories, one is according to their resistance to monoculture and soil exhaustion. Low sensitivity to monoculture has leek, celery, lettuce and pepper, medium sensitivity has tomato, cabbage, cauliflower, carrot, and peas, and high sensitivity has parsley and beet root. The most sensitive species to soil exhaustion are brassicas
(cabbage, cauliflower, broccoli), spinach, beet root, chard and beans, further less or no sensitivity at all has lettuce and fruit-bearing vegetables (tomato, pepper).
Vegetables are categorized according to fertilization demand. For organic vegetable production is specific application of the clean vegetables crop rotation where three groups of vegetables shifts:
• I group in the crop rotation – species fertilized abundantly with manure (2-6 kg/m2): potato, late cabbage varieties, kale, broccoli, cauliflower, Brussels sprout, pepper, tomato,
eggplant, sweet corn, celery, leek, cucumbers, melon and watermelon;
• II group in the crop rotation – species with less need for fertilization (1,5-2,5 kg/m²), are
using extended effect of manure decomposition (organic fertilizers have adverse influence on product quality): carrot, parsley, parsnip, early varieties of cabbage, kohlrabi,
onion, garlic, lettuce, spinach, chard, beet root, red radish (alternatively);
• III group in the crop rotation – species enriching soils with nitrogen, and species which
are not fertilized with manure as they are low users: peas, French beans, beans, fava
beans, various lettuce, rocket, radish, corn salad, curly parsley, chicory, endive.
When crop rotation is planned, one should keep in mind that legumes and root vegetables
do not stand manure. When vegetables from these three groups change in time and space
they make a three-filed crop rotation system. In the three-field crop rotation, crops in the I
group always come in the first field, crops in the II group take the second field, and vegetables in the III group come to the third field (Scheme 2). Their shifting make three-year cycle
of vegetable production (Table 2).
Scheme 2. Rotation of field within three years
First field Second field Third field
1.
year I group II group III group
2. year II group III group I group
3. year III group I group II group
Table 2. Sequencing of vegetables in the three-year crop rotation
Year I field II field III field
year Fruit-bearing vegetables, leek, brassicas
Carrot, parsley, parsnip, beet root, onion,
garlic
Legumes
year
Carrot, parsley, parsnip, beet root, onion,
garlic
Legumes Fruit-bearing vegetables, leek, brassicas
year Legumes Fruit-bearing vegetables, leek, brassicas
Carrot, parsley, parsnip, beet root, , garlic
Crop rotation in greenhouses is also applied and is obligatory measure ofharmful organisms control in such specific production conditions. In order to use all the production fields
throughout the year, intensive vegetable crop rotation is applied (change of 2-3 species on
the same field during the year), which is based on the three-field vegetable crop rotation.
During one vegetation period or a year, farmer on the same field continuously or in the same
time (intercropping) cultivates more vegetables species. It means that after harvesting of
one crop, the other one is sown, and even third, if conditions allow it. Intensive crop rotation is possible due to the different vegetables’ vegetation, difference in heat requirements
and resistance to low temperatures (kale, Brussels sprout, leek...). Therefore, we distinguish
main vegetables species and according to them are planned preceding and successive crops.
