Download A Basics of Botany

Tutorial
Organic Food Chain Management
Basics of Crop Production
Institute for Crop Production and Grassland Research
Prof. Dr. W. Claupein
compiled by Jens Poetsch (November 2006)
Contents
A
Basics of Botany
A.1
A.2
A.3
A.4
A.5
Taxonomy of higher plants
Plant morphology
Plant physiology
Usable plant parts
Checkup, references and further reading
B
Basics of Soil Science
B.1
B.2
B.3
B.4
Soil genesis and nutrient cycling
Soil characterisation
Particles, texture, structure, air and water regime
Checkup, references and further reading
C
Agricultural Crops
C.1
C.2
C.3
C.4
C.5
C.6
C.7
C.8
C.9
Cereals (starch crops)
Protein crops
Oil crops
Root and tuber Crops
Important tropical crops
Arable fodder cropping
Grassland
Renewable raw materials
Checkup, references and further reading
D
Crop Management
D.1
D.2
D.3
D.4
D.5
D.6
Crop life cycle and site adaption
Crop rotation
Soil cultivation
Sowing
Harvest
Checkup, references and further reading
E
Plant Nutrition and Fertilization
E.1
E.2
E.3
E.4
Plant nutrients
Fertilization
Nitrogen cycle
Checkup, references and further reading
F
Weed Management
F.1 Weed biology
F.2 Weed control
F.3 Checkup, references and further reading
Important Crops and Weeds
Units and Abbreviations
Index
A
Basics of Botany
A
Basics of Botany
A.1
Taxonomy of higher plants
The kingdom of plants is hierarchically structured in division, class, order, family,
genus and species, describing higher or lesser degress of relationship. Two examples for worldwide important crops are:
wheat (Triticum aestivum)
division
class
soybean (Glycine max)
seed-bearing plants (Magnoliophyta)
monocotyledons (Liliopsida)
dicotyledons (Magnoliopsida)
(Poales)
(Fabales)
family
true grasses (Poaceae)
legumes (Fabaceae)
genus
wheat (Triticum)
(Glycine)
bread wheat (T. aestivum)
soybean (G. max)
order
species
The scientific name of a plant, like e.g. Triticum aestivum for wheat, complies with
genus (Triticum) and species (aestivum).
Species are further divided in forms and cultivars (= varieties):
- forms may be the result of evolution or breeding; they describe strongly differing
genetic types within a species (like growth habit or site adaption)
- cultivars are the result of breeding activities and usually have closely defined agronomic properties
Almost all usable plants belong to the division of seed-bearing (“higher”) plants.
The lower divisions of ferns, mosses and algae only have specialized uses.
(Fungi are not plants but a separate kingdom.)
Agriculturally important classes are the Monocotyledons (including grain and fodder grasses, onions, orchids, palm trees) and Dicotyledons (including most deciduous trees, legumes and other herbaceous plants).
Cotyledons are the seed-leaves, the first leaves of a plantlet, already embodied in
the seed. The number (one or two) of cotyledons is one distinctive feature of
mono- and dicotyledonous plants. Many other features account for important differences in cultivation.
A.1–1
A
Basics of Botany
Cotyledons
Primary root
Monocotyledonous
plantlet (onion)
Franke, 1997
Dicotyledonous
plantlet (mustard)
A.1–2
A
A.2
Basics of Botany
Plant morphology
A higher plant consists of three basic parts: stem, root and leaves
The stem is divided by nodes. Each node can produce one or more leaves. The
axil of each leave contains a bud that may become a secondary stem.
The terminal buds are the parts where growth continues. Additionally, the internodes (the parts between nodes) are able to elongate, increasing plant height.
In the root hair zone most water and nutrients are absorbed. Larger (older) roots
are important for stability and transmittance of water and nutrients into the aboveground plant parts.
The inflorescence (the part bearing the flowers) is not a discrete plant organ but a
specialized part of stem and leaves that also originates from buds.
terminal buds
accessory bud
leaf
internode
node
secondary stem
main stem
cotyledons
primary root
secondary root
root hair zone
A.2–3
Scheme of a dicotyledonous
plant in vegetative state
(Franke, 1997)
A
Basics of Botany
raceme
ear
cob
umbel
Examples for different
inflorescences
(Franke, 1997)
composite raceme
composite ear
Simple inflorescences have an axis with flowers. Composite inflorescences have
an additional branching structure.
The inflorescence e.g. of wheat (Triticum aestivum), rye (Secale cereale) and barley (Hordeum vulgare) is a composite ear (only packed closer than in the picture).
The inflorescence of oat (Avena sativa) is a composite raceme (also called panicle).
Other examples for inflorescences are rapeseed (Brassica napus: raceme), maize
(Zea mays: cob), fennel (Foeniculum vulgare: umbel).
A.2–4
A
A.3
Basics of Botany
Plant physiology
For optimum growth plants need: warmth, water, nutrients, light and air.
Water is taken up from the soil and conducted upwards where it is finally transpired through the leaves. This upward flow carries nutrients from the soil to the
plant parts where they are needed.
Water use efficiency of crops may differ. As is shown in Fig. 5.12 durum wheat
(Triticum durum) may produce acceptable yields at low water supply, but bread
wheat (T. aestivum) profits more (steeper line) from additional water. Table 11.13
shows examples of total water consumption by some crops in one cropping season.
Note: “evapotranspiration” specifies the sum of direct evaporation from the soil and
transpiration through the plant. Millimeters (mm) as a unit for precipitation or
evapotranspiration are equal to litres per m2, because pouring one litre of water on
the area of one m2 makes a pond of one mm depth.
in: Pratley, 2003
A.3–5
A
Basics of Botany
Pratley, 2003
Sunlight is intercepted by plants, and a part of its energy is transformed to chemical energy in a process called photosynthesis. The energy is used to split aerial
carbondioxide (CO2) into carbon (C) and oxygen (O2).
Carbon is finally used to produce substances (“assimilates”) for energy storage
and transport (like sugar) or plant organic matter for growth.
There are two important biochemical energy-pathways. According to the number
of carbon atoms in the determining intermediate product they are called C3- and
C4-pathway.
If all other growth factors are abundant, growth of C3-plants is limited by CO2supply from the air. A further increasing light intensity can not be used by the
plants. Current CO2-content of the air is 380 ppm (= 0,038%, increasing through
fossil energy use).
C4-plants are more efficient in taking CO2 from the air and can make use of high
light intensities, where CO2-supply is not a limiting factor for them.
C3-plants are more efficient in converting light energy. At low light intensities C3plants have a higher photosynthesis rate than C4-plants. Moreover, C3-plants still
grow at low temperatures, while C4 plants need warmer climates.
In conclusion, most C4-plants originate from low latitudes (tropics and subtropics)
with high light intensity. Important C4-plants are maize, sugar cane, sorghum.
At higher latitude (north and south) C3-plants like wheat or rapeseed are more
widespread, but rize, bean and many other crops also are C3-plants.
A.3–6
A
Basics of Botany
photosynthesis rate
(dry matter assimilation)
C4-plants
(always sunlight adapted)
sunlight adapted C3-plants
shade adapted C3-plants
light intensity
Linder, 1989
C3-plants more efficient C4-plants more efficient
Shade adapted plants are particularly efficient at low light intensity, but their
maximum growth rate is strongly limited.
Better CO2 supply or efficiency also reduces water transpiration, because the plant
requires less air exchange. Thus, C4-plants are more water efficient than C3plants.
Air also contains oxygen (21%). To use the energy stored by photosynthesis,
plants need oxygen to breathe. The roots, in the absence of light energy, are dependent on assimilates from the upper plant parts and oxygen in the soil air.
Impact of CO2 concentration (318 vs 671 ppm) on plant physiological
parameters of spring wheat (Manderscheid et al, 1999)
CO2
Parameter
absorbed radiation (MJ/m2)
evapotranspiration (mm)
dry matter (g/m2)
normal
enriched
414
292
1919
413
225
2083
effect (%)
- 0,4
- 14,8
+ 8,5
in: Diepenbrock et al, 2005
A.3–7
A
Basics of Botany
After a period of vegetative growth most plants change to the generative stage:
producing flowers and eventually seeds.
Depending on the desired product, harvest may take place before flowering
(e.g. sugar beet, lettuce, asparagus).
In addition to producing seeds (generative propagation) many plants are able to
produce new plants from parts of themselves (vegetative propagation) - examples
are potatoe (tubers) or several weeds (thistle, couch grass).
Often seeds are the harvest product. For optimum propagation the plant concentrates energy (starch, oil), protein and other nutrients in the seed, which makes it a
valuable food object.
To make sure that flowering and seed production take place in a favourable season (temperature in colder climates, water supply in monsoon climates) plants
have different mechanisms.
- they can perceive day length: if days are too short or too long (depending on the
plant’s origin) the plant may not flower at all
- many plants have a “frost security system”: they will not flower before a certain
period of low temperatures has passed, the process being called “vernalization”
These mechanisms may affect site suitability and optimum sowing date
A.3–8
A
Basics of Botany
A.4
Usable plant parts
Basically all plant parts can be used.
Seeds of many crops have particularly high contents of special substances like
starch (cereals), protein (beans, peas) or oil (rapeseed, sunflower).
Fruits are the casing of developing seeds. At harvest they may be a mere container (like dry pods) or a store for additional nutrients and water (fruits and vegetables).
Bickel-Sandkötter, 2001
pod and seed of
common bean
(Phaseolus vulgaris)
open pod with septum and
seeds of oilseed rape
(Brassica napus)
berry cross-section of
tomato
(Solanum lycopersicum)
Other desirable harvest products are not related to seed production but to energy
storage of the plant.
For storing large amounts of assimilates, plants may develop expanded root or
stem parts. Examples are turnips, carrot, swede. The sugar beet (Beta vulgaris)
contains high amounts of sugar as energy store. The potato tuber (Solanum tuberosum) serves simultaneously as energy store and propagation unit. A stem that
contains large amounts of sugar is the sugar cane (Saccharum officinarum).
Other plant stems may be harvested for their good fibre characteristics, like hemp
(Cannabis sativa) or linen resp. flax (Linum usitatissimum).
Even inflorescences are edible harvest products. Cauliflower is an extremely expanded inflorescence.
Whole plants (aboveground, without roots) are harvested for animal feeding (hay
or green fodder) or energy purposes (burning).
Some plants may be used for diverse purposes by specialized breeding; for example rape-seed and swede are of the same species (Brassica napus).
A.4–9
A
Basics of Botany
(Bickel-Sandkötter, 2001)
swede
(Brassica napus)
cauliflower
(Brassica oleracea)
A.4–10
sugarcane
(Saccharum officinarum)
A
A.5
Basics of Botany
Checkup, references and further reading
What are the basic parts of a higher plant?
What is an inflorescence?
What are the major requirements for plant growth?
What is photosynthesis?
What is evapotranspiration, and how is it linked to plant growth and CO2
supply or efficiency of a plant?
What is the difference between C3 and C4-plants?
Which plant parts are usable, and what are their major contents?
References
BICKEL-SANDKÖTTER, S., 2001: Nutzpflanzen und ihre Inhaltsstoffe. Quelle und Meyer, Wiebelsheim
DIEPENBROCK, W.; ELLMER, F.; LÉON, J., 2005: Ackerbau, Pflanzenbau und Pflanzenzüchtung. Grundwissen Bachelor, Ulmer, Stuttgart
FRANKE, W., 1997: Nutzpflanzenkunde - Nutzbare Gewächse der gemäßigten Beiten, Subtropen und Tropen. 6., neubearb. u. erw. Aufl., Thieme, Stuttgart
LINDER, H., 1989: Biologie - Lehrbuch für die Oberstufe. 20., neubearbeitete Auflage, von H.
Bayrhuber, U. Kull, U. Bäßler, A. Danzer, Metzler, Stuttgart
PRATLEY, J. (Ed.), 2003: Principles of field crop production. 4th edition, Oxford University
Press, Melbourne
Further reading
EVANS, L.T., 1996: Crop Evolution, Adaptation and Yield. Cambridge Univ. Press, Cambridge, UK
PESSARAKLI, M. (Ed.), 2002: Handbook of Plant and Crop Physiology. Marcel Dekker, Inc.,
New York, Basel, Hong Kong
A.5–11
B
Basics of Soil Science
B
Basics of Soil Science
B.1
Soil genesis and nutrient cycling
http://ic.ucsc.edu
Soil is an ecosystem at the interface of lithosphere, atmosphere, hydrosphere and
biosphere.
Essential soil forming processes are physical and chemical weathering of rock
parent material and cumulative enrichment with dead and living organic matter.
Thus, the solid part of a soil consists basically of minerals and humus.
Air and water filled pores in the soil are essential for the survival of plant roots, soil
inhabiting animals and microorganisms.
Soil is also a production factor for agriculture. A fertile soil is characterized by a
balanced supply of plant nutrients, good water storage capacity, sufficient aeration
and high biological activity.
Plant and animal residues are subject to microbal decomposition in a process
called mineralization. Nutrients fixed in organic matter become (again) available
for root uptake by plants through mineralization.
Stable organic compounds in the decomposition process are transformed to humus and important for a good soil structure.
B.1–1
B
B.2
Basics of Soil Science
Soil characterisation
Ashman & Puri, 2002
The formation of different soil types depends on environmental variables such as
climate, parent material, organisms, topography and time.
According to the major processes in different depths, a soil can be divided in horizons which are often clearly visible in a vertical soil profile. This profile defines the
soil type.
The predominant part of agricultural activities takes place in the A horizon (20-30
cm). Deeper horizons are also penetrated by roots and add significantly to plant
available water and nutrients.
B.2–2
B
B.3
Basics of Soil Science
Particles, texture, structure, air and water regime
Ashman & Puri, 2002
Depending on parent material and soil formation history the particle size of a soil
will differ. Sand feels granulous, dry silt feels like flour, and clay is kneadable when
moist or hard when dry. Particles > 2 mm are referred to as gravel.
The proportion of sand, silt and clay in a soil is referred to as its soil texture. The
second term (as in “loamy sand”) describes the main character, the first term an
additional tendency.
Loam is a term for soil types, consisting to a fair degree of all three fractions.
Additionally, soils contain organic compounds, referred to as humus. Typical humus contents of agricultural soils are 1% to 5% by weight.
B.3–3
B
Basics of Soil Science
Ashman & Puri, 2002
Mineral particles and organic compounds from microbes, plant roots and animals
form aggregates referred to as crumbs.
Crumbs improve a soil’s structure and stability against compaction (elasticity effect) or crustification, and have a high water-holding capacity (sponge effect).
Earthworm castings are stable and nutrient rich crumbs.
B.3–4
B
Basics of Soil Science
Ashman & Puri, 2002
Ashman & Puri, 2002
45-50% of soil volume consists of pores. Pore-size depends on soil texture and
structure. Macropores will drain quickly (transmission). Meso- and micropores hold
water through capillarity, but water in micropores is held too tight for plants to be
available (residual water).
Macropores are important for soil aeration and growth of plant roots. Mesopores
are important for plant water supply.
Pore volume and pore-size distribution may be affected by soil compaction (e.g.
caused by cultivation). A good soil structure prevents compaction. Soils with a
weak structure may even be compacted by heavy rain and gravity.
B.3–5
B
Basics of Soil Science
Ashman & Puri, 2002
The tension at which water is held by capillarity is measured in MPa. For a specific
soil there is a definite correlation between water content and tension, which can be
shown in a moisture release curve.
There are two important points on the moisture release curve. At the permanent
wilting point there is only plant unavailable water (micropores) left in the soil. At
field capacity there is as much water stored in the soil as possible (only macropores remain air-filled). Each additional amount of water will drain quickly.
The water content between these points is referred to as plant-available water.
The soil volume corresponding to plant-available water can be read as the horizontal difference of water contents at PWP and FC.
The total amount of plant available water is determined by percentage of soil volume and depth of root penetrable soil. Typical magnitudes are 100 to 250 l/m2.
(for comparison: average annual precipitation in Germany: 600-900 l/m2).
Note: Precipitation in litres per m2 can also be measured in mm, because pouring
one litre of water on the area of one m2 makes a pond of one mm depth.
Soil aeration depends on soil texture and moisture. While macropores are usually
filled by air, mesopores may be filled by either air or water.
B.3–6
B
B.4
Basics of Soil Science
Checkup, references and further reading
Why is an unbalanced precipitation (e.g. wet spring and dry summer) more
adverse for crop water supply on sandy soil than on loamy soil?
Why does a clay soil store less plant-available water than loam, although it
contains more water in total?
What are the benefits of high biological soil activity for soil structure?
What are the characteristics of a fertile soil? How could different parameters be improved?
References
ASHMAN, M.R.; PURI, G., 2002: Essential Soil Science - a clear and concise introduction to
soil science. Blackwell, Oxford Berlin
Further reading
ASHMAN, M.R.; PURI, G., 2002: Essential Soil Science - a clear and concise introduction to
soil science. Blackwell, Oxford Berlin
B.4–7
C
C
Agricultural Crops
Agricultural Crops
The basic aim of agricultural activities is harvesting a high yield.
Yield is commonly indicated by weight per area. Typical units are t (tonne) or Mg
(Megagramme = 106 gramme = 1 t) per ha (hectare). 10 t/ha equal 1 kg/m2
In Germany the weight unit dt (decitonne = 0,1 t = 100 kg) is common. In the USA
yield is measured in bushel (US bush.) which is a unit of volume, but for each crop
there is a defined weight for one bushel, e.g. 1 bushel wheat = 27,2 kg and 1
bushel maize = 25,4 kg. The area also may be measured in different units, like the
chinese Mu (= 1/15 ha) or the american acre (= 4046,9 m2).
Yield may be refering to dry matter (DM, as a measure for actual growth efficiency
and accumulated sunlight) or fresh matter (including variable amounts of water).
Commonly, yield of grain crops is given at a uniform moisture content, e.g. of 14%
(= 86% DM) which represents the standard storage condition.
Yield of root and tuber crops is commonly given as fresh matter. For sugar beet it
may be given as sugar yield.
B.4–1
C
C.1
Agricultural Crops
Cereals (starch crops)
Cereals belong to the family of grasses (Poaceae) and are grown as staple foods
worldwide. They contain starch (=energy), protein (8-15%), minerals and further
favourable substances. Cereals are consumed as bread, pasta, cooked or as
mush.
Of high worldwide importance, depending on climate, are wheat, rice and maize.
Important cereals grown in temperate climates are wheat, rye, barley and oat.
Wheat, rye and barley produce ears (= spikes), while the inflorescence of oat is
called panicle. The ears of rye and barley have awns, usually longer in barley than
in rye.
awns
Bickel-Sandkötter, 2001
Wheat
(Triticum
aestivum)
Rye
(Secale
cereale)
Barley
(Hordeum
vulgare)
C.1–2
Oat
(Avena
sativa)
C
Agricultural Crops
Maize is a C4-plant of high productivity.
Maize produces separate male and female inflorescences. The female inflorescence is a cob (1-2 per plant) and finally bears the yield.
In colder climates maize may not always reach maturity but can also be grown as
a highly productive green fodder crop.
styles of female flowers
male inflorescence
(tassel)
female
inflorescences
(silt)
Bickel-Sandkötter, 2001
Cob
Maize
(Zea mays)
C.1–3
C
C.2
Agricultural Crops
Protein crops
Plants belonging to the family of legumes (Leguminosae) and producing seeds
with a protein content of 20-45% are referred to as proteincrops. They are used for
protein nutrition of humans and animals.
The seeds are usually harvested dry when pods open easily and seeds are storable. Alternatively, unripe (green) pods of some protein crops may be harvested
as vegetable (pea, garden bean).
Important protein crops in Europe are field pea and field bean.
The pea uses tendrils (parts of the leaves) to get a hold on other plants.
tendrils
flowers
pods
Field pea
(Pisum sativum)
Field bean
(Vicia faba)
climbing
not climbing
www.botanical-online.com
Bickel-Sandkötter, 2001
C.2–4
C
Agricultural Crops
In warmer climates soybean and common bean are grown.
The common bean has a large diversity of forms, from runner beans (long green
pods used as vegetable) to kidney beans or black beans.
Soybean is by far the most important protein crop worldwide. It contains approx.
20% oil and 40% protein. For this reason it is also grown as an oil crop.
A common feature of all legumes (comprising protein crops and fodder legumes) is
the formation of root nodules. These give the crops an important advantage in nitrogen supply. Nitrogen is an essential element for plant growth in general and
protein production in particular.
pods
root nodules
Soybean
(Glycine max)
Common Bean
(Phaseolus vulgaris)
Brücher, 1977
Bickel-Sandkötter, 2001
C.2–5
C
C.3
Agricultural Crops
Oil crops
Vegetable oil can be extruded from seeds rich in oil. Typical oil contents of those
seeds are between 30 and 50%.
Examples for oil seed crops are sunflower and rapeseed.
Vegetable oils have a higher nutritional value than animal fats.
There are also “non-food” (technical) uses for vegetable oils. One is the production
of biodiesel from rapeseed-oil.
High oil contents may also be found in fruits (olives, palm-oil).
http://bitininkas.tinklapis.lt
Bickel-Sandkötter, 2001
Sunflower
(Helianthus annuus)
Rapeseed
(Brassica napus)
C.3–6
C
C.4
Agricultural Crops
Root and tuber Crops
Many crops are grown for subterranean products like turnips, beets or tubers.
The potatoe is planted as a seed potato. From this tuber a whole plant evolves,
producing a stem and leaves, roots and new tubers. While the seed potatoe is
consumed in the process, new tubers can be harvested from the soil. The aboveground plant can not be used.
flower
Poisonous
potatoe
berry
Potatoe tuber
Seed potatoe (= old “mother” tuber)
Potato plant
(Solanum tuberosum)
C.4–7
C
Agricultural Crops
Turnips and beets are expanded roots (and lower parts of the stem), storing energy and other substances. In contrast to the potato they do not store energy for
propagation but for endurance.
Usually flowering is undesirable, because part of the stored substances would be
consumed for producing flower and seeds. So the crop must be harvested when
the maximum storage is reached.
An example of diverse forms of one species is Beta vulgaris:
- the sugar beet stores approx. 18% by weight of sugar in its root
- the forage beet produces less sugar, but has a high productivity as fodder crop
- the beetroot produces purple-red roots that are used as vegetable
- another form of Beta vulgaris is grown for its leaves as vegetable and called
chard or leaf beet; it has almost no beet
D
Bickel-Sandkötter, 2001
cultivated forms of Beta vulgaris:
sugarbeet (A), forage beet (B), beetroot (C), chard/leaf beet (D)
C.4–8
C
C.5
Agricultural Crops
Important tropical crops
Many other crops produce spices, luxury foodstuffs and other commodities.
Coffee originates in Africa and is today an important export product of middle and
south america. The fruit contains two seeds that are fermented, roasted and milled
to produce the well known hot beverage.
berry
bean
Coffee plant
C.5–9
C
Agricultural Crops
C.6
Arable fodder cropping
Green fodder plants can be grown on arable land. Usually the aboveground plant
matter is harvested 3-5 times a year. Total use over a period of two years is common.
Most important groups of arable fodder crops are legumes and grasses.
Legumes, like red clover, have a high feeding value and protein content.
Grasses, like annual ryegrass, have a high productivity and better storage suitability than legumes.
Growing of mixtures (“grass clover”) of two or more species for arable fodder production is very common. Mixtures have a higher productivity than monocultures,
and good storage and fodder qualities.
Arable fodder cropping improves soil structure and reduces weed pressure.
www.fk.no
Frame, Charlton, Laidlaw, 1998
Red clover
(Trifolium pratense)
Annual ryegrass
(Lolium multiflorum)
C.6–10
C
C.8
Agricultural Crops
Renewable raw materials
Important non-food uses for plant materials are fibre and energy production (including oil crops).
Hemp is a plant producing edible seeds, fibre (stem) and pharmaceuticals (flower).
Hemp fibre - like many plant fibres - can be used for textiles and technical purposes.
All plants or plant residues can be used for energy production. A specialized way
of “energy cropping” is the growing of so-called short rotation coppice. Fast growing trees, like the willow, are cut every 3-4 years for fuelwood production. Suitable
species can easily grow new shoots over a long period.
Hemp
Willow
C.8–12
C
C.9
Agricultural Crops
Checkup, references and further reading
Name some important crops for energy and protein supply in human nutrition.
What do cereals, protein crops and oilseeds have in common, concerning
agricultural production?
How could harvest of potatoes be accomplished mechanically?
When should beets and turnips be harvested?
What non-food uses of plants do you know?
What are the typical crops and production methods of green fodder?
References
BICKEL-SANDKÖTTER, S., 2001: Nutzpflanzen und ihre Inhaltsstoffe. Quelle und Meyer, Wiebelsheim
FRAME, J.; CHARLTON, J.F.L.; LAIDLAW, A.S., 1998: Temperate forage legumes. Wallingford,
CAB International
Further reading
MCMAHON, M.J.; KOFRANEK, A.M.; RUBATZKY, V.E., 2006: Hartmann's plant science :
growth, development, and utilization of cultivated plants. Upper Saddle River, NJ : Pearson
Prentice Hall
C.9–13
D
Crop Management
D
Crop Management
D.1
Crop life cycle and site adaption
A typical arable crop is annual, meaning that the vegetative period between sowing and harvesting is one year or less.
In temperate climates there are spring-sown and autumn-sown crops.
Spring-sown crops are sown after winter when the temperature required for the
respective crop is reached.
Autumn-sown crops are sown before winter and achieve a certain predevelopment. They have to endure the cold season, but in spring they have a
headstart on spring-sown crops. Due to their longer vegetative period in total they
have a higher yield potential.
All crops can be sown in spring. Additionally there are cultivars of several crops
with sufficient cold tolerance for autumn-sowing. It is important that they do not
develop flowers before winter, because these would not survive. This is achieved
by a plant mechanism called vernalization: the production of flowers is blocked until the plant has received a sufficient cold stimulus.
Typical autumn-sown crops in Germany are winter wheat (Triticum aestivum), winter barley (Hordeum vulgare), winter rye (Secale cereale) and winter rapeseed
(Brassica napus).
Harvest of autumn- and spring-sown crops takes place from summer until early
autumn, depending more on species than on sowing time.
Perennial crops, used for more than one year (e.g. forage crops), may be sown in
favourable conditions, but then have to survive all seasons.
Besides climate, soil conditions have a strong impact on cropping suitability.
D.1–1
D
D.2
Crop Management
Crop rotation
A crop rotation is a sequence of different crops that is repeated in a cycle of several years.
A “crop rotation” of one year, meaning that the same crop is grown on one field
over and over, is called monoculture. Typical impacts of this crop, like promotion of
specific pests or depriving of certain nutrients can accumulate.
Alternating crops reduces these problems and provides advantages like growing
nutrient demanding crops after nutrient mobilising crops, weed sensitive crops after weed competitive crops etc.
Typical crop rotations have a cycle of 3-4 years in conventional farming or 6-8
years in organic farming. An exemplary 7 year rotation in organic farming may be:
2 years grass clover, winter wheat, potatoes, spring barley, field pea, winter rye
To have a constant farm output every year, the arable area must be divided
equally to the years of the crop rotation. In the example a 70 ha farm may have 7
fields of 10 ha. Each field is cropped with another rotation member. Two fields will
be cropped with grass clover (one in the first, one in the second year).
Example of a 4-year crop rotation
year
field 1
field 2
field 3
field 4
2005
sugar beet
winter wheat
winter barley
oats
2006
oats
sugar beet
winter wheat
winter barley
2007
winter barley
oats
sugar beet
winter wheat
2008
winter wheat
winter barley
oats
sugar beet
2009
same as 2005
D.2–2
D
Crop Management
Pratley, 2003
D.2–3
D
D.3
Crop Management
Soil cultivation
historic tools for
soil cultivation
Diepenbrock, Ellmer,
Léon, 2005
Major aims of soil cultivation are: loosening of the soil, incorporation of organic
residues, weed suppression, optimizing conditions for sowing.
Cropping may compact the soil and decrease root permeability. Frequent loosening of the soil is recommended.
The most common system in Germany is the mouldboard plough. Bars of soil are
cut and turned for about 3/8 of a rotation (135°).
By “throwing” the soil it is fractured into natural crumbs with a good loosening effect. Organic residues and weeds are worked into the soil.
The new surface is relatively “clean” soil that is well suited for seedbed preparation.
Turning too much soil has negative effects on soil organisms.
A common rule for organic agriculture is: “turn shallowly, loosen deeply”
D.3–4
D
Crop Management
Ashman & Puri, 2002
furrow
turn-over angle
plough bar
The picture below shows three basic soil cultivation systems.
D.3–5
Schön, 1998
D
Crop Management
no mulch cover
bare soil
organic residues
“plough pan”
(subsoil compaction)
untilled subsoil
soil-turning tillage
tractor-cultivator
mulch cover
organic residues
worked in shallowly
continuous
change from tilled
to untilled soil
soil-loosening tillage
rotary
direct
sowing
mulch cover
organic residues
at soil surface
continuous
change from tilled
to untilled soil
no tillage
basic soil management systems (Schön, 1998)
D.3–6
D
D.5
Crop Management
Harvest
Grain crops can be harvested very efficiently by a combine harvester. This machine
- cuts the crop and feeds it in
- threshes the crop, to get the seeds from ears or pods
- separates seeds from straw and husks by sieves and wind
Pratley, 2003 (adapted from Kepner et al, 1982)
sieving
unit
threshing
unit
historical
D.5–9
cutting
unit
D
D.6
Crop Management
Checkup, references and further reading
What are annual and perennial crops?
What is autumn-sowing and what are its advantages and conditions?
What is a crop rotation, and what are its benefits?
What are the aims of soil cultivation?
Name three basic soil management systems. How well or not can they
achieve the aims of soil cultivation?
What are the characteristics of an ideal seedbed?
What is the meaning of dry matter yield, fresh matter yield
and yield at 86% DM?
What are the major tasks of a combine harvester, and what crops can it be
used for?
References
ASHMAN, M.R.; PURI, G., 2002: Essential Soil Science - a clear and concise introduction to
soil science. Blackwell, Oxford Berlin
DIEPENBROCK, W.; ELLMER, F.; LÉON, J., 2005: Ackerbau, Pflanzenbau und Pflanzenzüchtung. Grundwissen Bachelor, Ulmer, Stuttgart
LAMPKIN, N, 2002: Organic Farming. Old Pond Publishing, Ipswich
PRATLEY, J. (Ed.), 2003: Principles of field crop production. 4th edition, Oxford University
Press, Melbourne
SCHÖN, H., 1998: Landtechnik, Bauwesen - Verfahrenstechniken, Arbeit, Gebäude, Umwelt.
9., völlig neubearb. und erw. Aufl., BLV-Verl.-Ges., München
Further reading
LAMPKIN, N, 2002: Organic Farming. Old Pond Publishing, Ipswich
PRATLEY, J. (Ed.), 2003: Principles of field crop production. 4th edition, Oxford University
Press, Melbourne
D.6–10
E
Plant Nutrition and Fertilization
E
Plant Nutrition and Fertilization
E.1
Plant nutrients
Pratley, 2003
Table 6.1 shows the nutrients required by each plant.
Oxygen (O), carbon (C) and hydrogen (H) are derived from water and air.
All other elements must be supplied through the soil.
The distinction of macro- and micronutrients refers to the amounts required.
E.1–1
E
Plant Nutrition and Fertilization
There is a difference between absolute and relative nutrient availability.
Absolute availability refers to the total amount of nutrients in the soil.
However, the relative availability for a plant depends on several factors. Very important is the soil-pH (acid, alkaline or near neutral pH).
Some nutrients become chemically unavailable at extreme pH-values, even if the
total amount in the soil is high.
Particularly phosphorus (P) has a narrow optimum availablity window.
Note: aluminium (Al) is not a nutrient but toxic for plants at low soil-pH.
Ashman & Puri, 2002
E.1–2
E
E.2
Plant Nutrition and Fertilization
Fertilization
To recycle nutrients from animal production, manure is brought on the field. This
also increases humus content of the soil and has positive effects on soil structure
and biological activity.
In conventional farming nutrients are also added as synthetic “chemical” fertilizers.
Too high rates of fertilizer are not necessarily toxic. They may also promote diseases, lead to physiological imbalance or growth disturbance.
Ashman & Puri, 2002
E.2–3
E
E.3
Plant Nutrition and Fertilization
Nitrogen cycle
U.S. environmental protection agency
Nitrogen (N) is often the nutrient with the highest yield effect.
In conventional farming synthetic N-fertilizers are applied. These are not permitted
in organic farming.
The major N-source in organic farming is nitrogen fixation from the air by plants of
the legume family. These plants form a symbiosis with bacteria (rhizobia) that live
in so-called root nodules of the plant.
For this reason, legumes are an essential part of each crop rotation in organic
farming.
While other crops produce approx. 1 g of dry matter from the assimilation of 600
mg CO2, legumes must assimilate 1000 mg CO2 for the same growth, due to additional energy demand of the rhizobia. This is “the cost” of being N-self-sufficient.
E.3–4
E
E.4
Plant Nutrition and Fertilization
Checkup, references and further reading
What is the meaning of the term macronutrients and which plant macronutrients do you know?
What may be the reason if a phosphorus deficient plant does not react to
phosphorus fertilizing?
References
ASHMAN, M.R.; PURI, G., 2002: Essential Soil Science - a clear and concise introduction to
soil science. Blackwell, Oxford Berlin
PRATLEY, J. (Ed.), 2003: Principles of field crop production. 4th edition, Oxford University
Press, Melbourne
Further reading
MARSCHNER, H., 2003: Mineral nutrition of higher plants. Academic press, Amsterdam
MENGEL, K; KIRKBY, E.A., 2001: Principles of plant nutrition. Dordrecht, Kluwer
E.4–5
F
Weed Management
F
Weed Management
F.1
Weed biology
“Weed” is a term for plants not wanted in an agricultural field. These are usually
naturally occuring plants. Some species are especially favoured by certain agricultural activities and become dominant. Crops from earlier years, due to lost seeds,
may also become weeds (called “volunteer crop”) in another crop.
Important negative effects of weeds are:
- direct competition with the crop for water, light and nutrients
- quality reduction of harvest product due to contamination
- mechanical problems at harvest, especially if weeds are still green and tough
In conventional farming, the aim is often to wipe out all weeds chemically. However, weeds also have positive effects:
- better total root penetration and organic matter formation in the soil
- higher biodiversity in the field, promotion of beneficial organisms (= enemies of
pests) due to alternative habitats
As a result, in organic agriculture weeds are not destroyed but controlled. A certain
weed population is tolerated as beneficial. Only excessive growth must be confined to avoid yield or quality losses.
Lampkin, 2002 (in: Roberts, 1982)
F.1–1
F
Weed Management
Like all plants weeds can be annual or perennial, herbs (dicotyledons) or grasses
(monocotyledons).
Annual weeds germinate from seeds, grow and produce new seeds. Most weeds
produce between 100 and several thousands of seeds per plant. So weeds that
are allowed to spread their seed may be a bigger problem in the following year.
The life span of seeds (during which they can germinate) depends on species and
may be as low as 1-4 years, but for many weeds is rather 10-40 years.
Typically there are between 10.000 and 50.000 seeds per m2 in the soil. However,
only a small percentage meets favourable conditions for germination. Many seeds
are consumed by soil organisms before they ever germinate.
Perennial weeds like thistle (Cirsium arvense) or dock weed (Rumex crispus) have
a life cycle of more than one year. They commonly have the ability to store reserves in their root, and even if the aboveground plant dies by cold, hoeing or else,
it may resprout by use of its reserves.
F.1–2
F
F.2
Weed Management
Weed control
There is a difference between indirect and direct weed control:
- indirect weed control is achieved by soil cultivation (see there) and promoting a
good and competitive crop (e.g. by seedbed preparation, fertilizing etc.)
- direct weed control is applied in the crop with the aim to reduce the number of
weeds and avoid damage of the crop
Strategy A: destroy very young weeds with a tool that is survived by the already
larger crop plants. The harrow (Fig. 6.4) is used in this way. It is applied when the
crop is large enough to be unharmed. Young weeds are torn out or smothered with
soil. Weeds that are already larger (like the crop) will survive.
Harrows for weed control are more gentle than those for seedbed preparation.
Lampkin, 2002
Strategy B: destroy all plants between the crop rows. This is generally achieved
with a hoe that can also be used on a tractor. The weeds are cut closely below the
soil surface and effectively destroyed. Weeds standing in the crop row will survive.
Exact steering of the machine is required - else the crop will be destroyed, too.
single tool of a machine hoe
A combination of hoe and harrow is very effective and common.
There are lots of other tools, but the basic strategies are the same.
F.2–3
F
F.3
Weed Management
Checkup, references and further reading
What are weeds, and how can they be classified in terms of weed management?
What are the major negative and positive effects of weeds?
What is the difference between direct and indirect weed control?
What are the basic weed control strategies of hoe and harrow?
References
LAMPKIN, N, 2002: Organic Farming. Old Pond Publishing, Ipswich
Further reading
LAMPKIN, N, 2002: Organic Farming. Old Pond Publishing, Ipswich
F.3–4
Important Crops and Weeds
Important Crops and Weeds
botanical names
german
english
Starch Crops
Avena sativa
Hordeum vulgare
Secale cereale
Triticum aestivum ssp. vulgare
Triticum aestivum ssp. spelta
Triticum durum
Triticosecale
Zea mays
Hafer
Gerste
Roggen
Saat-, Weichweizen
Dinkel
Durum
Triticale
Mais
oat
barley
rye
wheat
spelt (wheat)
durum (wheat)
triticale
maize, corn
Oil Crops
Brassica napus ssp. napus
Helianthus annuus
Linum usitatissimum
Cannabis sativa
Raps
Sonnenblume
Lein, Flachs
Hanf
oilseed rape, rapeseed
sunflower
Flax, linseed
hemp
Protein Crops
Pisum sativum
Vicia faba
Glycine max
Erbse
Ackerbohne
Sojabohne
pea
faba bean, field bean
soybean
Root and Tuber crops
Beta vulgaris
Solanum tuberosum
Zuckerrübe
Kartoffel
sugar beet
potato
Forage Crops, Catch Crops
Brassica rapa ssp. oleifera
Lolium multiflorum
Medicago sativa
Phacelia tanacetifolia
Sinapis alba
Rübsen
Welsches Weidelgras
Luzerne
Phazelie
Weißer Senf
(bird or turnip) rape
Italian ryegrass
alfalfa, lucerne
phacelia
white mustard
Weeds
Elymus repens
Cirsium arvense
Galium aparine
Stellaria media
Quecke
Ackerkratzdistel
Klettenlaubkraut
Vogelmiere
quack-grass, common couch
creeping / Canada thistle
cleavers
common chickweed
Plants of Grassland
Alopecurus pratensis
Arrhenatherum elatius
Dactylis glomerata
Festuca pratensis
Lolium perenne
Phleum pratense
Poa pratensis
Trisetum flavescens
Trifolium pratense
Trifolium repens
Wiesenfuchsschwanz
Glatthafer
Knaulgras
Wiesenschwingel
Deutsches Weidelgras
Wiesenlieschgras
Wiesenrispengras
Goldhafer
Rotklee
Weißklee
meadow foxtail
tall oat grass
orchard grass or cocksfoot
meadow fescue
perennial or English ryegrass
timothy
Kentucky bluegrass
golden oat grass
red clover
white clover
Pappel
Weide
Miscanthus
Chinaschilf
Rutenhirse
poplar
willow
miscanthus
Renewable Raw Material
Populus spp.
Salix spp.
Miscanthus spp.
Panicum virgatum
switch grass
Units and Abbreviations
Units and Abbreviations
cm
centimter = 0,01 m
CO2
carbondioxide
DM
dry matter
dt
decitonne = 0,1 t = 102 kg
e.g.
for example (exempli gratia)
fig.
figure
ha
hectare = 104 m2
kg
kilogramme
l
litre = 0,001 m3
m
m
meter
2
squaremeter
Mg
Megagramme = 106 g = 1 t
mm
millimeter = 10-3 m
Mpa
Mega-Pascal (unit of pressure)
µm
micrometer = 10-6 m
pH
scale for acidity (0-7) or
alkalinity (7-14)
ppm
parts per million (0,0001 %)
P.T.O.
power take-off
t
tonne = 103 kg
Index
Index
acre.......................................................... B.4–1
loosening ................................................. D.3–4
assimilates............................................... A.3–6
Macropores .............................................. B.3–5
autumn-sown ........................................... D.1–1
maize ....................................................... C.1–2
biosphere................................................. B.1–1
Mesopores ............................................... B.3–5
bud........................................................... A.2–3
micropores ............................................... B.3–5
bushel ...................................................... B.4–1
mineralization........................................... B.1–1
C3-plants ................................................. A.3–6
Monocotyledons....................................... A.1–1
C4-plants ................................................. A.3–6
monoculture ............................................. D.2–2
capillarity.......................................B.3–5, D.4–7
mouldboard plough .................................. D.3–4
carbondioxide .......................................... A.3–6
Mu ............................................................ B.4–1
Cereals .................................................... C.1–2
nitrogen fixation ....................................... E.3–4
clay .......................................................... B.3–3
nodes ....................................................... A.2–3
clover ..................................................... C.6–10
non-food uses ........................................C.8–12
cob........................................................... A.2–4
nutrient availability ................................... E.1–2
combine harvester................................... D.5–9
nutrients ................................................... E.1–1
Cotyledons .............................................. A.1–1
oil seed crops........................................... C.3–6
crop rotation ............................................ D.2–2
permanent wilting point............................ B.3–6
crumbs..................................................... B.3–4
photosynthesis......................................... A.3–6
cultivars ................................................... A.1–1
plant-available water................................ B.3–6
day length ................................................ A.3–8
pores ........................................................ B.3–5
decitonne ................................................. B.4–1
potatoe ..................................................... C.4–7
Dicotyledons ............................................ A.1–1
proteincrops ............................................. C.2–4
direct weed control ...................................F.2–3
PTO shaft................................................. D.4–8
ear ........................................................... A.2–4
raceme..................................................... A.2–4
evapotranspiration................................... A.3–5
rhizobia .................................................... E.3–4
family ....................................................... A.1–1
rice ........................................................... C.1–2
fertile soil ................................................. B.1–1
roller ......................................................... D.4–7
field capacity............................................ B.3–6
root........................................................... A.2–3
forms........................................................ A.1–1
root hair.................................................... A.2–3
Fruits........................................................ A.4–9
root nodules ............................................. E.3–4
generative stage...................................... A.3–8
Sand ........................................................ B.3–3
genus....................................................... A.1–1
seed potatoe ............................................ C.4–7
grassland ............................................... C.7–11
seedbed ................................................... D.4–7
Green fodder ......................................... C.6–10
silt............................................................. B.3–3
harrow........................................... D.4–7, F.2–3
Soil ........................................................... B.1–1
hoe............................................................F.2–3
soil cultivation .......................................... D.3–4
humus...................................................... B.1–1
soil profile................................................. B.2–2
hydrosphere ............................................ B.1–1
soil structure ............................................ B.3–5
indirect weed control ................................F.2–3
soil texture ............................................... B.3–3
inflorescence ........................................... A.2–3
soybean ................................................... C.2–5
internodes................................................ A.2–3
species..................................................... A.1–1
leaves ...................................................... A.2–3
spring-sown ............................................. D.1–1
legumes ................................................... E.3–4
stem ......................................................... A.2–3
lithosphere ............................................... B.1–1
sugar beet................................................ C.4–8
Loam........................................................ B.3–3
tuber......................................................... A.4–9
Index
varieties.................................................... A.1–1
Water use efficiency.................................A.3–5
vegetative period .....................................D.1–1
Weed ........................................................F.1–1
vegetative propagation ............................ A.3–8
wheat....................................................... C.1–2
vernalization................................. A.3–8, D.1–1
Yield .........................................................B.4–1
volunteer crop .......................................... F.1–1