Pulses and their use in
crop-livestock farming systems
Prof. Dr. Anthony Whitbread
Georg-August-University, Göttingen
Crops and Productions Systems in the tropics
Lecture 29.11.11
Outline of lecture
•
•
Introduce systems where pulses are used.
Outline the multiple roles of pulses in the system:
– Uses and why farmers use them
– N fixation and nodulation
– Planting methods and soil nutritional requirements
•
Introduce some of the most common pulse species
– Cowpea
– Soybean
– Peanut
Lecture 1, we covered the classification of tropical farming systems*
where annual crops are a dominant/important component:
1.
2.
3.
4.
5.
Shifting cultivation systems
Semi-intensive rainfed systems
Intensive rainfed systems
Irrigated and flooded systems
Mixed annual/perennial systems
Cropping
frequency
increases
Pulses may be found in all systems listed above with the exception of the
shifting cultivation system, but are most common in #3, the intensive
rainfed systems
*Norman
M.J.T. (1979). Annual Cropping Systems in the Tropics. Gainesville, Florida:
University Presses of Florida, 276 pp.
Soil fertility decline
0.18
Soil N
14
Grain Prot
12
0.12
10
0.06
8
0 5 10 15 20 25 30 35 40 45 50
Period of cultivation (years)
Grain protein (%)
Soil total N (%)
16
Soil organic matter loss and soil fertility
• Reduces nutrient supply
• Reduces physical fertility
• Increases global CO2
• Most cropping systems rely on a legume ley to restore
soil fertility and Fix N
• Pasture or grain legumes for 1-2 years
• Fallow periods
What are pulses?
Alternative names: grain legumes (Hülsenfrucht-Deutsch),
Life cycle:
Perennial
• > 2 years – many years.
Annual
• < 1 year or 1 season – germinates, vegetatively grows, flowers and
dies.
Biennial
< 2 years or 2 season – germinates, vegetatively grows, often
flowering and fruiting in year 2 and then dying.
Method of propagation:
Usually sown, annually, inoculated with rhizobium, some additional
fertiliser (no or low N, but other nutrients as necessary- often P and
Mo are required)
Meeting human nutritional needs:
• Pulses play an important role in providing a protein rich source of food,
particularly where meat is not common e.g. Southern India.
• Supply essential amino acids (esp. Lysine) not in sufficient quantities in staple
cereals.
• Globally (1990 figures), plant derived protein supplies about 70% of human
intake – although rapid changes in dietary consumption is changing this.
• Examples of the most important pulses:
Pulses supplying seed/meal
Pigeonpea – Cajanus cajan (L.) Millsp.
Chickpea – Cicer arietinum (L.) (Desi and Kabulis types)
Lentil – Lens culinaris Medik (native to Middle East)
Cowpeas – Vigna unguiculata (L.) Walp.
French/Haricot bean or Phaseolus spp. – P. vulgaris L.
Pulses as oilseed crops (but may also supply seed/meal)
Bambara groundnut – Vigna subterranea (L.) Verdc.
Peanut – Arachis hypogaea (L.)
Soybean – Glycine max (L.) Merr.
Pulses in farming systems
How and why smallholder farmers in the tropics utilise pulses
Source: Kamanga et al. (2009). African Journal of Agricultural
Research Vol. 5(8), pp. 668-680.
Special requirements of grain legumes
Nodulation: Specific rhizobial strains Vs promiscuous legume varieties
The term rhizobia includes the genera –Rhizobium, Bradyrhizobium,
Sinorhizobium and several other minor groups.
Inoculation: involves obtaining a fresh and species appropriate strain,
coating the seed and planting into good soil conditions that favour
survival of the rhizobia.
Figure 6: Differences in nodule numbers between a wild type soybean plant (left), where the plant
controls the number of nodules to the minimum necessary to sustain its nitrogen needs, and a
supernodulation mutant (right), in which the plant has lost the ability to control nodule numbers the roots are “supernodulated” by rhizobia. Photo courtesy of Prof. Peter Gresshoff, University of Queensland and sourced from:
http://www.cilr.uq.edu.au/UserImages/File/Nodulation%20and%20Nitrogen%20Fixation%20Workshop.pdf
Some characteristics
of nodulation tropical
grain legumes.
• Plant roots exude
flavonoids to stimulate
rhizobia in the soil to
move towards the roots.
• Rhizobia infect the root
hairs, and multiply inside
of the infection thread.
Plant cortex cells divide
to form the nodule.
• Autoregulation is a plant
mechanism to control
nodule numbers
Source: Giller (2006). Nitrogen Fixation in
Tropical Cropping Systems. 2nd Edition,
CABI Publishing. p.142.
N Fixation
•
•
•
N fixation in Southern Australia in the range of 20-25 kg N/t dry
matter (regardless of species, soil type and environment).
N fixation is highly dependent on soil nitrate level
Not always a net contribution of N
 -41 to +135 kg N/ha for lupin
 -32 to +96 kg N/ha for peas
•
A high nitrogen harvesting Index (NHI) is likely for most grain
legumes under commercial production
100
m ungbean
90
s ira tro
80
lu c e rn e
la b la b
%Ndfa
70
60
50
40
R
2
= 0 .5 4
30
20
10
0
0
20
40
60
S o il n itra te (k g /h a )
80
100
Special requirements of grain legumes
Nodulation: Specific rhizobial strains Vs promiscuous legume varieties
The term rhizobia includes the genera –Rhizobium, Bradyrhizobium,
Sinorhizobium and several other minor groups.
Inoculation: involves obtaining a fresh and species appropriate strain,
coating the seed and planting into good soil conditions that favour
survival of the rhizobia.
Soil nutrition: In the tropics, highly weathered, leached, nutrient poor
soils are common. Acid soils, particularly common in the tropics (e.g.
Oxisols, Ultisols, some Alfisols), have usually low available phosphorus,
may strongly fix P, and have toxic concentrations of Aluminium and
Manganese.
Nutrient toxicity/deficiency and pH
pH Water 1:5
Impacts
Source: Constraints to cropping soils in the northern grains region-a decision tree” GRDC Northern
SSC program (Qld NR&W publication)
Planting methods: In traditional farming (esp. African), intercropping is
the norm, but relay planting and rotation are becoming more common
and the norm for the commercial farmer.
Intercropping: having more than 1 species planted simultaneously
(polyculture). Reasons include:
Tradition, risk management, potential for higher production/ha,
complementarity of crop types, low plant populations of each spp. (low
planting rate &/or poor seed quality).
Relay planting, a form of intercropping: involves 2 planting times with
the 1st crop (usually the staple, e.g. maize) planted on wide rows and the
2nd crop planted later to reduce competition.
Crop sequences (rotation): planting a single crop spp. (monoculture),
on an area of land –soil type, fertility, insects, weeds and disease
pressure will influence the need for rotation of sequence of spp.
Capturing the benefits of legume rotations
•
Under rainfed conditions, especially in semi-arid regions, capturing
the benefits of the ‘ley’ phase (forage, pulse, green manure) in
subsequent crops depends on many factors:
– How and when the ley is terminated.
– Building up soil water pre-sowing (decreases risk of crop failure)
– Maintaining the soil organic matter & structural benefits of the ley (N
losses)
•
Our approach to these complex issues is via modelling and field
experimentation
– 2 SIA courses cover these aspects:
*Experimental Methods in Tropical Agronomy (P19M)
*Crop Modelling for Risk Management (P16M)
Cowpea - Vigna unguiculata (L.) Walp.
• Probably centre of origin, West Africa.
• Grown extensively as a subsistence crop: vegetable (pods, flowers), seed,
cut and carry forage.
• Amongst the most drought tolerant of herbaceous tropical legumes.
• In Africa ‘bunch’ (grain) and ‘spreading’ (dual purpose) types.
Factsheet:
http://www.tropicalforages.info/key/Forages/Media/Html/Vigna_unguiculata.htm
http://www.uni-goettingen.de/en/technical-bulletins-for-limpopo-province-southafrica/305574.html
Soybean – Glycine max (L.) Merr. (Rehm&Espig p.94-97)
• Cultivated in China since ancient times, native to East Asia.
• Provides 35% of the worlds protein requirements – much of which is fed to
animals to produce animal protein.
• In the USA, 2nd most valuable crops and occupies ~15% arable land.
• Immature pods used as vegetables, seed used for soy sauce, cooking oil,
soybean milk, protein for curd/tofu….85% processed into meal and oil.
• Many believe soybeans to be a source of complete protein and to enhance
human health.
Photo: Francisco Mouriño
Soybean – Glycine max (L.) Merr. (Rehm&Espig p.94-97)
• Small erect branching annual.
• Growth duration 90-110 days (some 140 days)
• Photoperiod sensitive – sensitive to short daylength with duration of
vegetation growth, induction of flowering, length of flowering, pod filling,
related to photoperiod.
• Self pollinated
• Examples of systems
• Brazil – Rio grande do Sul: double crop summer soybean /winter wheat
• Argentina: summer cropping only, soybean- maize rotation.
• SE Asia: rotation with wet rice in intensive systems (some tolerance of
poor aeration.
Soybean – Glycine max (L.) Merr.
• The US, Brazil, Argentina and China are the largest producers (216 million t
produced in 2007 from 93 m ha). Only the last 35 years has soybean been
cultivated in South America
• Genetically modified soybean – Monsanto introduced Roundup Ready
soybean in 1995. In the US 93% of soybeans are GM.
• Roundup is used for weed control and its use in RR soybeans reduced the
use of more harmful herbicides.
• In 2010, the soybean genome was sequenced.
• In Argentina, soybean covers half of the pampas, with production on about
13.5 m ha (2011) – In 2009 the export trade was $3.2 b, half for China.
• There are polarised views on the success or otherwise of soybeans in
Argentina and other parts of South America, especially in regards to
impacts on the environment (e.g. Amazon).
Peanut – Arachis hypogaea (L.) (Rehm&Espig p.97-101)
• Also known as groundnuts, earthnuts (Note. Bambara groundnuts is a
different spp.)
• Centre of origin probably NW Argentina and S.Bolivia + sub-spp. from Brazil.
• Now also a major crop in W. Africa, India and USA.
• Widely cultivated as a marginal crop (low yielding).
• Features: production of subterranean fruit. After anthesis, the ovary elongates
and forms a peg which enters the soil 5-10 days later. This peg is where the
pod and seed (nut) forms.
Fig. 25 from Rehm&Espig. Arachis hypogaea. Carpophores
entering the soil (schematically). F1 = dried flower, Fr = fruit
Crops and Production Systems in the Tropics
Recommended reading
Rehm, S. and Espig, G. (1991). The cultivated Plants of the Tropics and
Subtropics. Verlag josef margraf. p 94-101.
Available from http://www.uni-goettingen.de/en/209930.html
For N fixation of pulse in cropping systems:
Giller, K.E. (2006). Nitrogen Fixation in Tropical Cropping Systems. 2nd
Edition, CABI Publishing. p.140-168
*