Low External Input Sustainable Agriculture (LEISA)

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Low External Input Sustainable Agriculture
(LEISA) approaches to soil fertility management

• Optimise soil conditions for plant growth
• Principles
• timely availability of water, air, nutrients
• good soil structure
• appropriate soil temperatures
• minimise toxicity and / or practices which lead
  to toxicity

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Optimising nutrient availability cycling
Principles
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• Limit nutrient losses by
• recycling of organic waste
• reduce leaching (e.g. by using bedding straw
• for cattle to conserve urine)
• reduce runoff soil erosion
• reduce burning of stubble
• use slow-releasing fertilisers such as rock
• phosphate
• nutrient pumping by deep rooted spp.
• limit nutrient export by producing crops with
• relatively high economic value compared to
• nutrient content (fruits, nuts, herbs)

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• Capture / manage nutrients by
• utilising legumes / N-fixing bacteria or
  blue-green algae
• encourage capture of (water and air-borne)
  sediments
• from outside flowing over farm
• make maximum use of livestock manure
• use green manures

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• Supplement nutrients by
• use of OM from off farm (e.g. agro-industrial
  waste)
• purchased fodder and/or concentrates

Use complementary systems e.g. .........
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• Manure handling improvement
• Improve quantity / quality by
• adjusting animal numbers / species
• improved feeds (more concentrates, more
  legumes,
• urea treatment of residues)
• minimise distances between collection
  application
• points (but N.B. effect of collection on
  non-arable land
• fertility)
• use chicken manure (sheds)
• bat droppings ?

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• Composting
• improves quality of organic fertiliser
• heaps or pits (latter better in hot climates
• - less oxidation)
• in situ applications

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• constraints
• availability of materials
• transport
• labour
• water
• cultural taboos
• oxidation (mainly where there is a hot dry
  season
• reduced by decreasing tillage intensity)

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• Green manures
• improve OM and N
• other elements translocated to top-soil
• cover crops such as yam bean (Pachyrrhizus
  erosus)
• Mucuna utilis suppress weeds such as Imperata
  spp.
• which may proliferate as a result of
  shortening or
• eliminating fallows

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• Forms include
• improved fallow (whole year or dry season
• pre-planting crop (in rice in India)
• alley cropping (prunings used as a mulch or
  incorporated)
• single trees in field
• (legumes such as Erythina poeppigiana cut for
  mulch)
• relay fallows (plant dry season green manure
  fallow
• before harvesting main crop, e.g. Tephrosia
  vogelii,
• Sesbania rostrata, Mucuna pruriens
• live mulches - food crops sown into cover crops
  such
• as Centrosema pubescns, Pueraria
  phaseoloides,
• Arachis prostrata after strips removed by
  herbicides or
• hand to reduce tillage operations
• azolla and blue-green algae

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Some green manure exotic species for improving
soil fertility include see table in handout
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Criteria for selection of plants for improved
fallow
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• Problems include
• shortage of land
• seasonal migration (India)

Can you think of others ...
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• Use of mineral fertilisers
• apply in low to moderate amounts in combination
  with
• organic fertilisers
• increase efficiency by control of weeds, crop
  pests,
• diseases, soil erosion, leaching, rotations
  (shallow then
• deep rooted crops), attention to timing (e.g.
  split
• applications for N), applying fertiliser below
  surface
• near roots
• use mild fertilisers for preference (e.g.
  "Thomas slag",
• thermo-phosphate, bone-meal)
• CAN better than urea better than AS
• mineralisation of rock phosphate accelerated by
  
• acidification (e.g. by adding to compost)

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• Vermiculture
• manure earthworms ? less manure (30
  reduction)
• vermicompost more earthworms
• surface application
• mass of earthworms produced 5 of manure
  weight
• reduces environmental contaminants in solution
• pH becomes more neutral

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• Examples of indigenous sources of nutrients
• termite mounds for sorghum / cowpea in Sudan
  Congo
• ant refuse for fertilising crops in Mexico
• Faidherbia albida / sorghum millet systems in
  Senegal
• mulch / shade / recycled nutrients
• use of weeds as green manure and mulch in
  Tanzania

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• Managing flows of solar radiation, water, air
• Principles
• Improve micro-climates by
• crops of different heights
• shade, wind protection
• Improve soil moisture by
• improving soil structure OM
• tillage
• mulches
• Reduce erosion by
• vegetative measures
• physical measures

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Mulches Zero tillage Wind breaks Water
harvesting Tied ridging Strip
cropping Permeable contour-line barriers Small
ponds
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Integrated farm systems Bio-intensive gardening
(example) - double dug beds
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• double dig raised beds 30 to 60 cm
• keep covered with crops or mulch
• liquid manure (40 kg of weeds dung in 200
• litre drum left for 3 weeks mix liquid 13
  with water,
• apply every 10 days)
• many spp. of veg. fruits

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Crop - livestock - fish-farming
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• Farmer involvement
• indigenous knowledge investigations / databases
• / self-awareness
• encouraging farmer to farmer spread / training
• farmer experimentation
• participatory technology development (PTD)
• exposure visits