Nutrient Balances in Farming Systems

1
Nutrient Balances in Farming Systems

• Henry Ssali
• Kawanda, National agricultural Research
  Organisation NARO

2
Uganda Soils

• Most are old/Highly weathered with little mineral
  nutrient reserves
• Rely on Soil organic matter SOM for nutrients
  and good physical properties
• SOM still the best indicator of soil fertility

3
SOIL MANAGEMENT

• SOM nutrients decrease during cropping phase
• Inputs org and inorg during cropping phase help
  maintain SOM/nutrients at higher levels
• With grass/improved fallows, nutrients in the
  topsoil are replenished recycling, BNF,
  depositions, transfer

4

• Soil analysis gives you the nutrient status of a
  plot at one given time
• In addition, need to know the nutrient stocks and
  what is happening to them relative to various
  activities/operations on a plot the entire farm

5
FARM COMPONENTS

• Farm usually has a number components/units
• Crops annual, perennial, high value etc
• Livestock
• Pastures
• Household including surrounding plots
• Others

6
Nutrient flows/balances

• Since soil productivity is dynamic, understanding
  flows and balances within a component and across
  components helps indicate
• Extent of nutrient accumulation/depletion
  mining
• Identify the major nutrient flows and
• What is likely to happen in future
  sustainabilityat plot, farm, district, system,
  region or national level

7
FLOWS

• INcps flows to CPS from outside the farm
• OUTcps flows out of CPS and the farm
• INaps flows to APS from outside the farm
• OUTaps flow out of APS and the farm
• INhhs flows to HHS from outside the farm
• OUThhs flows out of HHS and the farm
• INTflows flows between components on farm

8
Nutrient inputs

• IN 1 mineral fertilizers
• IN 2 organic inputs
• IN 3 atm deposition rain, dust
• IN 4 BNF symbiotic non-symbio
• IN 5 Sedimentation flooding/irrig
• IN 6 subsoil exploitation trees, etc

9
Nutrient outputs

• OUT 1 harvest leaving farm cps, aps, etc
• OUT 2 crop residues/manure leaving farm
• OUT 3 leaching below root zone
• OUT 4 gaseous losses den, volat, burn
• OUT 5 runoff and erosion
• OUT 6 consption ending in deep latrines

10
Nutrient flows/balances in Uganda

• The 1st was based on yield and input records
  coupled with generalized estimates of erosion
  and other processes as part of a SSA study
  Stoorvogel Smaling 1990
• Others have been more localised e.g. Pallisa,
  Mpigi, Iganga Kamuli (Wortmann Kaizzi,1998)
  Mayuge (Esilaba et al 2002)

11
Generalized
  Balance kg/ha/yr Balance kg/ha/yr Balance kg/ha/yr
Land class N P K
Good rainfall 1100, 58 -32 -5 -30
Uncertain rainfall 800, 11 -17 -3 -13
Problem area 1400, 27 -32 -3 -13

Country -29 -4 -27
Stoorvogel and Smaling, 1990
12
Farming systems
  Balance kg/ha/yr Balance kg/ha/yr Balance kg/ha/yr
Area N P K
Pallisa Teso extn -21 -8 -43
L. Victoria Banana-coffee -31 -4 -39
Wortmann and Kaizzi, 1990
13
Balances and LUTs

• Balances generally ve INs BNFgt Dep, OUTs
  erosgt harvestsgt leaching
• Annual crops largest area balance more -ve cf
  perennials land disturbance, low input use and
  poor soil cover, K problem for sold bananas w/o
  mulch,
• -ve balances increase with yields and access to
  markets
• Since yields are still low, LEISA land
  husbandry, FYM, lcc, residue mangmt, etc can
  reduce/maintain balances to near zero

14
(No Transcript)
15
(No Transcript)
16
(No Transcript)
17
Who mines most?
  Balance kg/ha/yr Balance kg/ha/yr Balance kg/ha/yr
Farmer Class Mayuge N P K
Good managers--farm level -36 -4 -66
Good managers--CPS -57 -9 -98

Poor managers--farm level -7 1 -10
Poor managers--CPS -23 -3 -27
Esilaba et al., 2002
18
Policies for land management subsequent pgms

• Collected data from randomly selected HH
• Provided an opportunity to understand
• how farmers are managing their farms in the
  different AEZs
• What the nutrient balances are over most of the
  country
• Sustainability implications as farmers
  increasingly produce for the market

19
Status 1

• Over 1300 plots with sufficient soils and
  socioeconomic data to estimate flows and balances
• Have made initial runs and are currently
  examining data/assumptions/protocols for errors

20
Status 2

• When this is complete will run data for the
  country plot , farm level
• Data can be linked to other spatial information
  collected AEZs, development domains, production
  zones, etc
• Early/rough indications
• farming in Ug is characterized by nutrient mining
  at the plot level mining mining in annuals gt
  perennial erosion and crop removal main
  culprits
• Nutrient stocks vary with LUTs AEZs

21
(No Transcript)
22
(No Transcript)
23
(No Transcript)
24
(No Transcript)
25
(No Transcript)