nutrient balances in farming systems
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Nutrient Balances in Farming Systems. Henry Ssali Kawanda, National agricultural Research Organisation [NARO]. Uganda Soils. Most are old/Highly weathered with little mineral nutrient reserves Rely on Soil organic matter [SOM] for nutrients and good physical properties

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nutrient balances in farming systems

Nutrient Balances in Farming Systems

Henry Ssali

Kawanda, National agricultural Research Organisation [NARO]

uganda soils
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
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]
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
farm components

Farm usually has a number components/units

  • Crops [annual, perennial, high value etc]
  • Livestock
  • Pastures
  • Household [including surrounding plots]
  • Others
nutrient flows balances
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 [sustainability—at plot, farm, district, system, region or national level]

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

nutrient inputs
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]

nutrient outputs
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

nutrient flows balances in uganda
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)
balances and luts
Balances and LUTs
  • Balances generally –ve; INs [BNF> Dep], OUTs [eros> harvests> 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
policies for land management subsequent pgms
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
status 1
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
status 2
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 > perennial; erosion and crop removal main culprits
    • Nutrient stocks vary with LUTs & AEZs