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High soil fertilty = high food production Establish soil fertlity with soil tests With only one soil test > 20 soil characteristics can be measured. Based on a single soil test fertilzation recommendations are given, but also additional information like a soil organic matter balance, and a water retention curve is given to farmers and their extension services.
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Arjan ReijneveldAugust 27, 2013
A grip on soil fertility
Dr. Arjan ReijneveldThe Netherlands
Soil fertility
Soil fertility = nutrient and water supplying and retaining capacity of the soil
Soil fertility is, since beginning of 20th century, established by soil tests
Soil tests:
until now
Soil tests until now
For every soil characteristic (N, S, P, K,…) a different method
- Time consuming chemical analysis
- Expensive
- Mostly based on knowledge of the 1960th - 1970th
Soil tests: nowadays
Soil tests: nowadays
Soil in a jar of glass
Analysed with near infra red method (NIR)
In every soil sample > 20 soil characteristics
> 20 soil characteristics
Among others: N-total
S-total
P-total and P saturation
Ca-, Mg-, K-, and Na-CEC
Plant available Ca and K
Soil texture (clay, silt, sand)
pH
CEC, Total C
Soil Organic Matter (SOM) Soil Organic Carbon (SOC)
CaCO3
From soil test to report
Those > 20 soil characteristics of the soil test are transformed to a report
On the report
● Fertilization recommendations (nutrients)● Among others Phosphorus
● Extra information● CEC
● Organic matter balance
● Soil structure
● Water retention curve
● Soil type
Example II
Example III
Example IV
Example I
Example IPhosphorus
Phoshporus (P)
Recommendations based on:● Plant Available P as well as on● Soil supplying capacity
Improved root development: better uptake of nutrients and less drought sensitive
Example IICEC
CEC and yield potential
13
CEC can be improved by:
Effective CEC improved by pH improvements
CEC improved by input organic matter- Crop residues
- Compost
- Animal manure
- Green manuring
- Organic fertilizer
Example IIIOrganic matter
Soil organic matter (SOM)
2.9 % SOM
mineralisation
Input through crop residues
Shortage, to be filled in with animal manure, compost, green manuring….
Not only a measurement but also information about maintaining soil organic matter content (balance)
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Improved SOM status
Improved soil workability
Less drought sensitve
Example IVWater
retention curve
Water retention curve
Plant available water
Wilting point
Field capacity
Water retention curve
Information about: Which fields are most drought sensitiveHow much mm of water can be irrigated
Too much irrigation ● water will leach to deeper soil layers● nutrients will leach
Finally
Sampling sites
NIR stations could be established everywhere (worldwide)
Higher soil fertility = higher production
With NIR technique much insight in soil fertilty
More insight can be used to optimise - Production (yield)- Product quality - Water use- Prudent use of minerals
Results of soil tests should be discussed with famers and extension services (advisors) to fully exploit its added value
In conclusion
Soil tests can contribute to
● Profitable farming
● Feeding a steadily increasing world population
FAO, 2012
