Soil Management
It is important to ensure correct fertilizer program.
- Without adequate initial fertilizer crop growth can be severely affected following
establishment
- Take soil samples 3-4 weeks before final land preparation (give time for analysis)
- (Basal fertilizer applied based on analysis recommendation during the final land
preparation)
- Orchard relatively clean cultivated has the risk of soil erosion
- Land with steep slopes: do contour planting(with provision for grassed waterways and
banks; waterways should be well established before planting)
Soil amendments: Liming
Lime in orchards on sloping land (where soil cations have been leached; where pH<5,0, i.e.
strong acidity)
Apply lime after the harvest
- Incorporate into the soil (15-30 cm depth, because lime has poor mobility in soil)
- Five to 7 kg per tree or 1 mt/hac for sandy loam; 1.5 m t/hac for silt loam or loam; 2
mt/hac for clay loam
- Mix manure or compost with lime material (for aeration and to avoid compaction)
- Do not apply chemical fertilizer at the same time as lime (reduces fertilizer efficiency)
Soil Amendments: Advantage of using Organic materials
- Soil organic matter generally low in tropical & sub-tropical orchards<2% because of
fast decomposition
- Soil organic matter enhances soil aggregates; good soil structure; good drainage &
aeration
- Increases cation exchange capacity & water holding capacity
- Serve as nutrient reservoir
Soil fertility Management
Nutrients are continually removed by plants: nutrients are stored in fruits’ wood branches and
dead parts of plants.
Stored nutrients are utilized for processing (food in the coming season or year; for bud initiation
and flower development)
Interaction between nutrients
 Antagonistic between N&P or K (increase in N depresses K uptake)
 Synergistic between N & C or Mg (increase in N, Ca & Mg uptake increases)
 Heavy P fertilization results in Fe chlorosis, Zn deficiency and Cu deficiency
In-service handouts 2007
Principles of Fertilizer Use
Balanced nutrients:
 Match fertilizer with crop requirements.
Crop variety characteristic
 Adjust fertilizer according to the crop variety.
Timing of fertilizer application
 Apply fertilizers when plants need the nutrients most.
Incorporation of fertilizers
 So that the nutrients are available where the plant needs them and are not lost by
volatilization or surface runoff.
Speed of nutrient uptake
 Will the nutrient be available to the crop when the crop needs it?
Soil and plant analysis: Base fertilizer recommendations on the results of soil and plant
analysis.
Fertilizer Management
General concept of fertilizer efficiency
“The Law of the Minimum Nutrient”
Growth is limited by the nutrient element present in the smaller quantity, even if all other
nutrients are present in adequate amounts.
“The Law of Diminishing Returns’
Yield increases is highest from the initial unit of fertilizer applied. As more fertilizer is added,
the yield increase becomes smaller and smaller.
Fertilizer Recommendation for Citrus
Citrus trees do not need to be fertilized heavily;
NPK are the principal components of the recommended fertilizer treatment.
Fertilizer application rate in citrus varies according to :
- Age old tree
- Fruit load
- Soil fertility
- Nutrient status of the tree
In-service handouts 2007
Fertilizer Recommendation for Nursery Plants
- Raised beds (drainage, root development)
- Root development environment (loose soils; well prepared bed with optimum pH)
- No standard practice for fertilizing citrus nursery plants
- N requirement is maximum
Recommended rate for fertilizers varies depending on factors like growth medium:
o Water-soluble fertilizer applied: one- two times a week
o Slow release fertilizers: mixed into the medium before transplanting (additional
fertilizer top-dressing may not be required at later stages)
Fertilizer Recommendation for Young Trees
- Young trees are usually fed on the Little and Often Principles
- Trees in the juvenile years are sustained if the soils have been well prepared before
planting with deep cultivation and organic matter addition
- Starter nutrients required on coarse textured soil
- Quantity of fertilizer applied increases with the age of the tree until trees cross its peak
production stage
- The area to which the fertilizer is applied also increases with the age of the tree
- The frequency of application of fertilizer decreases with the age of the tree
- Nitrogen & irrigation: most important for growth of young trees
Criteria for selection a fertilizer rate within the recommended range (N level of nursery trees:
lower levels of N if trees are from nursery with intensive nutrition program); fertilizer requirements
vary as crop load changes; e.g. replacement of N lost by crop removal is the largest requirement of
N
Soil type- trees planted in heavy soils require less fertilizer; less fertilizer required on better quality
soils
Land history : new planting on pasture or vegetable land – less fertilizer for 1-2 years
(accumulated OM mineralization)
Fertilizer source- reduced fertilizer rate with controlled released formulations
Fertilizer placement: fertilizer use efficiency is greatest when applied over root zone by hand
application; Optimal placement permits lower rates.
Application frequency & timing- require less if applied frequently at the right time (because of
less loss)
Tree age: rates increase gradually as tree size and production increase
Varieties – different varieties have different requirements
In-service handouts 2007
Fertilizer Recommendation for mature Trees
For working out fertilizer program of matured trees, it’s useful to analyze the nutrients removed
through leaf & soil analyses
Fruit production & quality are the principal considerations
Macro-nutrients- influence fruit quality both externally and internally
Fertilizer Recommendation Rate of N,P & K for citrus
Plant nutrient
Non-bearing g/tree/yr)
Bearing (g/tree/yr)
N
50-100
150-250
P2O5
20-50
50-100
K2O
100-150
200-350
Micronutrients
To be applied based on soil & plant analysis results
FYM
Time of application
After harvest & before spring flush
-doAfter harvest & before spring flush
When trees have the most fully expended
new leaves
To be applied depending upon availability
Note:
Recommended rate to be modified according to soil texture
- Gravel to coarse textured soils – an extra 30-40%
- Fine textured clay loan soils- reduce by 20-30%
- Grass in orchards- an extra 20-30% (nutrient competition) above recommended rate
Fertilizer Demand in Different Seasons
After harvest and before spring flush
Basal application- after harvesting during winter pruning season (restore tree vigor after fruit
production)
- Above 40% of the orchard’s total annual chemical fertilizer is applied at this time.
- Growers can improve soil condition by applying organic manure (30-60 kg/tree)
- Spring flush growth, blooming & early fruit development
- All applications of fertilizers should be followed by irrigation unless rain falls within this
period.
Fertilizer Application in Different Seasons
During fruit development
- Emphasis should be on additional dose of K fertilizers
- Helps improve both quality and size of the fruit
- No N if excessive growth of summer and autumn flushes especially in fertile orchards
with abundant rainfalls
- Infertile and gravel soils, extra fertilizers
In-service handouts 2007
Fertilizer Application Method
Circle banding
- Furrow (20 cm wide,30 cm depth around the tree in a circle beneath outer canopy)
Strip band application
- Suitable for old orchards (>10 years)
- Parallel furrows (20 cm wide, 30 cm depth) between rows of trees
Hole Placement
- 4-5 holes dug beneath outer canopy of each tree
- holes should be 15-20 cm diameter, 30 cm deep
In-service handouts 2007