Mineral Nutrition
& Management
Dr. Richard Rosecrance
California State University, Chico
Productivity & Profitability
Outline
1.
2.
3.
4.
Nutrient pathways to plants
N fertilization efficiency.
N budgeting, a method of accounting
for tree N demand & sources
N fertilizer selection & timing
How do nutrients get to the
plant roots?
1.
2.
3.
Nutrient Pathways to Roots
1. Root interception: Ca, (Zn)
2. Mass flow of water: N, Ca, Mg, S, B, (K), (Zn)
3. Diffusion: P, K, (Zn)
Cation Exchange Capacity
Nitrate In Groundwater
Nitrogen fertilizer efficiency trend in Nebraska
-1
Partial Factor Productivity (kg grain kg N )
80
70
Even with these improvements, average N
fertilizer uptake efficiency is only about 40%
of applied N with average yields of about 10
Mt per hectare. A 2-fold increase is possible!
60
50
40
30
y = 0.7153x - 1372.9
R2 = 0.7081
20
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
N efficiency
1.
2.
3.
4.
Amount & and seasonal patterns of N
use by trees
N availability from nonfertilizer
sources (i.e.irrigation water, cover
crops)
dynamics of fertilizer N availability
relationships between timing,
amount of fertilizer, and irrigation
water applied
Part 1 Concepts of
Fertilization
Midsummer leaf N
Concentrations



< 2.3% deficient
2.3 – 2.7% adequate
> 2.7% excessive
Terminal leaflet
on spur
Mid-Shoot
Leaf Samples
leaves
Seasonal Variation in LeafWhen
to
sample
leaves?
nutrient Concentrations
Using Leaf Analysis Results
to Adjust Fertilizer Practices

If Leaf N > above critical value,
fertilizer can be reduced or eliminated
for a year without impacting growth &
yield (esp. on heavy-textured soils)
N Use by the Tree

Forms of N absorbed by the tree
NH4+
 NO3

N Uptake -- Greatest between onset
of active shoot growth until late
stages of nut fill
N removal in crop
Walnut -40 lbs of N/ton of crop
 N removal calculators http://npk.nrcs.usda.gov/

Whole Tree N Contents by
Organ in Almond.
3000
H
a
r
v
e
s
t
2500
N contents (g)
2000
Uptake
1500
roots
trunk
canopy
leaves
fruit
1000
500
0
2/20
0
3/2
5/20
8/29
Excavation Date
9/29
Nitrogen budgeting to
determine how much to apply

N Losses
Nitrogen budgeting to
determine how much to apply

N Losses
Volatilization-N lost directly to
atmosphere

N in ammonium and urea
fertilizers may be released
to the atmosphere as
ammonia gas. (NH4+→
NH3)
pHs >7.5 ↑ volatilization.
 Volatilization from fertilizers
can be ↓ by rapid
incorporation

Effect of rainfall on Urea N
volatilization losses
Rainfall
Within days
N
after
Volatilization
application
Losses, %
0.4
2
0
0.4
0.1 to 0.2
0
3
5
5
10
10 to 30
30+
(Fox and Hoffman, Pennsylvania – N on no-till corn)
Denitrification
1.
2.
3.
soil microorganisms: soil nitrates → N2.
N loss ↑ when soils are warm and wet.
Denitrification losses are typically less
than 5% but can be higher under lowoxygen conditions
Losses with urea
Urea has no electrical charge, so it
moves readily in the soil with rain or
irrigation water.
 Volatilization losses from urea
fertilizers are low if urea fertilizers are
incorporated into the soil shortly after
application.

Nitrate Losses

Nitrate fertilizers
are generally
more costly per
unit of nitrogen
than are
ammonium
fertilizers. Nitrate
is highly mobile
in the soil.
Choosing & Using N Fertilizers

Su
Source: Ca Plant Health Association 2002
Worksheet Instructions
In order to use the nitrogen budgeting
approach you will need:
1. yield data for the past few years
2. irrigation records
3. irrigation water nitrate analyses
4. records of compost/manure
applications
5. estimates of cover crop yield and
nitrogen content
6. calculator
Nitrogen Fertilizer Timing
and Placement

Nitrogen recovery. Fertilizer recovery is greatest
when application coincides with periods of high
nitrogen demand by trees
Split applications.

A good rule of thumb is to apply onehalf to two- thirds of the fertilizer
nitrogen in spring, so it is available
during the main flush of spring shoot
growth. The remainder should be
applied by later during nut fill
Best Management Practices

Successful N management delivers
enough N to the crop to optimize
yield and profitability while ↓ losses to
water and air. Everyone wants the
nitrogen to end up in the crop. Thus,
the best management practices
(BMPs) presented here are identified
as sound practices from economic,
production and environmental
viewpoints.