Nutrient management

1
Nutrient management for organic vegetable
production in NC
Part I
http//compost.tamu.edu/demos/palopinto/compost.jp
g
2
Average rates of N, P2O5 and K2O
applied to vegetable crops in the US
(lbs/acre)
Nitrogen Phosphorus
Potassium
Why are these rates so high ?
http//www.ers.usda.gov/publications/sb969/sb969c.
pdf
3
Most growers believe that high rates of nutrients
are needed to produce high yields of high quality
vegetables
4
Jalapeno pepper production in Fresno County,
California Total cost of production 4392 Total
fertilizer costs 170
Fertilizer costs 4 of total costs
5
16 elements have been identified as essential
for the growth of all plants
Soil
C O H
N K Ca Mg P S
Cl Fe Mn Zn B Cu Mo
air water
macronutrients
micronutrients
V
Ni
Needed by some plants
Si
Co
Na
6
Micronutrients are critical components of enzymes
7
minerals
Soil solids contain nutrients
organic matter
8
Soil water contains nutrients
H20
H20
K
-
-
Ca2
H20
-
H20
H20
-
Mg2
-
H
Humus
-
H20
exchangeable ions
H20
H20
H20
Soil soup
Clay
H20
-
Na
H20
-
H20
H20
-
H20
-
K
H20
Ca2
H20
H20
9
Whats in the soil soup ??
Ca2
Cu3
DOM
NO3-
Ca2
Mg2
NO3-
H2PO4-
Ca2
Zn2
DOM
K
NO3-
K
Mg2
Ca2
NO3-
Mg2
Fe3
DOM
Ca2
SO4-2
Adapted from Brady and Weil (2002)
10
Which forms of nutrients are available to plants ?
solution
exchangeable
active OM
passive OM
weatherable minerals
11
Re-seasoning the soup
Highly buffered
Poorly buffered
Modified from Havlin et al. (1999)
12

Crop yield
Deficiency Symptoms
Nutrient availability
13
http//www.extension.umn.edu/distribution/horticul
ture/components/M1190fig1.htm
14
(No Transcript)
15
Understanding nutrient uptake
H20
Root exudates activate soil microbes
Transpirational stream
H20
Root growth
16
?
Feed the soil vs. Feed the crop ?
Both strategies are important !
Healthy roots need available nutrients !
Unhealthy roots use nutrients inefficiently
Acute root disease
Chronic root malfunction
17
The acid infertility complex
18
Nutrient availability varies with pH
19
Understanding aluminum toxicity
Toxic forms of Al are bioavailable at low pHs
Aluminum toxicity is minimal above pH 5.5
http//www2.ctahr.hawaii.edu/tpss/research_extensi
on/rxsoil/alroot.gif
20
100
75
50
Percentage of maximum cation exchange capacity
25
Exchangeable Al3
0
Brady and Weil (2002)
21
Micronutrient deficiencies frequently occur
when naturally acid soils are over-limed
http//www.fftc.agnet.org/library/image/bc51002p7.
html
Avoid over-liming !!
22
http//hubcap.clemson.edu/blpprt/acid2-chart1.gif