Plant Specific Fertilization

NUE Workshop

Paul Hodgen

Plant specific Fertilization

If we could fertilize each plant, how much could be stolen by the neighbors shortly

after application?

Where does the newly taken up N go in the plant?

The Experiment- Applied 1.2 g of depleted N Ammonia Nitrate

(AN) (34-0-0) 15 cm below one plant.- Applied 1.2 g of regular N of AN 15 cm below

the 4 neighboring plants on each side.- Used a syringe, made a well hole and injected N

source at a 45 degree angle to place directly under each plant.

- N was applied on July 5th(V9) and July 25th(VT)- Plants were harvest on July 15th (V12) and August 1st (R1) respectively.

14N NNatural abundanceNNatural abundance

The Experiment

-Plants were separated into three parts.V9- Top leaf and whorl, Stem, Bottom

Leaves (9 replications)VT- Leaves, Stem and tassel, Immature

Ear(10 replications)

-Forage was dried for 72 hours and weighed.

-Plant Population was 77,500 plant ha-1

-All equipment was cleaned with Ethanol betweenreps.

14N NNatural abundanceNNatural abundance

All plants were kept separate until sent for lab analysis. Then the neighboring plants were combined to from one sample for each part.

Plant # 0 1 2 3

Results: First Harvest (V12)

H Letters indicate significant difference at the alpha = 0.05 level.

Table 1 : Average biomass data for each plant part of the first harvestVegetation Part Plant location from depleted

source Weight (g)

Leaves

0 64a H1 65a2 66a3 68a

Stem

0 77a1 78a2 81ab3 84b

Top leaf and whorl

0 57a1 57a2 57a3 57a

H Letters indicate significant difference at the alpha = 0.05 level.

Table 2 : Average N concentration for each plant part for the first harvest.

Vegetation Part Plant location from depleted source %

Leaves

0 2.1a H1 2.4 b2 2.3ab3 2.3ab

Stem

0 1.3a1 1.1a2 1.1a3 1.0a

Top leaf and whorl

0 2.5a1 2.6a2 2.4a3 2.5a

Results: First Harvest (V12)

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 1 2 3Plant location away from depleted N source

15N

(%)

Bottom Leaves Stem Top leaf and Whorl

AB B B

a

bx

cc

yyz z

Results: 15N concentration First Harvest V12

0

0.5

1

1.5

2

2.5

3

3.5

0 1 2 3Plant location away from depleted N source

Dep

lete

d N

Upt

ake

(mg)

Bottom Leaves Stem Top leaf and Whorl

B

A

B B

a

bbc

c

x

y

zz

Results: 14N uptake First Harvest V12

Table 3: Depleted N uptake at V12

plantDepleted N taken UP

(mg) % of total

0 5.7 60

1 2.6 28

2 0.9 10

3 0.2 2

Total 9.5

Results: Depleted N taken up at first harvest V12

Now lets look at what happens at the start of the Reproductive growth stages

Results: Second Harvest (R1)

H Letters indicate significant difference at the alpha = 0.05 level.

Table 4: Average biomass data for each plant part for the second harvest.

Vegetation Part Plant location from depleted source Weight (g)

Leaves0 78a H1 79a2 82a3 83a

Stem + Tassel

0 104a1 103a2 112ab3 113b

Ear0 87a1 89ab2 95ab3 96b

H Letters indicate significant difference at the alpha = 0.05 level.

Table 5 : Average N concentration for each plant part for the first harvest.

Vegetation Part Plant location from depleted source %

Leaves

0 2.6a H1 2.5a2 2.5a3 2.4a

Stem and Tassel

0 0.5a1 0.5a2 0.6a3 0.5a

Ear

0 1.4a1 1.5a2 1.4a3 1.3a

Results: Second Harvest (VT)

Results: Second Harvest (VT)

H Letters indicate significant difference at the alpha = 0.05 level.

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

0 1 2 3Plant location away from depleted N source

15N

(%)

Leaves Stem and Tassel Ear

A B B B

x

y z z

ab c c

0

0.5

1

1.5

2

2.5

3

3.5

0 1 2 3Plant location away from depleted N source

Dep

lete

d N

Upt

ake

(mg)

Leaves Stem and Tassel Ear

x

yz z

AB B B

ab bb

Results: Second Harvest (VT)

H Letters indicate significant difference at the alpha = 0.05 level.

Table 3: Depleted N uptake at R1

plantDepleted N taken UP

(mg) % of total

0 2.7 76

1 0.7 20

2 0.2 4

3 0 0

Total 3.5

Results: Depleted N taken up at 2nd harvest R1

Summary

- N placed under a single plant can be taken up by two neighboring plants.

-5 plants are competing for a same resourcesbelow ground.

- Newly taken up N is shuttled to developing plantstructure.

- Supports the need to insure no early season N stress.

Questions ??