Plant Specific Fertilization NUEWorkshop 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 5 th (V9) and July 25 th (VT) - Plants were harvest on July 15 th (V12) and August 1 st (R1) respectively.

14 N N Natural 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 between reps.

14 N N Natural 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 #

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 harvest Vegetation Part Plant location from depleted source Weight (g) Leaves 0 64a H 165a 266a 368a Stem 077a 178a 2 81ab 384b Top leaf and whorl 057a 1 2 3

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 H b 2 2.3ab 3 Stem 01.3a 11.1a a Top leaf and whorl 0 2.5a 1 2.6a 2 2.4a 3 2.5a Results: First Harvest (V12)

A B B B a b x c c y yz z Results: 15N concentration First Harvest V12

B A B B a b bc c x y z z Results: 14 N uptake First Harvest V12

Table 3: Depleted N uptake at V12 plant Depleted N taken UP (mg)% of total Total9.5 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) Leaves 0 78a H 179a 282a 383a Stem + Tassel 0104a 1103a 2 112ab 3113b Ear 087a 1 89ab 2 95ab 396b

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 H 1 2.5a a Stem and Tassel 00.5a a 30.5a Ear 0 1.4a 11.5a 2 1.4a 3 1.3a Results: Second Harvest (VT)

H Letters indicate significant difference at the alpha = 0.05 level. A B B B x y z z a b c c

x y z z A B BB a b b b Results: Second Harvest (VT) H Letters indicate significant difference at the alpha = 0.05 level.

Table 3: Depleted N uptake at R1 plant Depleted N taken UP (mg)% of total Total3.5 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 resources below ground. - Newly taken up N is shuttled to developing plant structure. - Supports the need to insure no early season N stress.

Questions ??