The Rural Voice, 1986-02, Page 17bushels versus 82 bushels for the
N/P team. Obviously, the effect is
more than simply additive. So we
say 1 + 1 = 2 when the action is
independent, but 1 + 1 = 3 or
more when there is positive in-
teraction.
Looking further at other
treatments in the same study raises
questions (Table 4). What would
additional nitrogen do? Would
more phosphorous give further
response? What is the proper
balance at higher levels? With
higher amounts of N and P, will
negative interactions with other
elements — maybe zinc or
manganese or boron — develop?
Phosphorous/Potassium
The difference that positive P/K
interactions can make in soybean
yield and profit is shown in the
data of Table 5.
In the New York Studies (Table
6), the members of a balanced P/K
team interacted favourably to pro-
duce the best yields of cabbage.
Note that K was so limiting at the
36 Ib. rate that response to P was
small, but increased appreciably at
the higher more balanced rates.
However, 34 lbs. of P2O5 with 576
lbs. of K2O apparently was inade-
quate and so far out of balance
that it produced an unfavorable ef-
fect.
Phosphorous/Zinc
Negative interactions with
micronutrients can become severe
when pushing for top yields.
Results on corn in Kansas given in
Table 7, illustrate how negative
responses can be turned to positive
interactions. Adding phosphorous
without zinc had a negative effect
on yield and so did the addition of
zinc without phosphorous. When
both were used, a substantial
positive interaction occurred, in-
creasing yield by 44 bushels, over
the treatment without either.
Summary
We have discussed interaction
effects on yield and the economic
consequences. Quality can also be
influenced in significant ways,
especially in vegetables.
I'll sum up by saying high yield
is where the action is. The interac-
tions are there too. The challenge
to researchers is to learn more
about them. Farmers will need to
make better use of positive interac-
tions in order to maintain a
reasonable profit capability in
years ahead.
More and more, fertility balance
and bank balance will be highly
correlated.11
The right interaction is a total
system or total package of
practices in the right combination
and amounts.
Tabie 1
Don't stop short of positive interaction on alfalfa
Increase
over
P205 K20 Yield Check
Ibs.IA lbs./A TIA
O 0 4.3
150 0 5.8 1 5
O 300 6 7 2 4
150 300 7 2 2 9
Source: Rutgers University
N
lbs /A
0
180
180
180
Table 2
NPK effects on corn
P205
Ills /A
60
60
0
60
Source: University of Illinois
K20
lbs /A
90
0
90
90
Table 3
Yield
bu /A
41
96
111
143
Profit
$/A
-92.60
10.95
50.70
115.18
Nitrogen and phosphorous interaction effect on corn
Increase
over
N P205 Yield Check
lbs /A lbs /A bu /A bu /A
O 0 41
200 0 50 9
O 160 58 17
200 160 123 82
Source: University of Illinois
Table 4
What is the proper balance for higher corn yields?
lbs IA
0
0
0
100
200
100
100
200
200
Source: University of Illinois
P205
lbs /A
0
30
0
30
P205
lbs /A
0
BO
160
0
0
BO
160
80
160
Table 5
Positive P•K interactions can make
a difference with soybeans
K20
lbs /A
0
0
120
120
Yield
bu /A
24
26
37
45
Source: Virginia Polytechnic Institute
A balanced P•K
Table 6
Yield
bu /A
41
51
58
40
50
89
94
114
123
Profit
S/A
-30.00
2640
21.60
54.00
team can produce higher cabbage yields
P205
lbs IA
34
137
34
137
Source: Cornell University
K20
lbs./A
36
36
576
576
Table 7
Yield
TIA
19.0
20.0
17.5
28.0
Turn negative responses on corn Into positive interactions
P205
lbs./A
0
80
0
80
Source: Kansas State University
Zn
lbs /A
0
0
20
20
Yield
bu /A
131
119
109
175
FEBRUARY 1986 15