8000


 7000

 6000

S5000

z 4000

3000

 2000

 1000

 0


 35 -

 30-

 >25 -
 60
 20

 15

 10

 5

 0-



 35
 30
S25

S20
z15
 S10
 5
 0



 45
 '40
 P35 -
 S30
 025
 z
 S20
 15-
 10-
 5
 0-


0 2 4 6 8 10 12 14 16 18


0 2 4 6 8 10 12 14 16 18
 Age (years)


 8000
 7000
 6000
 S5000
 '4000
 Z 3000
 0
 Z 2000
 1000
 0



 9000
 8000
4 7000
S6000
S5000-
S4000-
~3000
z 2000
 1000
 0


0 2 4 6 8 10 12 14 16 18


0 2 4 6 8 10 12 14 16 18


0 2 4 6 8 10 12 14 16 18
 Age (years)


Average KCI Extractable N03-N, NH4-N and Combined N03-N and
NH4-N at Each Site. In Graphs (a), (c), and (e) Nutrient Values Are
Expressed in Milligrams Nutrient Per Gram of Soil. In Graphs (b),
(d), and (f), Nutrient Values Are Expressed in Grams of Nutrient per
Square Meter to a Depth of 20 cm.


7-63


0 2 4 6 8 10 12 14 16 18


Figure 7.11.