Fertilizer Value of Residues

1
Fertilizer Value of Residues

• Dave Franzen
• NDSU Extension Soil Specialist

2

• Residues are receiving attention recently
• because-
• Dry areas only had residues to feed.
• There are moves to remove residues
• for transformation into ethanol.
• Plant nutrient value of the residues is
• much greater than in the past.

3
Value of N 2006- 25 cents/lb 2009- 80
cents-1/lb Value of P2O5 2006- 25
cents/lb 2009- 1-1.25/lb Value of K2O 2006-
18 cents/lb 2009- 70 cents/lb
4
Ton of wheat straw- 13 lb N, 3.5 lb P2O5,
23 lb K2O Ton of
corn stalks- 22 lb N, 6 lb P2O5, 32 lb K2O Ton
of switchgrass- 22 lb N, 9 lb P2O5, 45 lb K2O
5
Condition, maturity and grain yield in relation
to residue makes a difference in nutrients
removed-
Stover yield of corn removed at three dates and
N, P and K removed (From September 17)
(From Franzen, 1976)
6
Residue from corn that does not make grain can
contain over 100 lb N, 40 lb P2O5 and 100 lb
K2O. K2O in corn residue depends on how long
the residue remains in the field. K2O can leach
out of dead plant tissues. N and P do not, unless
substantial N is stored in plant cells as
nitrate.
7
Residue from wheat that did not produce grain
contains more N, P and K than residue from a
normal wheat crop. A ton of non-grain producing
residue can contain 80 lb N, 30 lb P2O5, and 45
lb K2O.
8
Switchgrass contains more N before maturity than
afterwards. N is translocated into the roots
during maturation. Lower amounts of N is left in
the residue when the grass is mature. However,
biomass is reduced compared with earlier harvest.
9
Corn residue contains more N in the lower stalk
than the upper stalk. Cobs contain very low
levels of N, P or K. Cutting high reduces the
nutrients removed from corn residue
harvest. Removing only the cobs minimizes
nutrients removed from the crop and maximizes
carbohydrate.
10
Corn grain- 1.3 N, 0.26 P, 0.35 K Corn
stover- 0.5 N, 0.1 P, 0.9 K Corn cobs- 0.33
N, 0.03 P, 0.45 K
11
Nutrients in residues are only partially
available. Fresh residues may release 1/3 of
their N the first year if conventional till.
No-till residue nutrient release is slower-
perhaps only 20 of N. Residues also release P
to the next crop. Potassium leaches from residue
and most is probably available to the next crop.
12
Residues and residue decomposition are included
into our fertilizer recommendations. Our basic N
recommendations assume that a small grain was
grown the year before. Residues with high N
(alfalfa, green sugar beet leaves) and crops
that enhance N availability the year following
production (annual legumes) are the basis of
our previous crop N credit.
13
Burning residue removes N and S in the smoke,
but P and K remain.
14

• If wheat or corn residues are removed
• from a field-
• The net N, P and K in the field decreases.
• The amount of N made available for
• crop uptake actually INCREASES
• the next year.
• P and K available to the next crop is
• slightly lower, but imperceptibly so.

15
Removal of residues every year will result in
organic matter depletion over time.
16
QUESTIONS?