How much fertilizer nutrients do I remove when I bale peanut vines is
a very popular question in the Southeast peanut belt. You would think
the answer is simple and straightforward. However, there are a number
of things that make this question hard to answer. One is, do modern varieties
yield less vines than older peanut varieties? And, are there more vines
produced with higher pod yields?
Some preliminary research in Georgia has shown that most modern varieties
yield about the same amount of vines per acre. As far as the more yield,
the more vines, unless the peanut yield is well below average and vine
production is obviously reduced (i.e. “not lapped”), then
vine yield should be about the same, regardless of pod yields.
What Are You Really Getting?
So, how much vine can I expect to remove? This is actually a
very different question than how much vine is produced. I first realized
this during discussions with county agents. I have always used the number
produced years ago (using Florunner, I believe) that a 3,000 pound per
acre peanut yield will produce 6,000 pounds of vines per acre. I even
raked up some vines from different peanut varieties to verify this. But
the numbers the county agents were getting, based on how much their farmers
were removing, were not adding up.
It didn’t take too long to figure out that when I raked the vines
by hand, I was recovering everything. This is very different from a farmer
using a hay baler. In fact, baling efficiency seems to vary greatly, depending
on how the vines are windrowed, how dry they were before picking and how
soon you bale them after picking.
Baling efficiency seems to be somewhere around 50 percent (may be higher
and may be lower). So out of that 6,000 pounds of vines per acre, you
are talking about removing approximately 3,000 pounds. This seems to add
up according to county agents that say you usually get two and a half
to three large round bales of vines per acre. Of course, the weight of
the round bales can vary too, probably anywhere from 800 to 1,200 pounds,
with 1,000 pounds being a good average.
What Is The Nutrient Value?
Now, how many nutrients are being removed in the vines? Again,
this can be tricky depending on how you go about it. When I raked up peanut
vines by hand and had them analyzed, the vines averaged 1.7 percent N,
0.35 percent P2O5 and 2.1 percent K2O. Multiplied by 3,000 pounds, this
would be about 50-10-60 pounds of N-P2O5-K2O per acre in the vines. However,
if you go out and sample the vines from farmers’ bales, you can
get something significantly less than these numbers, depending on how
good a job of baling was done. This is especially true if a lot of the
vine leaves are left in the field, which is where a lot of the nutrient
content is believed to be, compared to the stemmy vines themselves.
Which leads us to the ultimate question...the bottom line. How much
are the vines worth in terms of fertilizer value if I leave them in the
field? Or, another way of looking at it, how much fertilizer value am
I losing when I remove vines from the field?
This obviously depends on the cost of fertilizer nutrients that have
recently skyrocketed to an all time high. Even if you use fairly conservative
estimates of N-P2O5 and K2O costs of 70-80-50 (cents per pound), then
the vines would be worth $30 for N, $8 for P2O5 and $30 for K2O for a
total of $73 per acre. This estimate could be considered slightly high
due to the fact that the N in peanut vines is not nearly as readily available
as N in commercial fertilizer.
The Value Of Not Removing The Vines
On the other hand, this estimate could be considered low if you
place any value at all to the carbon or organic matter you are removing
from the field. Granted, it is very hard to put a dollar value per acre
on organic matter, but there should be little argument that soils in south
Georgia are “organic matter challenged” and that organic matter
can improve the productivity of our soils.
Ultimately, there are a lot of factors to consider when determining how
much value is removed with peanut vines.
This is not a new question. In fact, a UGA economist addressed this question
in 1988 and concluded that “peanut vine removal may not pay,”
which was also the title. Twenty years later, I am going to reach the
same conclusion, especially with higher fertilizer prices and the higher
value placed on increasing organic matter in our soils, and that is why
we should be looking more at the value in NOT removing peanut vines from