🚀 go-pugleaf

I was surprised to read that the "harvest index" of corn has improved
from 20-25% 50 years ago to 50-55% currently! This is a common
misconception and I am curious about its origin.

As far as I know,  harvest index in corn has remained the same during
the last six decades of corn breeding in the US, that has resulted in
about a six fold increase in yield (about 22 to 130 bu/a). [Some
reported data may indicate a small increase in harvest index, but
that is an artefact of the experimental procedure, i.e., yields
should be compared at the optimal plant density for grain yield].
Surprisingly, harvest index was about 50% 60 years ago and has not
changed despite all other changes that have occurred during this
time.

Could it be that the "harvest index fallacy" is the result of  an
extrapolation of experimental results for wheat to corn (and other
crops)?





> To:            nobody@net.bio.net
> Date:          Thu, 19 Feb 1998 16:20:34 -0500 (EST)
> From:          "Kenneth L. Buhr, Agronomy" <KLB@gnv.ifas.ufl.edu>
> Reply-to:      maize@net.bio.net
> Subject:       Re: Converting bushels to weight?

> Warren,
> 	There is an easy answer and a not-so-easy response to your question
> of maize bushel weights.  First the easy answer -
>
> 	# 2 yellow corn is 56 lbs per bushel
>


> 	Now, if you are looking at total biomass production, the current
> figures for "harvest index" are around 0.55, or 55% of the above-ground
> biomass is grain.  (That is up from 0.20 - 0.25 fifty years ago - plant
> breeding success in selection for improved grain partitioning.)
>
> 	Probably significant also is the fact that # 2 yellow maize is
> 15.5 percent moisture.  What is it for the vegetables that you are
>considering?
> Possibly 80% or more?  I am not sure what you are doing with the conversions,
> but if you are looking at dry matter, you will need to look at moisture
> content and compensate.  There is a formula for that, as well.
>
> 	Ken
> 	Agronomy, U of Florida
> 	klb@gnv.ifas.ufl.edu
>
>
>
>

     Thys Tollenaar,
     Professor,
     Crop Science Dept.,
     Univ. of Guelph, N1G 2W1
     tel. <91> (519) 824-4120, ext. 3851
     fax  <91> (519) 763-8933