Saturday, October 6, 2012

Sorghum Puzzler

Last January I was trying to see if applying fish emulsion could help some Oats that had yellowing leaves and seemed to be struggling.  Now where the sorghum is growing on the same area it is doing much poorer than where nothing was applied. The fish emulsion jug had no label but I later found out that the fish emulsion, 3-1-1, was actually 1% urea and 1% ammonical nitrogen! I really prefer my N to go into the beds in an organic form.  The oats seemed to yield better with the fish emulsion, but now the sorghum which followed is doing poorly compared to the control section.  Could more of the soil OM been somehow oxidized with the N application??  I asked a soil scientist and was told that generally additions of N are always correlated with net increases in OM.  Perhaps then the oats which received the fish emulsion were more vigorous and took more nutrients from the soil than the oats that did not receive fish emulsion.  Or perhaps it is that Sorghum, when faced with a low N situation  grows taller and lankier?  You can see that the taller Sorghum does appear to be a tad N deficient compared to the smaller but lusher green Sorghum in the plot which had earlier received fish emulsion.  Post a comment if you have any ideas what could be going on.

Ancient wisdom on compacting wet soil

The earliest surviving work of Latin prose is Di Agricultural by Cato the Elder.  It's an interesting manual that deals mostly with running a large wine and olive operation.  It is evident though that even highly specialized farms in his time were somewhat self sufficient in that all the workers (usually slaves) and animals were fed from the farm and many of the building materials for baskets and trellises were sourced from on site.  The crops in order of importance are listed as vineyard, irrigated garden, willow planting, olive orchard, meadow, grain land, planting of forest trees for foliage, vineyard on trees and acorn wood.  It was assumed that the olive oil and the wine were to be the principal source of income, everything else was mostly for the maintenance of the farm organism.

I found one passage especially interesting:

Terram cariosam cave ne ares, neve plostrum neve pecus inpellas. Si ita non caveris, quo inpuleris, trienni fructum amittes.

Beware of plowing soil that is wet above and dry below, or of driving a wagon or flock over it.  If you do not beware you will lose three years profit where you have driven over the land.

Here Cato uses the term "cariosum", which the translator Brehaut uses Columella's (another old Roman) description to explain: "Whenever plowing is done, we shall be on our guard to keep the soil from being worked when it is muddy or when it is half wet from light rains, which state of soil farmers call varia or cariosa.  It means when after a long drought a light rain wets the upper part of the soil but does not reach the lower part."

I remember working on a farm where the tractor had been driven a little to early through a wet field and for the rest of the season there were deep tire ruts that dried into rock hard compacted trenches that water could not penetrate.

So what was good for the soil in the second century BC is still good for the soil today.  Though looking at the above picture one might as well phrase it, what was bad for the soil in the second century BC is still bad for the soil today.