[Terrapreta] cover cropping as a charcoal in soil evaluation.

[Richard Haard]

Terrapreta reading listers

My introduction to using charcoal in soil for agricultural purposes  
came in 2004 at the conference held at University of Georgia.  
Returning and very enthused to give it a try I set up some experiments  
using purchased lump charcoal and inoculation of red alder with  
Frankia, a root nodule, nitrogen fixing organism.

That winter, 2004-5 I met by way of conversations on line with the  
gasification list, John Flottvik and learned about his work with a  
pilot plant pyrolyser. At the time he was working less than an hour  
drive from our farm just across the border in British  Columbia. John  
graciously offered to donate a tote of charcoal powder for my research  
program.

Finally, John here are some results from that work. !!

At the time three of our adjacent fields were fallow and we were cover  
cropping with gray oats beginning in early fall. We grow in these  
fields native plants in small blocks. Sometimes as many as 100 species  
of plants. It was interesting to note that mineral uptake by the  
different crops showed in the cover crop then uniformly planted on the  
field. Here is an image of that gray oats cover crop taken fall 2004.  
Note that on the far left the cover crop had already been worked down  
and on the right the field had heeled in stock. In the foreground a  
general mottled growth in the gray oats can be seen from differing  
fertility.

Wouldn't it be interesting then to treat several bands of these fields  
with this charcoal powder, crop the field for 2 years and then use a  
later cover crop planting to determine if the charcoal was having an  
effect on the soil fertility. We then worked in the gray oats and  
treated two bands of 6 seedbeds (each seedbed is 50 inches by 500  
feet.) with aisles for tractor wheels, making 8 feet. The charcoal  
powder was mixed with commercial compost and applied to each seed bed  
strip with a manure spreader. We never did have a weight of the  
charcoal in the tote but I estimate we put 100 lbs of charcoal on each  
strip. Quite a bit of it as you can see in these images went airborne  
but the soil surface wound up black in the right places. Here,  here  
and here are several images to show what we did at that time is our  
charcoal application

The untreated beds were given compost without charcoal powder and the  
entire field received a single treatment of  commercial fertilizer, a  
5 - 10 -10 with micronutrients , a formulation we are no longer  
using.  After planting, a light application of urea was used in late  
June when the seedlings were well established. Typically on our farm,  
a bare root nursery, we harvest parts of each field and leave the rest  
for harvest in second year. The blank spots in the field are usually  
filled in with transplants and our normal cycle of cropping any field  
is then completed in 2 growing seasons. Worst case happened though for  
this charcoal experiment as we were not able to clear the entire 3  
fields and reestablish cover crop because we needed the production  
space and replanted without fallowing.

We were able to cover crop one side of field 3 that had 2 rows treated  
with charcoal powder and the remainder untreated. My cover crop this  
spring was an early planting of mustard (Brassica). We planted the  
mustard in March and have just worked it in on June 12. The results  
are most encouraging to me but because we were not able to treat the  
entire 3 fields in this way will have to wait for more conclusive  
observations and soil testing.  These pictures show very distinct  
differences in growth of the mustard cover crop that received charcoal  
powder versus untreated. As we are replanting the entire set of fields  
spring 2009 then the next opportunity to view this cover crop effect  
will be 2011 or 12.

My conclusion is that we need to be conducting long term evaluation of  
charcoal effects in soil. This cover crop method may be the best way  
to show beneficial effects. Our soil management methods are pretty  
much mainstream in that we use commercial fertilizer and urea. Here is  
an indication that the use of charcoal has a positive effect on soil  
fertility and that the use of charcoal may reduce the need for  
fertilizer applications at our present usage rates.

Rich Haard, Fourth Corner Nurseries, Bellingham, Washington
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