Agriculture Reference
In-Depth Information
These figures assume that in the livestock based system there are enough animals, and
hence manure, to provide fertility for grain crops without recourse to additional areas of
green manure. In other words, growing grain in a self-sufficient organic mixed farming sys-
tem requires the correct balance of livestock to arable to ensure adequate fertilization. The
standard textbook on organic farming in England by Nicolas Lampkin states that typical
whole farm rotations on mixed livestock farms might require five hectares of clover ley or
lucerne for two hectares of cash crop (2:5); or on a more intensive farm, six hectares of
clover to four hectares of cash crop (4:6). In effect, organic mixed farm rotations, which
have roughly two thirds of their land given over to nitrogen fixing plants, are more or less a
mirror image of stockfree rotations which have roughly a third given over to nitrogen fixing
plants - the difference being that a proportion of the livestock farm's ley is fed to animals
before finding its way onto the crops. The 5:2 Co-operative Wholesale Society experiment
listed is an exact mirror image of the 2:5 rotation described by Lampkin.
A comparison of the performances of these whole farm systems shows that the difference
between them is fairly slender. Take for example an imaginary seven hectare farm. A stock
free system with two hectares of leguminous green manure for every five hectares of grain
crops would produce five hectares worth of crops. An organic system feeding dairy cows
would produce two hectares of grain crops, plus 5 hectares of ley for dairy produce, includ-
ing a little beef. Assuming the nutritive value of the five acres of ley is equal to the nutritive
value of the crops, at a conversion ratio of three to one the dairy produce will be equivalent
to the crops which could be grown on a third of those five hectares, namely 1.6 ha. So on
a seven hectare plot the dairy system would be producing the equivalent of 3.6 ha of crops,
against five hectares for the stockfree farm - or a ratio of 1.39:1 in favour of the stockless
system. If the livestock were beef fed at a 10:1 feed conversion ration, the ratio would be
2:1, ie the vegan farm would be producing exactly twice as much as the beef farm.
The above example compares a fairly extensive livestock system with a relatively intens-
ive stockfree system. If we compare Lampkin's 4:6 livestock rotation with the more typical
2:1 stockfree rotation, we find that a dairy farm produces four hectares' worth of crops,
plus another two hectares' worth from the ley, or six hectares' worth altogether, whereas a
stockless farm harvests 6.6 ha of crops - a ratio of 1.1:1 in favour of the vegan system. If
the livestock were beef, the ratio would be 1.43:1 in favour of the stockfree farm.
As a matter of interest, a Norfolk rotation, producing wheat and barley for beer and bread
for human consumption on two hectares and animal feed (turnips and clover) on two hec-
tares, is a very intensive 2:2 system. If all this animal feed were fed to dairy cows at a con-
version ratio of 3:1, it would produce the equivalent in milk products of 0.66 ha of wheat,
giving a total of 2.66 ha worth of crops for the entire four hectares. This is exactly the same
as the yield from a stockless system with 33 per cent of the land devoted to green manure.
However the 2:2 system is probably not a fair comparison since Coke and other practition-
ers of this rotation were probably also bringing in fertility from outlying land with sheep.
