DOING THE MATH: How much food to actually feed a community.

[dlollard]

Peak soil. Topsoil tops oil!

And then there's peak water too ....

It seems to me that intelligent and creative human beings can drastically accelerate the formation of topsoil where they live. I look at abandoned parking lots downtown, and wherever leaves accumulate and rainwater flows, soil and grasses and weeds grow. And that's without any help from hominids.

Admittedly, the desperate situations of, say, N. Africa, and a chunk of Australia, will require more careful attention--or at the very least, our abandonment of the areas.

don

[arvmehta]

From the Huffington which is quoted from a study by Vandana Shiva

The polycultures of traditional agricultural systems have evolved because more yield can be harvested from a given area planted with diverse crops than from an equivalent area consisting of separate patches of monocultures. For example, in planting sorghum and pigeon pea mixtures, one hectare will produce the same yield as .94 hectares of sorghum monocultures and .68 hectares of pigeon pea monoculture combined. Thus one hectare of polyculture produces what 1.62 hectares of monoculture can produce. This is called the land equivalent ratio (LER).

Increased land-use efficiency and higher LER's have been reported for polycultures of millet/groundnut (1.26); maize/bean (1.38); millet/sorghum (1.53); maize/pigeon pea (1.85); maize/cocoyan/sweet potato (2.08); cassava/maize/groundnut (2.51). The monocultures of the Green Revolution thus actually reduced food yields per acre when compared with mixtures of diverse crops. This falsifies the argument often made that chemically intensive agriculture and genetic engineering will save biodiversity by releasing land from food production. In fact, since monocultures require more land, biodiversity is destroyed twice over -- once on the farm, and then on the additional acreage needed to produce the outputs a monoculture has displaced. Not only is the productivity measure distorted by ignoring resource inputs (focussing only on labour), it is also distorted by looking at a single and partial output rather than the total food output.

A myth promoted by the one-dimensional monoculture paradigm is that biodiversity reduces yields and productivity while monoculture increase yields and productivity. [...] Planting only one crop on an entire field as a monoculture will of course increase its yield. Planting multiple crops in a mixture will have low yields of individual crops, but will have high total output of food.

The Mayan peasants in the Mexican state of Chiapas are characterised as unproductive because they produce only two tonnes of corn per acre. However, the overall food output is twenty tonnes per acre. In the terraced fields of the high Himalayas, women peasants grow Jhangora (barnyard millet), marsha (amaranth), tur (pigeon pea), urad (black gram), gahat (horse gram), soybean (glysine max), bhat (glysine soya), rayans (rice bean), swanta (cow pea), and kodo (finger millet) in mixtures and rotations. The total output, even in bad years, is six times more than industrially-farmed rice monocultures.

[dlollard]

^^ wow. I mean, I've long understood how polyculture works and can give more net productivity, but wow. To think how much we've lost ... I mean, how much we have yet to gain by playing with systems like this. Thanks for sharing.