what are the disadvantages and advantages of mixed croping?

Question

Agriculture

Answer 1

mono-crop, and especially GM, provide a standard uniform product that can be "patented" by the big seed co. and sold to the global food businesses.
However they needd large inputs of agro-chemicals (a plus for the seed producers that also produce herbicides), and they are vunerable to pest & disease, because once a pest or disease finds the weakspot it can run through the crop in no time. Also if there is a difference in climate irrigation etc then the whole field will suffer.

mixed cropping is the system evolved by nature to maximumise output (convertion of sunlight to bio-mass) in most eco-systems.
- this is the principle underpinning "permaculture".
mixed cropping, even different varieties of the same species, provides resaistance to pest & disease.
eg growing mixed potatoe varieties in a clover ley in 12m strips between row of trees means very little blight damage - see Elm Farm resarch papers a year or so back.

Also mixing nitrogen fixing plants reduces need for fertiliser and ploughing which reduces problems of errosion and water run-off. Water retention is also helped. There are lots of symbiotic relationships between plants, moulds, soil bacteria, worms, predators etc and even the local climate eg rainfall or frost.

The drawback is the farmers need to be informed about what grows in their particular field and preferably save the seed best adapted to their need - not forced by bank managers and supermarkets to buy a one-size fits all GM product (from government funded research & students) and then try and fit the environment to the crop.

in short:
mono-crop = $$ possible high yield, high risk for growers
mixed crop = reliable yield if slightly less than theoretical maximum = sustainable farming and food security

Answer 2

People used to plant one type of crop in an area. Like cotton for example, rows and rows of cotton plants all needing the same nutrients to grow. All those cotton plants deplete or use up all the boron in the soil and cotton plants eventually all die. So to keep that from happening farmers started mixing up the plants so they don't use up all the nutrients at once, if they are real clever they'll plant the crops that restore the nutrients that the crop next to it uses up and vice versa.
A major disadvantage is irragation that water logs the soil. Also mixed cropping sometimes uses a lot of man made fertilzers to be at peak production which can change the ph of the soil making it less productive.
Hope I helped.