The Dreaded Southwest Weeds

The community garden has been invaded by the two most persistent and invasive "weeds" of the Southwestern U.S.: bermuda grass and nut grass.  The bermuda grass is unfortunately the result of the garden bordering our school's soccer field.  There's nothing I can do about that!  The nut grass has popped up on its own, enjoying the unusually moist, rich soil of the desert.  My question for you is, how do you take care of these two weeds?  I have been digging them out of the garden, but it truly is an uphill battle!!  Here is the research I have gathered on these two nuisances.......

C. dactylon (bermuda grass) is found in the U.S., mostly in the southern half of the country and in warm climates. It is fast growing and tough, making it popular and useful for sports fields, as when damaged it will recover quickly. It is a highly desirable turf grass in warm temperate climates, particularly for those regions where its heat and drought tolerance enable it to survive where few other grasses do. It has a relatively coarse-bladed form for different turf requirements. It is also highly aggressive, crowding out most other grasses and invading other habitats, and has become a hard-to-eradicate weed in some areas. This weedy nature leads some gardeners to give it the name of "devil grass".  Bermuda grass has been cultivated on saline soils in California's Central Valley which are too salt-damaged to support agricultural crops; it was successfully irrigated with saline water and used to graze cattle.  This grass is given significant importance in Hinduism due to its medicinal values and dedicated especially to Lord Ganesha.  Cynodon dactylon has been studied at the University of Allahabad in India, and has been suggested for treatment of urinary tract infections, prostatitis, syphilis, and dysentery.  It is also used in traditional cultures for toothache.

Cyperus rotundus (nut grass) is one of the most invasive weeds known, having spread out to a worldwide distribution in tropical and temperate regions. It has been called "the world's worst weed" as it is known as a weed in over 90 countries, and infests over 50 crops worldwide.  Its existence in a field significantly reduces crop yield, both because it is a tough competitor for ground resources, and because the roots release substances harmful to other plants. The difficulty to control it is a result of its intensive system of underground tubers, and its resistance to most herbicides. It is also one of the few weeds that cannot be stopped with plastic mulch.  Weed pulling in gardens usually results in breakage of roots, leaving tubers in the ground from which new plants emerge quickly. Ploughing distributes the tubers in the field, worsening the infestation; even if the plough cuts up the tubers to pieces, new plants can still grow from them. In addition, the tubers can survive harsh conditions, further contributing to the difficulty to eradicate the plant.  Most herbicides may kill the plant's leaves, but most have no effect on the root system and the tubers.