354 THE FUTURE OF ARID LANDS 
phorus. The obvious approach was to apply sufficient phosphorus 
so that the desired plants could be grown. However, all attempts 
to establish Medicago hispida failed, although many elements were 
tried. Such fertilizer plots overseeded in later years with trifoliate 
clovers gave remarkable forage yields, averaging three to four 
times that of the unimproved range. In fact, T. Airtum succeeded 
even without additions of phosphorus. 
The lesson to be gained is that one plant will succeed on a soil 
where another has failed. This idea is not new, for it is the very 
basis of successful agriculture, but perhaps the idea has not been 
carried far enough in our thinking about range lands. 
In addition, then, to climatic adaptation we have established 
the fact that two other factors must be considered: soil and the 
plant species. 
If we think of the plants on the range as a crop, the next con- 
sideration is how to harvest it. In other phases of agriculture, 
special harvesting methods are generally required, depending on 
the crop. For example, it is readily appreciated that lettuce, bar- 
ley, and cotton have different harvesting requirements. 
In most agricultural crops a weed 1s recognized as a weed, e.g., 
Amaranthus spp. in cotton. This also applies to some of our range 
weeds. It is recognized, too, that the weeds reduce crop yields by 
competing with the crop for water and nutrients. A poisonous 
plant such as Ha/ogeton, and extremely undesirable ones such as 
Hypericum perforatum, and some of our brush species stand out 
as special problems and their control may be attacked in orthodox 
ways. 
In general, however, the problem of weeds and weediness on our 
ranges is not so simple. It is often one of degree. 
On much of California’s foothill ranges the cover includes the 
following winter annuals. They may be grouped into two classes: 
Undesirable Desirable 
“the weeds” “the crop” 
Gastridium ventricosum Erodium botrys 
Festuca spp. Bromus mollis 
Hordeum spp. Avena spp. 
Bromus rubens Trifolium spp. 
B. rigidus Erodium cicutarium 
Medicago hispida 
