PLANT MORPHOGENESIS FOR SCIENTIFIC MANAGEMENT OF RANGE RESOURCES 



201 



cause tanks or dams and shearing sheds coincided 

 with texture contrast soils. 



Charley and Cowling (4) have shown the haz- 

 ardous nature of nutrients in Australian arid 

 area soils. Many of the soils are polygenetic in 

 nature, and have formed in more humid eras than 

 the present, Small soil losses of 5 to 10 cm. trun- 

 cate soils carrying perennial saltbush (Atriplex 

 vesicaria He ward ex Benth) pastures, and critical 

 amounts of nitrogen, phosphorus, and organic 

 carbon are lost. They postulate that these losses 

 can limit regeneration even where water is ade- 

 quate, as on a furrowed area. 



It is most important that the soils which are 

 susceptible to near irreversible degradation be 

 recognized. Consequently, the identification and 

 description of the rangeland in terms of its land 

 units or types are prerequisites to development 

 and proper use. This inventory must then be 

 expressed in terms of the practical capability and 

 limitations of each land type. It provides a 

 basic guide to fencing, water provision, and graz- 

 ing management. 



Examples of the value of land type surveys and 

 grazing assessments are available in parts of 

 Australia. In Central Australia an area of ap- 

 proximately 26 million hectares of arid pastoral 

 land was surveyed, mapped, and described in 

 terms of land systems (22) by a team of Com- 

 monwealth Scientific and Industrial Research Or- 

 ganization (C.S.I.R.O) scientists. A major 

 drought followed, which led to erosion and a 

 serious decline in production throughout the area. 

 The administrators of the area requested advice 

 on the matter, and the N.S.W. Soil Conservation 

 Service was able to use the land system survey 

 as a basis on which to recommend management 

 practices and safe grazing capacities for each 

 holding (6). 



More recently, a land unit survey was con- 

 ducted on a much smaller area of 1.2 million 

 hectares in northwestern New South Wales. This 

 area is more closely settled, and consequently re- 

 quired the greater detail of the land unit rather 

 than the land system. A grazing assessment of 

 each land unit and holding was carried out. The 

 latter work was conducted on a cooperative basis 

 between the University of N.S.W., C.S.I.R.O and 

 the N.S.W. Soil Conservation Service. 



Grazing Assessment 



The major problem in the past has been ex- 

 cessive livestock numbers. As a first step in 

 future development, grazing pressure must be 

 reduced in a logical manner. 



As a starting point, it is appropriate to deter- 

 mine the number of stock which can safely graze 

 an area in the long term, under present manage- 

 ment practice. Sophisticated grazing systems can 

 be developed from this basis. Land type provides 

 a realistic basis on which to assess grazing ca- 

 pability, the potential for development, and need 

 for restrictions. 



Condon (5) described a method of assessing 

 grazing capacity of arid land in Australia. The 

 method depends upon establishing a safe grazing 

 capacity for a relatively large, uniform area of 

 country, for which records are available. Each 

 factor affecting grazing is then recognized, and 

 rating scales are allocated for the factors, which 

 include rainfall, soils, topography, tree density, 

 drought forage, pasture type, condition or ero- 

 sion, and barren areas. The assessments are made 

 on each land system, land class, or land unit 

 within a holding. 



The accuracy of the method depends upon the 

 reliability of the input data. Some obvious limi- 

 tations will be apparent, In particular, interac- 

 tions are not considered, for example, a group 

 of land classes on the one holding as compared 

 with a holding with one land class. 



However, the method is an improvement over 

 traditional methods, which are based solely on 

 what similar country (a holding as a whole) has 

 carried in the past. Adjustments are made after 

 a deficiency has become obvious. Where an as- 

 sessment has been too high, an adjustment is not 

 made until obvious deterioration has occurred. 

 Deterioration has often been critical and per- 

 manent. 



An example of a holding with this experience 

 occurs in central New South Wales. The holding- 

 is on the low woodlands range type, with long- 

 term, average annual rainfall of approximately 

 330 mm. It is being invaded by inedible scrub and 

 is affected by sheet erosion. It covers over 40,000 

 hectares and was settled before 1880. An early 

 survey (1919) reported that the holding was a 

 very well grassed, open woodland. A report in 



