Agriculture sensu lato can be defined in various ways. Lawes [16] and Prado [17], defined it as a process of artificialization and decision taking about nature, with some specific human purposes, such as producing food, fiber, leather, wood or landscape beauty. It is, therefore, a process of transformation with a given objective, involving nature, stakeholders and technology. In this context, agriculture sensu lato includes numerous activities related to multiple land use for production purposes (vegetable garden, forestry, aquaculture, livestock, etc.), protection (of soils, fauna, banks, landscapes, etc.) and recreation (agrotourism, camping, sports, entertainment, and so on).
During the seventies, when hard productivity technologies were being enforced, agriculture was defined as putting a harness to solar energy through plants for human purposes [18]. An earlier definition, 1814, describes it as science of managing farmland [19]. The latter definition is consistent and complements, as well as, integrates the above ones; it combines Nature and its artificialization with land management, organized around rural properties. In all these definitions the ecosystem is essential and a priority.
On the other hand, agriculture can be defined as an economic activity related to the sustainable production of crops and its transformation into elements which can be consumed by man. Many people perform this activity as a way to live [20]. This definition expresses the policy approach of the farmers’ associations and some of the Ministries of Agriculture, who tend to consider agriculture as a mere business, when it should be seen as a central component for integral rural development.
In recent decades, agriculture has been looked upon only as an agribusiness, which takes away much of its significance and meaning, leaving it only as a minor branch of the economy [21]. In Chile, in general this began mainly during the second half of last century and continues today. Agriculture has been restricted to crops, economy and enterprise, overlooking its farm dimension and in many cases causing the degradation of the natural resources of the country [11, 22, 23] Unlike this, the traditional large farm (hacienda) for the first 300 years after the conquest and colonization of America was the major territorial, social, economic, and management unit, later complemented with other styles of farm in all its forms [24, 25].
In the early Christian age, at the time of Columella [26, the original paper written during the 1st century aD], there was talk of re-rustic, referring mainly to the rurality, which is complemented by the urbanity that takes place in small towns and villages in the territories of Babylon, Greece and Rome [27, 12]. It was necessary to supply the cities with abundant food; thus, it was necessary to develop specialized farms with efficient production processes. The English word farming derives from here, differentiating it from cropping and husbandry (analogous to agriculture in Castilian). Farming can be defined as the arrangement, management and administration, of rural lands, which achievement center on the territory articulated by technological activities related to agriculture sensu lato [11, 28].
Ecology is incorporated formally and rigorously since the twenties, adding the ecosystem in the year 1935 [29], and becoming generally known between the sixties and seventies. It is difficult to argue that modern agriculture can develop sustainably without incorporating the ecology as a fundamental paradigm. This due to the agricultural matrix land generated from the artificialization of the natural ecosystem forming rural properties, and due to expansion of the agricultural frontier as generalized as a worldwide phenomenon [1, 2, 23, 30].
Symbolically, the artificialization (A) of nature, or agriculture, can be represented as [15]:
A = К/^a ■ ^21) (1)
where:
TCa: Set of operators of artificialization for a state of artificialization "a"
Zn: State of the ecosystem to time n=0, previous to time n=1
Z0 ^ Z1: Change of the state of the ecosystem from Zo to Zi.
From an operational point of view, the farm can be defined as "an organized unit of decision making, an area of renewable natural resources, connected internally and limited externally, which aim is to make agriculture" [31, 32]. Formally, the farm (P) consists of [15]:
P = f (S, Z, ф, oa) (2)
where:
S: Space-time, L3 x T (length3 x time)
Z: Spatio-temporal units of renewable natural resources
Ф: Inter or intra flow of matter, energy or information
oa: Answer or output as a function of artificialization
