Martín F. Garbulsky and V. Alejandro Deregibus
[The graphics and data in this profile have been provided by the authors and the designations employed and the presentation of material in this information product do not imply the expression of any opinion whatsoever on the part of the Food and Agriculture Organization of the United Nations concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries].
The Argentine territory, in the southern portion of
South America, runs from the Tropic of Capricorn to the southern tip of
the continent (55º 58’ S). Extending for 3,700 km North to South and covering
2,791,810 sq km, it is bordered by the Atlantic Ocean,
Indigenous population, colonization, independence and national organization. The first humans migrated into the Argentine territory twelve or thirteen thousand years ago and settled in small groups of hunters and gatherers. By a thousand years ago people all over the territory had acquired some sort of agricultural/horticultural activity, using the fertile banks of some rivers after floods receded, irrigating some valleys in the arid west or burning patches in the forests of the humid northeast (Barsky and Gelman, 2001).
A great variety of human groups and living patterns
were found in the native population at that time, estimated at half a
million by the Spanish conquerors of this vast territory (in the sixteenth
century). These groups were very diverse in terms of culture and organization
and many were nomads. More advanced cultures had developed in the northwest,
near the Andes, on the present border with
In the fifteenth century some of the present main cities
were founded: Santiago del Estero (1553), Buenos Aires (1536-1580), Mendoza
(1561), Santa Fe (1573) and Córdoba (1573). The viceroyalty of the Rio
de la Plata was created in 1776, extending over the present territories
Peace was restored in 1820, but the formation of a stable
government remained unresolved. Throughout most of the following decade
a state of anarchy prevailed in the United Provinces, further compounded
by war with
One of the most important tasks for agricultural development
during the late nineteenth century was the completion of the conquest
of the Pampas as far as the Río Negro so the threat of hostile Native
Americans from that direction was eliminated. This so-called War of the
Desert (1879-1880) opened up vast new areas for grazing and farming. After
Initial herbivory and introduction of domestic
There were neither herbivores of regular size nor their carnivorous predators in most of the Argentine territory when the Spaniards arrived. Such grassland steppes became an ideal open niche for the European cattle and horses whose population grew spontaneously into huge herds that roamed freely throughout the vast territory. The abundance of large herbivores changed the landscape, soil and grazing lands’ structure; high tussock canopies developed into more nutritious and softer forages and topsoil fertility increased.
Indians and the Spaniards easily hunted such cattle
population on horseback. The possibility of exploiting their hides and
salting some meat (biltong) marked the economic activity and allowed the
growth of many settlements during the colonization period. Authorities
of the principal cities of the region granted hunting permits and organized
expeditions (“vaquerías”) throughout the seventeenth century, activities
that stopped by the mid eighteenth century because of the decimation of
the wild cattle population. From then onwards, large cattle operations
were developed for cattle raising (called “estancias” as Spanish government
appointed people to “stay”). Significant areas were operated by the Jesuit
Catholic Congregation who imprinted a strong cultural landmark in many
Regions. In the West and North West of Argentina mules were produced and
cattle raised to supply the silver mines in Potosi (actually
Until recently it has been usual to find mixed
animal and crop production in Pampas ranching operations; this was meant
to maintain soil fertility as three to five years of crops were followed
by a similar period of pastures. In the past decade, the increases that
occurred in principal crop prices plus the possibility of minimum tillage
of the soils, has determined the expulsion of cattle from the prime crop
areas. As in many other parts of the world, Argentine producers became
specialized either as farmers or as ranchers. Agricultural activity accounts
for 30% of
Table 1. Cultivated area and average yields for main crops in Argentina. Empty cells mean lack of statistics. SAGPyA, 2004
Table 2. Topographic distribution
Major soil types
Table 3. Land area by soil
order in continental
|3. CLIMATE AND AGRO-ECOLOGICAL ZONES
Rainfall events in the Argentine plains are determined
by a continuous struggle of air masses: humid winds from the Subtropical
Atlantic Ocean enter the Argentine Northern and Central territory while
dry winds from the Patagonian region vary in relative strength according
to the seasons. Dominant warm winds enter freely and deeply into the Northern
and Central territory during the warm season releasing plenty of rain
until desiccated in the west. In the cooler season a vast sector of
Mean annual temperatures range from 5 ºC in the southern
continental extreme to 25 ºC in the north. The 20 ºC and 13 ºC isotherms
are used to separate the Pampas from the Chaco and Patagonian regions
(Figure 3b). In humid
|4. RUMINANT LIVESTOCK PRODUCTION SYSTEMS
After an initial period of exploitation of feral cattle, with the establishment
of estancias, extensive, grazing-based commercial cattle raising began
and became increasingly important. Sheep were added to cattle and horses
during the nineteenth century; their population expanded rapidly and reached
a peak in the Pampas at the turn of the twentieth century. Until the development
of packing industries the main animal products marketed were hides, fat,
wool and salt meat (biltong for slaves in
Although some native cameloids are exploited commercially for small quantities of hair/wool or for draught and “criollo” cattle are still found in many areas, almost all ruminants used for commercial purposes were absorbed by foreign breeds. An important work of selection and improvement of each breed occurred in the country and new breeds were designed. Breeder’s associations promote each breed, implementing national and local contests every year for showing and selling purebred animals. Ranchers attend these events in great numbers as they are very interested in the genetic improvement of their cattle.
Here we describe cattle population and productive parameters for five regions that partially fit the grazing regions (Figure 6, Table 4) Regions differ not only in their total stock but also in terms of their productive profile. The Pampas has about 62% of the national cattle stock. Patagonia has less than 2% of the national cattle stock but accounts for 59% of the national sheep stock. The highest proportion of cows are in the Campos and Eastern Chaco, showing the importance of cow/calf operations in this area. The remaining 14% of cattle is in semiarid regions of the country. Slaughter for human consumption is mainly of steers (Table 4).
Table 4. Cattle industry parameters
for each Argentinean region and for the whole country.
Breeds. The temperate grazing lands of
Only some native cameloids continue to be used. Each breed is used depending on the environmental conditions and the productive goals of the commercial operations. Several non-governmental organizations are the local references for each breed.
In 2001, most of the beef (2.7 million ton/year), lamb (35 thousand ton/year - FAOSTAT figure is higher) and milk (10,000 million litres/year) produced was consumed domestically, as export to many countries is forbidden for sanitary reasons (e.g. foot and mouth disease). Cattle and dairying industries account for only 6% of exports (INDEC, 2001).
Distribution of stock-rearing areas
The great range of agro-ecological zones has led to the development of many livestock production systems adapted to the ecological and economic conditions in each zone. These systems have been described in Section 5 alongside details of the pasture resource, in order to simplify reading and avoid repetition.
Cattle ranches are settled on the periphery of the Pampas Region, in the Flooding Pampa or in any other place where cropping is not possible. Environmental, historic and economic reasons have determined such heterogeneous distribution of cattle throughout the country. Sheep are most important in Patagonia. Most subsistence producers are in North-Western Patagonia, the Puna and the Andes steppes. Dairying and fattening has traditionally been associated with the pampas, often in rotation with crops; high crop prices and new technology has led to increased specialisation in crop production, and livestock (mainly cattle) are now being squeezed out of the cropping areas.
Marketing of animal products has strongly changed during the last decade. Central “on hoof” markets used to concentrate the greater part of the transactions (e.g. Mercado de Liniers). Today, direct trading between the ranchers and buyers (e.g. supermarkets, whole-sale butchers), has the greater part of the market. However, on-hoof markets still determine the prices for several types of animals. For the milk market, dairy operations use to sell the milk directly to the factories. Three main companies concentrate 70% of the milk produced in the country. There are many medium and small factories, mostly in the Pampas.
Principal constraints and problems in livestock
THE PASTURE RESOURCE
(i) Campos and Espinal Forest
The humid to super-humid North Eastern territory of Argentina shows to the north marshes or pastures that grow on acid sandy (deep) and rocky (shallow) soils and, to the south, a savannah (known as the Espinal Forest) growing on strong clayish soils. These Mega thermic Grazing lands are dominated by warm season grasses (C4), progressively reducing the densities of both cool season grasses (C3) or legumes. As cattle cannot graze down the low quality forage biomass (60% digestibility or less) produced during the long warm season, a large biomass accumulates and senesces during autumn (April), loses quality further (up to 3% protein content) in winter (July) and has to be burned before the onset of the next growing season (September). Mass accumulation shades out the initial autumn growth of cool season grasses causing scarce forage production during winter that is heavily and continuously grazed. As low forage quality in the cold season affects cattle nutrition, stocking rates are low (Pizzio et al. 2000).
Grasses of the Panicoideae, Chlorideae, Andropogoneae and Oryzeae tribes dominate the grasslands that grow on these shallow and phosphorus deficient soils (less than 3 ppm), legumes present are of species of Adesmia sp., Desmodium sp. and Rhynchosia sp., while just a few C3 grasses of the Agrosteae and Stipeae tribes thrive for a few months.
Various grassland types are found in these Campos and Espinal Forest, classified according to the dominant species and physiognomy.
Tall grasslands: this is the typical vegetation of the Campos occupying humid to super humid areas. Andropogon lateralis, the dominant species, is non-grazeable when the canopy is dominated by its wiry red flower stalks. When well grazed, this grass has a leafy appearance associated with medium and short grasses of acceptable forage quality as “Jesuits grass” (Axonopus compressus), Bahia grass (Paspalum notatum), Dallis grass (Paspalum dilatatum), some other Paspalum spp. (P. almum, P. plicatulum), Bothriochloa laguroides or Rottboellia selloana. When Andropogon is dominant and lightly grazed, biomass production may exceed 7 ton ha-1 year-1. Other tall grasses dominate north western areas of this Campos Region and the Humid Chaco, such as Elionurus muticus ( on well-drained sandy soils), Sorghastrum agrostoides and Paspalum intermedium.
Medium grasslands: in the open Campos and in-between the sparse tree canopy of Prosopis spp. and Acacia spp. of the Espinal Forest, grows this herbage layer capable of producing 4-5 ton of forage ha-1 year-1. In it soft grasses such as Axonopus argentinus, A. compressus, Bothriochloa laguroides, Paspalum notatum, P. dilatatum and Panicum milioides cover the soil densely and offer quality forage during the warm season. This grassland has a great capacity to recover its condition when moderately grazed, and when rests are allowed some cool season grasses appear (Stipa neesiana, Briza subaristata) and legumes (Adesmia punctata, Desmodium incanum, Rhynchosia senna, Medicago polymorpha and Trifolium polymorphum). When this occurs, these grasslands show some forage growth during the cool season, determining increases in secondary productivity.
Short grasslands: coarse grasses like Aristida jubata and Bouteloua megapotamica make a low density cover with infertile and alkaline soils; its forage productivity is low (1 ton DM ha-1 year-1). These grasslands are grazed by sheep.
Swamp grasslands: Grasses and Cyperaceae with aerenchyma cover areas with 20-30 cm of standing water. Species like Echinochloa helodes, Eriochloa punctata, Paspalidium paludivagum, Leersia hexandra, Luziola peruviana dominate the dense canopy. These grasslands have good forage production (6 ton DM ha-1 year-1) allowing heavy stocking and rapid weight gains of cattle during the warmer half of the year.
Cultivated pastures: a minimum area (200 000 ha) of native pastures has been replaced with Setaria anceps, Digitaria decumbens (Pangola grass), Brachiaria spp., and other improved forages. No legumes nor cool season grasses are successfully grown; a major drawback as there is much need to improve forage quality and winter production.
Extended degradation processes of both soil and vegetation are observable in this Region. Different factors combine to cause such degradation: hilly terrain, sandy or clayish soils, intense rainfall events, overgrazing, deforestation or non authorised fires. Almost 10 % of the Region’s area (840,000 ha) has been classified as severely eroded and another three million hectares is degrading.
Cattle population and secondary production:
(ii) Chaco Forests
[Click here for a paper on The Gran Chaco by Fernando Riveros.]
This subtropical savanna occupies the central northern
Humid Chaco savannahs:
The landscape is completed by vast grazing lands that form a shallow network that drains excess water towards the East, extending over almost three million hectares. In the intermediate slopes may be seen palms (Copernicia alba) and an herbaceous stratum dominated by tall grasses such Elionurus muticus (on well drained sandy soils), Sorghastrum agrostoides (on periodically flooded soils) and Paspalum intermedium (on frequently flooded soils). The forage quality of these grasslands depends of the density of regular quality middle-sized companion grasses such as Chloris ciliata, Setaria geniculata, Sporobolus indicus. Within the drains (that are continually flooded) swamp grasses grow such as Leersia hexandra, Luziola peruviana, Paspalidium paludivagum, Eriochloa punctata, Echinochloa helodes which form dense swards of good forage when leafy. Finally, marshes in deeper water are dominated by Panicum prionitis, a non-grazed tall grass.
A distinctive feature of this region is its herbaceous leguminous flora that varies according to soils phosphorus levels, ranging from very rich in forested soils to poor in saline soils bordering the drains. Species such as Adesmia muricata, Aeschynomene rudis, Discolobium leptophyllum, Desmanthus virgatus, Desmodium canum, Dolichopsis paraguariensis, Indigofera parodiana, Lathyrus nigrivavlis, Neptunia sp., Phaseolus lathyroides, Vicia graminea, Vigna luteola and others improve forage quality and activate nitrogen circulation in these grasslands. Where nitrogen is fixed, cool season grasses such as Bromus inermis, Agropyron scabrifolium and Phalaris angusta grow, further improving forage quality. Unfortunately, continuous grazing and frequent fires have reduced these species heavily, and they are now found only in grasslands in good to excellent condition, mostly relicts.
The southern area of this humid sub-region is a vast basin of almost one million hectares, characterized by frequent floods, saline soils and marshes dominated by Spartina argentinensis.
Sub-Humid and Semi-arid Chaco grazing lands:
Chaco’s Potential and Ecosystem Fragility
Forage production varies widely throughout the Argentine Chaco depending on precipitation, length of the rainy season and domination of tree, shrub or tall grass canopies. Forage biomass production in open spaces ranges from 5 to 1.5 tons per year in the East and from 2 to 0.5 tons per year in the West, being almost nil in winter months. Forage quality depends of the presence of medium sized warm season grasses, herbage legumes and cool season grasses. As grasslands lose condition and are dominated by tall grasses that overtop the best species, herbage accumulates during the summer losing digestibility and protein content. The absence of cool season grasses further aggravates this problem in winter.
The cattle population of the Argentine Chaco is less than three million, giving a stocking rate of 10 or more hectares per head. This is only justifiable in a 500 to 1,000 mm rainfall area because scarcity of water points impedes adequate cattle distribution, and poor forage quality means that millions of tons of coarse herbage remain ungrazed to be burned at the end of each winter.
The Pampas Region occupies about 50 million hectares, extending from the 2 °C to the 13 °C isotherm (Figures 3b and 6), enjoying a temperate climate with mild winters without snow-fall (Soriano 1991). Precipitation range decreases gradually from 1,200 mm in the northeast to 500 mm in the ecotonal change to the Monte region. Rainfall is evenly distributed through the year in the eastern wettest areas, while is just concentrated during the warm season in the west.
This Region is characterized by its lack of native trees, flat terrain, fertile soils, extended croplands and native or cultivated pastures. As soils are fertile and summers shorter and milder than in the North, many C3 grasses and temperate legumes species grow during the cooler seasons in these grazing lands. In this way, a seasonal alternation occurs with species of one (C4) or the other (C3) photosynthetic syndrome. Such sequential combination of species characterizes its Meso-Thermic grazing lands.
Species alternation maintains green grass year-long and is ideal for resource utilisation in a seasonally variable climatic environment, where mild water deficits during the summer are better overcome by C4 grasses. From the forage point of view, temperate grasses and legumes of good forage quality (above 20% protein and 70-80% digestibility) allow total utilisation during winter of the remnant biomass of summer grasses. Because of this, there is seldom accumulation of forage during winter in these humid grazing lands.
Native humid grasslands cover the Flooding Pampa, some parts of Entre Ríos Province and most river and stream banks. The warm season components of these grasslands are water efficient, nutrient efficient and regular quality C4 grasses of the Panicoideae, Chlorideae, Andropogoneae and Oryzeae tribes. Alternating seasonally with them, thrive C3 grasses of the Agrosteae, Aveneae, Festuceae, Phalarideae and Stipeae tribes. As soil fertility increases to the West of the Paraná River and South of the Río de la Plata, a myriad of herbaceous legumes grow (Cassia sp., Crotalaria sp., Desmanthus sp., Phaseolus sp., Vicia sp., etc.).
Flooding Pampa grasslands
Because of its flat relief and high water table, more than 60% of the soils of the Flooding Pampa are halo-hydromorphic complexes and associations. The commonest soils are natraquolls, associated with natraqualfs and natrabolls. The degree of sodicity of the soils depends on the depth and salinity of underground water, as well as soil denudation caused by continuous grazing. Soils in the higher parts (15% percent of the whole area) are deeper and have a higher productive capacity, being commonly used for the cultivation of cash crops or improved pastures of fescue (Festuca arundinacea), white clover (Trifolium repens) and Lotus corniculatus. The rest of the area is natural grassland, with the distribution of communities related to the excess of water and salinity. Summer droughts are frequent,with halomorphism and limited soil water storage.
The typical physiognomy of the Flooding Pampa is extended, treeless grasslands (except where trees are planted) and its community is dominated by Dallis grass (Paspalum dilatatum), Bothriochloa laguroides and Briza subaristata. Paspalum quadrifarium and Stipa trichotoma are bunch grasses which dominate the south western part of the area. Where water covers the land during the cooler months the plant community is dominated by Leersia hexandra, Luziola peruviana, Paspalidium paludivagum, Echinochloa helodes and Glyceria multiflora. Communities on halomorphic soils show a low steppe aspect, with sparse cover; the dominant grasses are: Distichlis scoparia, Sporobolus pyramidatus, Chloris berroi, Hordeum stenostachys, Paspalum vaginatum and Diplachne uninervia
Non saline grasslands produce about 5 ton DM ha-1 year-1 with a clear summer peak, a pattern that contrasts with the small variation in standing crop greenness. Forage productivity in winter (July) is 5 kg DM ha-1 day-1, being 30 kg DM ha-1 day-1 in December and January (Sala et al. 1981, Paruelo et al. 2000). Scarce winter production is caused by the depletion of cool season grasses caused by continuous overgrazing of domestic cattle, after windmills and fences were developed 100 years ago. The dominance of warm season grasses and loss of nitrogen fertility further prevent the establishment of cool season grasses every autumn. Low winter productivity controls the carrying capacity and determines the production system of the area: cow-calf operations. Almost 3.5 million cattle roam the six million hectares of the Flooding Pampa, with two million calves exported annually to be raised on pastures in cropland or feed yards. Annual secondary production may be estimated at 90 kg per hectare.
Winter productivity may be significantly increased by hard early autumn grazing or herbicide spraying of the warm season grasses, followed by nitrogen fertilization. This promotes the establishment and growth of annual ryegrass (Lolium multiflorum), an excellent quality exotic grass that thrives well in intermediate communities. Phosphate fertilization may also increase cool season grass production by promoting the density of herbaceous legumes (Lotus tenuifolius and Trifolium repens) that enrich soil nitrogen through fixation. With higher winter forage production, heifers and yearlings may be raised in this sub region grazing lands, increasing three fold annual secondary production.
Cropland Pampas cultivated pastures
Cultivated pastures are grazed by steers, yearlings
or dairy cattle. Forage legumes like lucerne (Medicago sativa),
clovers (Trifolium repens, T. pratense) and birdsfoot trefoil (Lotus
corniculatus) fix nitrogen that is transferred to grasses such as
tall fescue (Festuca arundinacea), canary grass (Phalaris aquatica),
brome (Bromus catharticus), cocksfoot (Dactylis glomerata),
rye grasses (Lolium perenne and L. multiflorum) or Agropyron
elongatum. ANPP of these non fertilised sown pastures during the first
and second year is higher than those given above (8-10 ton DM ha-1
year-1), although plant death and depletion of soil nutrient
availability significantly reduces such productivity during following
years (Oesterheld and León, 1987). When pastures are adequately fertilised
(principally with P), primary production may achieve 12 to 15 ton DM ha-1
year-1 or even more. This primary production allows 500 kg
Nowadays, cash crop prices and the higher profits of agriculture have led to a decrease of cattle numbers in this area. To this add genetically modified soybeans and modern non tillage practices, that reduced the need of pastures / cash crops rotation to maintain soil fertility.
(iv) Semi arid grasslands, Dry forest and Monte shrubland
This region extends along the centre west of
The landscape is hilly and vegetation is open forest dominated by caldén, a leguminous tree (Prosopis caldenia). Other woody species in this forest are chañar (Geoffroea decorticans), jarilla (Larrea sp.) and molle (Schinus fasciculatus). The herbaceous stratum is a group of short grasses with good forage quality, as the unquillo (Poa ligularis), flechilla negra (Piptochaetium napostaense), flechilla fina (Stipa tenuis), gramilla cuarentona (Sporobolus cryptandrus) and pasto plateado (Digitaria californica). Medium sized tussock grasses of low or very low forage quality increase as grasslands deteriorate: Stipa tenuissima, S. gynerioides, S. brachychaeta and Elionurus muticus. Forage productivity is estimated at 1.7 ton DM ha-1 year-1.
Grass steppes are interspersed within the Caldén forest and on higher topographic sites, usually associated with sand dunes. The wind from the west and south west has formed the topography in the past. Today wind is mainly from the north and is an important cause of soil erosion. From August to November, the driest period, fires and dust storms occur. Chañar tree patches can occur inside these grass steppes. Summer grasses with an acceptable quality are the most important grasses (Bothriochloa springfiedii and Schizachyrium plumigerum). In good areas Sorghastrum pellitum is still present, a grass with a remarkable forage quality and production when grazed. In degraded areas Elionurus muticus, a very low quality grass became dominant. Forage production in a good condition grassland can achieve 1.5-2.2 ton DM ha-1 year-1, mainly in summer.
Forage production is both spatially and temporally variable (Figure 9). In piedmont communities of Larrea divaricata (1, 500 m) in Mendoza, total litter yield varied from one to more than five ton DM ha-1 year-1. (Martinez Carretero and Dalmasso 1992). The herbaceous stratum accounts for 130 to 500 kg DM ha-1 year-1 of the total productivity (Braun Wilke 1982). Because of low wool prices, sheep were displaced by cattle as the main domestic ruminant in this area. Nowadays, cattle numbers continue to grow because of their displacement from agricultural areas.
Central Semi-arid Region’s Potentiality
(v) Patagonian cold semi desert
The Andes determine the climate of Patagonia. The N-S axis of the Andes forms an orographic barrier for humid air masses that blow from the Pacific Ocean. The air discharges a great part of its humidity on the Andes, generating the Valdivian rainforest and the sub-antarctic temperate forest, with mean annual precipitation above 2,000 mm. East of the Andes the climate is drier. Mean annual temperature in Patagonia varies between 15 °C in the north and 5 °C in the south. Minimum average monthly temperature is above 0 °C for almost the whole of Patagonia. Precipitation in most of the Patagonian steppes ranges between 125 mm in the centre to 500 mm in the west and falls mainly in winter (April to September). Strong and dry west winds, principally in summer, are a principal feature of the Patagonian climate.
Extra-Andean Patagonia is dominated by plateaux and plains composed of basalt, sand and clay. Soils development is low, with low water holding capacity and organic matter levels. The ranges are grazed by sheep, with the largest population in the country. Four districts are distinguished in Extra-Andean Patagonia (León et al 1998): a) Central shrub steppes, b) Western shrub grass steppes, c) Sub Andean grass steps and, d) Magellanic grass steppes. As in most desert regions oases form in riparian areas, providing abundant, fresh and palatable forage during spring and early summer.
Shrub steppes in the Central District extend over 15 % of the region, from Río Negro to Santa Cruz provinces and from the occidental district on the west to the ocean and the San Jorge gulf district to the east. This corresponds to a transition zone between the semi desert and the shrub-grass steppe. The most representative vegetation is a low shrub steppe; species are Chuquiraga aurea, Nassauvia glomerulosa, Nassauvia ulicina and Chuquiraga avellanedae (quilenbai), and Acantholippia seriphioides (tomillo). Depending on latitude and topographic position different proportions of grass mainly of the genera Stipa and Poa can be found. Forage production is estimated at 490 kg DM ha-1 year-1 with the peak in November.
Shrub steppes of the San Jorge gulf district
extend on the plateaux adjacent to the gulf. Two main vegetation types
can be found in this district: the tall shrub steppes dominated by Colliguaja
integerrima associated with other shrubs such as Senecio filaginoides,
S. bracteolatus and grasses of the genus Stipa (S. humilis
and S. speciosa). The second vegetation type is a grass-shrub steppe
dominated by Festuca pallescens and F.
Shrub grass steppes of the occidental district are widely distributed between 38º to the north and 46º30´ to the south. The 70º meridian is the eastern limit. The shrub component of this steppe is 60-180 cm tall while the tussock grasses are 10-50 cm tall, covering approximately 50% of the soil. One of the most important communities is dominated by grasses of the genera Stipa (S. speciosa; coirón amargo, S. humilis;coirón llama) and Poa lanuginosa (pasto hilo). Good forage quality grasses which are less frequent include Bromus setifolius (cebadilla patagónica) and Hordeum comosum (cebada patagónica). The shrub layer is dominated by Senecio filaginoides (charcao o mata mora), Mulinum spinosum (neneo) and Adesmia campestris (mamuel choique). Berberis heterophylla (calafate) and Schinus polygamus (molle) are other less important shrubs: average primary production is 560 kg DM ha-1 year-1, ranging from 210 to 750 kg DM ha-1 year-1 (Fernandez et al. 1991; Jobbagy and Sala 2001). Primary production is on average equally divided between grasses and shrubs.
Shrub grass steppes of the Sub-Andean district occupy a narrow portion on the eastern slope of the Andes and constitutes the ecotone between the forests and the shrub grass steppes from Neuquén in the north to Tierra del Fuego in the south. Annual precipitation is over 300 mm. The physiognomy is very homogeneous grassland with a very low shrub cover, except in highly degraded sites. Festuca pallescens (coirón blanco), Rytidosperma picta and Lathyrus magellanicus are the dominant species of this area. Forage production may reach 900 kg DM ha-1 year-1 with a peak production in December (Bertiller and Defosse 1990).
Grass steppe of the Magellanic district is located in southern Santa Cruz and northern Tierra del Fuego with a cold and oceanic climate. Vegetation physiognomy is a grass steppe dominated by Festuca gracillima 30-40 cm. tall.
Meadows - wherever water flows from springs or aggregates in very different topographic positions (slopes and valleys), it is associated with meadows that occupy less than 5% of the whole territory. These are dominated by grasses and cyperaceous species and are highly productive, forage production reaching 7,000 kg DM ha-1 year-1. Overgrazing on these areas induces denudation and salinization and gully formation from water and wind erosion.
Land Use and Animal Production
A hundred years of continuous grazing by domestic herbivores hampered the ecological sustainability of the Patagonian steppes. Several authors consider that grazing had a main role in the environmental and productive degradation in Patagonia. The Patagonian sheep population has declined over the last decades from 20 million in 1952 to 11 million in 1993. Highly selective sheep foraging has reduced the density and vigour of the highest quality plant species.
(vi) Puna and High Andes grass steppes
The vegetation is characterized by grass and shrub-grass steppes, halophyte steppes and meadows (Ruthsatz and Movia 1975; Cabrera 1976). In terms of vegetation, the Puna is close related to Patagonia, because of the common dominant genera. Grasses primarily belong to the genera Calamagrostis, Agrostis and Festuca and shrubs of the genera Fabiana, Lepidophyllum, Chuquiraga, Nardophyllum, Mulinum and Adesmia. Characteristic formations include five main communities:
1. Shrub steppe dominated by Fabiana densa, Baccharis boliviensis and Adesmia horrida;
2. Cardonales, dominated by Trichocereus pasacana
3. In the wettest areas, small forest dominated by Prosopis ferox (fabaceae) or Polylepis tomentella (rosaceae).
4. Meadows with Scirpus atacamensis, Heleocharis atacamensis, Juncus depauperatus, Plantago tubulosa, Hypsela oligophylla
5. On saline and temporally wet soils, Festuca scirpifolia, Juncus balticus and Hordeum halophilum.
|6. OPPORTUNITIES FOR IMPROVEMENT OF FODDER
Several technologies may improve the carrying capacity in the semi-arid rangelands, such as
(i) water development,
Improvements in forage production and utilisation will not increase beef output from Argentinean rangelands, without an adequate nutritional management of the grazing animals. The lack of nitrogen and phosphorus supplementation to satisfy animal requirements determines the nationwide inefficiency of beef cattle production and low weaning percentage (barely 60%). Prolonged dry winter periods reduce protein content in the forages provided by the semiarid rangelands. Senesced summer grasses that overtop the winter ones (and prevent their growth) determines the need for autumn and winter nitrogen supplementation in the humid grazing lands. As the soils of this humid region lack phosphorus, good conception rates and fast animal growth is hampered. Nutritional limitations of P may be overcome through an adequate supplementation programme and by soil fertilization. Energy deficiencies in winter are overcome easily by grain supplementation and grassland cultivation.
Pasture seed production and marketing
Table 6. Pasture seed production and importation for 2000/01. The eight named forages in the table represent almost 90% of the seed produced. [NB. only certified seed is considered for produced and imported seeds, but non-certified seed is an important part of the market, thus the discrepancy between totals].
|7. RESEARCH AND DEVELOPMENT ORGANIZATIONS
Institutional structure The National Secretary for Agriculture, Livestock Production, Fisheries and Food leads the national politics on the area. Each of the provinces has its own federal secretary for the area. Several national institutions such as the INTA, the SENASA and the universities (see links below) are important for local research and development.
Links The key organizations and their current areas of activity/interest with relevance to pasture and animal production are as follows:
National Secretary for Agriculture, Livestock Production and Fisheries www.sagpya.mecon.gov.ar/
National Institute for Agriculture and Animal Production Technology (INTA). www.inta.gov.ar
National Animal Health Service www.senasa.gov.ar/
National Patagonian Centre, Arid Zones Ecology www.cenpat.edu.ar/ecozoaridas/idxingle.htm
Institute for Arid Zones Research www.cricyt.edu.ar/institutos/iadiza/default.htm
Faculty of Agronomy, Universidad de Buenos Aires www.agro.uba.ar
Faculty of Agronomic Sciences, Universidad Nacional del Litoral www.fca.unl.edu.ar/
Darwin Institute, www.darwin.edu.ar/
Chamber of Seed Traders (CSBC), www.argenseeds.com.ar/
Argentine Association of Regional Consortiums for Agricultural Experimentation (AACREA), www.aacrea.org.ar/
Argentine Association for Animal Production (AAPA) www.aapa.org.ar/
Laboratory for Regional Analysis and Remote Sensing, www.agro.uba.ar/lart
Argentine Rural Association (SRA), www.ruralarg.org.ar/
Federación Agraria Argentina, www.faa.com.ar/