OPUNTIA SPP. FOR FODDER AND FORAGE PRODUCTION IN ARGENTINA: EXPERIENCES AND PROSPECTS

Juan C. GUEVARA and Oscar R. ESTEVEZ

INTRODUCTION

Cactus is extensively used as an emergency livestock feed during times of extreme droughts, i.e. a kind of “drought insurance” (Le Houérou, 1994), in arid and semi-arid areas of the world (northeast Brazil, Mexico, southern Africa, USA, and the Mediterranean Basin).

Cactus plantations in Argentina have increased from around 90 ha in 1993 to 840 ha in 1997. Most of the plantations are located in the Provinces of Tucumán (39%), Catamarca (22%), Santiago del Estero (14%), La Rioja (12%) and Salta (10%) (Ochoa de Cornelli, 1997). Among the main traditional, current and potential uses of cactus (Barbera, 1995), the consumption of fruits, fresh or processed in syrup, is the most important in Argentina (Ochoa de Cornelli, 1997). Most of the cactus producers use cactus as an activity complementary to their agricultural systems. Cactus production is very popular in smallholder operations, where the cladodes are used as forage for cattle and goats (Ricarte et al., 1998), although mainly in winter, when the water supply for livestock is limited (Ochoa de Cornelli et al., 1992).

A few studies and experiences have been reported on cactus as fodder and forage in Argentina. The ecological productivity and the nutrient content of the cladodes (Braun et al., 1979), the current status of plantations (Ricarte et al., 1998) and their productivity under different management practices (Reynoso et al., 1998) have been studied for Opuntia ficus-indica L. f. inermis (Web.) Le Houérou in Los Llanos of La Rioja Province.

Our studies with Opuntia spp. began in the Mendoza plain at the end of 1995 in response to the suggestions of Le Houérou (1995a). The experiments comprised effect of fertilizers, irrigation and planting distances on the above-ground biomass production (experimental work still in progress at time of writing); evaluation of plant survival and production in marginal lands (Guevara et al., 1997); micropropagation of O. ellisiana, material with low availability of planting stock (Juárez and Passera, 1998); and cold hardiness of Opuntia species and clones (in progress). At the same time, the economic feasibilities of cactus plantations for cattle (Guevara et al., in press) and goat production (Guevara et al., 1999) have been assessed.

This chapter summarizes the studies and experiences in Argentina on opuntia for forage production and its prospects.

BIOCLIMATIC CLASSIFICATION OF THE ARID AND SEMI-ARID ZONES

Data from around 40 weather stations were classified (Le Houérou, 1999) based on two main indices: the rainfall (R) to potential evapotranspiration (PET) ratio (R/PET), representing the water stress; and the mean daily minimum temperature of the coldest month (m), representing the winter thermal stress. These two criteria allowed the construction of the orthogonal matrix shown in Figure 8. The discriminating threshold values in the classification were:

The weather stations were also classified according to the rainfall regimes: tropical (over 70% of annual precipitation falling during the summer season); Mediterranean (over 70% of annual precipitation as winter rains); and well balanced (between 40 and 60% of annual rainfall in winter).

The absolute minimum temperatures for most of the weather stations ranged from -5°C (La Rioja) to -13.9°C (Chos Malal, Neuquén). The lowest temperatures recorded were -18°C (El Divisadero, Mendoza) and -23.6°C (Malargüe, Mendoza).

Figure 9. Location of weather stations in arid and semi-arid zones of Argentina

KEY TO SITES

1 Santiago del Estero
2 Andalgalá
3 Tinogasta
4 Catamarca
5 Chilecito
6 La Rioja
7 Chepes
8 S.J. de Jachal
9 Punta del Agua
10 San Juan
11 Barreal
12 Villa Dolores
13 Mendoza
14 La Paz
15 El Divisadero
16 San Carlos
17 San Rafael
18 General Alvear
19 Malargüe
20 San Luis
21 Unión
22 Santa Isabel
23 Puelches
24 Chos Malal
25 Las Lajas
26 Cutral-Có
27 Cipoletti
28 Choele Choel
29 Río Colorado
30 Maquinchao
31 San Antonio Oeste
32 Carmen de Patagones
33 Puerto Madryn
34 Trelew
35 Sarmiento
36 Comodoro Rivadavia
37 Gobernador Gregores
38 Puerto San Julián
39 Puerto Santa Cruz
40 Lago Argentino
41 Río Gallegos

MAIN CONSTRAINTS FOR CACTUS PLANTATIONS

Temperature

Under different climatic conditions, the thermal limit for frost-sensitive species such as Opuntia ficus-indica is indicated by an m of 1.5 to 2.0°C in the arid steppes of North Africa (Le Houérou, 1995b).

The authors’ observations from several species and clones established in the Mendoza plains suggest that winter cold temperatures are the major limitation to cultivation of cactus in this area. When night temperatures in El Divisadero dropped to -17°C in August 1999, the young cladodes from 9-month-old plants of O. ficus-indica were almost destroyed, while the 3-year-old plants of O. ficus-indica, O. spinulifera Salm-Dyck f. nacuniana Le Houérou, f. nov. and O. robusta Wend. had mean frost damage of 25, 5 and 2%, respectively.

Experiments to evaluate forage production of the cold-hardy forage species O. ellisiana Griff. and the cold-hardy clone #1233 (hybrid between O. lindheimeri Engelm. and some unknown parent) have recently begun in the Mendoza plains. This material is being tested because O. ellisiana was not damaged when temperatures at Kingsville, Texas, dropped to -12°C in 1989 (Gregory et al., 1993). Furthermore, O. ellisiana experienced no damage and clone #1233 had only slight damage from this freeze when temperatures of -20°C were recorded on a site located about 500 km north of Kingsville (Wang et al., 1997).

According to Han and Felker (1997), the average water use efficiency (WUE) of O. ellisiana was 162 kg H₂O per kg DM. This is among the highest WUE of any plant species measured under long-term field conditions.

However, O ellisiana is a slower growing species compared to O. ficus-indica. In fact, the productivity O. ellisiana/O. ficus-indica ratio ranged from around 0.35 (Han and Felker, 1997) to 0.5 (H.N. Le Houérou, pers. com.). Considering that the WUE measured for O. ficus-indica was 250-300 kg H₂O per kg DM (Le Houérou, 1996a), the WUE of O. ficus-indica is about 55 to 85% lower than O. ellisiana. Thus, we can assume that the lower productivity of O. ellisiana could be explained by its higher transpiration ratio. Clone #1233, introduced by P. Felker at Santiago del Estero, has exhibited high above-ground biomass productivity there (P. Felker, pers. com.).

Rainfall

Cactus and other drought-tolerant and water-efficient fodder shrubs (DTFS) can survive under rainfall as low as 50 mm in a particular year, but with neither growth nor production (Le Houérou, 1994). Mean annual rainfall of 100-150 mm corresponds to the minimum required to successfully establish rainfed plantations of DTFS (Le Houérou, 1994), provided soils are sandy and deep (Le Houérou, 1996a). These limits can be applied in the Mediterranean Basin, and North and South America (Le Houérou, 1994). Thus, cactus plantations are eliminated from the arid (R/PET < 0.03; R < 50 mm) and hyper-arid (0.03< R/PET < 0.06; 50 < R < 100 mm) regions of Argentina.

Land tenure

Land tenure often constitutes a paramount constraint. The establishment of shrub plantations requires long-term planning, relatively heavy investments and therefore land tenure security that provides possible returns for such heavy investments. Land tenure and the control of livestock movements are therefore prerequisites for shrub development (Le Houérou, 1996b).

ABOVE-GROUND BIOMASS PRODUCTIVITY

Soil texture and rainfall are the main factors related to productivity of O. ficus-indica (Table 29). On sandy soils, productivity ranges from 2.1 to 2.4 t DM/ha/year in areas with 300 mm of rainfall. This translates into mean rainfall-use efficiency (RUE) of 7.4 kg DM/ha/year/mm. These yield and RUE values are lower than those in arid lands under mean annual rainfall of 200 to 400 mm on deep, sandy soils (3 to 9 t DM/ha/year and 15 to 22.5 kg DM/ha/year/mm, respectively) when competition from native vegetation and weeds was kept under control (Le Houérou, 1996a). The low yield from El Divisadero cactus plantation is probably due to its unweeded condition, as they produced 300% less biomass production than weeded plots (Felker and Russell, 1988). On silty sand soils, productivity reached only 0.75 t DM/ha/year at a site with rainfall slightly higher than 200 mm, i.e. a RUE factor of only 3.5.

Table 29. Above-ground biomass production from Opuntia ficus-indica in Argentina

Sources: (1) Braun et al., 1979. (2) Reynoso et al., 1998. (3) Present authors’ data. (4) n.a. = not available.

MICROPROPAGATION OF OPUNTIA ELLISIANA

O. ellisiana was multiplied from explants containing areolas using in vitro culture techniques (Juárez and Passera, 1998). The sterilization procedure that showed the best results (only 12% areolas infected) consisted of the immersion of the entire cladodes in sodium hypochlorite plus Tween 80, and then in benzalkonium chloride solution.

Explants were cultivated in Murashige and Skoog culture medium, supplemented with sucrose and different Indole-3-butyric acid (IBA) and 6-benzylaminopurine (BAP) concentrations, at 27±2°C, 100% relative humidity and a 16-hour photoperiod. Explants in the medium containing 2.25 mg/litre BAP and 2.0 mg/litre IBA showed 100% shoot development in 35 days of culture. The mean shoot length was 10.2 mm after 49 days.

A 100% root induction in shoots was obtained in a medium with 5 mg/litre IBA after 12 days in culture. The highest numbers of roots were obtained when the entire shoots were cultivated in a medium supplemented with 5 mg/litre and 10 mg/litre IBA after 48 days of culture.

The acclimatization of in vitro regenerated plants was accomplished in a greenhouse and the plants showed good performance when transferred to soil.

ECONOMIC FEASIBILITY OF FORAGE OPUNTIA PLANTATIONS

Cattle production

The economic feasibility of 50, 100 and 200 ha cactus plantations in the Mendoza plains was examined by simulation models (Guevara et al., in press). Models were run with 200, 300 and 400 mm annual rainfall and two management systems: cut-and-carry (CAC) for pen feeding, and direct browsing (DB). The study was based on several assumptions related to spacing and density strategies, planting material availability, yield and utilization schedule, nutrient content of the pads, composition of cattle daily ration, and opportunity cost of prohibited grazing.

Two approaches were used to assign monetary values to the cactus feed and the range forage forgone by livestock. In the first approach, the shadow prices were calculated using the regional prices of metabolizable energy (ME) and crude protein (CP) in concentrates (EP shadow price). In the second approach, the authors assumed the shadow price to be the price of steer meat on the hoof at the producer level (SM shadow price). This latter approach also assumed a conversion rate of 115.4 MJ of ME per kilogram of liveweight gain (Le Houérou, 1989). Thus, the monetary values (US$ per tonne DM) were 95.4 (EP) and 66.3 (SM) for cactus and 102.2 (EP) and 59.4 (SM) for range forage production.

Information obtained through the establishment and monitoring of experimental cactus plantations in the Mendoza plains was used to estimate the establishment cost (Figure 10). The values correspond to the mean of the two shadow prices. This cost ranged from around US$ 1 490 (50-ha plantation; EP shadow price) to US$ 850 (200-ha plantation; SM shadow price) in the CAC system,

Figure 10. Average establishment cost of cactus plantations in the Mendoza plains according to plantation size and management system

(Source: Guevara et al. in press)

Using 12% as the capital opportunity cost and the shadow price of meat, cactus production was found to be feasible in DB systems with 300 mm rainfall on a 100 ha plantation and with 400 mm rainfall on a 50 ha plantation; and in the CAC systems with 100-200 ha plantations and 400 mm

Figure 11. Internal rates of return (IRRs) from cactus plantations in the Mendoza plains according to plantation size, rainfall and management system

(Source: Guevara et al., in press)

The economic analysis did not take into account the secondary benefits mentioned by Le Houérou (1994, 1996a), such as runoff and erosion control, climate buffering, increased land fertility, landscaping and amenities, stabilization of animal production and reduction in the cattle water requirement. This resulted in a very large underestimation of the economic impact of cactus plantations.

Without the incorporation of cactus plantations, the cow-calf operation size necessary to yield positive returns in the Mendoza plains was estimated to be 37 500 ha (Guevara et al., 1996). If a 3-year cactus production accumulation and a daily consumption of 36 kg of fresh cactus material per animal unit (AU) were assumed, the cactus plantation required to feed all the cattle (1580 and 2270 AU in areas with 300 and 400 mm rainfall, respectively), for the entire year in this cow-calf model would be about 0.3% of the ranch size. This cactus plantation would increase the current ranch investment by 7 to 10% (Guevara et al., 1996).

Goats for meat production

The study addressed small-scale stockmen (50-200 does), located in areas with mean annual rainfall below 200 mm (Guevara et al., 1999). Their goat production systems have the following characteristics: (i) goats are basically fed on rangelands, (ii) most of the goats kid in the dry season (autumn-winter), when the forage on offer is insufficient to meet the nutrient requirements for goat lactation; and (iii) there is high kid and doe mortality as a consequence of the feed deficit in this period.

A simulation model examined costs and benefits derived from the introduction of cactus plantations into these goat production systems. Several scenaRíos were generated by varying the goat herd size (50, 100, 150 or 200 does) and the annual rainfall probability (f) from 0.1 to 0.9.

The assumptions were, in general, the same as those described earlier. However, some particular aspects were included in the study. Cactus plantations could be established in bare areas near settlements of the herders where no grazing currently occurred due to overgrazing and wood extraction. Herbaceous vegetation, which could grow in the inter-row alleys, was scarce and therefore the opportunity cost of prohibiting grazing in the cactus plantation was not considered. Only 10% of the wages were included as goat herder opportunity cost. The method of management proposed was cut-and-carry.

This type of management is recommended for areas in which there is insufficient grazing discipline and therefore a high risk of cactus plantation destruction (Le Houérou, 1989).

A decrease in doe annual mortality from 10 to 2% and an additional annual amount of kids per goat were considered as the direct benefits derived from the reduction of forage deficit in the autumn-winter period. An external benefit was the reduction of water consumption by goats in terms of the monetary value of the labour not used for obtaining water.

Figure 12 shows the establishment cost of cactus plantations for three selected rainfall probabilities. Costs ranged from US$ 525/ha (50-head goat herd; f 0.1) to US$ 242/ha (200 head goat herd; f 0.9). The cost of establishment could be considered high and not all the stockmen could afford such investment. The cost of installing the fence, the main item of the establishment cost in most of the scenaRíos analysed, could be reduced if thorn hedges were considered. Thorn bush fences could be established for only 40% of the cost of metal fence (Le Houérou, 1989). A fence made of a double row of spiny cactus at a distance of 1 m and a space of 1 m between plants should be established at least two years before cactus planting (Le Houérou, 1989).

The annual additional amount of kids required to reach an internal rate of return (IRR) equal to the opportunity cost of capital (12%) is shown in Figure 13. This amount increased as annual rainfall probability increased, i.e. as cactus production decreased. An annual additional amount of 0.2 kid per goat seems possible in practice because of supplementing goats with spineless cactus. In a 50-head goat herd, the threshold of 0.2 kids is reached at f 0.5. The same number of kids is attained at f 0.7 to f 0.8 in 150- and 200-head goat herds.

If dependable rain (f 0.8) is considered, the additional kids per goat required to reach 12% IRR would range from 0.21 to 0.29 for 200- and 50-goat herd size, respectively. Further research is needed to establish, under field conditions, the actual additional amount of kids that might be obtained as a consequence of supplementing goats with spineless cactus in the dry season.

Figure 12. Total costs of cactus plantation establishment and fence installation cost in the Mendoza plains, for three annual rainfall probabilities (f) and four goat herd sizes

(Source: Guevara et al., 1999)

Figure 13. Annual additional amount of kids per goat required to reach 12% IRR in the Mendoza plains according to annual rainfall probability and goat herd size

(Source: Guevara et al., 1999)

PROSPECTS AND RECOMMENDATIONS

Cactus plantations could be successfully developed in most of the arid and semi-arid zones of Argentina, provided frost-tolerant species or clones were used. The trials that have been carried out indicate that O. spinulifera Salm-Dyck and O. robusta are the most frost-tolerant species and hence the most promising for cactus forage production programmes.

The establishment cost of cactus plantations appears to be high and out of reach of most ranchers and graziers. Intensive research and extension efforts are needed to make cactus plantations more attractive to them in terms of feed value, their role as “drought insurance” and economic benefits, and in particular reducing the cost of establishment. At the same time, government should consider appropriate incentives and legal tools favouring security of land tenure.

The system applied in Tunisia for Acacia saligna and in Syria for Atriplex halimus (Le Houérou, 1996b) could be adopted in Argentina. It is based on the planting of state-controlled land. Such plantations, usually fenced and excluded from stock, are opened to graziers on a temporary basis, subject to payment of a grazing fee, under the control of the Forest Service, who decides on the time of plantation use, on the number of animals admitted and on the fee per animal/day to be paid.

Furthermore, in Tunisia, there are legal incentives for fodder production development. These incentives include state assistance through loans, when economically justified, for establishing fodder shrub plantations, in particular using spineless cacti, saltbushes and acacias (Le Houérou, 1996b).