RESEARCH WORK
Agrosilvopastoral designs in the context of developing a sustainable livestock production. Notes for knowledge
J. M. Iglesias, F. Funes-Monzote, Odalys C. Toral, L. Simón y Milagros Milera
Estación Experimental de Pastos y Forrajes "Indio Hatuey". Central España Republicana, CP 44280, Matanzas, Cuba
E-mail: jesus.iglesias@indio.atenas.inf.cu
ABSTRACT
The objective of this work was to review the utilization of agrosilvopastoral systems in different subtropical regions, with emphasis on Cuban conditions. In it the main concepts of these agroforestry systems are described, as well as the advantages and disadvantages of their application. The principal outputs and designs of different agrosilvopastoral systems studied in Cuba, Brazil and Colombia are analyzed, showing the possibility of their implementation under conditions of high fragility and productive limitations, without altering the ecological stability and with acceptable economic results. An important part of the work is the description of the characteristics of home gardens in Cuba, which are highly diverse regarding the quantity of species and varieties, and very complex and varied in structure and associations. To increase the use of agrosilvopastoral systems in the context in which current livestock production systems are developed is recommended, due to their economic-productive results and their contribution to the balance of agroecosystems.
Key words: Agrosilvopastoral designs, mixed home gardens.
INTRODUCTION
The serious affectations of natural resources and the current economic and social crisis several countries go through have revitalized the interest in achieving an accelerated and sustained development of agriculture, which will only be reached when production strategies are in agreement with the rational use of the ecosystem. In this context, visualizing the livestock production activity in agroforestry systems constitutes a valid, necessary and current approach in research and training for livestock development in the tropics.
With the application of agroforestry techniques, the agricultural and livestock production activities acquire a permanent character: their development does not require high inputs, because the machinery use is minimum, no high doses of fertilizers or pesticides are necessary to sustainably maintain the production system. In this sense, agroforestry systems are presented as a challenge for the livestock production sector, for being an economically viable, socially accepted, solution, and which does not produce environmental damage.
Under the name agrosilvopastoral systems (ASPS) a group of land use techniques is gathered, implying the deliberate combination or association of a ligneous component (forestry or fruit) with livestock and/or crops on the same land (Nair, 1985; Nair, 1989), with significant ecological and/or economic (Kapp, 1989), or only necessarily biological interactions (Somarriba, 1998), among the components.
According to Pardini (2007), they are complex systems, which integrate pastures, forage crops, varied crops, animals and different resources, including forestry and agriculture. The integration can occur within the resource (for example, pasture associated to trees), within the farm (livestock grazing cereal stubble and in the forest), or within a large territory (examples associated to nomadism and transhumance).
The objective of this work is to review the utilization of agrosilvopastoral systems in different subtropical regions, with emphasis on Cuban conditions.
Advantages and disadvantages of the use of agrosilvopastoral systems
Several authors have analyzed the advantages and disadvantages of ASPS. According to Ruiz (1983), some of the factors that favor the presence of livestock production in ASPS are:
On the other hand, it is also important to acknowledge that there are also disadvantages. The most important ones are:
Implementation of agrosilvopastoral arrangements in established forest and fruit areas
The current economic situation undergone by developing countries of the American subtropical area has forced to reorient productive systems, for which the recovery of these agrosilvopastoral technologies has began, mainly aiming at allowing livestock production activities under high fragility conditions and with productive limitations, where a more efficient economic management is sought, altering only slightly the ecological stability; this contributes to reach sustainability of the production systems and, subsequently, improve the living conditions of the rural population (Renda et al., 1997).
In this sense, Merlán et al. (2005) showed the economic feasibility of the implementation of an agrosilvopastoral system as compared to the traditional forestry system, from the determination of the expenses and the incomes generated by each activity, and the cost-benefit ratio of the new implemented system.
The inclusion of sheep for grazing in forest plantations and the development of beekeeping in that forestry area, propitiated the diversification of production and income increase for the farmer and the system, with values over 40 000 pesos, as compared to only 1 711 pesos in the traditional extractive system. Thus higher net profits (12 491,6 pesos) were achieved and the cost-benefit ratio was higher than one (2,87), which implied obtaining earnings.
On the other hand, Mosquera et al. (2005) transformed forestry areas of Albizia saman and Enterolobium cyclocarpum and of the fruit trees Pauteria mammosa (mamey) and Mangifera indica (mango) into integrated systems with animal grazing, where they included cattle and sheep as an additional source of income in the farm.
As a result of this agrosilvopastoral design the floristic composition of the companion pasture was remarkably improved, decreasing the maintenance and weeding expenses of the plantations. Sheep meat productions of 61 g/animal/day and 0,54 t of meat/year were achieved; while the annual average milk production was 4,0 kg/cow, with a total production of 1 423 kg, in addition to an increase in the pod and fruit production of the tree species (0,63 and 0,86 t/ha for A. saman and E. cyclocarpum and 9,2 and 10,1 t/ha in mango and mamey, respectively).
Calzadilla (cited by Renda et al., 1997) obtained similar results regarding animal production, by introducing animals of the Pelibuey sheep breed under a four-year-old plantation, constituted by Khaya nyasica, Khaya senegalensis and Swietenia macrophylla, in order to utilize the existing availability of pasture biomass (Panicum maximum) under the tree canopy. With a stocking rate of 11 animals/ha, in the category of growing ewes, 66 g of daily gain were obtained, while in fattening it was 57,5 g/animal/day.
The fruit tree yield is in correspondence with the one obtained by Muñoz et al. (2001), who achieved increases in the number of harvested products, in total production and in the fruit yield from 0,5 to 6,0 t/ha, in an agricultural/livestock production integrated system under fruit trees. Also Ramos et al. (2001) obtained an increase in the number of harvested products (from one to more than 15) and in the yield (0,9-5,6 t/ha), in a farm based on the livestock production/agriculture integration.
Use of the agricultural component in the establishment of grazing-browsing systems
In the integrated establishment of trees, pastures and livestock, several concerns of farmers stand out, and among the most frequent ones are: the lack of income due to the relative low growth rate of trees, the optimum spatial and temporary location of the species included and their selection.
In this sense, several studies have been conducted in order to contribute to the adequate orientation about the establishment of agrosilvopastoral arrangements adjusted to the biological, technological, social and economic realities of different regions of the American subtropics, where the inclusion of the agricultural component has had as its objective making a better use of the soil and obtaining short-term additional productions and incomes, while the tree reached adequate growth for the introduction of the animals.
Regarding this, Roncallo et al. (2009) planted beans (Phaseolus vulgaris) and corn (Zea mays) simultaneously with leucaena in the spaces between rows of this ligneous plant. Arrangements were evaluated with the later inclusion of forage grasses (Botriochloa pertusa and P. maximum) and double-purpose livestock production, through the following treatments: A) monocrop of B. pertusa; B) leucaena associated to B. pertusa, and C) leucaena associated to P. maximum cv. Tanzania.
If production costs per hectare are estimated in 1 507 pesos and based on an average yield of 194 kg of beans/ha, the system generated an additional income of 403 400 pesos/ha; while the bean planting could be performed in both semesters during the first year of establishment of the tree.
Regarding the growth of leucaena, increases were recorded in height, higher than 20,5 and 29,0 cm in the plants associated with bean and corn, respectively, as compared to the non-associated ones, which can be ascribed to the weed control additionally made in the crops.
The milk composition analyses recorded better indicators in agrosilvopastoral systems as compared to the B. pertusa monocrop. In the arrangements of leucaena with P. maximum and leucaena with B. pertusa it showed total solid contents higher than 1,23 and 1,09%; likewise, the fat contents were higher in 0,68 and 0,71%, respectively; this effect can be ascribed to the higher nutrient supply contributed by agrosilvopastoral arrangements.
These authors (unpublished data) evaluated an agrosilvopastoral arrangement composed by Pachira quinata, Leucaena leucocephala, P. maximum cv. Tanzania, Clitoria ternatea and Manihot esculenta (cassava), where P. quinata was planted at a distance of 7 m between rows and 3 m between plants and L. leucocephala was sown amid the rows (3,5 m) of the P. quinata trees, with a separation of one meter between plants. In the first establishment stage, in the free spaces of the rows between P. quinata and L. leucocephala, cassava was planted, with a planting distance of 1 x 1 m. Once the cassava was harvested, the area occupied by it was established with P. maximum and C. ternatea, using a planting density of 6 kg seed/ha in both species.
Acceptable yields of cassava/plant (5 688 kg) were obtained, which is equivalent to an estimated production per ha of 32,5 t and to 58% of the production in monocrop. This difference is associated to the higher population established in the monocrop (10 000 plants/ha vs 5 714 plants/ha in the agrosilvopastoral design).
No effect was apparent of the animals on P. quinata in the evaluation period (120 days); on the contrary, 36 months after transplant to the definitive site and taking into consideration the planting density of 467 trees/ha, it produced 13,4 m3 of timber/ha and 0,028 m3/tree.
From the economic point of view, the indicator internal rate of return (IRR) showed that the technological proposal is viable, with a profitability of 76% and a net present value of the economic cash flow of 24 406 873,82 pesos. Likewise, the investment return factor in time for the system occurred in the second year, due to the cassava production and sale.
The economic kindness found in this agrosilvopastoral system corroborates the conclusions reached by Roncallo et al. (2009), who stated the need for different technological alternatives for the traditional beef and bull fattening systems of the micro-region Valle del Cesar, which show low profitability and little competitiveness.
In Brazil the Compañía Minera de Metais for zinc production, in the Minas Gerais state, developed since 1993 their own technology of reforestation with hybrid eucalyptus clones (Eucalyptus camaldulensis x Eucalyptus grandis, Eucalyptus camaldulensis x Eucalyptus urophylla and Eucalyptus camaldulensis x Eucalyptus tereticornis) well adapted to the local edaphoclimatic conditions, productive and which showed higher quality timber for obtaining multiproducts (Dubè et al., 2001).
At the moment of establishing the rotational agrosilvopastoral system these eucalyptus clones were used, planted at a distance of 10 m between rows and 4 m between trees to allow rice (Oryza sativa var. Guaraní) plantations between rows in the first year, soybean (Glycine max var. Doko, Conquista and Vitória) in the second year, and pasture (Brachiaria brizantha) since the third year, with a stocking rate estimated in 1,0 AU (animal unit)/ha in the summer and 2,0 AU/ha in the summer. Ninety days after the pasture insertion cattle fattening began.
From this design calves are acquired biannually and a necessary period of two years is considered for fattening. Thus, every two years the fattened bulls are sold and substituted by calves to begin a new fattening cycle.
The one-year-old Zebu calves (Bos indicus), and with an average weight of 75 kg, are sold after two years with 225 kg live weight, ready to be slaughtered. At slaughter the yield reaches a mean of 75 kg of beef per hectare and per year. Thus, the firm slaughters 1 500 bulls/year.
In order to delimit the reforested areas and control the understory, since they are 11 years old, the trees are used as living poles, forming the so-called eucacerca. In it, galvanized wire is passed through perforations in the trees, as if they were normal poles. In time the trees progressively close the holes and the wire is inserted in the wood, forming a highly resistant fence. The eucacerca costs approximately $300 USD per built kilometer, while the conventional fence costs $1 200 USD (Anonymous, 1998). Thus, a living fence allows reducing material and labor expenses, and only the expense of galvanized wire is maintained.
The incomes are obtained from the sale of the following products: rice, soybean, fattened cattle, and timber for the sawmill and the energy. The production of each product is multiplied by the corresponding sale price to obtain the income value per product. The productivity is considered to be 23,33 m³/ha/year and 60% of the timber produced is for energy and 40% for the sawmill. Eucalyptus is cut when it is 11 years old and a production of 257 m³/ha is obtained, from which 154 m³ (60% of 257 m³) are for energy and 103 m³ (40% of 257 m³) for the sawmill.
In the last 15 years this practice has been widespread in Cuba, with special attention to the cultivation of short-cycle grains and cucurbitaceous plants during the establishment of silvopastoral systems (Iglesias and Hernández, 2005; Simón, 2005). This modality of «Cuban taungya» consists in planting corn, beans, squash, watermelon, cucumber and other crops, simultaneously with leucaena and other forage trees, in dairy farms and development units selected for the implementation of large-scale silvopastoral systems. Once the short-cycle crops are harvested, the land is ready to plant the pastures of the system, which should not interfere with tree growth, because they reach for that stage an adequate height and develop a strong root system which allows them their later growth and exploitation.
The difference between this taungya modality and the traditional system is that the future of trees is not timber production, but animal browsing, for which the crop planting is done only once and they are immediately substituted by pastures.
Reyes et al. (2000), in a dairy unit of the Nazareno Livestock Production Enterprise (Havana), without irrigation, studied the feasibility of intercropping black beans (P. vulgaris) during the establishment stage of L. leucocephala in paddock areas of that dairy unit.
The tree was planted in strips, with minimum soil preparation, and a randomized block design with three repetitions was used. The treatments were: A) two leucaena rows (control); B) two leucaena rows plus two bean rows; and C) two leucaena rows plus one bean row. Beans were planted simultaneously with leucaena, on both sides of its rows.
No significant differences were found in the indicators height and branch number in leucaena; while the utilization of P. vulgaris allowed obtaining 0,9-1 t of additional grain/ha, as well as 2-2,5 t of harvest residue for feeding ruminants, which also meant an additional capital of 9 000 pesos, if the price of beans is considered as 9 pesos/kg.
These results coincide with the reports made by Simón and Cruz (1998), who stated that the investment in the promotion and development of silvopastoral systems can be reduced if tree planting is accompanied by agricultural crops with a short production cycle.
When comparing the traditional tillage system with the strip system, a 53,4%-reduction was found of the fuel expense, if an estimate of 94,38 and 43,93 L/ha is considered for each system. These results corroborate the statements made by Simón et al. (1998) who when using strips reduced the soil preparation works in 40-50%, which cost varied between 24 and 30 pesos/ha.
The practice of this system contributes important earnings for livestock production farmers involved in the establishment of trees for milk and meat production. The costs for establishing a hectare of silvopastoral system vary between 226,91 and 346,85 pesos depending on whether the establishment is made on established pastures (strips) or on areas to be planted (conventional preparation). By sowing short-cycle crops during the plantation establishment between 448,0 and 10 140,0 pesos/ha are obtained because of harvest sale, for which in most cases the initial investment is paid, even without exploiting the livestock production system (table 1).
To recover the investment in planting the trees according to current prices, from 1,2 physical ha of beans are necessary for the conventional method to 11,0 physical ha of cassava (strips); while squash and sweet potato occupy intermediate positions.
On the other hand, Padilla et al. (2000), when evaluating the effect of intercropping Vigna unguiculata and Z. mays with L. leucocephala cv. Peru and P. maximum cv. Likoni, concluded that the plants per square meter, plant height, branches per plant and yield (t of dry matter/ha) of leucaena were not affected due to the planting of Guinea grass, corn and beans, and there was no competition among these species. The best option was the intercropping of three bean rows in May at the moment of planting leucaena, followed by the plantation of three Guinea grass rows in July, as there was a contribution in quantity and quality of total produced biomass. The bean yields were 0,45-0,75 t of grain/ha.
In Camagüey, Cuba, Soto et al. (2006) also intercropped short-cycle crops during the establishment of grazing areas of L. leucocephala cv. Peru, in order to determine the performance of height and yield in leucaena, as well as the incidence of weeds, pests and diseases. A randomized block design with four replications was used for each treatment: 1) Leucaena plus Sesamum indicum; 2) leucaena plus Sorghum vulgare cv. INIA Dorado; 3) leucaena plus Vigna sinensis; and a control (leucaena). The best results in pest and disease control, as well as in weed incidence, were found in the treatments with crops, and particularly in the case of S. indicum; it was also observed that in those treatments where the companion crop was used, the time for reaching the approximate height of 2 m as establishment criterion was reduced (Ruiz and Febles, 1987; Iglesias, 2003). On the other hand, the contribution made by the crops (S. indicum, S. vulgare and V. sinensis) to the reduction of the establishment time of leucaena, confirms the statements made by Padilla et al. (2001) regarding that intercropping does not affect its establishment.
The use of mixed home gardens
Another agrosilvopastoral arrangement that occupies an outstanding position in the livestock production systems of the American subtropics to cover the basic needs of families or small communities, are mixed home gardens, which are highly diverse in quantity of species and varieties, and very complex and varied in structures and possible associations (Altieri, 1991; Lok, 1998). They consist in a complex of perennial or semiperennial plants which are found around farmers' houses, integrated to agricultural (tubers, fibers, vegetables, fruits, stimulants), livestock (small animals, even bees) and forestry production (timber, firewood, poles), and generally include medicinal and ornamental plants.
In the northwestern mountains of the Cauca Valley (Murgueitio, 2000) they are called gardens for human and animal security, where protein banks are combined with other forage and human-food plants. In some places more than 20 species share the forage plots. The plants are organized in rows through the slope and forage trees (Trichanthera gigantea, Erythrina edulis, Morus sp., Urera), shrubs (Boehmeria nivea, Malvaviscus sp., Tithonia diversifolia), herbaceous or succulent plants (Musa sp., Alocasia macrorrhiza, Xanthosoma sp., Bidens pilosa, Impatients sp., Symphytum peregrinum), climbing plants (Sechium edule) are cultivated combined with such plants as corn, climbing bean, cassava, arracacha (Arracacia xanthorrhiza) and Andean fruit trees such as Solanum quitoense, Cyphomandra betacea, Rubus glaucus and Passiflora ligularis,. Forage cutting is performed at the same time unripe corn, green beans and tubers are harvested for human consumption. Corn leaves and stems, bean pods, cassava leaves, the smallest tubers and banana fruits and pseudostems are mixed with foliages, which in turn are used to feed cattle, pigs and poultry.
At present there is renewed interest by researchers, farmers and technicians in several-strata polycrops, systems similar to those mentioned above, but accompanied by one or more strata of other vegetation for purposes different from forage, especially timber cultivation (for furniture, construction, poles, firewood) with fast-growing trees (Cordia alliodora, L. leucocephala var. Salvador, Montanoa quadrangularis, Juglans neotropica, Quercus humboldtii), which are subject to frequent pruning in order to allow the passage of sunlight. Palm species are also studied (Roystonea regia, Bactris gasipaes, Ceroxylon alpinum, Attalea butyracea) to harvest in the future the racemes for animal feeding. Other ornamental plants can occupy an intermediate stratum, such as Heliconiaceae, or the system floor, such as Anthurium sp., which require little light.
In the case of Cuba, the main characteristic of mixed home gardens is the wide variety of agricultural, forestry and fruit species, in addition to the animals that are included in them, which turns them into integrated agrosilvopastoral systems. Among the most widely used plant species in mixed home gardens are: garlic (Allium sativum), pineapple (Ananas comosus), peppers (Capsicum sp.), squash (Cucurbita pepo), cassava (M. esculenta), banana (Musa sp.), corn (Z. mays), etc.
The most preferred fruit species by farmers are: mango (M. indica), bitter orange (Citrus aurantium), lemon (Citrus limon), avocado (Persea americana), coconut (Cocos nucifera), soursop (Annona muricata) and guava (Psidium guajava).
Among the non-fruit trees are: Bursera simaruba, G. sepium, Hibiscus elatus, R. regia and Cedrela odorata. Medicinal plants are not discarded in this type of agroforestry system, being very necessary in zones far from urban areas and health centers. Among the most outstanding are: Costus spiralis, Lippia alba, Foeniculum vulgare, Chrysantellum americanum, Mentha citrasa, etc.
Animal rearing can be diverse, mainly including hens, pigs, sheep and goats, and sometimes dairy cattle and horses.
Funes Monzote (2000) developed a system where 50% of the farm or garden area is constituted by dairy livestock, based on the associations of pastures with legumes, living fences and shade trees; while the rest of the area is divided into several agricultural subsystems, dedicated to short-cycle crops in polycrops (beans with corn; cassava with corn; squash with corn; corn with cassava and peanut), varied vegetables, spices and medicinal plants and fruit trees (fig. 1).
In this type of system everything is delimited by living fences with multipurpose legumes (G. sepium, L. leucocephala) and other ligneous plants.
In general, it can be stated that traditional mixed home gardens are a contribution to the farmer's serenity and happiness, due to their aesthetic and recreational value, as they are an extension of the house, because they constitute his/her workshop, the place where children are raised, a large source of fruits, vegetables and tubers, a shock absorbing means in scarcity periods, a live drugstore and, in addition, a source of resources for generating income from the surplus.
As conclusion, it should be emphasized that the above-described agrosilvopastoral systems are complex, due to the combination of animals with multipurpose, timber-yielding, fruit, forage trees, shrubs and different legumes, as well as grasses for pasture, which ensure not only a diversified and stable production, but also the balance of the agroecosystem. The multiple economic benefits can also be inferred, as compared to isolated economic activities, due to the diversity of resources and agricultural practices that are implemented, which balance climate and market fluctuations. They maintain soil fertility and vegetation productivity for long time periods, for which increasing their use is recommended in the context where current livestock production systems are developed.
