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Agroforestry Systems in the Brazilian Semi-Arid Region

Jorge Ribaski' and Eduardo A. Menezes'°EMBRAPA - Agricultural and Livestock Research Center for the

Semi-Arid Tropic (CPATSA) - Petrolina - PE - Brazil p73

Abstract

This paper gives a brief overview of theBrazilian semi-arid region, presenting some of itsproblems, limitations and potentialities. Withinthis context, it emphasizes the urgent need ofagric~tural diversification due to the high risks towhich rainfed agriculture is subjected. Based onthe potentialities, and on the characteristics ofthe region, it is suggested the use of agroforestrysystems as an important alternative for increasinçand improving the regional agriculturalproductivitv. minimizing ecological probterns.Among the intercropping systems, thesilvopastoral ones, that is, the association offorest and livestock activities, are presented asthe most viable alternative for best utilizing thesoil productive capacitv. assuring a greatersocio-economical stability to farmers:-Anotheralternative presented is the utilization of trees asliving fences and windbreakers. The latter has agreat potential for irrigated areas. In addition,some research data are presented regardingagroforestry systems where emphasis has beengiven to the utilization of multipurpose treespecies. Among the tree species studied so far,the genera Prosopis, Leucaena, Mimosa andEucalyptus have been outstanding. Regarding thenon-arboreal forage species, the genera Cenchrus,Urochloa and Opuntia have had more attention.

Introductíon

The agroforestry systems have lately beena subj~c: of grea: importance du~ tp soilproductivitv and social problems associated withwood production, food and ecological aspects.TheBrazilian semi-arid region is a typical example,showing poor soils with low fertilitv. where thereis a big pressure over the plant resources. Theexploration of these resources has beeninadequate and intensive, which has contributedfor the vegetation degradation, endangering theunsafeecological equilibrium of this region.

The interest on reforestation has greatlyincreased as a result of natural scarcity of woodas well as the regional look for forest productsfor use in farms and for fuel.

ror the above reasons the agroforestrysystems have large possibilities of use and cangive ..significant contribution to a more coherentdevelopment of the region.This paper shows the research lines in ourResearch Center and some of the main resultsalong thirteen years of research. This researcharea began after the establishment of the NationalForest Research Program in 1978, which had theimportant technical assistance of the InternationalCouncil for Research in Agroforestry (ICRAF).

Characterization of the Region

Northeast Brazil is situated between 1°and 18°30' South Latitude and between 34°30'and 48°20' West Longitude. It has an area of1.55 million krn", which represents 18.2 % of thecountry area and covers nine States.

In this region, with diverse characteristicsand potentialities, submitted to periodicaldroughts, there is a semi-arid area with about 115millions hectares and a population of 24 millionsinhabitants. It is about 70% of Northeast Brazilarea and 13% of Brazil, holding 63 % of NortheastBrazil population and 18.5% of the country. Thishuge area and large population, together withother restrictive factors, make limitations toactions of intervention which aim its development(SILVA, 1985).

According to IBGE (1980), 93% of therural properties in Northeast Brazil have an areaequal to or less than 100 ha and re], ssent only7% of the region, while 7% of the total ruralproperties have an area grE-aterthan 100 ha anr'represent 70% of the total area of the region,most of them being unproductive latifundia.

The rainfall distribution in the region isvery irregular, with annual means varying from250 to 1,000 mm, most fall,ng between Februaryand May (GOLFARI and CASER, 1977). Other

638

characteristics are: very intense insolation withannual mean of 2,800 hours; low relativehumidity, with annual means around 60%, andhighpotential evapotranspiration, with an annualmeanof 2,000 mm (EMBRAPA, 1979).

The region is also characterized by havingsandy shallow soils with low water holdingcapacity, vulnerable to erosion and with loworganicmatter content (EMBRAPA, 1979).

The vegetation is composed of a group oftreesand shrubs which receive the generic nameof "caatlnça", where there is a predominance ofLeguminosae, generally thorny, with small anddeciduous leaves which fali in the dry periodIGOLFARIand CASER, 1977).

Plant Resourees Exploration System

The exploration of plant resourcesconsistsbasically of wood extraction for generalusein the farms and for commercialization, andalsoas native forage species rsr animal feeding.These resources become important sources oftuel and food for the maintenance anddevelopment of the rural areas. However, thisexploration is made with no criterion.

In this region, the plant resources showlow wood productivity with mean volumesbetween 15 and 20 rn' lha (TAVARES et ai,1969; Tavares et. st., 1970;-J..ima et. et., 1978;IBDF,1988). The use of these resources in anintensive way, with no reposition of exploredtrees, has caused the degradation of thevegetation.

On the other side, beef cattle raising inthis region shows low productivltv. mainly as aresultof food scarcity in the dry period, whenthe availability of native forage is greatlyreduced.The "caatinga" vegetation neither showsadequatecharacteristics for pasture nor provideslhenutritional requirements of the animais duringa long period of the year, due to its poorherbaceousstratum and its deciduous behaviour.Consequently, its carrying capacity is very low,around13 ha/animal (SALVIANO, 1989).

Potentialities and Possibilities of Uses ofAgroforestry Systems in the ~m~·Arid

, Region

The research works at Northeast Brazil,particularly at the Agricultural and LivestockResearch Center for the Semi-Arid TropicICPATSA),which belongs to Agricultural Brazilian

Research . Agency (EMBRAPA), have tried tooptimize and/or maximize the use of natural andsocio-economic resources, seeking a betterperformance of the regional agriculture byincreasing production. productivitv, resistance toadverse clirnatic effects and improving theecological equilibrium through adequatemethodologies and technologies.

In the forest research area, theagroforestry systems constitute importantalternative for the increase of the regionalproductivity and the exploration of degraded soils.

These svsterns have the objective ofrat'onalizinq t..e use of the soil, trying to increaseits total productrvity through the p73 sequentialor simultaneous production of wood, food and

-,.:forage in the same piece of land (BENE et ar;-1977).

Statistical data show that in the Braziliansemi-arid region the probability of succeeding indrvland agriculture (rainfall dependent) is of 3 outof 10, i. e., three out of ten years. It shows thehigh risk of this activitv. ev.dencinç the need foraurícuttura! diversity. According to FREIRE et ai(1982), the farrners recognize this problem asthey dedicate the largest areas for extensivecattle raising.

Several atternpts of intercropping weremade in the region, involving forest and cropspecies, having most of them showed to beunviable, mainly due to poor yields of the cropspecies as a result of climatic effects.Unfortunately, many of these experiences are notregistered on the account of the negative results.50 the agroforestry systems involving cattleraising seem to be the most viable way to betterutilize the productive capacity of the soil and toassure the farmer more socio-economic stability.

On the other side, the trees in theagroforestry systems play another importantfunction as besides yielding wood, fruits orforage they can also be used as living fences,windbreakers, support to apiculture and otheruses in the farm.

The livinq fences are not frequently foundin the Braziliar semi-arid (RIBASKI, 1986).although they are an important agroforestryoption due to the natural lack of wood for barbedwire fences (the most common tvpe in the region)associated with high costs. The living fencesshow more advantage than fences made withposts and stakes since they have lower costs.long life, ecological benefits and possibility ofyielding economical by-products (BUDOWSKI,1987).

In the irrigated areas, the use ofwindbreakers appears as an excellent alternative

for minimizing the undesirable effects of winds,which are very frequent in the region. Theseprotection systems avoid crop lodging anddamage, soil erosion and contribute to reduceevapotranspiration. In doing 50, the watereconomy is improved in these areas, which is acritical point in the water lacking regions.

Some Research ResuJts in the BraziJianScmi-Arid Region

Selection of potential tree species

The experimental trials with tree speciesaiming at identifying potential materiais for use inagroforestry systems have given promisingresults. Twenty-five species and 160provenances of the genus Eucs/yptus were testedin the States of Pernambuco, Paralba, Rio Grandedo Norte, Ceará and Bahia. The species E.csmaldu/ensis and E. tereticornis outstand theothers, showing mean yields of 70 m3/ha atseven years of age, which represents four timesthe mean yield of the native vegetation. Also, thespecies of the genera Prosopis (mesquite).teuceen« ("Ieucena"), Mimosa ("sabiA") andG/iricidis (·gliricidia") have shown a goodperformance, with the advantage of beingmultipurpose trees (fuel, charcoal, stakes, forage,Jjving fences, windbreakers, nitrogen fixation,shading, etc) (RIBASKI and LIMA, 1982; SOUZAand CARVALHO, 1984; PIRES et. s/., 1985;SILVA, 1986; DRUMOND et. et., 1989; OLIVEIRAand DRUMOND, 1989).

More than ten species of the genusProsopis were introduced in the Braziliansemi-arid region. P. iuüttore, P. oettids, P. sttinis.P. cinererie, and P. velutine have been consideredas potential species for contributing to increasethe production of wood, fuel and food for theanimais (LIMA, 1'390).

Shading forage palm wih Prosopis ju/iflora

, In the Brazilian semi-arid region,intercropping P. iutiüor« with forage palm(Opuntia ficus-indica) is a well known practiceamong small and medium farmers and hascontributed with them to maintain their livestockduring the dry periods. Forage palm is a memberof the Cactaceae family, used for feeding theanimais in the dry period, rich in water (over90%), mucilage and mineral salts, but poor inprotein (COSTA et ai, 1973).

639Al VES (1982) states the hypothesis that

shading forage palm with P. iutittore in a 5 m x 5m spacing can give benefits to the forage palm,increasing its yield and longevity.

One experimental trial was carried out atCPATSA in order to study the influence of P.iu/iflora shading on forage palm. The shadingintensity is a function of the row spacing (5 mx 5 m, 7 m x 7 rn, 1° m x 1° m, and 12 m x 12m). Forage palm was planted in a 2,0 m x 0,5 mspacing. The results of the first evaluation ofpalm yield, made after a cut at three years of age,showed no significant difference amongtreatments regarding dry matter yie/d. We shouldemphasize that in this period the trees were stillin development, having a mean canopy areaaround 16 m2 (ALBUOUEROUE et. st., 1986).

Intercropping Prosopts ju/iflora with buffe/ grass

Research works carried out in the drya-reasof Northeast Brazil have shown that buffelgrass (Cenchrus ci!iaris) can increase food supplyduring the whole year and, consequently, improvelivestock performance. However, other resultsshow that during the dry period, the protein leveiof cultivated pastures, including buffel grass, isnot always sufficient for maintaining andincreasing the weight of the animais (SALVIANO,1984).

Intercropping cultivated pastures withLeguminosae can overcome their nutritionaldeficiency. However, buffel grass is a verydominant species well adapted to regions of lowrainfall and there are few species which can beintercropped under these conditions. AYERSA(1981) suggests the use of silvopastoral systemsfor these regions, indicating the tree species ofthe genera Acacia and Prosopis as the mostpromising ones.

Research works conducted atPetrolina-PE, Northeast Brazil, showed that P.julitlors, when planted in an area with buffelgrass, suffered from the competition, especiallyfor water consumption. At trirty months of age,P. iu/iflora total dry matter yield was 17.0tons/há and 2.7 tons/há. respectively, single andintercropped. The proportional difference betweenthese two treatments was 540%. However,positiva tendencies were noted indicating that P.iu/if/ora can improve the quality of buffel grasspasture in protein content due to greater nitrogenconcentration found in the grass dry matter whenintercropped with that species.

Aiming at establishing a silvopastoralsystem involving those two species, it is

640

recommended that P. ju/if/ora should be plantedtwo to three years before buffel grass, in order toassure a good initial establishment of the treespecies. It is also advisable to avoid the presenceof animais in the area during the initialdevelopment of the trees (RIBASKI, 1988).

"CBl System" - an alternative for beef eattleraising in the semi-arid.

ePA TSA has been carrying out studieswith the cbietive of identifying beef cattle raisingsystems capable of significantly increasing meatproduction in the semi-arid region, which is atraditional importer of this product. _

The "CBL System" ("Caatinga" vegetation+ Suffel grass + Leucaena) makes the rationaluse of the "caatinga" associated with grazing inbuffel grass area during the dry period and directaccess to Leucaena paddocks followed by itsconsumption as hay. This system has the goal ofreducing the slaughtering age from 4-5 years to3' years, taking into cansideration the regionalmean of 320 kg of liveweight.

In the "CBL System" the butfel grass andLeucaena areas together represent approximately10% of the "caatinga" area, being the Leucaenaarea 20% of the buffel grass area. This systemwas compared with the traditional sole "caatinga"system (C) and with the "caatinga" + buffelgrass system (CB).

The partial results for weight gain show asignificant better performance of the group ofanimais in the "CBL systern" over the ones onlhe "C system", but a moderate performance overthe group of animais in the "CB system". Theaverage weight at the end of the third year forthe animais in the "CBL system" was 342.7 kg,representing an increase of 220% with regard tolhe initial weight (107.1 kg). 48% greater thanlhe increase obtained in the "C system" (158.5kg), but only 16% greater than the one obtainedin the "'CB system" (200.5 kg).

Although the economical analysis has notyet been run, the data apparently do not indicateadvantage af the "CBL system" aver the "CB".However, a small percent increase on theLeucaena area over tt "l buffel grass area and thehaymaking of the total Leucaena area before theend of the raining period allowed a significantdifference in weight gain through a greaterconsumption of this species between the twogroups (GUIMARBES FILHO, EMBRAPA-CPATSA. not publishedl.

Evaluation ot 8 silvopastoral system invohringthe intereropping of Euca/yptus camB/dultmsiswith Ioraqe grasses.

The cultural practices for the maintenanceof reforested areas are essential for a good initialdevelopment of the plants in order to obtainsatisfactorv results in the future production ofwood and by-products. Hawever, this activitv isone of the most expensive in the proeess ofestablishment of forest populations, being evenworse depending on the qualitv and quantitv ofthe herbaceous stratum to be removed.

On the other side, this stratum which is tobe removed, sometimes with diffieulty throughthe use of hoes, clearinç or herbieides, ean be apotential source of food for livestock, mainly byits possible aeceptance and protele value. So, thepraetiee of silvopastoral systems is an importamehoiee not only beeause of minimization 01 laboreosts for maintenanee and proteetion of thereforested area but also because of better soiluse, allowing the simultaneous yield of plant andanimal outputs.

A research work is being earried out atCPATSA with the objective of testing thetechnical and eeonomical viability of asilvopastoral system involving E. camaldulensisintercropped with forage grasses adapted to theregion, as follows: urochloa grass (Urochloamosambicensis), butfel grass (C. citieris) and sabipanie (Panicum maximum).

The E. cama/dulensis population, at eightyears of age, had part of its area (0.75 ha) wiredin after having been invaded by the grasses. Theevaluation of the ground cover showed anoccupation of 63% of the area with grasses,represented by 90% of uroehloa grass and 10%of buffel and sabi panic grasses, with an averageof 8.75 % of erude protein.

Thirty-month old animais weighting 230kg were introduced in the experimental area twotimes (1991 and 1992). where they stayed forthree months, in a stocking rale of 2.7animals/ha. The results for weight gain in the twoperiods showed a mean increase of 60 kg/animal,corresponding to 600 g/animal/day. These valuesare equivalent to the average obtained with otheranimais vvith the same characteristics and in thesame period, in pasture of buffel grass cv. Biloela,which is the most grown cultivar in the region(RIBASKI and OLIVEIRA, EMBRAPA-CPATSA - notpublished) .

The volumetric yield of E. camaldulensiswas significantly changed after the presenee ofthe animais in the experimental area (T test. P <0,10). The total increment (1990-1993) in the

silvopastoral system was 22% greater than in theconventional system with no grazing.

Use of windbreakers in irrigated areas

The expansion of irrigated areas in the region hascaused some ecological problems. The areaswhich were before covered with nativevegetation are being replaced by commercialplanting of many different crops (tomatoes,watermelons, grapes, beans, mangoes, guava,bananas and onions) in continuous irrigationareas exposed to ali different c1imatic andbiological factors due to lack of naturalprotection from the native v,agetation. This is aworrying situation, mainly in respect to windaction which is very frequent in the region.During the dry period, between July and October,wind can reach velocity superior to 250 km/day(AMORIM NETO, 19891. causing serious damageto agriculture.

The use of windbreak barriers turns out tobe an important way to minimize thoseundesirable aspects and to promote agriculturalyield increase. Four windbreakers were set up inexperimental fields in Petrolina(PE) andJuazeiro(BA), where there is a predominance ofEucalyptus tereticornis due to its adaptation tothe region and its architecture (Iarge leaf areaand uniform distribution of the branches along itstrunk).

The measurements on one of thewindbreakers at 17 months of age showed amean height of 7.4 m and diameter of 7.5 cm fortwo rows of E. tereticornis in a spacing of 2.5 m(within the row) and 1.25 m (between rows).The evaluations of the influence of windbreakerson agriéultural yield will only be made after thesecond year. However, it is important to point outthe excellent performance of the E. tereticornisunder these conditions, reaching an estimatedmean yield of 50 m3/ha/year (RIBASKI,EMBRAPA-CPATSA - not published).

These initial results become a neweconomical activitv through the possibility offorest exploration in irrigated areas. Thereforestation in narrow strips with four to fiverows of E. tereticornis can be managed for woodproduction besides the use as windbreakers.

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