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Ten year balances of organic matter and nutrients in agroforestry systems at CATIE, Costa Rica
Forest Ecology and Management, 45 ( ! 991 ) 173-183 Elsevier Science Publishers B.V., Amsterdam
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Ten year balances of organic matter and nutrients in agroforestry systems at CATIE, Costa Rica H . W . F a s s b e n d e r a, J. B e e r b, J. H e u v e l d o p b, A. I m b a c h c, G . E n r i q u e z c a n d A. B o n n e m a n n b ~Technical Forestry Faculty. GOttingen. Federal Republic of Germany bCATIE-GTZ Agroforestry Project. Turrialba. Costa Rica and Eschborn, Federal Republic of Germany CCATIE. Turrialba, Costa Rica
ABSTR ACT Fassbender, H.W., Beer, J., Heuveldop, J., lmbach, A., Enriquez, G. and Bonnemann, A., 1991. Ten year balances of organic matter and nutriems in agroforestry systems at CATIE, Costa Rlca. For. Ecol. Manage., 45: 173-183. In the 'Experimento Central' of CATIE (Centro Agron6mico Tropical de Investigaci6n y Ensefianza, Turriaiba, Costa Rica) studies on organic matter and nutrient cycling have been carrie, out in the following agruforestry systems, planted in 1977: - Theobroma cacao with Cordia alliodora and Erytbrina poeppigiana; Coffea arabica with the same shade trees; Cynodon plectostachyus (star grass) associated with the same trees. Results are presented and discussed using the T. cacao systems as an example. The accumulation of organic matter, measured for the different species (leaves, branches, trunks, roots, fruits and litter) at an age of 5 years (1982) and of 10 years is very large: 50.3 and !10.6 t ha -t for ~: cacao/C. alliodora. The average cacao bean harvest at an age of 6-10 years reached 1036 and 1057 kg ha- ~a- t under shade of C. alliodora and E. poeppigiana, respectively. Total stem volume growth of C. alliodora is presently 9.6 m 3 ha-~ a -~. Measurements of the natural leaf fall and of prunings were made over 5 years, reaching 8.1 i/3.29 t ha- ~a- ~for T. cacao/C, alliodora and 9.29/13.57 t ha- ~a- ~for T. cacao/ E. poeppigiana, respectively. With the values obtained, quinquennial models for organic matter and nutrients are presented and discussed. -
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INTRODUCTION High expectations have been raised in recent years about the potential of a g r o f o r e ~ t r y as a m a j o r l a n d m a n a g e m e n t a l t e r n a t i v e f o r s u s t a i n a b l e p r o d u c t i o n a n d f o r t h e m a i n t e n a n c e o f s o i l f e r t i l i t y i n t h e t r o p i c s ( B e e r e t al., 1987; Fas.~bender, 1987; N a i r , 1987; S a n c h e z , 1987; Y o u n g , 1 9 8 7 ) . The management and improvement of agroforestry systems should be based
0378-1127/91/$03.50 © 1991 Elsevier Science Publishers B.V. All rights reserved.
174
H.W.FASSBENDERETAL.
on a satisfactory understanding of their structure and function. This is a complex task, since these systems (and especially the interactions) are complicated and many aspects must be taken into consideration; theretbre, the use of models for organic matter, nutrients and water has been proposed (Nair, 1984; Fassbender, 1987; Fassbender et al., 1988). These models are based on an evaluation of the reserves in each of the compartments within the system, and measurements of the interactions and transfers as well as the gains and losses (Nair, 1984; Alpizar et al., 1986; Fassbender, 1987; Fassbender et al., 1988). In the 'Experimento Central' of CATIE (Centro Agron6mico Tropical de Investigaci6n y Ensefianza, Turrialba, Costa Rica) long-term studies have been carried out to provide a basis for models of organic matter, water and nutrient cycles for the following agroforestry systems: - Theobroma cacao (3 X 3 m, l 111 trees ha- ~) with shade of Cordia alliodora or Erythrina poeppigiana (6 x 6, 278 trees ha- t ); - Coffea arabica ( 1 X2 m, 5000 trees ha-m ) under the same shade trees; - Cynodon plectostachyus (star grass) associated with the same shade trees. In this article, some of the results for these systems with T. cacao are presented as an example of an evaluation of a ten-year-working period ( 19771987). MATERIALSAND METrIODS Details of the "Experimento Central" at CATIE have been described before (Alpizar et al., 1986; Beer et al., 1987; Fassbender et al., 1988; Heuveldop et al., 1988; Imbach et al., 1989). For the models presented in this publication, the following values were considered: above ground biomass at age 5 (Alpizar et al., 1986) and 10 (Beer et al., 1990), using non-destructive methods for the compartments of the shade and crop trees (leaves, branches, stems, pods) and the litter layer; fine root biomass, irrespective of species, at age 5 and 10 (Alpizar et al., 1986; Beer et al., 1990); reserves of organic matter and nutrients (N, P, K, Ca, Mg) in the mineral soil and vegetation, based on chemical analysis of samples (Diaz-Romeu and Hunter, 1978), at ages 0, 5 and 9; - cacao production (beans and husks) during 9 years ( 1979-1987 ) (Heuveld o p e t al., 1988; Beer et al., 1990); - growth rates of C. alliodora measured once or twice per year (stem diameter at breast height, total height of the trees and hence calculated stem volume increments) (Somarriba and Beer, 1986; Heuveldop et al., 1988; Beer et al., 1990); - natural leaf fall measured continuously for 5 years ( 1983-87); samples col-
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ORGANICMATTERANDNUTRIENTSINAGROFORESTRYSYSTEMS
175
lected every seven days, separated into leaves a n d b r a n c h e s a n d chemically analysed ( H e u v e l d o p et al., 1988; Beer et al., 1990); - p r u n i n g residues o f T. cacao a n d E. poeppigiana m e a s u r e d o v e r two years ( 1 9 8 5 - 8 7 ) (Beer et al., 1990); - nutrient input with rainfall a n d o u t p u t with percolating water m e a s u r e d d u r i n g one year ( I m b a c h et al., 1989); - rate o f fertilization with N, P, K applied to the e x p e r i m e n t (Alpizar et al., 1986). RESULTS AND DISCUSSION Cacao production
C a c a o p r o d u c t i o n started in the s e c o n d year a n d gradually increased to the sixth year ( 198 3), after which it stabilized showing n o r m a l a n n u a l variations (Table 1 ). TABLE I Average annual production of beans of Theobroma cacao associated with Cordia alliodora or Erythrina poeppigiana 1979-1987 (Beer et al., 1990), (kg ha- ' a- i ) Period
0-5 year 6-10 year
System T. cacao/C, alliodora
T. cacao/E, poeppigiana
306 1036
377 1057
~The cacao beans made up 41% of the dry pod weights. There were no significant differences in the agricultural production between the two systems. T i m b e r produce'ion
G r o w t h rates o f C. alliodora are representative for the Atlantic zone o f C o : , ~ Rica although the growth in height was less t h a a expected (Table 2~, TABLE2 Growth rates of Cordia alliodgra associated with Theobroma cacao (Beer et al., 1990) Age (year)
Diameter
Height
(cm)
(m)
Stem volume ( m 3 ha -I )
5.3 10.5
17.8 24.1
10.6 15.0
31.6 77.6
176
H.W. FASSBENDERET AL.
(Somarriba and Beer, 1986). St.em volume at age 10.5 year was 77.6 m 3 hawith an average growth rate over the last 3 years of 9.6 m 3 ha- ~a - ~. The timber ofE. poeppigiana has no commercial value. The economic implications of the agricultural and/or timber production in these agroforestry systems, which have a great potential in the region, can only be evaluated with long-term studies; C. alliodora rotations are currently between 17-27 years (Somarriba and Beer, 1986). Biomass in tree and crop compartments
The biomass in both systems increased to 87 and 111 t ha- i over 10 years, showing a difference of 24 t ha- ~ in favour of the T. cacao/C, alliodora plots (Table 3). The difference in biomass accumulation during the last five years was especially evident in the stems of the shade trees, corresponding in C. alliodora to 81% of the biomass. However, the biomass increase of stems of TABLE 3 Biomass reserves in the systems of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (AIpizar et al., 1986; Bee1 et al., 1990), (t h a - t ) Biomass
System T. cacao with C alliodora
Age5 Above-ground biomass Fine roots Litter layer Total Age 10 Above-ground biomass Fine roots Litter layer Total
9.8
T. cacao with C alliodora
31.9
8.3
4.2 4.4 50.3 35.9
15.6 1.8 7.1 32.8
49.7
27.2
9.8 15.2 i 10.6
37.9 5.7 16.5 87.3
TABLE 4 Increase in biomass in the two studied agroforestry systems (Beer et al., i 990) Year
1982, age 5 1987,age 10
System T. cacao with C. aliiodora
T. cacao with C. alliodora
(t ha-' )
(%)
(t ha-t )
(%)
50.3 110.6
t00 219
32.8 87.3
100 266
ORGANIC MATTER AND NUTRIENTS IN AGROFORESTRY SYSTEMS
177
E. poeppigiana during this period was apparently larger ~r. real terms ( 16.6 vs
21. l t ha -m, respectively), even though these shade trees were subjected to regular intensive pruning. In the last five years, the increase in total T. cacao biomass under C. alliodora was considerably larger than the increase in shade tree biomass. This was associated with a large change in T. cacao branch biomass (20 t ha -I ). Differences in the leaf biomass and the litter layer can be explained as a consequence of the different methodologies, as well as phenological differences resulting from seasonal and climatic variations. Total biomass increased in a corresponding manner in both systems over the second five year period as shown in Table 4. Production o f plant residues
There was no significant difference between systems in the production of T. cacao residues (Table 5). The difference in residue production was especially related to the pruning management of E. poeppigiana. The pruning of leguminous trees in agroforestry systems (e.g., Erythina spp., Inga spp., Gliricidia spp., Albizzia spp.) alters the environment of the associated crop spe-
cies, and thus affects crop physiology (e.g., flower, fruit development), produces mulch (nutrient inputs and erosion control) and may release N fixed in root nodules (Nair, 1984; Sanchez, 1987; Fassbender, 1987; Fassbender et al., 1988). The monthly litterfall pattern depends on the physiological and phenological characteristics of the species involved in the systems, and the prevailing climatic conditions. The leaf fall of T. cacao plants occurred continuously with some seasonal variation. The leaf fall of C. alliodora occurred mainly during the dry season from February to June, because of the deciduous characteristics of this species. Natural residue production ofE. poeppigiana is deTABLE5 Naturallitterfalland pruningresidueinputsin the systemsof TheobromacacaowithCerdiaalliodora or Ervthrinapoeppigiana (Beer et al., 19~3), (t ha- i a- ~) Input
T. cacao C. alliodora System leaves total leaves branches
Natural 4.40 Pruning 3.291 Speciestotal 7.69
2.88 -
qneludedleavesand branches.
0.83 3.71
8.11 3.29 11.40
T. cacao E. poeppigiana System leaves total leaves branches 3.93 3.801 7.73
4.62 3.76
0.74 6.01 15.13
9.29 13.57 22,86
178
H.W.FASSBENDERETAL.
termined by the management strategy, with reduced leaf fall after semi-annual, partial pruning (50%), when vigorous regrowth occurs.
Orggnic matter in mineral soil Total soil organic matter reserves are given in Table 6. The highest values and increments were attained in the T. cacao/E, poeppigiana system, with an increase of 41.6 t ha -~, in comparison with 1.5.3 t ha -~ for T. cacao/C, a!liodora. This difference is presumably a consequence of larger litter inputs under E. poeppigiano (see above) and is possibly also the result of different decomposition rates of the litter. However, the differences between years, agroforestry systems and depths are not statistically significant (Beer et al., 1990), probably because of the relatively high initial values of humus in the soil. A very important conclusion is that both agroforestry systems, at the least, maintain soil organic matter. TABLE 6 Total soil organic matter reserves, calculated from concentrations and soil bulk density, 0-45 cm soil depth (t ha - ' and relative values ), ( Beer et al., 1990) Year
1977, age0 1982, age5 1986, age 9
System T. cacao with C. alliodora
T. cacao with E. poeppigiana
(t h a - ' )
(relative value)
(t ha-~ )
(relative value)
168.3 188.3 183.3
100 112 109
198.4 229.4 240.0
100 116 121
Models for organic matter cycles Figure 1 shows the five-yearly models (age 6 to 10) for organic matter in the agroforestry systems of T. cacao/C, alliodora and T. cacao/E, poeppigiana in Turrialba, Costa Rica. The reserves are the average of the biomass measurements, litter and humus determinations at ages 5 and 10; the transfer values are the averages of the determinations during the five year period. Values for T. cacao pods are shown in brackets in Fig. I to indicate that the cacao pod biomass was not always present but is transitory and the data refer to the removal of biomass as an annual mean over five years (1983-1987). Besides the information directly available in Fig. 1, the following other important criteria can be derived for the characterization of the agroforestry systems:
179
ORGANIC MATTER AND NUTRIENTS IN AGROFORESTRY SYSTEMS
RESIDUES NATURALPRUNING| C:ALLIO DJRA 2.88 1 LEAVES 0.63 l BRANCHES STSMS T. CACAO 4.40 t.SS LEAVES LTI BRANCHES STEMS 11.40 FRUITS
I
e.,, S'EB- l LITTER DECOMPOSITION ~RO6TS 4.~t~...,
' l SOIL I O-15cm
RESI0UES
NATURALPRUNING 4,6~: 3,75
40.8 B. 2 6.6 32.0
E_..POEPPIGIANA LEAVES
2B,7] 1.8
STEMS
I
i
22.9 i 14.0
5,5
BRANS
Iz~3 l ~ r ~
,.Bil 7.0 I
HUSKS
[
03
RESPIRATIOI'i
..... _J
. . . . . . . .
"
1.4B
t.29
13.S'r.
I
LI':TE"
o ECOMPOSITION
,..~ [ SOIL .......
I'." I "~" "
[
I IRE.......
234.7'
76.1
O-IGcm
892
15-30cm
62.e
IS-30cm
B4.T I
30.45cm
47.2
30-45cm
60.8
Phltamass: Avero(jQof two delerrnlnatmns,1982{Syeorsold)QndlgO7[lO1RorsQtd) Soil reserves: Averageof i . o delermirlotions,1982,19e6 Cacao horvQst: Avero(;eof fi~,eylor$ [1983-1987) Relldue prQduction:Notuml littetfoll avelageof fi,,elecn (1983-1957) Prun~g res~Jes.o~erogeof twoleofs(1985-tBBT)
Fig. 1. Quinquennialaveragemodelsfor organicmatterin the systems Cordia alliodora- Theobroma cacao and Erythrina poeppigiana - Theobroma cacao (Reservest ha-I; Transferst ha-I a-I).
- net primary production, - yield export index, and - recycling index. The annual net primary production can be estimated by adding the aboveground and root biomass increments (Table 3), the cacao production (Table 1 ) and the production of plant residues (Table 5). The net primary production of these agroforestry systems was fairly high compared to other natural forest ecosystems and agroecosystems (Jordan, 1985; Fassbender, 1987) and indicates that these agroforestry systems are sustainable (Table 7). The average, five yearly, harvest index for cacao production under Cordia alliodora was 3.2% and under Erythrina poeppigiana was 4.2%. "[he proportions of biomass removed in the harvested product were, therefore, low. It should be noted that in many cacao plantations, the husk is left on the ground and its recycling represents a source of humus. Under experimental conditions, the husks have been removed from the plots. Finally, the organic matter recycling in these agroforestry systems can be expressed as the quotient between the annually produced plant residues (Table 5) and the above-ground biomass (Fig. 1 ), by species or by system. Table 8 shows the five yearly results for these agroforestry systems. The high values of the recycling index for T. cacao and E. poeppigiana in-
180
H.W. FASSBENDEREl" AL.
TABLE 7
Net primary production between ages 5 and 10 for the systems of Theobrc':z,: cacao with Cordia alliodora or Erythrina poeppigiana (t h a - ~a - =) Product
System T. cacao/C, alliodora
T. cacao/E. .7oeppigiana
Phytomass increase Crop
Tree Roots
Agricultural production Cacao harvest Production of residues Fine root renewal Total
5.22 3.56 1.12
3.78 4.46 0.78
2.52 i 1.40 4.36 28.18
2.54 22.86 i.83 36.25
TABLE 8
Recycling index for the systems of Theobroma
cacao
with Cordia alliodora or Erythrina poeppigiana
(%)
System C. alliodora with T. cacao by species by system
9.1
E. poeppigiana with T. cacao 33.6
i 7.9
56.7
43.4 51.4
dicate that only a part of the organic matter remained stable in the system. Continuous recycling of biomass and nutrients occurred.
Nutrient pools in the agroforestry systems Similar models can be compiled for nutrients in agroforestry systems (Fassbender, 1987; Fassbender et al., 1988 ). However, nutrient models are more complex because of the different forms (total, extractable, available) of the nutrients in the mineral soil, management practices (fertilization, liming), and some important ecological processes (N fixation by legumes, input with rainfall and output with leaching water). Accumulation of tGtal N in biomass shows fairly well-defined tendencies for each system (Table 9). At age 5, T. cacao/C, alliodora accumulated 447 kg ha-~ of N compared to 393 kg ha- ~ for T. cacao/E, poeppigiana. At age 10 the respective values were 765 and 722 kg ha- ~ of N. Thus the difference in N uptake during the 10 year experimental period was 43 kg ha-~ of N in
ORGANIC MATTERAND NUTRIENTSIN AGROFORESTRYSYSTEMS
! 81
TABLE 9 Nutrient accumulation in the biomass of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (kg h a - i ) Biomass
System
T. cacao/C, alliodora
Age 5 ~ Tree Crop Roots Litter layer Total Age 102 Tree Crop Roots Litter layer Total
T. cacao/E, poeppigiana
N
P
K
N
P
K
233 99 39 76 447
29 12 4 5 50
243 99 21 I0 373
156 103 22 I 12 393
16 !0 2 9 37
122 49 18 12 201
245 223 99 198 765
16 42 6 15 79
103 248 57 11 419
206 249 63 204 722
20 29 2 19 70
283 195 27 15 520
~Alpizar et al. (1986). 2Unpublished provisional values.
TABLE 10 Nutrient inputs and outputs in the systems o f Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (Fassbender et al., 1988; Heuveldop et al., 1988; Imbach et al., 1989; and unpublished provisional values), age 6-10 (kg h a - ' a -s ) Transfer
System
T. cacao/C, alliodora
Internal transfer Natural iitterfall Pru::ing residues Total Outputs Cacao yield Leaching Total Input Rainfall Fertilization Total
T. cacao/E, poeppigiana
N
P
K
N
P
K
129.0 40.1 169.1
19.8 4.1 23.9
37.7 35.4 73.1
198.3 248.8 447.1
17.6 22.1 39.7
25.8 151.5 177.3
23.1 6.0 29.1
4.7 0.6 5.3
34.3 2.2 36.5
28.4 6.0 34.4
4.7 0.7 5.4
29.5 1.8 31.3
5.0 87.5 92.5
0.2 34.4 34.6
2.5 32.4 34.9
5.0 87.5 92.5
0.2 34.4 34.6
2.5 32.4 39.9
182
H.W. FASSBENDER ETAL.
favour of T. cacao/C, alliodora, as a result of extra accumulation in the stems and branches of the shade tree. The ve.D' small values for P accumulation indicate the low mobility of this element in agroecosystems. Available P, which may gradually be accumulated in the vegetation, is a very small fraction of total P (Fassbender, 1987 ). The average values of K uptake at age 10 years were 419 and 520 kg h a - ' for T. cacao in association with C. alliodora and E. poeppigiana, respectively. Without fertilization this would imply a notable depletion of the original exchangeable soil K ( 1977:577 and 713 kg ha- m,respectively).
Nutrient internal transfers, inputs and outputs The rates of nutrient transfer for the T. cacao/E, poeppigiana system were normally higher than those of the T. cacao/C, alliodora system, largely because of pruning of the leguminous tree (Table 10). Therefore, the nutrient cycles for T. cacao/E, poeppigiana turnover are faster in comparison with T. cacao/C, alliodora (assuming that decomposition rates are not drastically different). CONCLUSION
The results obtained for the cycles of organic matter and nutrients in these agroforestry systems illustrate complicated patterns. The experimental conditions - climate and soil - are quite favour~ble at the 'Experimento Central' at CATIE. Therefore, studies should be initiated in zones with different ecological and soil conditions, where economic and sociological observations should also be encouraged. ACKNOWLEDGEMENTS The dedicated field work of Mr Jorge Alvarez and the preparation of the manuscript by Mrs Lilliam Ugalde and Miss Rosaura Solano are gratefully acknowledged. The authors thank Dr Carlos Ramirez, Dr Donald Kass and Mr J. Haggar for their constructive comments. Financial and technical support were provided by the Deutsche Gesellschaft f'fir Technische Zusammenarbeit (GTZ) and by CATIE. REFERENCES Aipizar, L., Fassbender,H.W., Heuveldop,J., F61ster,H. and Enriquez, G., 1986. Modelling agroforestrysystemsof cacao ( Theobromacacao) with Cordiaalliodoraand Erythrinapoeppigia~zain Costa Rica. 1. Inventoryof organicmatter and nutrients.Agrofor.Syst.,4: 231257. Beer, J., Fassbender,H.W. and Heuveldop,J., 1987. Advancesin agroforestryresearch. Proceedingsof a Seminar,CATIE,Turrialba,CostaRica, 379 pp.
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183
Beer, J., Bonnemann, A., Chavez, W., Fassbender, H.W., lmbach, A.C. and Martel, I., 1990. Modelling agroforestry systems of cacao (Theobroma cacao) with Cordia alliodora and Erythrina poeppigiana in Costa Rica. V. Productivity indices, organic matter models and sustainability over ten years. Agrofor. Syst., 12: 229-249. Diaz-Romeu, R. and Hunter, A., 1978. Metodologia c~e Muestreo de Suelos, Amilisis Quimico e lnvestigaci6n de lnvernadero. CATIE, Turrialba, Costa Rica, 62 pp. Fassbeoder, H.W., 1987. Modelos Edafol6gicos de Sistemas Agroforestales. CATIE, Turrialba, Costa Rica, 475 pp. Fassbender, H.W., Alpizar, L., Heuveldop, J., F61ster, H. and Enriquez, G., 1988. Modelling agroforestry systems of cacao ( Theobroma cacao) with laurel (Cordia alliodora) and pot6 (Erythrina poeppigiana ) in Costa Rica. Ill. Cycles or organic matter and hutrients. Agrofor. Syst., 6: 49-62. Heuveldop, J., Fassbender, H.W., AIpizar, L., Enriquez, G. and F61ster, H., 1988. Modelling agroforestry systems of cacao ( Theobroma cacao) with laurel (Cordia alliodora) and pot6 (Er.vthrina poeppigiana) in Costa Rica. II. Cacao and wood production, litter production and decomposition. Agrofor. Syst., 6: 37-48. lmbach, A.C., Fassbender, H.W., Borel, R., Beer, J. and Bonnemann, A., 1989. Modelling a~,roforestry systems of cacao ( Theobroma cacao ) with laurel (Cordia alliodora) and pot6 ( Er.vthrina poeppigiana) in Costa Rica. IV. Water balances, nutrient inputs and lixiviation. Agrofor. Syst., 8: 267-287. Jordan, J., 1985. Nutrient Cycling in Tropical Forest Ecosystems. Wiley, New York, 190 pp. Nair, P.K.R., 1984. Soils Aspects ofAgroforestry. ICRAF, Nairobi, Kenya, 164 pp. Na|r, P.K.R., i 987. Soil productivity under agroforestry. In: H.L. Gholz (Editor), Agroforestry: Realities and Possibilities. Nijhoff, Holland, 227 pp. Sanchez, P., 1987. Soil productivity and sustainability of agroforestry systems. In: H. Steppler and P.K.R. Nair (Editor.~j, Agroforestry, A Decade of Development. ICRAF, Nairobi, Kenya, pp. 205-223. Somarriba, E. and Beer, J., 1986. Dimensiones, volfimenes y crecimiento de Cordia alliodora en sistemas agroforestales. CATIE, Turrialba, Costa Rica, Boletin T~nico 16, 23 pp. Young, A., 1987. Soil productivity, soil conservation and land evaluation. Agrofor. Syst., 5: 277-292.
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Ten year balances of organic matter and nutrients in agroforestry systems at CATIE, Costa Rica H . W . F a s s b e n d e r a, J. B e e r b, J. H e u v e l d o p b, A. I m b a c h c, G . E n r i q u e z c a n d A. B o n n e m a n n b ~Technical Forestry Faculty. GOttingen. Federal Republic of Germany bCATIE-GTZ Agroforestry Project. Turrialba. Costa Rica and Eschborn, Federal Republic of Germany CCATIE. Turrialba, Costa Rica
ABSTR ACT Fassbender, H.W., Beer, J., Heuveldop, J., lmbach, A., Enriquez, G. and Bonnemann, A., 1991. Ten year balances of organic matter and nutriems in agroforestry systems at CATIE, Costa Rlca. For. Ecol. Manage., 45: 173-183. In the 'Experimento Central' of CATIE (Centro Agron6mico Tropical de Investigaci6n y Ensefianza, Turriaiba, Costa Rica) studies on organic matter and nutrient cycling have been carrie, out in the following agruforestry systems, planted in 1977: - Theobroma cacao with Cordia alliodora and Erytbrina poeppigiana; Coffea arabica with the same shade trees; Cynodon plectostachyus (star grass) associated with the same trees. Results are presented and discussed using the T. cacao systems as an example. The accumulation of organic matter, measured for the different species (leaves, branches, trunks, roots, fruits and litter) at an age of 5 years (1982) and of 10 years is very large: 50.3 and !10.6 t ha -t for ~: cacao/C. alliodora. The average cacao bean harvest at an age of 6-10 years reached 1036 and 1057 kg ha- ~a- t under shade of C. alliodora and E. poeppigiana, respectively. Total stem volume growth of C. alliodora is presently 9.6 m 3 ha-~ a -~. Measurements of the natural leaf fall and of prunings were made over 5 years, reaching 8.1 i/3.29 t ha- ~a- ~for T. cacao/C, alliodora and 9.29/13.57 t ha- ~a- ~for T. cacao/ E. poeppigiana, respectively. With the values obtained, quinquennial models for organic matter and nutrients are presented and discussed. -
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INTRODUCTION High expectations have been raised in recent years about the potential of a g r o f o r e ~ t r y as a m a j o r l a n d m a n a g e m e n t a l t e r n a t i v e f o r s u s t a i n a b l e p r o d u c t i o n a n d f o r t h e m a i n t e n a n c e o f s o i l f e r t i l i t y i n t h e t r o p i c s ( B e e r e t al., 1987; Fas.~bender, 1987; N a i r , 1987; S a n c h e z , 1987; Y o u n g , 1 9 8 7 ) . The management and improvement of agroforestry systems should be based
0378-1127/91/$03.50 © 1991 Elsevier Science Publishers B.V. All rights reserved.
174
H.W.FASSBENDERETAL.
on a satisfactory understanding of their structure and function. This is a complex task, since these systems (and especially the interactions) are complicated and many aspects must be taken into consideration; theretbre, the use of models for organic matter, nutrients and water has been proposed (Nair, 1984; Fassbender, 1987; Fassbender et al., 1988). These models are based on an evaluation of the reserves in each of the compartments within the system, and measurements of the interactions and transfers as well as the gains and losses (Nair, 1984; Alpizar et al., 1986; Fassbender, 1987; Fassbender et al., 1988). In the 'Experimento Central' of CATIE (Centro Agron6mico Tropical de Investigaci6n y Ensefianza, Turrialba, Costa Rica) long-term studies have been carried out to provide a basis for models of organic matter, water and nutrient cycles for the following agroforestry systems: - Theobroma cacao (3 X 3 m, l 111 trees ha- ~) with shade of Cordia alliodora or Erythrina poeppigiana (6 x 6, 278 trees ha- t ); - Coffea arabica ( 1 X2 m, 5000 trees ha-m ) under the same shade trees; - Cynodon plectostachyus (star grass) associated with the same shade trees. In this article, some of the results for these systems with T. cacao are presented as an example of an evaluation of a ten-year-working period ( 19771987). MATERIALSAND METrIODS Details of the "Experimento Central" at CATIE have been described before (Alpizar et al., 1986; Beer et al., 1987; Fassbender et al., 1988; Heuveldop et al., 1988; Imbach et al., 1989). For the models presented in this publication, the following values were considered: above ground biomass at age 5 (Alpizar et al., 1986) and 10 (Beer et al., 1990), using non-destructive methods for the compartments of the shade and crop trees (leaves, branches, stems, pods) and the litter layer; fine root biomass, irrespective of species, at age 5 and 10 (Alpizar et al., 1986; Beer et al., 1990); reserves of organic matter and nutrients (N, P, K, Ca, Mg) in the mineral soil and vegetation, based on chemical analysis of samples (Diaz-Romeu and Hunter, 1978), at ages 0, 5 and 9; - cacao production (beans and husks) during 9 years ( 1979-1987 ) (Heuveld o p e t al., 1988; Beer et al., 1990); - growth rates of C. alliodora measured once or twice per year (stem diameter at breast height, total height of the trees and hence calculated stem volume increments) (Somarriba and Beer, 1986; Heuveldop et al., 1988; Beer et al., 1990); - natural leaf fall measured continuously for 5 years ( 1983-87); samples col-
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ORGANICMATTERANDNUTRIENTSINAGROFORESTRYSYSTEMS
175
lected every seven days, separated into leaves a n d b r a n c h e s a n d chemically analysed ( H e u v e l d o p et al., 1988; Beer et al., 1990); - p r u n i n g residues o f T. cacao a n d E. poeppigiana m e a s u r e d o v e r two years ( 1 9 8 5 - 8 7 ) (Beer et al., 1990); - nutrient input with rainfall a n d o u t p u t with percolating water m e a s u r e d d u r i n g one year ( I m b a c h et al., 1989); - rate o f fertilization with N, P, K applied to the e x p e r i m e n t (Alpizar et al., 1986). RESULTS AND DISCUSSION Cacao production
C a c a o p r o d u c t i o n started in the s e c o n d year a n d gradually increased to the sixth year ( 198 3), after which it stabilized showing n o r m a l a n n u a l variations (Table 1 ). TABLE I Average annual production of beans of Theobroma cacao associated with Cordia alliodora or Erythrina poeppigiana 1979-1987 (Beer et al., 1990), (kg ha- ' a- i ) Period
0-5 year 6-10 year
System T. cacao/C, alliodora
T. cacao/E, poeppigiana
306 1036
377 1057
~The cacao beans made up 41% of the dry pod weights. There were no significant differences in the agricultural production between the two systems. T i m b e r produce'ion
G r o w t h rates o f C. alliodora are representative for the Atlantic zone o f C o : , ~ Rica although the growth in height was less t h a a expected (Table 2~, TABLE2 Growth rates of Cordia alliodgra associated with Theobroma cacao (Beer et al., 1990) Age (year)
Diameter
Height
(cm)
(m)
Stem volume ( m 3 ha -I )
5.3 10.5
17.8 24.1
10.6 15.0
31.6 77.6
176
H.W. FASSBENDERET AL.
(Somarriba and Beer, 1986). St.em volume at age 10.5 year was 77.6 m 3 hawith an average growth rate over the last 3 years of 9.6 m 3 ha- ~a - ~. The timber ofE. poeppigiana has no commercial value. The economic implications of the agricultural and/or timber production in these agroforestry systems, which have a great potential in the region, can only be evaluated with long-term studies; C. alliodora rotations are currently between 17-27 years (Somarriba and Beer, 1986). Biomass in tree and crop compartments
The biomass in both systems increased to 87 and 111 t ha- i over 10 years, showing a difference of 24 t ha- ~ in favour of the T. cacao/C, alliodora plots (Table 3). The difference in biomass accumulation during the last five years was especially evident in the stems of the shade trees, corresponding in C. alliodora to 81% of the biomass. However, the biomass increase of stems of TABLE 3 Biomass reserves in the systems of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (AIpizar et al., 1986; Bee1 et al., 1990), (t h a - t ) Biomass
System T. cacao with C alliodora
Age5 Above-ground biomass Fine roots Litter layer Total Age 10 Above-ground biomass Fine roots Litter layer Total
9.8
T. cacao with C alliodora
31.9
8.3
4.2 4.4 50.3 35.9
15.6 1.8 7.1 32.8
49.7
27.2
9.8 15.2 i 10.6
37.9 5.7 16.5 87.3
TABLE 4 Increase in biomass in the two studied agroforestry systems (Beer et al., i 990) Year
1982, age 5 1987,age 10
System T. cacao with C. aliiodora
T. cacao with C. alliodora
(t ha-' )
(%)
(t ha-t )
(%)
50.3 110.6
t00 219
32.8 87.3
100 266
ORGANIC MATTER AND NUTRIENTS IN AGROFORESTRY SYSTEMS
177
E. poeppigiana during this period was apparently larger ~r. real terms ( 16.6 vs
21. l t ha -m, respectively), even though these shade trees were subjected to regular intensive pruning. In the last five years, the increase in total T. cacao biomass under C. alliodora was considerably larger than the increase in shade tree biomass. This was associated with a large change in T. cacao branch biomass (20 t ha -I ). Differences in the leaf biomass and the litter layer can be explained as a consequence of the different methodologies, as well as phenological differences resulting from seasonal and climatic variations. Total biomass increased in a corresponding manner in both systems over the second five year period as shown in Table 4. Production o f plant residues
There was no significant difference between systems in the production of T. cacao residues (Table 5). The difference in residue production was especially related to the pruning management of E. poeppigiana. The pruning of leguminous trees in agroforestry systems (e.g., Erythina spp., Inga spp., Gliricidia spp., Albizzia spp.) alters the environment of the associated crop spe-
cies, and thus affects crop physiology (e.g., flower, fruit development), produces mulch (nutrient inputs and erosion control) and may release N fixed in root nodules (Nair, 1984; Sanchez, 1987; Fassbender, 1987; Fassbender et al., 1988). The monthly litterfall pattern depends on the physiological and phenological characteristics of the species involved in the systems, and the prevailing climatic conditions. The leaf fall of T. cacao plants occurred continuously with some seasonal variation. The leaf fall of C. alliodora occurred mainly during the dry season from February to June, because of the deciduous characteristics of this species. Natural residue production ofE. poeppigiana is deTABLE5 Naturallitterfalland pruningresidueinputsin the systemsof TheobromacacaowithCerdiaalliodora or Ervthrinapoeppigiana (Beer et al., 19~3), (t ha- i a- ~) Input
T. cacao C. alliodora System leaves total leaves branches
Natural 4.40 Pruning 3.291 Speciestotal 7.69
2.88 -
qneludedleavesand branches.
0.83 3.71
8.11 3.29 11.40
T. cacao E. poeppigiana System leaves total leaves branches 3.93 3.801 7.73
4.62 3.76
0.74 6.01 15.13
9.29 13.57 22,86
178
H.W.FASSBENDERETAL.
termined by the management strategy, with reduced leaf fall after semi-annual, partial pruning (50%), when vigorous regrowth occurs.
Orggnic matter in mineral soil Total soil organic matter reserves are given in Table 6. The highest values and increments were attained in the T. cacao/E, poeppigiana system, with an increase of 41.6 t ha -~, in comparison with 1.5.3 t ha -~ for T. cacao/C, a!liodora. This difference is presumably a consequence of larger litter inputs under E. poeppigiano (see above) and is possibly also the result of different decomposition rates of the litter. However, the differences between years, agroforestry systems and depths are not statistically significant (Beer et al., 1990), probably because of the relatively high initial values of humus in the soil. A very important conclusion is that both agroforestry systems, at the least, maintain soil organic matter. TABLE 6 Total soil organic matter reserves, calculated from concentrations and soil bulk density, 0-45 cm soil depth (t ha - ' and relative values ), ( Beer et al., 1990) Year
1977, age0 1982, age5 1986, age 9
System T. cacao with C. alliodora
T. cacao with E. poeppigiana
(t h a - ' )
(relative value)
(t ha-~ )
(relative value)
168.3 188.3 183.3
100 112 109
198.4 229.4 240.0
100 116 121
Models for organic matter cycles Figure 1 shows the five-yearly models (age 6 to 10) for organic matter in the agroforestry systems of T. cacao/C, alliodora and T. cacao/E, poeppigiana in Turrialba, Costa Rica. The reserves are the average of the biomass measurements, litter and humus determinations at ages 5 and 10; the transfer values are the averages of the determinations during the five year period. Values for T. cacao pods are shown in brackets in Fig. I to indicate that the cacao pod biomass was not always present but is transitory and the data refer to the removal of biomass as an annual mean over five years (1983-1987). Besides the information directly available in Fig. 1, the following other important criteria can be derived for the characterization of the agroforestry systems:
179
ORGANIC MATTER AND NUTRIENTS IN AGROFORESTRY SYSTEMS
RESIDUES NATURALPRUNING| C:ALLIO DJRA 2.88 1 LEAVES 0.63 l BRANCHES STSMS T. CACAO 4.40 t.SS LEAVES LTI BRANCHES STEMS 11.40 FRUITS
I
e.,, S'EB- l LITTER DECOMPOSITION ~RO6TS 4.~t~...,
' l SOIL I O-15cm
RESI0UES
NATURALPRUNING 4,6~: 3,75
40.8 B. 2 6.6 32.0
E_..POEPPIGIANA LEAVES
2B,7] 1.8
STEMS
I
i
22.9 i 14.0
5,5
BRANS
Iz~3 l ~ r ~
,.Bil 7.0 I
HUSKS
[
03
RESPIRATIOI'i
..... _J
. . . . . . . .
"
1.4B
t.29
13.S'r.
I
LI':TE"
o ECOMPOSITION
,..~ [ SOIL .......
I'." I "~" "
[
I IRE.......
234.7'
76.1
O-IGcm
892
15-30cm
62.e
IS-30cm
B4.T I
30.45cm
47.2
30-45cm
60.8
Phltamass: Avero(jQof two delerrnlnatmns,1982{Syeorsold)QndlgO7[lO1RorsQtd) Soil reserves: Averageof i . o delermirlotions,1982,19e6 Cacao horvQst: Avero(;eof fi~,eylor$ [1983-1987) Relldue prQduction:Notuml littetfoll avelageof fi,,elecn (1983-1957) Prun~g res~Jes.o~erogeof twoleofs(1985-tBBT)
Fig. 1. Quinquennialaveragemodelsfor organicmatterin the systems Cordia alliodora- Theobroma cacao and Erythrina poeppigiana - Theobroma cacao (Reservest ha-I; Transferst ha-I a-I).
- net primary production, - yield export index, and - recycling index. The annual net primary production can be estimated by adding the aboveground and root biomass increments (Table 3), the cacao production (Table 1 ) and the production of plant residues (Table 5). The net primary production of these agroforestry systems was fairly high compared to other natural forest ecosystems and agroecosystems (Jordan, 1985; Fassbender, 1987) and indicates that these agroforestry systems are sustainable (Table 7). The average, five yearly, harvest index for cacao production under Cordia alliodora was 3.2% and under Erythrina poeppigiana was 4.2%. "[he proportions of biomass removed in the harvested product were, therefore, low. It should be noted that in many cacao plantations, the husk is left on the ground and its recycling represents a source of humus. Under experimental conditions, the husks have been removed from the plots. Finally, the organic matter recycling in these agroforestry systems can be expressed as the quotient between the annually produced plant residues (Table 5) and the above-ground biomass (Fig. 1 ), by species or by system. Table 8 shows the five yearly results for these agroforestry systems. The high values of the recycling index for T. cacao and E. poeppigiana in-
180
H.W. FASSBENDEREl" AL.
TABLE 7
Net primary production between ages 5 and 10 for the systems of Theobrc':z,: cacao with Cordia alliodora or Erythrina poeppigiana (t h a - ~a - =) Product
System T. cacao/C, alliodora
T. cacao/E. .7oeppigiana
Phytomass increase Crop
Tree Roots
Agricultural production Cacao harvest Production of residues Fine root renewal Total
5.22 3.56 1.12
3.78 4.46 0.78
2.52 i 1.40 4.36 28.18
2.54 22.86 i.83 36.25
TABLE 8
Recycling index for the systems of Theobroma
cacao
with Cordia alliodora or Erythrina poeppigiana
(%)
System C. alliodora with T. cacao by species by system
9.1
E. poeppigiana with T. cacao 33.6
i 7.9
56.7
43.4 51.4
dicate that only a part of the organic matter remained stable in the system. Continuous recycling of biomass and nutrients occurred.
Nutrient pools in the agroforestry systems Similar models can be compiled for nutrients in agroforestry systems (Fassbender, 1987; Fassbender et al., 1988 ). However, nutrient models are more complex because of the different forms (total, extractable, available) of the nutrients in the mineral soil, management practices (fertilization, liming), and some important ecological processes (N fixation by legumes, input with rainfall and output with leaching water). Accumulation of tGtal N in biomass shows fairly well-defined tendencies for each system (Table 9). At age 5, T. cacao/C, alliodora accumulated 447 kg ha-~ of N compared to 393 kg ha- ~ for T. cacao/E, poeppigiana. At age 10 the respective values were 765 and 722 kg ha- ~ of N. Thus the difference in N uptake during the 10 year experimental period was 43 kg ha-~ of N in
ORGANIC MATTERAND NUTRIENTSIN AGROFORESTRYSYSTEMS
! 81
TABLE 9 Nutrient accumulation in the biomass of Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (kg h a - i ) Biomass
System
T. cacao/C, alliodora
Age 5 ~ Tree Crop Roots Litter layer Total Age 102 Tree Crop Roots Litter layer Total
T. cacao/E, poeppigiana
N
P
K
N
P
K
233 99 39 76 447
29 12 4 5 50
243 99 21 I0 373
156 103 22 I 12 393
16 !0 2 9 37
122 49 18 12 201
245 223 99 198 765
16 42 6 15 79
103 248 57 11 419
206 249 63 204 722
20 29 2 19 70
283 195 27 15 520
~Alpizar et al. (1986). 2Unpublished provisional values.
TABLE 10 Nutrient inputs and outputs in the systems o f Theobroma cacao with Cordia alliodora or Erythrina poeppigiana (Fassbender et al., 1988; Heuveldop et al., 1988; Imbach et al., 1989; and unpublished provisional values), age 6-10 (kg h a - ' a -s ) Transfer
System
T. cacao/C, alliodora
Internal transfer Natural iitterfall Pru::ing residues Total Outputs Cacao yield Leaching Total Input Rainfall Fertilization Total
T. cacao/E, poeppigiana
N
P
K
N
P
K
129.0 40.1 169.1
19.8 4.1 23.9
37.7 35.4 73.1
198.3 248.8 447.1
17.6 22.1 39.7
25.8 151.5 177.3
23.1 6.0 29.1
4.7 0.6 5.3
34.3 2.2 36.5
28.4 6.0 34.4
4.7 0.7 5.4
29.5 1.8 31.3
5.0 87.5 92.5
0.2 34.4 34.6
2.5 32.4 34.9
5.0 87.5 92.5
0.2 34.4 34.6
2.5 32.4 39.9
182
H.W. FASSBENDER ETAL.
favour of T. cacao/C, alliodora, as a result of extra accumulation in the stems and branches of the shade tree. The ve.D' small values for P accumulation indicate the low mobility of this element in agroecosystems. Available P, which may gradually be accumulated in the vegetation, is a very small fraction of total P (Fassbender, 1987 ). The average values of K uptake at age 10 years were 419 and 520 kg h a - ' for T. cacao in association with C. alliodora and E. poeppigiana, respectively. Without fertilization this would imply a notable depletion of the original exchangeable soil K ( 1977:577 and 713 kg ha- m,respectively).
Nutrient internal transfers, inputs and outputs The rates of nutrient transfer for the T. cacao/E, poeppigiana system were normally higher than those of the T. cacao/C, alliodora system, largely because of pruning of the leguminous tree (Table 10). Therefore, the nutrient cycles for T. cacao/E, poeppigiana turnover are faster in comparison with T. cacao/C, alliodora (assuming that decomposition rates are not drastically different). CONCLUSION
The results obtained for the cycles of organic matter and nutrients in these agroforestry systems illustrate complicated patterns. The experimental conditions - climate and soil - are quite favour~ble at the 'Experimento Central' at CATIE. Therefore, studies should be initiated in zones with different ecological and soil conditions, where economic and sociological observations should also be encouraged. ACKNOWLEDGEMENTS The dedicated field work of Mr Jorge Alvarez and the preparation of the manuscript by Mrs Lilliam Ugalde and Miss Rosaura Solano are gratefully acknowledged. The authors thank Dr Carlos Ramirez, Dr Donald Kass and Mr J. Haggar for their constructive comments. Financial and technical support were provided by the Deutsche Gesellschaft f'fir Technische Zusammenarbeit (GTZ) and by CATIE. REFERENCES Aipizar, L., Fassbender,H.W., Heuveldop,J., F61ster,H. and Enriquez, G., 1986. Modelling agroforestrysystemsof cacao ( Theobromacacao) with Cordiaalliodoraand Erythrinapoeppigia~zain Costa Rica. 1. Inventoryof organicmatter and nutrients.Agrofor.Syst.,4: 231257. Beer, J., Fassbender,H.W. and Heuveldop,J., 1987. Advancesin agroforestryresearch. Proceedingsof a Seminar,CATIE,Turrialba,CostaRica, 379 pp.
ORGANICMATTERANDNUTRIENTSIN AGROFORESTRYSYSTEMS
183
Beer, J., Bonnemann, A., Chavez, W., Fassbender, H.W., lmbach, A.C. and Martel, I., 1990. Modelling agroforestry systems of cacao (Theobroma cacao) with Cordia alliodora and Erythrina poeppigiana in Costa Rica. V. Productivity indices, organic matter models and sustainability over ten years. Agrofor. Syst., 12: 229-249. Diaz-Romeu, R. and Hunter, A., 1978. Metodologia c~e Muestreo de Suelos, Amilisis Quimico e lnvestigaci6n de lnvernadero. CATIE, Turrialba, Costa Rica, 62 pp. Fassbeoder, H.W., 1987. Modelos Edafol6gicos de Sistemas Agroforestales. CATIE, Turrialba, Costa Rica, 475 pp. Fassbender, H.W., Alpizar, L., Heuveldop, J., F61ster, H. and Enriquez, G., 1988. Modelling agroforestry systems of cacao ( Theobroma cacao) with laurel (Cordia alliodora) and pot6 (Erythrina poeppigiana ) in Costa Rica. Ill. Cycles or organic matter and hutrients. Agrofor. Syst., 6: 49-62. Heuveldop, J., Fassbender, H.W., AIpizar, L., Enriquez, G. and F61ster, H., 1988. Modelling agroforestry systems of cacao ( Theobroma cacao) with laurel (Cordia alliodora) and pot6 (Er.vthrina poeppigiana) in Costa Rica. II. Cacao and wood production, litter production and decomposition. Agrofor. Syst., 6: 37-48. lmbach, A.C., Fassbender, H.W., Borel, R., Beer, J. and Bonnemann, A., 1989. Modelling a~,roforestry systems of cacao ( Theobroma cacao ) with laurel (Cordia alliodora) and pot6 ( Er.vthrina poeppigiana) in Costa Rica. IV. Water balances, nutrient inputs and lixiviation. Agrofor. Syst., 8: 267-287. Jordan, J., 1985. Nutrient Cycling in Tropical Forest Ecosystems. Wiley, New York, 190 pp. Nair, P.K.R., 1984. Soils Aspects ofAgroforestry. ICRAF, Nairobi, Kenya, 164 pp. Na|r, P.K.R., i 987. Soil productivity under agroforestry. In: H.L. Gholz (Editor), Agroforestry: Realities and Possibilities. Nijhoff, Holland, 227 pp. Sanchez, P., 1987. Soil productivity and sustainability of agroforestry systems. In: H. Steppler and P.K.R. Nair (Editor.~j, Agroforestry, A Decade of Development. ICRAF, Nairobi, Kenya, pp. 205-223. Somarriba, E. and Beer, J., 1986. Dimensiones, volfimenes y crecimiento de Cordia alliodora en sistemas agroforestales. CATIE, Turrialba, Costa Rica, Boletin T~nico 16, 23 pp. Young, A., 1987. Soil productivity, soil conservation and land evaluation. Agrofor. Syst., 5: 277-292.