An evaluation of a collection of amphicarpic Centrosema rotundifolium showed considerable variability among the six accessions tested, regarding above- and below-ground seed production. Dry-season forage yields were very low but rainy-season yields reached acceptable levels. Contents of crude protein, P and Ca were intermediate to high (CP and P) or low (Ca). Three accessions are suggested for on-farm testing in association with grasses in order to explore the plant persistence implications of belowground seed production under practical conditions. Furthermore, the potential of this amphicarpic species for the conservation of sandy soils deserves attention

González, S.

Rodríguez, I.

Schultze-Kraft, R.

English

University of Kentucky

University of Kentucky UKnowledge International Grassland Congress Proceedings XIX International Grassland Congress Evaluation of Centrosema rotundifolium for Sand-Soil Savannas in Eastern Venezuela I. Rodríguez Fondo Nacional de Investigaciones Agropecuarias, Venezuela R. Schultze-Kraft University of Hohenheim, Germany S. González Fondo Nacional de Investigaciones Agropecuarias, Venezuela Follow this and additional works at: https://uknowledge.uky.edu/igc  Part of the Plant Sciences Commons, and the Soil Science Commons This document is available at https://uknowledge.uky.edu/igc/19/14/8 This collection is currently under construction. The XIX International Grassland Congress took place in São Pedro, São Paulo, Brazil from February 11 through February 21, 2001. Proceedings published by Fundacao de Estudos Agrarios Luiz de Queiroz This Event is brought to you for free and open access by the Plant and Soil Sciences at UKnowledge. It has been accepted for inclusion in International Grassland Congress Proceedings by an authorized administrator of UKnowledge. For more information, please contact UKnowledge@lsv.uky.edu. ID # 14 - 08EVALUATION OF Centrosema rotundifolium  FOR SAND-SOIL SAVANNAS IN EASTERNVENEZUELAI. Rodríguez1, R. Schultze-Kraft2 and S. González11Fondo Nacional de Investigaciones Agropecuarias (FONAIAP), CIAE-Anzoátegui, Apartado 212,El Tigre, Anzoátegui, Venezuela, ciae@reacciun.ve; 2University of Hohenheim (380), D-70593Stuttgart, GermanyAbstractAn evaluation of a collection of amphicarpic Centrosema rotundifolium showed considerablevariability among the six accessions tested, regarding above- and below-ground seed production.Dry-season forage yields were very low but rainy-season yields reached acceptable levels. Contentsof crude protein, P and Ca were intermediate to high (CP and P) or low (Ca). Three accessions aresuggested for on-farm testing in association with grasses in order to explore the plant persistenceimplications of belowground seed production under practical conditions. Furthermore, the potentialof this amphicarpic species for the conservation of sandy soils deserves attention.Keywords: Amphicarpy, dry-matter production, seed production, crude protein, phosphorus,calciumIntroductionCentrosema rotundifolium Mart. ex Benth. is one of the four-amphicarpic species of theimportant tropical genus Centrosema. It is a little-known, perennial, trailing species whichmainly because of three factors was considered worthwhile of evaluation for the sand-soilsavannas in Eastern Venezuela: (1) amphicarpy (the phenomenon that a plant is able to produceboth above-ground and below-ground seeds) because of which C. rotundifolium has beensuggested to have the potential of being a particularly persistent legume (Schultze-Kraft et al.,1997); (2) its adaptation to acid, low-fertility soils such as the oxisols in the Colombian LlanosOrientales (Schultze-Kraft et al., 1994); and (3) its origin – sand soils of semiarid to dry-subhumid Brazil (Schultze-Kraft et al., 1990) – according to which the species should be adaptedto similar environments in Eastern Venezuela such as the Mesa de Guanipa, Anzoátegui.Material and MethodsThe evaluation experiment was conducted during 1995-97 at the FONAIAP research stationCentro de Investigaciones Agropecuarias del Estado Anzoátegui (CIAE-Anzoátegui) in El Tigre,Anzoátegui state, Venezuela (8°51' N, 64°12' W, 265 masl) on a very sandy (87% sand) and acid(pH 4.9) oxisol with low cation exchange capacity and low base saturation. The climate issemiarid with a mean annual temperature of 26.5 °C and a mean precipitation of 1040 mm/yeardistributed from May to November.The germplasm used was a C. rotundifolium collection provided by the CentroInternacional de Agricultura Tropical (CIAT), Colombia, comprising six accessions, viz. CIAT5260, 5283, 5521, 5721, 25120, and 25148. The experimental design was RCB with fourreplications. Seeds were sown 1995 into 7.5-m2 single-row plots with a basic fertilizationconsisting of P2O5, K2O, MgO, and S (50, 50, 20, and 16 kg/ha, respectively); since there was noappropriate rhizobium inoculum available, a starter dose of 20 kg N/ha was also applied. At theend of the establishment phase, twelve weeks after sowing, soil cover and flowering intensitywere assessed. Subsequently and during the first dry season, all ripe aboveground seeds werecollected by periodic hand-picking (1-2 times/week). At the middle of the dry season, adestructive harvest of underground seeds was performed in two replications by sieving the 0-5cm soil layer of the whole plot. During the subsequent rainy season such "destructed" plotsrecuperated completely from seed remnants in the soil and from tuberous-root regrowthmeristems. Dry-season dry matter (DM) forage production was assessed on the basis of two 0.25-m2 samples/plot five months after a standardization cut at the beginning of the subsequent dryseason. Rainy-season DM forage production was measured during the subsequent rainy seasonby performing two 8-week interval cuts after a standardization cut at the onset of the rainyseason. Material of both cuts was used to determine crude protein (%N x 6.25), phosphorus andcalcium contents in whole plants. Statistical treatment consisted of analysis of variance and theDuncan test of significance.Results and DiscussionEstablishment and seed production (Table 1). All accessions established well and didnot show any nutrient deficiency or disease symptoms, or any major damages by insects. With amean of 70%, soil cover 12 weeks after sowing was satisfactory and only the difference betweenthe highest (CIAT 25148) and the lowest (CIAT 25120) covers was significant. The range offlowering intensity was wide (3-54%), the most prolific (and earliest) flowering accession beingCIAT 25120. Both above- and below-ground seed production varied considerably. Accessionswith low aboveground seed yields tended to have high belowground yields and vice-versa (e.g.CIAT 25148 and 25120, respectively). On average, seed production belowground was more thanthree times higher than aboveground.Forage production and contents of crude protein and minerals (Table 2). With amean yield of 107.2-kg/ha dry season forage production was low. It varied considerably amongaccessions but only the difference between the highest and lowest production (CIAT 5620 andCIAT 25120, respectively) was statistically significant. Rainy-season production did not showany major differences though accession CIAT 5620 tended to be superior. Likewise, with valuesaround the respective means of 23.5%, 0.41%, and 0.60, there were no significant differencesamong accessions regarding crude protein, P, and Ca contents (except for the highest and lowestCa values).Discussion and conclusions In comparison with the perennial C. pubescens (Ferguson etal., 1990) the seed production potential – mainly belowground – of C. rotundifolium is very high.Whereas forage production during the dry season is very low, rainy-season DM yields are closeto those of other Centrosema species reported from the same site by Flores (1986). The crude-protein values of C. rotundifolium are in line with those of other Centrosema species (Lascano etal., 1990); the P contents are considerably higher and the Ca contents lower than the suggestedrespective critical values for near-maximum production (Salinas et al., 1990). The collectiontested showed only a moderate degree of variability. For the El Tigre conditions, accessionsCIAT 5260, 5721, and 25148 (eventually even a mixture of them) are suggested for on-farmtesting of C. rotundifolium/grass associations under grazing. Such studies should also clarify therelationship between belowground – grazing independent? – Seed production and legumepersistence. It is furthermore suggested to explore the potential of C. rotundifolium for soilconservation (e.g. sand dune stabilization).ReferencesFerguson J.E., Hopkinson J.M., Humphreys L.R. and de Andrade R.P. (1990). Seedproduction of Centrosema species. Pages 221-243 in R. Schultze-Kraft and R.J. Clements, eds.Centrosema: Biology, Agronomy, and Utilization. Centro Internacional de Agricultura Tropical(CIAT), Cali, Colombia.Flores, A. (1986). Centrosema (DC.) Benth. en Venezuela. FONAIAP, Estación ExperimentalAnzoátegui, El Tigre, Venezuela, 20 p. (unpublished).Lascano C.E., Teitzel J.K. and Eng Pei Kong (1990). Nutritive value of Centrosema andanimal production. Pages 293-319 in R. Schultze-Kraft and R.J. Clements, eds. Centrosema:Biology, Agronomy, and Utilization. Centro Internacional de Agricultura Tropical (CIAT), Cali,Colombia.Salinas J.G., Kerridge P.C. and Schunke R.M. (1990). Mineral nutrition of Centrosema. Pages110-149 in R. Schultze-Kraft and R.J. Clements, eds. Centrosema: Biology, Agronomy, andUtilization. Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia.Schultze-Kraft R., Williams R.J. and Coradin L. (1990). Biogeography of Centrosema. Pages29-76 in R. Schultze-Kraft and R.J. Clements, eds. Centrosema: Biology, Agronomy, andUtilization. Centro Internacional de Agricultura Tropical (CIAT), Cali, Colombia.Schultze-Kraft R., Keller-Grein G., Cárdenas E. y Díaz Bolívar F. (1994). Potencial deCentrosema rotundifolium como leguminosa forrajera. Pasturas Tropicales 16: 2-8.Schultze-Kraft R., Schmidt A. and Hohn H. (1997). Amphicarpic legumes for tropical pasturepersistence. Proceedings of the XVIII International Grassland Congress, Winnipeg andSaskatoon, Canada, Vol. 1, pp. 1-13 to 1-14.Table 1 - Soil cover and flowering intensity of a Centrosema rotundifolium collection at the endof the establishment phase, subsequent above-ground seed production, and below-ground seedharvest during the dry seasonSeed yield (kg/ha)Accession(CIAT No.)Soil cover(%)Flowering intensity(above-ground) (%) Above-ground Below-ground5260        63   ab            19   bc           567   a             894   ab5283        68   ab              8   cd           382   ab             822   ab5521        70   ab              3   d             63   bc             907   ab5721        77   ab            14   bcd           204   ab           1267   a25120        54   b            54   a           571   a             611   b25148        87   a            26   bc               9   c           1208   aMean        69.8            20.4           299             952S.E.          6.4              3.3           293             318a,b,c,d: Values within a column followed by the same letter do not differ significantly at P<0.05(Duncan test)Table 2 - Forage production of a Centrosema rotundifolium collection during the dry and rainyseasons, and contents of crude protein, phosphorus and calcium in entire plants (means of two 8-week rainy-season cuts)Forage yield (kg DM/ha)Accession(CIAT No.) Dry season* Rainy season**  Crudeprotein  (%)P(%)Ca(%)5620      184.0   a              2418             22.5          0.43     0.63   a5283        68.7   ab              2223             23.4          0.39     0.62   a5521      128.7   ab              2203             23.9          0.45     0.52   b5721      170.7   a              2392             23.8          0.42     0.59   ab25120        16.7   b              2088             23.8          0.42     0.59   ab25148        74.3   ab              2142             23.6          0.40     0.64   aMean      107.2              2244             23.5          0.41     0.60S.E.        99.0                358               1.1          0.11     0.11a,b,c,d: Values within a column followed by the same letter do not differ significantly at P<0.05(Duncan test); in columns without letters, there are no statistically significant differences.*   5-month production** Cumulative production of two 8-week cuts

Evaluation of \u3ci\u3eCentrosema rotundifolium\u3c/i\u3e for Sand-Soil Savannas in Eastern Venezuela

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Evaluation of \u3ci\u3eCentrosema rotundifolium\u3c/i\u3e for Sand-Soil Savannas in Eastern Venezuela

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