SCREENING OF WOODY AND SHRUB LEGUMES FOR AGRO-FORESTRY SYSTEMS BASED ON BIOMASS PRODUCTION, N YIELD AND BIOLOGICAL N2 FIXING CAPACITY

Abstract

A field study was carried out to identify the suitable tree species for agrolorcstry systemsbased on their biomass production. N yield and Nrfixing capacity at the ExportAgriculture Research Station. Matalc for a period of 9 months. I'N isotope dilutionmethod was used for the assessment or the proportion of N2 derived through fixation (Pfix).Gl iricidi« spiurn (g+iric idia). Calliandra calothvrsus (calliandru). Lcucacna leucoccpha!a(lcucacna). Ervthrina suhumhrancc (Erythrina). Albizia [alraturi« (Albicia) and AI'(/Iiamangium (acacia) were used as N2-fixing species and SCIII/a siamea (siamca), SCI/I/aspettabilis (Spcctnhilis). both are non-nodulating legumes. and Michaella chantpaca(michalia) were used as non Ny-fixing reference species.

Total dry matter yield of non Ns-Iixing reference crop spcctabilis was significantly (pO.05)higher than all the species. Among the fixing species. Calliandra produced the highestbiomass though the value is not significantly (p~O.O.'i) different from gliricidia, lcucacnaand siamca. Acacia and michaclia recorded the lowest yields.

Highest leaf. twigs and root NIl,) was found in crythrina and the highest trunk N% wasassociated with gliricidia. Leaf NIYr,of spcctahilis was less than that of gliricidin andcrythrinu but total N yield of spcctabilis was the highest due to high biomass production.Among the six fixing species highest N yield was found with calliandra and the value isover two fold higher than that for gliricidia. Acacia and michaclia recorded the lowest nyields.

Highest Pfix values for whole plant was found with alhizia followed by g liricidia,cnlliandra. crythrina, lcuccana and acacia. The trend is common for the values based onall the three reference crops. Total Ns-fix iug capacity 01" calliandra recorded the highestvalue followed by lcucacnn, gliricidia, albizia. crythrina, and acacia. Ny-Iixing valuescalculated based on siamea and spcctabilis revealed N-fixing species calliandra, lcucacnaand gliricidia have thc capacity to fix 19.51-23.11. 15.77-19.79 and 13.IO-l4.42g Nplant I. The values equivalent to 1<)5-231. 15X-19X and 13l-l44kg of N ha').

S. spcctabilis. C calothyrsus, L. leucocephala and G. sepium produced higher biomassand higher N yields over the others. Total N fixing capacity of C calothvrsus. L.leucoccphal« and G. septum were superior to the other species. However, wheremaintenance of soil N status is considered further studies arc recommended to evaluate thelitter quality and N transferring ability before a firm recommendation is made.