This study examined the hypothesis that incorporation of Gliricidia sepium (Jacq.) Walp.) (gliricidia), a fast-growing, nitrogen-fixing tree, into agroforestry systems in southern Malawi may be used to increase the input of organic fertilizer and reduce the need for expensive inorganic fertilizers. The productivity of maize (Zea mays L.), pigeonpea (Cajanus cajan L.) and gliricidia grown as sole stands or in mixed cropping systems was examined at Makoka Research Station (latitude 15° 30 S, longitude 35° 15 E) and a nearby farm site at Nazombe between 1996 and 2000. Treatments included gliricidia intercropped with maize, with or without pigeonpea, and sole stands of gliricidia, maize and pigeonpea. Trees in the agroforestry systems were pruned before and during the cropping season to provide green leaf manure. Maize yields and biomass production by each component were determined and fractional light interception was measured during the reproductive stage of maize. Substantial quantities of green leaf manure (2.4 to 9.0 Mg ha1 year1) were produced from the second or third year after tree establishment. Green leaf manure and fuelwood production were greatest when gliricidia was grown as unpruned sole woodlots (c. 8.0 and 22 Mg ha1 year1 respectively). Improvements in maize yield in the tree-based systems also became significant in the third year, when c. 3.0 Mg ha1 of grain was obtained. Tree-based cropping systems were most productive and exhibited greater fractional light interception (c. 0.6 to 0.7) than cropping systems without trees (0.1 to 0.4). No beneficial influence of pigeonpea on maize performance was apparent either in the presence or absence of gliricidia at either site in most seasons. However, as unpruned gliricidia provided the greatest interception of incident solar radiation (>0.9), coppicing may be required to reduce shading when gliricidia is grown together with maize. As pigeonpea production was unaffected by the presence of gliricidia, agroforestry systems containing gliricidia might be used to replace traditional maize + pigeonpea systems in southern Malawi.
Tag: gliricidia
Biomass production and root distribution of eight trees and their potential for hedgerow intercropping on an ultisol in Southern Sumatra
The results are reported of 2 experiments with exotic and local tree species, in order to assess their suitability for alley cropping on an acid soil, and as part of a nitrogen management project carried out in Lampung. The first experiment was an alley cropping trial established in 1986 and 1987 on a site cleared of secondary forest in 1986. The hedgerow species tested were Calliandra calothyrsus, Gliricidia sepium, Leucaena leucocephala, Peltophorum pterocarpa [P. pterocarpum] and Erythrina orientalis, with Mucuna pruriens var. utilis used initially as a leguminous cover crop. Tree spacing was 4 m between rows and 0.5 m within rows. Regular pruning and intercropping with food crops started in 1988. The trees were pruned every 4 months to 1 m height for 3 consecutive growing seasons (forming a hedge 40 cm wide), and thereafter the regime was adapted according to the crop. Dry weight production and N yield of prunings (which were added to the soil) was recorded, and differences in canopy shape and root distribution between the species (and their potential effects on crops) discussed. C. calothyrsus produced the most biomass, and E. orientalis the least. The second experiment examined the effect of stem pruning height and root pruning on 6 leguminous tree species (Calliandra calothyrsus, Cassia siamea, E. orientalis, Peltophorum pterocarpum, G. sepium and Albizia falcataria) and one non-legume (Peronema canescens). The trees were planted in February 1988 on a plot recently cleared of forest vegetation in rows 2 m apart, and with an inter-row spacing of 0.5 m. Root pruning was done in December 1988 (and annually thereafter) by digging a 20-cm deep trench 50 cm from the tree row. Pruning heights of 50, 75 and 100 cm were tested at 4-8 month intervals. Observations were recorded on biomass production at pruning, canopy shape, specific leaf area, light interception at ground level and root distribution, dry weight, density and nodulation. Lower pruning heights led to less biomass production and an increase in the number of branch roots originating from the stem base. A. falcataria and Peronema canescens did not tolerate regular pruning well. Consistent effects were not demonstrated of root pruning on biomass production in relation to stem pruning. Overall, the results demonstrate that the most suitable species for alley cropping on this acid soil is the relatively deep rooted Peltophorum pterocarpum; otherwise alternating hedgerows of P. pterocarpum and G. sepium are suggested as suitable. P. pterocarpum formed the densest canopy in a small hedge volume when pruned in a 3-month-cycle. Calliandra calothyrsus produced more biomass and supplied more nitrogen than any other species but would need more regular pruning to avoid shading intercrops; this could be compensated for by growing the trees at greater inter-row distances. The other species tested were all less suitable for alley cropping.