s:3163:"%T Biomass production and root distribution of eight trees and their potential for hedgerow intercropping on an ultisol in Southern Sumatra 
%A Hairiah, K. 
%A van Noordwijk, M. 
%A Santoso, B. 
%A Syekhfani, M.S. 
%X 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. 
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