Article II. Fine root and nodule dynamics ofperiodically pruned hedgerow tr'ees in a tropical alley cropping system
Chesney, Patrick E.
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Fine root and nodule production and turnover in pruned 2- and 8-year-old Elytlzrina poeppigiana (Walp.) O.F. Cook trees were estimated under humid tropical conditions by applying the compartment flow rnodel (CFM) to fine root and nodule biomass and necromass measured in sequentially talcen core samples. Shoot pruning intensities compared were complete pruning (Le. complete removal ofshoots) and partial pruning (i.e. retention of one branch on the pruned stump). The CFM provided reasonable estimates ofnodule dynamics but did not apply well to fine root data. Over a five-month observation period, nodule production versus turnover in completely and partially pruned 2-year-old trees was 97 vs. 79 kg ha'l and 191 kg vs. 171 kg ha,l, respectively. CorTesponding values in 8-year-old trees were 45 vs. 44 kg ha'l and 44 vs. 29 kg ha'l. Fine root production versus turnover in completely and partially pruned 2-year-old trees was 19 vs. 26 kg ha'l and 63 vs. 41 kg ha'l; estimated values in 8-year-old trees were negative. Senescent nodules and fine roots pass to soil organic rnatter via decomposition. Partially pruned 2-year-old trees added 75 kg ha'l more decomposed nodules and 1 kg ha'l less fine roots to soil than completely pruned trees. Partially pruned 8-year,old t1'ees contributed 19 kg ha'l less decomposed nodules and 5 kg ha'l more decomposed fine 1'oots than completely pruned 8-year-old E poeppigiana trees. Nodule and fine root tumover was compensated for by new production at 10-14 weeks afier pruning. The retention of a branch on the pruned E poeppigiana tme stump allows better fine root and nodule survival, and contributes more to organic matter and N recycling compared to traditional complete pruning, due to higher tree biomass production.