K. Hairiah, M. Van Noordwijk, G. Cadisch
Three types of cropping systems, cassava-based intercropping, hedgerow intercropping and legume cover crop rotations, were evaluated in 1994-1997 in Northern Lampung, Sumatra. The purpose of this experiment was to quantify the C and N flows returned within and transported out of plots and crop yields of different cropping systems. Cassava-based systems were not stable and yields declined over time. Intercropping cassava with rice increased cassava fresh tuber weight by 5-48% compared to the monocropping system. The hedgerow intercropping gave lower maize, rice, groundnut and cowpea yields than could be obtained in a crop rotation with legume cover crops. Maize grain yields in the 80-20 rice/maize mixture were about 0.4 Mg ha -1 in the rice - groundnut rotation and about half as much when intercropped with cassava or hedgerows. Rice yields intercropped with cassava or with hedgerows were about 1 Mg ha -1 less in year 2 and 3 than those grown in rotation with groundnut. The rice yield in the first cropping season was only about 1 Mg ha -1 , but in the second and third year yields in the rice - legume rotation increased to around 2 and around 3 Mg ha -1 , respectively. This increase occurred despite a decline in soil organic matter content. The cassava-based systems removed much more C (7 Mg ha -1 yr -1 ) than the other systems, while less was returned (about 0.5-2 Mg ha -1 ) to the soil. In the hedgerow intercropping system about 2.5 Mg C ha -1 yr -1 was returned to the plot as biomass pruning and crop residues and about 1.5 Mg C ha -1 yr -1 was removed from the plot as yield. In the cover crop rotation 2.6 Mg ha -1 yr -1 of C was returned to the plot as crop residues plus Mucuna (only the 2nd year) and Cowpea biomass, and about 1.1 Mg ha -1 yr -1 was removed from the plot. The hedgerow intercropping systems gave an N surplus of about 15-50 kg ha -1 yr -1 returned to the soil; while the balance was 10-20 kg ha -1 yr -1 for the cover crop rotation systems and the cassava-based systems showed a negative N budget of about 60 kg ha -1 yr -1 .
Faculty of Agriculture, Brawijaya University, Malang, Indonesia; ICRAF SE Asia, Bogor, P.O. Box 161, Indonesia; Department of Biological Sciences, Wye College, University of London, Wye, Kent TN25 5AH, United Kingdom
