Crop yield, C and N balance of three types of cropping systems on an Ultisol in Northern Lampung

Three types of cropping systems, cassava-based intercropping, hedgerow inte rcropping and legume cover crop rotations, were evaluated in 1993-1997 in N orthern Lampung, Sumatra. The purpose of this experiment was to quantify th e C and N flows returned within and transported out of plots and crop yield s of different cropping systems. Cassava-based systems were not stable and yields declined over time. Interc ropping cassava with rice increased cassava fresh tuber weight by 5-48% com pared to the monocropping system. The hedgerow intercropping gave lower mai ze, rice, groundnut and cowpea yields than could be obtained in a crop rota tion with legume cover crops. Maize grain yields in the 80-20 rice/maize mi xture were about 0.4 Mg ha(-1) in the rice - groundnut rotation and about h alf as much when intercropped with cassava or hedgerows. Rice yields interc ropped 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 f irst cropping season was only about 1 Mg ha(-1), but in the second and thir d year yields in the rice - legume rotation increased to around 2 and aroun d 3 Mg ha(-1), respectively. This increase occurred despite a decline in so il 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 ret urned to the plot as biomass pruning and crop residues and about 1.5 Mg C h a(-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 M ucuna (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 s urplus of about 15-50 kg ha(-1) yr(-1) returned to the soil; while the bala nce 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).