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

AbstractThree 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 monocrop-ping 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

Are High Carbon Stocks in Agroforests and Forest Associated with High Plant Species Diversity?

Conserving plant diversity and retaining terrestrial carbon stocks are targets for environmental policy and appear to be generally compatible. However, detailed information on the way both respond to agroforestry management is lacking. Rubber and fruit tree agroforestry systems combine planted trees and trees that are tolerated or actively managed that derived from natural vegetation. The research aimed to evaluate plant species diversity, vegetation structure, and C stock in rubber agroforestry system (AF) and secondary forest grown in silty clay and sandy soils in Pulang Pisau Regency, Central Kalimantan province. A number of multistrata agroforestry systems was compared to the secondary (natural) forests (SNF) of the area; these included Fruit-Based Rubber Agroforestry (AFB) of about 100 years of age, Old Rubber Agroforestry (ARO) and Young Rubber Agroforestry (ARY). The highest C stock was found in AFB (415 Mg ha-1), while the average C stocks of other AF and SNF were 217 Mg ha-1. A plant diversity index (H') was only weakly correlated to aboveground C stocks. Including the farmer-managed agroforests in schemes to reduce emissions from deforestation and forest degradation is relevant, as their carbon stocks match or exceed those of remaining forests in the area

Plant Species Diversity in Relation to Carbon Stocks at Jangkok Watershed, Lombok Island

The area around Jangkok watershed has changed, dividing it into some land use systems. This research aimed to study the effect of plant species diversity onC-stocks, and to analyse the characteristics of land use systems based on their similarity. The observations were carried out on 18 plots representing six land use systems in Jangkok watershed (Lombok Island) i.e. primary forest (PF), disturbed forest (DF), Mahogany- woodlot (MW), candlenut- agroforestry (CA), multistrata- agroforestry (MA), and simple- agroforestry (SA).The species diversity level was measured using Shannon-Weiner diversity index, whileC-stocks according to the method of RaCSA (Rapid Carbon Stock Appraisal). Results showed that forest conversion to agricultural land usesreduced the number and density of the species, average wooddensity andtree basal area. The PF represented the highest biodiversity index (3.46), while the other land uses were categorised in medium and low. Largest C-stock wasfound inPF and in(30 years old) of MWaveraged of 500 Mg ha-1, while the lowest was in SAof 68 Mg ha-1, while in other land uses was 219 Mg ha-1.The quantity of C-stock was not related tospecies diversity and its density, but closely related (pof tree (R2=0.84), basal area of all sizes tree (R2=0.86), and with the basal area of big trees (diameter > 30 cm) (R2=0.71). Based on the number and species density, agroforestry system (MA and CA) resembled the characteristics of natural forest (DF and PF)./spanEN-GBspan style