Agroforestry systems may play a critical role in reducing the vulnerability of farmers' livelihood to droughts as tree-based systems provide several mechanisms that can mitigate the impacts from extreme weather events. Here, we use a replicated throughfall reduction experiment to study the drought response of a cacao/Gliricidia stand over a 13-month period. Soil water content was successfully reduced down to a soil depth of at least 2.5 m. Contrary to our expectations we measured only relatively small nonsignificant changes in cacao (À11%) and Gliricidia (À12%) sap flux densities, cacao leaf litterfall ( 1 8%), Gliricidia leaf litterfall (À2%), soil carbon dioxide efflux (À14%), and cacao yield (À10%) during roof closure. However, cacao bean yield in roof plots was substantially lower (À45%) compared with control plots during the main harvest following the period when soil water content was lowest. This indicates that cacao bean yield was more sensitive to drought than other ecosystem functions. We found evidence in this agroforest that there is complementary use of soil water resources through vertical partitioning of water uptake between cacao and Gliricidia. This, in combination with acclimation may have helped cacao trees to cope with the induced drought. Cacao agroforests may thus play an important role as a drought-tolerant land use in those (sub-) tropical regions where the frequency and severity of droughts is projected to increase.

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<p>One way to control or slow down the nutrient release rate from fertilizer is by coating technique.  Nowadays the use of biodegradable coating materials for slow-release fertilizer (SRF) is preferable because of environmental issues.  This research was aimed to make SRF using starches and cellulose as the coating materials and to test the release rate of the nutrients.  Five kinds of starches (cassava, corn, sago, wheat, and glutinous rice) and carboxymethyl cellulose (CMC) were used as coating material for granulated NPK fertilizer.  The coated fertilizers (NPK SRF) were tested for their leaching rate in the soil by percolation experiment.  The results showed that the kind of starch used influenced the release rate of the NPK SRFs. The NPK SRF coated with sago starch exhibited slow release rate and low leached nutrients which also resulted in slow growth of corn plant, as expected of SRF.  The use of starch and CMC as biodegradable coating materials in this research has a possibility to affect the microbial activity in the soil so that the nutrient release became faster than the uncoated NPK fertilizer.</p>

Indonesia has around 14 million ha of peatlands which constitutes 7.4% of Indonesia’s land area and very potential to be developed to support national development, especially related to economic strengthening and in enhancing employment opportunities. An expand areas of peatlands in Indonesia are already being utilized for forest plantation of Acacia crassicarpa. To gain clues in understanding how the chemically poor ecosystems can support the plantation, nutrient cycles. The research was carried out in Acacia crassicarpa plantation areas in South Sumatra, Jambi, and Riau, respectively representing shallow, medium, and deep peat. Data collection includes chemical characteristics of the peat, decomposition rate of the litter, fluctuations of the water table, and growth and production of the Acacia crassicarpa. The results show that: a) Acacia crassicarpa growth and production on peatlands much more depend on the nutrient cycles than on the chemical characteristics of the original soil; b) Leaf-fall and the speed of decomposition respectively from the highest to the lowest, are Riau (deep peat), South Sumatra (shallow peat), and Jambi (medium peat); and c) The more leaf-fall produced and the faster the decomposition, the faster is the nutrient cycles and hence the highest is the production of plant biomass.