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Figure 1: Effect of biochar, charcoal and biodigester effluent on biomass yield of water spinach in the first harvest |
Figure 2: Effect of biochar, charcoal and biodigester effluent on biomass yield of water spinach in the second harvest |
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Reducing Greenhouse Gas Emissions from Livestock and Soils |
A biotest was carried out at the research centre of Champasack University, Lao PDR to determine the effect of biochar , charcoal and biodigester effluent on growth of water spinach. The fifteen treatments in a completely randomized 3*5 factorial arrangement with 3 replications were: soil amender (biochar or charcoal or none) at 40 tonnes/ha and level of effluent (0, 25, 50, 75 or 100 kg N/ha) applied to samples of soil held in fifteen litre capacity plastic baskets. Sixty seeds of water spinach were planted in each basket. After germination, some seedlings were removed to balance the number in each basket (40 seedlings) for the rest of the experiment. The plants were irrigated every morning and evening. Measurements were made of height, number of leaves, and weight of above-ground biomass after 35 days and again (regrowth) after a further 35 days.
Both soil amenders (biochar and charcoal) gave similar improvements in water holding capacity of between 27 and 38%. Soil pH was increased from 4.7 to 6.5 due to addition of biochar. Biochar increased foliage yield of the water spinach in both the first and second harvests, but there was no apparent effect on foliage growth from application of charcoal. In the first harvest (Figure 1), there were curvilinear responses to biodigester effluent for biochar and charcoal amenders, with the peak occurring at between 50 and 75 kg N/ha. For the un-amended soil the response was linear with the highest yield at 100 kg N/ha. In the second harvest (Figure 2), the response to effluent for the biochar amender was again curvilinear with the peak at 50-75 kg N/ha; by contrast the response to effluent with the charcoal amender was linear with maximum yield requiring 100 kg N/ha. On the un-amended soil there was no relationship between effluent level and biomass yield.
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Figure 1: Effect of biochar, charcoal and biodigester effluent on biomass yield of water spinach in the first harvest |
Figure 2: Effect of biochar, charcoal and biodigester effluent on biomass yield of water spinach in the second harvest |
