Publication Type Conference Paper
Year of Publication 2015
Conference Name Climate-Smart Agriculture Conference
Authors Macedo, J.Souvanhnachit M.Rattanavong S.Maokhamphiou B.Sotoukee T.Pavelic P.Sarkis M., and Downs T.


Climate change and climate variability pose significant risks to smallholders in the rainfed lowlands of Lao PDR. Increased surface temperatures, declining rainfall, persistent drought and depleting soil nutrients all serve to impact agricultural productivity and livelihoods. This study investigates the impact of five treatments on soil nutrients, moisture, plant growth, and yield of water spinach (Ipomoea aquatica). The treatments tested were rice husk biochar only, biochar inoculated with manure, manure tea, inorganic fertilizer and the control. The costs and benefits of the treatments were also assessed. The randomized complete block design was used to assign five treatments and eight replications to the experimental units. Biochar was produced through slow pyrolysis. Soil physical properties were assessed with the visual soil assessment method and 15-randomized soil samples were collected for chemical analyses. Sprinklers were used for irrigation and a weather station installed to monitor the climate. Descriptive statistics and analysis of variance were used to analyze the data. Costs-benefits evaluation of the treatments was conducted to determine the net benefits relative to the initial costs ratio. The analysis of variance of mean yield indicates that the difference in yield among the treatments was highly significant. The computed F value (8.28) was higher than the tabular F value (2.64) at the 5% level of significance. The calculated coefficient of variance of mean yield was 17.33%. The net benefits to initial costs ratio of treatments suggest that the control (4.11), biochar inoculated with manure plus NPK (1.64), and biochar plus manure tea (1.01), and biochar inoculated with cattle manure (0.93) are most preferred. The net benefits and initial costs evaluation of treatments is important to assess whether utilizing these treatments would impact smallholders’ livelihoods. The results of this study contribute to the evidence that biochar could play an essential role to mitigate climate change risks by enhancing soil quality and increase agricultural productivity.

Note: Statistical results and CBA ratio modified on 3/29/2015 after further cross-validation.

Irrigation Groundwater Quality for Agricultural Usability in Biochar and Fertilizer Amendments among Smallholders Irrigators in Ekxang Village, Vientiane Province, Lao PDR

1J. Macedo, 2M. Souvanhnachit, 3S. Rattanavong, 4B. Maokhamphiou, 4T. Sotoukee, 4P. Pavelic, 1M. Sarkis, 1T. Downs

 1 Department of International Development, Community, and Environment, Clark University, Worcester, MA. U.S.A.

2 Department of Water Resources Engineering, National University of Laos, Vientiane, Lao PDR

3Independent Consultant, Washington DC, U.S.A.

4 International Water Management Institute Vientiane, Lao PDR.

 Climate change risks pose significant challenge to smallholder irrigators who rely on rainfed agriculture for their livelihoods. Increased mean surface temperatures, varying rainfall, increasing evaporation and declining soil moistures all serve to impact productivity. Groundwater irrigation poses promising potential for agricultural productivity and the livelihoods of smallholders. Groundwater irrigation for agriculture use requires constant water quality monitoring. This excerpt is part of a field research, which assessed the impacts of biochar and fertilizer treatments on soil nutrients status, soil moisture, irrigation groundwater quality for agricultural use on the growth and yield of water spinach (Ipomoea aquatica). Groundwater quality was monitored to determine the levels of electric conductivity (EC) and total dissolved solids (TDS) determinants of salinity and sodium, calcium, and magnesium to calculate the sodium absorption ratio (SAR) to estimate sodicity. The methods involved daily field tests to measure EC, TDS, pH, temperature, and detailed chemical analysis. The results indicate that the mean EC (0.021 dS/m; SD = 0.010) is significantly less than the salinity tolerance threshold for water spinach (< 1.3 dS/m) and the mean TDS (12 ppm; SD = 4.5) with soil pH of 6.6. The results suggest that the irrigation groundwater quality was suitable for agriculture and the chance of salinity was significantly low. The computed SAR 0.174 was significantly lower than the normal level (<10) above which soil water permeability could result from sodic soil condition. The results demonstrate that groundwater use for agriculture could assist smallholders adapt to climate change risks, but judicious use requires constant monitoring of groundwater quality and resources to increase crop yield and improve soil health.

 Key Words: Salinity, Sodicity, Groundwater Quality, Electric Conductivity, Total Dissolved Solids, Sodium Absorption Ratio

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