Photo: David Brazier/IWMI Photo :Tom van Cakenberghe/IWMI Photo: David Brazier/IWMI Water for a food-secure world W. Mekuria, A. Noble, C.T. Hoanh, M. McCartney, O. Sengtaheuanghoung, N. Sipaseuth, S. Douangsavanh, S. Langan, K. Getnet The potential role of soil amendments in increasing agricultural productivity and improving livelihood of smallholders in Lao PDR 15 th NAFRI Anniversary, 9-10 April 2014, Vientiane, Lao PDR

Water for a food-secure world 1. Introduction  In the Lao PDR, 75% of food production is dependent on smallholder agricultural systems that are under serious threat due to: -Soil erosion -Poor soil fertility -Climate variability.  Change in agricultural systems should increase production while preserving or improving soil quality.  Low-cost organic and clay-based soil amendments can be considered as options.  For technological adoption, evaluating economic viability of technologies in the perspective of smallholder farmers is critical.

Water for a food-secure world Objectives  In this study, we investigated the impacts of organic and clay-based soil amendments on: -Maize yield (MY) and total nutrient uptake (TNU) -Crop Water Productivity (CWP) -Soil variables influencing changes in MY & TNU -Economic returns

Water for a food-secure world 2. Materials and Methods 2.1 Study Area Fig. 2 Rainfall amount (mm) during the growing periods Fig. 1 Study areas

Water for a food-secure world Continued … Fig. 3a Daily rainfall distribution at Naphok Fig. 3b Daily rainfall distribution at Veunkham

Water for a food-secure world 2.2 Experimental design  Structured field experiments were established (2011 and 2012) with maize as the test crop.  Randomized complete block design  10 treatments: Ct (control) - Bc (rice husk biochar) - Bcc (composted biochar) - Co (compost) - CM (clay manure compost) - Bt (Bentonite clay) and combinations).  Three replications  All treatments were applied in 2011.

Water for a food-secure world 2.3 Estimation of maize yield  Maize ears were harvested from the three interior rows (22.5 m 2).  Shelling percentage  Adjusted to dry mass & standardized to 15.5 % moisture content.  Mean plot yield was converted into a per hectare yield. Harvesting Weigning

Water for a food-secure world 2.4 Soil and plant sampling and analyses  Soil samples from the m depth were collected in 2011 and  A total of 60 composite soil samples were collected.  SOC, NPK, CEC, pH ….

Water for a food-secure world 2.5 Determination of Et o and CWP  ET o was determined on daily time step using the FAO Penman-Monteith method (Allen et al., 1998).  Crop Water Productivity (CWP) was determined by using the crop water use obtained after simulating the environmental variables using AquaCrop model (FAO, 2011).  The CWP of the treatments was determined using the equations: where: CWP et (Y) is the crop water productivity of evapotranspiration of grain yield.

Water for a food-secure world 2.6 Economic Valuation  To determine the costs and benefits of soil amendments over two cropping seasons (2011 and 2012), we applied a cost-based value method.  The Economic value of increase maize yield in monetary terms is determined as the additional maize yield × local market price  The additional costs incurred due to the use of soil amendments were also expressed in monetary value.  Marginal (additional) benefits were compared with marginal costs to determine the economic returns (profitability).

Water for a food-secure world 3. Results and Discussion Fig. 4 Maize grain yield as affected by treatments

Water for a food-secure world … Continued Fig. 5 Crop water productivity as affected by treatments

Water for a food-secure world 3.2 Explaining variables – Total Nutrient Uptake Fig. 6 Total nutrient uptake at Veunkham (a) and Naphok (b) (a) (b)

Water for a food-secure world Continued …  The improvement in soil properties resulted from soil amendments  Significant treatment effects were observed among treatments in: o soil pH o TOC o Ca++, o Mg++ & o CEC VariablesVeunkhamNaphok r values at p < Soil pH CEC0.46 Ca Mg SOM0.70 Table 2 Relationships between maize yield and soil properties

Water for a food-secure world 3.3 Revenues from yield increments over two cropping seasons Fig. 7 Additional yield gains and revenues

Water for a food-secure world 3.4 Implications for sustainable agriculture  Locally available low-cost soil amendments significantly increased maize yield over a period of two years.  These yield improvements would generate a Net Present Value (NPV) of about 48.7 to US$ ha -1 at Naphok and about to 1,294.9 US$ ha -1 at Veunkham.  Such yield improvement while improving key soil properties and economic viability can be considered as an opportunity for sustainable agricultural production.

Water for a food-secure world 4. Conclusions  Application of organic and clay-based soil amendments and their combination can be effective in improving agricultural productivity, total nutrient uptake and crop water productivity.  Locally available low-cost soil amendments are economically viable options.  It is possible to enhance agricultural productivity by using soil-based interventions within the capacity of the smallholders.  Organic and clay-based soil amendments can have a significant positive effect in improving the resilience of smallholder farmers to climate variability through: -Increasing agricultural productivity and income -Restoring soil organic carbon.

Water for a food-secure world List of publications from this study Mekuria, W., O. Sengtaheuanghoung, C.T. Hoanh and A. Noble. (2012). Economic contribution and the potential use of wood charcoal for soil restoration: a case study of village-based charcoal production in Central Laos. International Journal of Sustainable Development & World Ecology. 19:5, Mekuria, W., K. Getnet, A. Noble, C.T. Hoanh, M. McCartney, S. Langan (2013). Economic valuation of organic and clay-based soil amendments in small-scale agriculture in Lao PDR. Field Crops Research 149(1): Mekuria, W. and A. Noble (2013). The role of biochar in ameliorating disturbed soils and sequestering soil carbon in tropical agricultural production systems. Applied and Environmental Soil Science, Mekuria, W., A. Noble, M. McCartney, C.T. Hoanh, S. Douangsavanh, S. Langan (2014). Enhancing crop water productivity in rainfed production systems through organic and clay-based soil amendments in Lao PDR. Submitted to European Journal of Agronomy.

Water for a food-secure world ControlClay-ManureComposted biochar