Soil management for raising crop water productivity in rainfed production systems in Lao PDR

This study investigated the impacts of organic- and clay-based soil amendments, and their combinations on crop water productivity (CWP) using maize as a test crop. On-station field trials were established over two consecutive years at the Naphok and Veunkham sites in Laos. At each site, 10 treatments were applied in a randomized complete block design with three replications. The treatments were control, rice husk biochar (10 t ha-1), bentonite clay (10 t ha-1), compost (4 t ha-1), clay-manure compost (10 t ha-1), rice husk biochar compost (10 t ha-1), bentonite clay + biochar, bentoniteclay + compost, biochar + compost, and bentonite clay + biochar + compost. All treatments were applied in 2011. Significant (p < 0.05) treatment effects in CWP and growing period evapotranspiration were determined. At Naphok, differences between the amended and control plots in CWP varied between 0.1 and 0.6 kg m-3 in 2011 and from 0.1 to 0.4 kg m-3 in 2012, whereas differences at Veunkham varied between 0.3 and 1.0 kg m-3 in 2011 and from 0.05 to 0.29 kg m-3 in 2012. At both sites, CWP in 2012 was significantly lower than 2011. Our results illustrate that organic- and claybased soil amendments improve CWP, indicating that soil-based interventions could be suitable options for improving agricultural productivity.