This project aims to improve profitability and sustainability of water use in groundwater-dependent smallholder farming systems in South Central Coastal Vietnam.
The groundwater resource in South Central Coastal Vietnam is vulnerable to overexploitation and pollution due to nutrient and contaminant leaching. Improving knowledge of groundwater resources will improve planning and regulation of their use and boost livelihoods on farms through more productive water and nutrient use. Improving the productivity and sustainable management of low fertility sands through improved water and nutrient use efficiency are common priorities for South Central Coastal Vietnam and Western Australia.
The outputs are a groundwater model of the regional groundwater balance and its economic value for agriculture in South Central Coastal Vietnam now and into the future, training modules for Vietnamese farmers, options for increasing soil productivity, and an economic analysis of the whole farm benefits and costs of implementing promising new technologies. The project will demonstrate and disseminate the outputs to encourage adoption by farmers and influence policies and initiatives.
The overall aim of this project is to increase crop productivity of low fertility sands through improved water and nutrient use efficiency in groundwater dependent smallholder farming systems in south-central coastal Vietnam (SCC VN) for profitable and sustainable outcomes by
assessing groundwater utilisation and quality in targeted areas within Binh Dinh and Ninh Thuan provinces in SCC VN;
evaluating methods to improve on-farm water use efficiency and to overcome soil constraints; and
determining promising soil and water management technologies for adoption by farmers and developing scale out and communication programmes for SCC VN
The project commenced in June 2014.
Geospatial information is being acquired on weather (precipitation and evaporation), land use, topography, soil types and watertable elevations for the La Vy river basin. A map of the La Vy river basin, that lies in the focus area of Binh Dinh province, has been developed using the current available information by Nong Lam University (NLU) and will be further developed as more information becomes available. SWAT and Groundwater models will be used at Flinders University and NLU to fill knowledge gaps for future assessment of groundwater utilisation. Division 7 will procure 5 years of previous rainfall and evaporation data.
Lack of data on the stage height of the river and the lack of a monitoring station are hampering parameterizing of surface and groundwater models. NLU is planning to install one long-term monitoring station at the outlet of the La Vy river. Additional stream level monitoring will also be implemented at the confluences of the sub-catchments subject to the availability of equipment.
Little information exists on surface and groundwater quality. Hence, a comprehensive sampling of surface and groundwater was carried out by Division 7 and DONRE in April 2015 in the La Vy river basin comprising sampling from 11 drilled wells, 96 open (dug) wells, and 11 stream locations. Chemical and physical parameters including water temperature, pH, colour, smell, taste, total dissolved solids, electrical conductivity, dissolved oxygen, salinity, nitrates/nitrites and phosphates were also measured. The data will be analysed to select groundwater-monitoring locations.
The initial survey identified an average open well depth of just over 4.5 m, an average drilled well depth of 8 m and corresponding average depths to water of 2.5 and 6 m, respectively. Groundwater pH varied between 2.3 -7.6, with most being slightly acidic. Water in the river had an average pH value of 5.5. In general, nitrate and nitrite concentrations were low in the groundwater and river water, although values up to 50 mg nitrate /L were detected in the groundwater. Measured levels of phosphates were slightly higher, with average values of 3 and 4.5 mg/L in open and drilled wells, respectively. These values warrant further investigation. Salinity was generally low, averaging just under 0.3 dS/m. Sampling campaigns will now be conducted for groundwater and surface water from different locations, 4 times per year to assess variability in the water quality.
IAS has commenced monitoring of the water quality in An Hai and Nhon Hai communes of Ninh Thuan province. As per the initial monitoring program, water quality varies with location in Ninh Thuan, and in some samples both electrical conductivity (EC) and nitrate levels were found to be above the permissible limits. Salt intrusion from sea is a likely cause for high EC values, whereas, high fertiliser rates and manure seems to be the source of nitrate in the groundwater. Open wells generally had higher values of nitrate than in tube wells. Monitoring of water quality will commence in other communes of Ninh Thuan to provide a more comprehensive view of water quality in coastal regions of the province.
The Farm economic model (FEM) is being used by HCE and NLU to assess the economic value of groundwater after training by Peter Gartrell, Department of Agriculture and Food West Australia. NLU and HCE are collecting data to parameterise the model for peanut and mango.
Hue University of Agriculture and Forestry (HUAF) examined response to K and S by using different forms and rates of fertilizers for peanut and mango and are assessing on-farm nutrient balance in cropping systems. In 4 sands from Ninh Thuan, and 4 sands from Binh Dinh, K and S were limiting nutrients restricting peanut growth. From the 4 field peanut experiments conducted in Binh Dinh, 2 each on different forms of K (KCl, K2SO4 and K40%) and rates (0, 60, 90 and 120 kg K2O/ha) and 2 for different forms of S (K2SO4 , (NH4) 2SO4 and NPK 16-16-8-13S) and rates (0, 15 and 30 kg S/ha), application of 120 kg of K2SO4/ha performed best, yielding 3.9 t/ha and 3.6 t/ha in Cat Hiep and Cat Hanh communes. Similarly, the blend of NPK (16-16-8-13S) at 30 kg of S/ha performed best yielding 3.3 and 3.8 t/ha in Cat Hiep and Cat Hanh communes, respectively. Of the 2 field experiments in Cat Hiep and Cat Hanh communes on integrated nutrient management, application of 8 t/ha of manure in combination with 40 kg N, 90 kg P2O5 and 500 kg of lime and combination of 10 t/ha biochar with 40 kg N, 90 kg P2O5 and 500 kg of lime achieved higher yields than inorganic fertilisers alone.
ASISOV conducted several experiments on peanut and mango testing irrigation technologies (sprinkle, perforated hose pipe) and an irrigation scheduling method (minipan) relative to farmers’ practices. Sprinkler irrigation guided by mini-pan increased peanut yield by 15% in comparison with farmers’ practice, both in Cat Hanh and Cat Hiep communes, Binh Dinh province. Irrigation with sprinkler guided by minipan in sandy soils of Ninh Thuan also increased peanut yield by 15% and saved nearly 71% of water when compared with farmers’ practice.
One of the experiments conducted on Cu deficient sand in Ninh Thuan failed to show a response to Cu as a result of sugarcane straw applied to the field to restrict wind erosion. The level of Cu in the sugarcane straw was sufficient to overcome Cu deficiency. The experiment is now being repeated in sands of Binh Dinh after screening for Cu and B deficient soils using the double pot technique.
Module based training programmes for soil (sand addition?), water (mini-pan, sprinkler, perforated hose and farmers practice) and nutrient management (manure + inorganic fertilisers, biochar + inorganic fertilisers) technologies for farmers were developed by ASISOV and the consultant (Dr Ho Dang). Training was also conducted by them for extension officers of DARD, Binh Dinh and the technicians from communes of Binh Dinh. A field demonstration of the effectiveness of soil, water and nutrient management technologies was conducted by ASISOV and a field day for 70 people was organized to show the treatment effects. Integrated irrigation and nutrient management was shown to be the most cost effective exercise by reducing number of irrigations, saving labour costs and increasing yields.