Central coastal Vietnam is the driest part of the country with most of the rain falling in only 3-4 months of the year. Rainfall in the wet season can be very intense causing flooding and erosion. It also has extensive areas of sandy soils which have low nutrient content and organic matter. In the long dry season agriculture in the region is highly dependent on irrigation water which is often in short supply. This project will develop, evaluate and extend practices which aim to increase the efficiency of use of scarce irrigation water and improve soil management in horticultural tree crops in central coastal; Vietnam and subtropical NSW. The projects activities in Vietnam are focussed in the provinces Ninh Thuan and Binh Binh.

The project aims to
Assess the potential sources, availability and costs of irrigation water in landscape units long central coastal Vietnam;
Identify current farmer practices and perceptions in relation to irrigation water and nutrient management.
Increase the technical capacity of the Agricultural Sciences Institute for Southern Coastal Central Vietnam
Evaluate water and nutrient management strategies to improve productivity and profitability of tree crops and resource use efficiency.

The water resource assessment indicates that irrigation from shallow groundwater is the dominant water source for farms in Binh Dinh. The sandy soils here occur across a flat to undulating riverine landscape extending 30 km from the coast. The watertable fluctuates from 4-6m between the wet and dry season. Wells are common and are used for both irrigation and domestic supplies. There are some farm dams and these fill from both groundwater and surface runoff.
There are three types of water resources for irrigation in the sandy soil area of Ninh Thuan. First, the coastal wind blown sands dune systems act as recharge areas for fringing wetlands and groundwater fed streams. Second, surface storage in small dams of runoff water and spring fed dams are found in the mid and upper sub-catchment valley floors and mountain toe slopes containing weathered granite colluvium. Third, groundwater and diverted river water are used in the alluvial levee soils on the floodplain near the river which is mainly sandy loams. Irrigation wells within a few kilometres of the coast have become saline due to seas water intrusion. Government reservoirs have been constructed in the higher parts of the catchment in Binh Dinh and Ninh Thuan to supply water for irrigation and hydroelectricity and more are planned.
A survey of farmer practices was conducted in Ninh Thuan and Binh Dinh. The survey questioned 150 farmers in each province about their farming system, water use and fertilizer use. Ninety five percent of farmers surveyed use wells for household water and irrigation. Irrigation water in Ninh Thuan is usually available for 3-6 months of the 9 month dry season. Most farmers use both animal manure and urea with most fertiliser being applied to high value crops such as vegetable, grapes, and apple. Nearly all farmers heavily cultivate the soil to construct furrows for water distribution.
As part of the capacity building objective, an irrigation course developed by NSW DPI was adapted to suit Vietnamese needs, translated and presented to a group of 30 Vietnamese researchers, extension officers and some NGO staff. The course ran over 3 days and covered soil and soil water characteristics, plant water requirements and scheduling, and assessing and managing locally appropriate irrigation systems to meet crop needs efficiently. The Vietnamese partners intend to use this course as part of a process for increasing farmer irrigation skills and productivity.
A nutrient management experiment and an irrigation experiment have been established on red ferrasol soils on the Alstonville Plateau, NSW. The nutrient management experiment is evaluating the effects on incorporation of biochar (10 t/ha, green waste and cattle feetlot waste biochars) on forage production (pinto peanut and annual ryegrass). Initial results indicate that dairy waste char enhanced growth of rye grass in the presence of N fertiliser and increased available nutrients. This was not the case with green waste char.
A simple daily crop-soil water balance model has been partially constructed to assess the average irrigation requirement of a closed canopy crop for each month of the year. The model also calculates the probability that soil moisture will exceed a given amount during each month of the year. The model uses long term climatic data (rainfall and potential evapotranspiration), crop factors, irrigation amount and rootzone soil water capacity as inputs. Following further testing and refinement, the model has application for assessing irrigation management strategies in both NSW and Vietnam. An irrigation experiment is being established on a blue berry orchard to evaluate partial irrigation strategies. These experiments will be used for training activities with visiting Vietnamese scientists.

Accomplishments during the second year of this project include: 1) establishment of cashew and mango irrigation field experiments and demonstration trials in Binh Dinh and Ninh Thuan provinces; 2) establishment of biochar field experiments with groundnut and cashew in Binh Dinh province; 3) completion of soil nutrient management workshop and intensive small group technical sessions for Vietnamese team; 4) Binh Dinh cashew farmer field day held by the Vietnamese partner; 5) establishment of blueberry irrigation experiments in NSW; 6) completion of biochar field experiment in NSW; 7) two key members of the Vietnamese team delivered a presentation at the Asia Pacific Biochar Conference, Gold Coast, Australia, and visited NSW Department Primary Industries, Wollongbar and Alstonville in May 2009.
The Vietnamese partner has established four irrigation trials in Binh Dinh and two in Ninh Thuan that aim to demonstrate that cashew and mango yields can be increased by extending irrigation beyond flowering (current practice). The impact of extending irrigation beyond flowering plus irrigation during the pre-wet season first vegetative flush of cashew is also being assessed in a replicated field experiment established in Binh Dinh. A second field experiment in Binh Dinh aims to evaluate alternating root wetting. Irrigation scheduling using mini-evaporation pans is being introduced through each of these trials and drip irrigation is being introduced in one of the Ninh Thuan demonstration trials. Positive yield responses to irrigation scheduling using the mini-evaporation pan, drip irrigation and extending irrigation beyond flowering have been achieved in the Ninh Thuan cashew field trials. Unfortunately, unseasonal, frequent rainfall has been detrimental to irrigation field trials in Binh Dinh. These field trials will be repeated in the third year of the project, which will hopefully see less rainfall.
In Ninh Thuan, a table grape field trial was established to demonstrate how irrigation scheduling using mini-evaporation pans and using drip irrigation can be applied to improve water and nutrient use efficiency and reduce nutrient leaching. Irrigation using the mini-evaporation pan has reduced irrigation inputs by more than 30% without any apparent consequences for grape yield or quality. Widespread farmer adoption of these simple, inexpensive irrigation strategies could reduce nutrient leaching at the catchment scale which will ultimately deliver environmental and community health benefits by improving the quality of groundwater used for drinking, livestock and irrigation.
In June 2008, a soil nutrient management workshop was delivered in Binh Dinh province. Most of the 30 participants are involved in the project at a leadership or technical level. Practical demonstrations in monitoring nutrient leaching were presented to equip participants with skills for assessing strategies to reduce nutrient leaching. Participants were also introduced to the concept of nutrient budgeting, thus laying a foundation to be further built upon by ACIAR project SMCN 2007/109 "Sustainable and profitable crop and livestock systems for south central coastal Vietnam" which commences June 2009.
In addition to the irrigation trials, two field experiments have been established to investigate biochar soil amendments to improve the water and nutrient holding capacity of sandy soil. The effects of biochar on plant nutrient uptake and fertiliser use efficiency is being examined on cashews and groundnut. The first season's results from these experiments will be available mid-2009. Preliminary biomass and yield assessments indicate positive yield responses for both cashew and groundnut crops.
In April 2009, the Vietnamese partner conducted a very successful cashew farmer field day in Phu Cat district, Binh Dinh. One hundred letters of invitation were distributed and eighty people attended. The day was also attended by local and national television and print media. The program covered multiple components of cashew cropping systems including pest control, nutrient and irrigation management. Farmers were introduced to mini-evaporation pans, biochar as a soil amendment and were shown the cashew irrigation and biochar field experiments.
In NSW, a field experiment has been established near Wollongbar to evaluate the application of water budgeting, deficit irrigation and partial rootzone drying (PRD) for achieving water use efficiencies in blueberry production. Demonstrating a plant physiological response to PRD and deficit irrigation treatments has been made difficult by frequent and above average rainfall throughout the duration of the field study. However, all irrigation strategies have shown substantial water use efficiency gains in comparison to the standard "rule of thumb" farmer practice. A stomatal closure response to PRD was observed during a glasshouse experiment with blueberry plants. This response was not accompanied by a reduction in plant turgor, indicating that, under more demanding field conditions, PRD could potentially be used to conserve water by reducing transpiration in blueberry plants.
A biochar soil amendment field experiment conducted at Wollongbar, NSW has been completed. Results from the experiment have demonstrated a statistically significant 20% dry matter biomass yield increase for annual ryegrass grown in soil amended with biochar made from cattle feedlot residues when combined with NPK fertiliser. Without the addition of NPK fertiliser, feedlot biochar increased plant uptake of N, P and K by 7, 14 and 26% respectively. Biochar made from municipal greenwaste did not deliver such results but both biochars increased soil C by 0.5%.

Over the past two cropping seasons a prolonged wet season followed by two typhoons affected cashew field experiments. This year unseasonably hot conditions at flowering resulted in nut-set failure across Ninh Thuan and surrounding coastal provinces and yields recorded from field trials were well down on previous seasons. The situation is of concern as many cashew farmers will receive little to no income from their orchards this year. Binh Dinh province did not experience the same climatic extremes and cashew yields here indicate benefits from following guideline fertiliser inputs and scheduling irrigation using mini-evaporation pans.

Soil moisture and water table monitoring in Binh Dinh indicates that cashew trees planted in lower lying areas access shallow groundwater. This may explain why at least one Binh Dinh cashew farmer achieves high yields despite irrigating only once at flowering. Delaying irrigation until groundwater has fallen below a threshold has potential to reduce the irrigation season by several weeks. Groundwater uptake by cashew trees, and the need to adjust irrigation scheduling accordingly, is being examined as part of current field activities but a more extensive assessment is needed.

Irrigation scheduled using a mini-evaporation pan demonstrated a 53% reduction in water use, compared with the farmer standard practice of daily flood irrigation, without affecting yields in a Ninh Thuan table grape trial. Monitoring at this trial site confirmed heavy leaching of nutrients below the root zone under flood irrigation and raised electrical conductivity and high nitrate levels in underlying groundwater. A gravity fed drip irrigation system trialled with table grapes in 2008-2009 proved to be troublesome. Following subsequent communications the NGO supplier, International Development Enterprise (IDE), has begun developing a cost effective pressurised drip system. ASISOV, Ninh Thuan and a farmer from Ninh Hai, who has been using pressurised drip irrigation with grapes for 6 years, are assisting IDE in trialling the new system with tomato and chilli crops into which grape seedlings have been planted. The results from this trial are promising.

A groundwater quality survey was conducted in Ninh Hai district in March 2010. Thirty one irrigation wells were assessed for salinity and nitrate levels. Groundwater salinity ranged from EC 2 to 13 dS/m, averaging EC 5.5 dS/m. These EC levels are considered high for sensitive crops including most vegetables. Thirty percent of the wells had nitrate levels above 250 mg/L. A survey of Ninh Hai farmers indicated that flood irrigation is carried out daily and that variable but high rates (>1000kg N/ha) of fertiliser are commonly applied. Anecdotal evidence indicates that groundwater salinity problems occur extensively along the coastal strip of southern central Vietnam. An unrealised opportunity exists to target Ninh Hai for research to identify amelioration strategies with the outcomes potentially having broader impacts across the region. Such strategies may involve improved fertiliser and irrigation management, soil amendments and hydrological solutions.

Experiments involving rice-husk biochar soil amendments continue to produce promising results. The initial biochar-groundnut experiment reported in 2008-2009 has been repeated on the same site and replicated at several other sites. It is apparent that rice-husk biochar is enhancing soil moisture availability to plants. This appears to be a major factor involved in higher biomass and nut yields observed in biochar treated soil. The results also implicate biochar in increased plant nutrient uptake and increased rates of soil carbon deposition. Initial cost benefit analysis indicates that, at a cost similar to manure, biochar will provide a financial benefit in peanut production. This is before factoring in the potential to reduce fertiliser inputs which still needs to be assessed. Continuing the existing biochar experiments for 5 years (preferably 10 years) will provide an opportunity to evaluate the longevity of biochar affects and the potential for longer term economic benefits.
Activities within Australia have also seen excellent progress. The most recent results from an ongoing biochar-pasture field experiment indicate that feedlot biochar significantly increased soil phosphorus availability over a three year period. Non-char soil carbon has also increased at a faster rate (up to 0.8% Dumas C) in feedlot and greenwaste biochar amended soils than in unamended soil.

Outcomes from a completed blueberry irrigation experiment in NSW demonstrated the inefficiencies of the industry standard 'rule of thumb' approach to irrigation with a 21% (0.77 ML/ha) reduction in water use achieved by scheduling irrigation based on Penman-Monteith ETc estimates. Applying regulated deficit irrigation during late spring to early autumn achieved a 32% (1.33 ML/ha) water saving without significantly reducing berry yield or quality. Plant responses to partial rootzone (PRD) drying observed during glasshouse trials were not repeated in the field experiment. However, results from the glasshouse trial indicate that it would be feasible to repeat a PRD field experiment under more favourable conditions.

Another highlight from the past year was a visit to Australia by five members of the Vietnamese project team who each undertook intensive training during their two week stay.