25th Asian-Pacific Weed Science Society Conference
13-16 October, 2015, Hyderabad, India
Diagnostic survey of a rice-based cropping
system in Vietnam with emphasis on weedy
rice (Oryzasativa f. spontanea)
Bhagirath Singh Chauhana, Ofelia S. Namuco, Leo Angelo L.
Ocampo, Tran Thi Ngoc Son, Tran Thi Anh Thu, Nguyen Ngoc Nam,
Le Ngoc Phuong, and Ali AhsanBajwa
aQueensland
Alliance for Agriculture and Food Innovation (QAAFI), The University
of Queensland, Toowoomba, Queensland 4350, Australia
Nghia Nguyen
Department of Soil Science, College of Agriculture and Applied Biology, Cantho
University, Vietnam
Introduction
- Mekong Delta, Vietnam, covering about 4 million ha, is a
major rice-producing area in Vietnam.
- 80% of the 17 million inhabitants in the Mekong Delta were
engaged in rice cultivation, producing half of the country’s
total rice production.
-Declining water resources, limiting labour availability,
increased cropping intensity, enhanced production
requirement, depleting soil fertility, diminishing resource use
efficiency, associated environmental hazards, and climatic
catastrophes, from transplanted method  direct seeding
from seeds sown in the field.
* Advantages of DSR:
- Crop establishment is earlier.
- More efficient for labor and
water use than puddled transplanted rice.
* Disadvantages of DSR:
- Heavy weed infestations
- Poor crop establishment
- Panicle sterility
- Diseases, pathogens and insects
- Nutrient management,
- Yield stagnation
- DSR in the Mekong Delta region involves four seeding methods: wet seeding, water
seeding, zero-till seeding, and dry seeding.
- The most common is wet direct-seeded rice (WDSR), which involves soaking the
seeds in clean water for 24 h and then incubating them for 24 - 36 h.
- The pre-germinated seeds are then broadcasted on the surface of drained and
puddled soil, which is then irrigated after a few days.
- Weedy rice infestation which is one of the main constraint of WDSR can cause a yield
loss of 16% or even more.
- No much information about weedy rice in the WDSR system in the Mekong Delta,
Vietnam and as well farmers’ familiarity with weedy rice (Oryza sativa f. spontanea),
particularly the extent of weed occurrence and infestation in this region have been
published.
Objectives
1. To address weedy rice problems and management in WDSR in some
locations of the Mekong Delta region of Vietnam.
2. To study farmers’ familiarity with weedy rice (Oryzasativa f.
spontanea), particularly the extent of weed occurrence and infestation
of the DSR in the region.
Materials and methods
1. Diagnostic survey locations:
- 3 different locations in Can Tho city:
1) Phuoc Thoi (sub urban district)
2) Thoi Lai (rural district)
3) Co Do (rural district)
Each location: 34 rice farmer households were surveyed.
Established in 2012 and 2013 dry seasons.
- Majority of the farmers in these localities practice WDSR
- Rice fields are inundated before November,
2. The structure of survey questionnaire:
The final questionnaire focused on farmers’ cultural practices:
1. The use of DSR,
2. Seedling establishment
3. Land preparation
4. Irrigation
5. Fertilizer
6. Pesticide usage.
7. Weed-related questions dealt with weed infestations and farmers’
familiarity with weedy rice (i.e., features of weedy rice and its management
and control.
- The data were analyzed and interpreted through descriptive statistics by ranking
or paired t-test.
- The FH responses for each category or statement as percentage (or percent of
surveyed farmers) for each year were averaged across the 102 FHs
- The cost and return analysis for each of the three districts for two years was
based on yield and profit and was computed as follows:
(1) Gross return = Grain yield (t.ha-1) x Selling price (USD per ton)
(2) Total inputs (USD.ha-1) = Labor + Materials + Other costs
(3) Net profit = Gross return – Total inputs
Results
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Source: Chauhan et al., 2015
Conclusions
- Wet direct seeding of rice is a very popular crop establishment method in many parts
of Vietnam, including Phuoc Thoi, Thoi Lai, and Co Do districts in the Mekong Delta
region.
- Crop establishment was not a problem at the three chosen sites because irrigation
was available.
- The farmers took advantage of the residual moisture after the rains (or when the
floods recede) to establish the WDSR crops.
- Seed supply was not a constraint because farmers usually saved seeds for the
following season; one alternative is seed exchange activities.
- Farmers realized that high seeding rate (between 100 and 300 kg ha-1) to cover losses
from poor germination and predation was not economical.
- Weedy rice infestation was the worst problem encountered in WDSR at the survey
sites.
- Most farmers were aware of the presence of weedy rice in their fields and
the damage it does to the crop.
- In weedy rice infested areas, there is further scope to increase rice yield.
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