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Working with farmers to develop practical weed management techniques for direct-seeded rice in the Philippines

Sally Marsh1, Madonna Casimero2, Rick Llewellyn1, and Jesusa Beltran2

1 Agricultural and Resource Economics, The University of WA, Crawley, WA 6009. Email:
Philippine Rice Research Institute, Munoz, Nueva Ecija, Philippines. Email:


A number of economic and environmental forces are driving changes in rice planting techniques and weed management in the Philippines and Asia generally. These forces include reduced water availability, increased labour costs and increased herbicide availability. Both flooding and manual weeding are traditionally important for weed management in rice, and herbicides become the potential weed control substitute in systems with reduced water availability and higher labour costs. With direct seeding there is less use of flooding and manual weeding for weed control and an increased reliance on herbicides, potentially leading to an increased likelihood of herbicide resistance developing. In this paper we describe a project in two regions in the Philippines involving on-farm trials and farmer/researcher learning, planned over a four year timeframe, with the aim of testing and adapting an Integrated Weed Management (IWM) system that will be both profitable and practical for farmers.

Three key learnings: (1) learning on weed management techniques needs to be encompassed within a farming systems framework; and (2) good weed control can be obtained using IWM techniques; but (3) both external and internal constraints to the use of IWM exist and affect farmers’ use of IWM techniques for weed control. Work with farmers to develop a suitable, effective and practical IWM system is on-going, and results from a broader socio-economic survey will be used to help target extension needs beyond the participants in the trial work.

Key words

participatory farmer research, participatory action research, technology adaptation


In the Philippines and throughout Asia generally, a number of economic and environmental forces are driving changes in planting in irrigated rice from transplanting to direct seeding. Traditional rice transplanting techniques involve the replanting into flooded fields of young rice plants grown in seedling plots. In direct seeding, pre-germinated seeds are sown directly, often by broadcasting, on saturated soil in the rice fields. The major driving forces leading to an increase in direct seeding throughout Asia are considered to be rising labour costs, reduced water availability, increased availability of effective herbicides for weed control, and the need to intensify rice production systems through double or triple cropping (Pandey et al 2002).

Labour requirements to establish rice by transplanting are high, and increasing wage rates and labour scarcity because of off-farm migration are associated with the move to direct seeding (Balasubramanian and Hill 2002). Pandey and Velasco (2002) estimate that direct-seeding saves labour, particularly drudge labour such as transplanting, by as much as 50 percent. The ready availability of effective herbicides has enabled their use to replace manual weeding, another high labour use activity. Problems with water availability are also affecting the move to direct seeding of rice. Water and land resources are under pressure in Asia as urban and industrial sectors expand (Nguyen and Ferrero 2004). In the Philippines, there is only enough water to grow rice on half of the irrigated area during the dry season (IRRI 2001). Direct seeding is perceived as a water-saving technology with a potential to use less water than transplanted rice (Pandey and Velasco 2002).

Since 1995, the international price for rice has fallen in real terms, and at the same time, the costs of rice production have increased (Nguyen and Ferrero 2004). Direct seeding can both increase yields per hectare through double or triple cropping, and reduce costs. Pandey and Velasco (2002) report a lower average yield in direct-seeded rice, but a higher net profit because of savings in labour costs and higher total output because of a shift to double cropping. However, direct seeding results in more problems with weed control because the weeds emerge at the same time as the rice in fields that, unlike with transplanted rice, are not initially flooded. Weeding in direct-seeded rice fields is also more difficult as the rice does not grow in easily-traversed rows.

The Philippines has an agriculture-based economy, with rice the main crop and main food staple. There are over 2 million household farms with land areas on average of around 1.5 hectares. The proportion of rice area in the Philippines planted using direct seeding is substantial, and has been estimated at 42 percent (Pandey and Velasco 2002). In this paper we discuss work with farmers in two major rice-growing regions in the Philippines where direct seeding has been widely adopted (Marsh et al. 2005), Nueva Ecija in Central Luzon and Iloilo in the Western Visayas (Figure 1), to adapt an Integrated Weed Management strategy first developed by scientists at the Philippines Rice Research Institute (PhilRice). This work is a four-year collaborative project funded by the Australian Centre for International Agricultural Research (ACIAR) involving socio-economists, weed scientists and farming systems specialists from PhilRice and socio-economists, extension and herbicide resistance specialists from the University of Western Australia. In the remainder of this paper we briefly discuss weed management in direct-seeded rice, outline the theoretical approach being followed for the development and adaptation of the technology, and then discuss the initial implementation of on-farm IWM trials and farmer/researcher learning that has occurred so far.

Figure 1. Map of the Philippines, indicating the regions of Central Luzon and the Western Visayas.

Weed management in direct-seeded rice

A mix of cultural practices, water management, herbicides, and manual or mechanical weeding methods can be used to manage weeds in direct-seeded rice. A variety of cultivation methods can be used for weed control, all of them focused on good land preparation for weed control, such as repeated cultivation of the land to kill weeds prior to seeding, stale seedbed techniques, and thorough levelling. Stale seedbed techniques typically involve initially wetting the field and allowing weeds to germinate, followed by ploughing and then flooding for another 7-10 days to kill the initial flush of weeds, and then puddling and levelling the soil for planting (e.g. Balasubramanian and Hill 2002; Casimero and Juliano 2004).

All these cultural techniques require field availability prior to planting, availability of sufficient water when needed, and machinery and/or labour to carry out the multiple cultivations. In areas where direct seeding has allowed triple planting, the first mentioned may not be possible. Water availability can be an issue in some areas, and if machinery or labour must be hired for multiple cultivations this is also potentially a problem, both in terms of availability and cost. However, good cultural practices offer a solid foundation for effective weed control in direct-seeded rice.

Water management has traditionally been used to control weeds in transplanted rice crops immediately after transplanting. The availability of effective pre-emergence herbicides has allowed direct seeding techniques to be employed, with cultivation techniques and pre-emergence herbicides used to control weeds in the crucial first 7-10 days after seeding when water levels must be low: sufficient to keep the soil saturated but not flooded to allow root growth and seedling establishment (Balasubramanium and Hill 2002). Because of this, direct seeding is often first adopted by farmers for the dry season crop when it is easier to control for flooding. Once the crop is established, water management can be used to control weeds in the same way as for transplanted crops.

Cost and drudge labour factors aside, manual weeding is initially difficult in broadcast-sown rice because of the high plant density and the difficulty of differentiating grassy weeds from rice plants. Manual weeding can be just as effective as herbicides at later growth stages (Man and Mortimer 2002), but post-emergent herbicides are commonly used. In the Philippines, farmers apply herbicides from one to three times per crop to manage weeds in direct-seeded rice (Casimero and Juliano 2004). Other measures that can be used to control weeds in direct-seeded rice include the use of weed-competitive rice varieties, seed clean of weed seeds, and high seeding rates. In the Philippines, higher seeding rates are commonly used for direct seeding, but farmers often use their own rather than certified seed. Chin and Mortimer (2002) identify rice seed contamination with weeds as one of the major causes of weed infestations in direct-seeded rice.

Johnson et al. (2003) identify a number of issues that become important as farmers in developing countries increase their use of herbicides. One is the facilitation of information flows to enable farmers to make informed decisions about weed management. Much of the information available to farmers about herbicides in developing countries comes from the private sector through suppliers, who often only provide limited information about the use of their own products, and generally not information about the integration of other weed management techniques such as cultivation and water management with herbicide use. Understanding by farmers of herbicide action on weeds, aside from rates and weeds killed, is generally poor. Valverde (2003) notes that farmers in developing countries can be misled by the introduction of new products that are actually members of the same mode-of-action (MOA) group, and frequently tank-mix products with different brand names but which contain the same active ingredient. In the Philippines, for example, there are over 30 herbicide products containing butachlor, a commonly used herbicide on rice fields, each with a different product name (Fertilizer and Pesticide Authority 2003).

Even in a situation of good farmer awareness and scientific knowledge about weeds and herbicide resistance, the economics associated with optimal farmer use of herbicides and alternative weed management options is complex. Biological researchers often stress the need to change weed control management in rice paddy fields in order to prevent or delay herbicide resistance (e.g. Calha et al. 2004). However, experience has shown that there are often a number of socio-economic factors that act against farmers investing in the prevention of herbicide resistance (Pannell and Zilberman 2001; Llewellyn et al. 2005). Farmers confront immediate problems, often under severe financial constraints, which force short-term decision making.

The problem being addressed in the project is summarised in Figure 2. Various external factors are creating a favourable economic environment for the adoption of direct-seeded rice. Weed control becomes more difficult with direct-seeded rice and various weed control measures are in danger of being compromised: water management by water scarcity and inadequate irrigation infrastructure; manual weeding by rising labour costs; and herbicides by potential resistance issues. Experience in other rice growing countries has demonstrated that the weed management demands of direct seeding can lead to changes in weed communities (Ho et al. 1987; Moody 1996; Man and Mortimer 2002), increasing problems with ‘weedy rice’ species (Chin and Mortimer 2002; Ferrero 2003), and set rice growers on a path to herbicide resistance problems (Valverde and Itoh 2001). With these issues in mind, work in the project is focussed on testing and adapting an Integrated Weed Management (IWM) system that will be both profitable and practical for farmers.

Figure 2. Factors affecting weed management in direct-seeded rice in the Philippines, and possible responses.

Promoting IWM through village-level integration: the theoretical approach used by PhilRice

Many technologies generated through research and on research stations are found to be unsuitable when introduced into field conditions, and hence are not adopted by farmers. PhilRice has found it important to adapt technologies in partnership with farmers in villages so that the technologies are applicable and suitable for local farming systems. An essential part of the concept is the involvement from project initiation of local government and local leaders, including the municipal agricultural officer and agricultural technicians, and village leaders. This approach also recognises that agricultural activities are often organised on a village basis (e.g. irrigation activities, timing of planting, training).With the involvement of farmers and local people, feedback and learning can highlight the reasons why certain methods are not adopted and how the results may change when taken from laboratory to field conditions (Kilpatrick et al. 1999; Fulton et al. 2003). Additionally, farmer-directed research is better able to understand and relate to the farmer target audience and their farming system (Murdoch et al. 2003).

Village-level technology integration is a form of farmer participatory research. It takes into account the traditional or best farming practices of farmers and also involves the active participation of farmers in managing simple experiments on-farm. It enables researchers to map farmers’ perceptions and evaluation of technologies, and see if these are compatible with farmers’ farming systems and traditional knowledge. Farmer evaluation provides information on how they assess the agronomic, economic and socio-cultural impact of these technologies in their particular farming circumstances. The process encourages farmer participation, observation, evaluation and critical thinking, develops decision-making skills, and gives a sense of ownership of the technology being adapted on their farms. The technologies, when fine-tuned and adapted, can then be brought to other areas with the same prevailing farming conditions for up-scaling (Figure 3).

Village-level integration in the context of IWM aims to 1) educate and improve farmers’ decision-making abilities to develop and incorporate IWM within their own farming systems, 2) enhance the adoption of IWM in their environment, and 3) ensure increased productivity of the farming community. The economic component of the technology, through increased productivity or reduced costs, is essential. Five closely linked activities are implemented (Figure 4):

  • participatory problem analysis and finding solutions through focus group discussions and participatory resource appraisal;
  • capacity enhancement through farmer field schools;
  • experiential learning in the on-farm participatory technology development trials;
  • communication support through information materials such as newsletters, posters, and radio and TV if appropriate; and
  • technology synthesis where the new and traditional knowledge of farmers blend together to form, in this case, an adapted IWM technology.

Figure 3. Rice-based farming systems technology generation/verification, adaptation and promotion pathway of PhilRice (Source: Casimero 2005).

The most important partners in the technology adaptation are the farmers and the communities where PhilRice works. The active participation of the local leaders in the provinces, towns and villages play a key role as local support is needed to continue the implementation of activities after the project is done. Lack of local support is perhaps the main reason why government-introduced projects die after funds are exhausted.

The approach outlined above is theoretically consistent with the Technology Development extension model as proposed by Coutts et al. (2005), with its key underlying philosophy that specific technological change requires a focused participative effort involving all stakeholders. Elements that can be used to assess projects under this model are suggested by Coutts et al. (2005) as including:

  • Issue or need identified by industry or community or endorsed by representatives.
  • Facilitation provided to mobilise and assist in process.
  • Process to inform and involve stakeholders in problem definition and determining approaches to tackling it.
  • Committees and/or forums to provide on-going local input and feedback from those apart from hand-on participants.
  • The process is designed to allow researcher/experts and producers/community participants to work together.
  • There is a strong on-farm/on-site trial and demonstration and assistance component.
  • Benchmarking is a key feature of tracking benefits and progress.
  • Other supporting mechanisms are available to assist development and integration – such as incentives, policy, etc.
  • Training in relevant areas is made available.

A number of issues have been raised about farmer-directed/farmer-participative research and approaches that rely on learning through farmer field schools. A possible limitation of farmer-directed research can be that there is a great variation between groups and therefore scaling-out of the information obtained could be limited (Coventry et al. 2003). There are also issues due to the time costs associated with implementing and maintaining participative research (Carberry 2001), and maintaining the technology adoption after direct support ceases (Casimero 2005). Farmer field schools have been criticised as being time and resource costly, and a number of studies have failed to find evidence that learning and technology adoption addressed in farmer field schools spreads much beyond the participants (e.g. Tripp et al. 2005).

Figure 4. Village-level integration of Integrated Weed Management (adapted from Casimero 2005).

Adapting a new Integrated Weed Management technology with Filipino farmers

The project collaborators explored a number of issues and their differing experiences before the commencement of the field work. This resulted in a wider range of issues being scoped in the initial PRAs and included in the farmer field schools. For example, perceptions on herbicide resistance and weed sources were scoped in the PRAs, and discussions about long term weed management using seed bank control, and short term control in the current crop using weed control indicators resulted in new activities added to the field schools.

Problem scoping, on-farm trials and training

Following the approach outlined in the previous section, four Participatory Resource Appraisals (PRAs) were conducted in Nueva Ecija and Iloilo in August 2004 to scope weed management practices and weed management issues in the survey sites. Municipal agricultural officers in these two areas were approached and they, together with agricultural technicians, advised which villages might be suitable for the project (e.g. villages where farmers were practising direct seeding). Participants in the PRAs were chosen in consultation with the municipal officials and village leaders in the selected village and included village leaders, local agricultural technicians and farmer leaders (about 15-20 people in each group). Key findings from the PRAs included:

  • Weed control was confirmed as a major problem for farmers, but other rice production issues such as control of golden apple snails and insects were also important.
  • Farmers relied on herbicides to control weeds, but also used cultural and water management.
  • Farmers could identify weeds, but had poor knowledge about which herbicides should be used to control specific weeds.
  • Farmers had observed shifts in weed populations and the emergence of new problem weeds.
  • Farmers and agricultural technicians were unaware of the risks of herbicide resistance associated with continued use of the same mode-of-action herbicides.

Towards the end of each PRA the proposed weed control technology and associated ACIAR project was explained and discussed. There was general interest in the idea of cultural management for weed control (because of cost savings), however there was a mixed reaction to the technology – some thought it would work and others thought it would be difficult. Consensus was reached that they wished to participate in the project.

Following the PRAs and discussions with local agricultural technicians and community leaders (including the municipal mayor who was briefed on the planned project work), farmer co-operators for 40 on-farm field trials were identified (10 in each of four villages in the municipalities of Barotac Nuevo and Dingle in Iloilo, and Aliaga and Rizal in Nueva Ecija). Care was taken to ensure that the co-operators represented a good spread of farmers: progressive, average, and poor managers; some female; a range of socio-economic groups. A number of local village leaders were included amongst the co-operators. The first field trials commenced for the dry-season crops in Oct/Nov 2004 in Iloilo and January 2005 in Nueva Ecija, with 100m2 IWM plots and “standard farmers’ practice” (FP) plots side-by-side. Standard farmers’ practice was decided by discussion and consensus among the participating farmers, so that it was consistent across the FP plots. Farmers implemented their own trials with the guidance of PhilRice staff and local extension workers. Co-operators received certified seed and herbicides for the IWM plot.

Training took place in the four villages before the field trials commenced and farmers were taught the “stale-seedbed” technique in preparation for practising it in their own fields. The follow-up work plan involved season-long weekly training and field work in the villages focussed on integrated rice crop management, with weed management as one the focus topics to educate and teach farmers the science of weeds and integration of weed management practices. Participatory technology demonstrations and field work on a range of rice crop management issues were conducted, including integrated pest management, nutrient management and integrated weed management. An exercise on the seed bank was conducted to introduce the concept of the seed bank and long-term weed management to farmers.

Farmers received weekly visits from field workers during the growing season to discuss issues with the trials. Field days were held at each village site of the on-farm trials. About 50 people were present at each field day, and farmer co-operators in each province cross-visited the other municipality for the field days. Field days included field plot visits, presentations by farmer co-operators and an open forum.

Results from the first season of trials indicated that good weed control was obtained in IWM plots in all trial sites. Yields were generally higher in villages located at the head (Dingle and Rizal), rather than tail (Aliaga and Barotac Nuevo), of the irrigation system. Overall, results obtained from these four on-farm trial sites were consistent in indicating a better weed control, increased yields, and higher profits with the use of IWM. Comparing the grain yields obtained from the IWM and FP plots, a minimum of 0.5 t/ha was added to the yield with the use of IWM in areas where water supply was limiting. With the application of IWM, farmers in both sites in Nueva Ecija and Iloilo increased their yields by 10% and 15%, respectively. In sites with readily available water as in Dingle and Rizal, the yield advantage obtained was 0.7 t/ha. Indicative figures for the cost and return analysis showed that with IWM, farmers obtained an added profit ranging from US$54.5/ha in areas where water was limiting to US$132.8/ha in areas with good water supply.

Evaluation, reflection and adaptation

After the harvest of the trials, follow-up evaluation sessions are held with the farmer co-operators and local extension workers in each village. Each farmer presents their own trial results and talks about problems experienced in conducting the trial. After the first trial season a number of problems were identified:

  • In the two villages at the tail of the irrigation systems (Aliaga, Nueva Ecija and Barotac Nuevo, Iloilo), there were problems in implementing the longer cultivation period and intermittent irrigation required for the IWM plot because of lack of available water. In Iloilo, water issues were raised at the field days when farmers from villages at the head and tail of the system were both present, and talks on resolving water availability issues have commenced. These farmers have also now approached the national government about the need to address the deteriorating condition of their irrigation facilities.
  • A number of farmers were concerned about the price disadvantage suffered (around P3/kg) from the delay in seeding (and thus harvest) because of the longer cultivation time required for the IWM plot. Ideas to overcome this were discussed, including adjusting the land preparation time to start earlier, and growing shorter-season varieties.
  • Weeds had different names in each region and village, and work with PhilRice researchers has commenced to develop a common understanding of weed names.

The next crop, planted in July 2005, was the wet season crop and some farmer co-operators in Aliaga decided to transplant this crop. Co-operators in all villages asked if the IWM and FP plots could be increased to 1000m2, as the smaller plots were difficult to handle. The initial trial site is part of the enlarged trial site (to allow seed bank effects of the IWM treatment to be monitored over time). Assistance being received by individual farmers now is equivalent to approximately P250 for seed and P600 for herbicides (approximately P40 = AUD$1). The Farmer Field Schools were not repeated but some ongoing training on specific weed management issues was conducted, and farmer co-operators in Dingle acted as facilitators and trainers for a season-long rice production training in another community. It has been noted that some farmer co-operators are implementing components of the IWM technology on the rest of their farm.

Before the next dry season crop, to be planted in December 2005 – January 2006, discussions will be held with farmers to decide on how the technology can be adapted. Problems experienced in Barotac Nuevo especially are likely to require considerable on-farm research work with farmers to adapt the land preparation to address water constraints. After the wet season trials farmers have said that they wish to increase the trial plots to 5000m2, but PhilRice has said they can only support seed and fertiliser for 1000m2 plots. It remains to be seen if farmers will fund seed and herbicide inputs for larger trial plots themselves. In Aliaga, it has been decided to support another community (with on-farm trials and FFS training) who are keen to try the IWM technology on direct-seeded crops in both wet and dry seasons.

Field measurements and farmer records will be used to assess the effectiveness of the weed control provided by IWM and FP plots, and the economic results from the trial plots. In conjunction with the trial work, research is underway to screen for possible herbicide resistance in weeds from areas and farms where it has been established that spraying has been intensive and continuous. So far, preliminary results indicate the likelihood of resistance in a number of weed populations. If these results are confirmed, they will confer a new urgency for an effective and profitable IWM strategy.


The challenge with programs such as this adaptation of an IWM technology is to expand the findings and encourage adoption beyond the participants in the trial work. Involvement of local leaders and extension workers in the trials, and participation of local communities in field days and training is being encouraged to address the wider adoption of the technology. In Dingle, an initially very sceptical municipal mayor is now talking enthusiastically about IWM. Another possible approach will be to institutionalise an adapted IWM technology (possibly differing for areas with different water availability) within PhilRice recommended rice crop production strategies.

To provide insights on weed management issues over a wider area, a survey of 400 farmers covering all municipalities in Nueva Ecija and Iloilo was conducted in late 2004. The survey included questions about current weed management practices; past, current and anticipated herbicide use; perceptions of water availability for the dry season crop; perceptions of the effectiveness of various weed control strategies; and concerns about herbicide use. It is hoped that these data will allow better targeting of the technology to areas where issues and concerns may be similar, and also provide an indication of possible constraints to adoption and hence better targeting of extension messages. For example, the data show that farmers generally use shorter land preparation periods and higher seeding rates that those recommended as part of the IWM technology. Farmers also perceive that a longer land preparation time would not be as effective as a weed control strategy using both pre- and post-emergence herbicides.


Learning from this project is only at an early phase but already a number of issues that will drive the adaptation and adoption of the technology have become apparent. Water supply is obviously a key issue, affecting the ability to apply water management methods (e.g. intermittent irrigation) and a longer land preparation period for weed control. Another issue is the possibility of herbicide resistance in a number of weed populations. The project is already building networks and links among farmers, and among local extension people. This was identified as a good outcome of the trial work and FFS training in evaluation sessions. A further challenge will be to improve the involvement and participation of the private sector (herbicide dealers) in the trials and training. The on-farm trials will be on-going in further seasons over the next three years and the technology will be adapted to local situations in consultation with farmers, village leaders and extension workers, with the aim of achieving a suitable, effective and practical IWM system. Results from a broader socio-economic survey will be used to help target extension needs beyond the participants in the trial work.


The authors gratefully acknowledge funding and support for this work from the Australian Centre for International Agriculture Research. We also acknowledge the valuable assistance with fieldwork of PhilRice researchers and project team colleagues: Edwin Martin, Dindo Donayre, Leylani Juliano and Elmer Talon. We have also been assisted in the training and fieldwork by our collaborators at the Western Visayas Integrated Agricultural Research Centre in Iloilo.


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