Farmers’ assessment of soil quality in rice production systems

NJAS - Wageningen Journal of Life Sciences 58 (2011) 31–38

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Farmers’ assessment of soil quality in rice production systems A.C.R. Lima a,∗ , W.B. Hoogmoed b , L. Brussaard c , F. Sacco dos Anjos d a

Department of Soils, Federal University of Pelotas, Campus Univesitário s/n. Caixa Postal 354, Cep: 96010-900. Pelotas-Rio Grande do Sul, Brazil Farm Technology Group, Wageningen University, Wageningen, The Netherlands c Department of Soil Quality, Wageningen University, Wageningen, The Netherlands d Department of Agrarian Social Sciences, Federal University of Pelotas, Campus Univesitário s/n. Pelotas-Rio Grande do Sul, Brazil b

a r t i c l e

i n f o

Article history: Accepted 4 August 2010 Available online 2 October 2010 Keywords: Brazil Local soil knowledge Soil quality indicators

a b s t r a c t In the recent past there has been increasing recognition that local knowledge of farmers can yield insight into soil quality. With regard to constraints and possibilities for the production of irrigated rice in the south of Brazil there is no documentation on local soil knowledge. The goals of this study were to answer the following questions: (1) Which soil quality perceptions do rice farmers have? (2) Which soil quality indicators are most important to them? (3) Do rice farmers use their knowledge about soil quality indicators when making soil management decisions and developing sustainable management? The study was carried out in the municipality of Camaquã-Rio Grande do Sul, Brazil. The research methods used included semi-structured interviews alternated with group discussions. Farmers named eleven characteristics as good indicators for soil quality: earthworms, soil colour, yield, spontaneous vegetation, soil organic matter, root development, soil friability, rice plant development, colour of the rice plant, number of rice tillers and cattle health. Out of these, three indicators were found to be useful in farmers’ decision-making: spontaneous vegetation, rice plant development and soil colour. The potential use of local knowledge for maintaining soil quality and developing sustainable land management is discussed. © 2011 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved.

1. Introduction The success of maintaining or enhancing soil quality depends on our understanding of how the soil responds to agricultural land use. Concern about soil quality is not limited to agricultural scientists, natural resource managers, and policymakers, but also farmers have a vested interest in soil quality [1,2]. A growing number of ethnopedological studies on local soil knowledge have been published over the last two decades, demonstrating an increased recognition of farmers’ knowledge offering insight into soil quality, which can guide future research to develop sustainable land use (e.g., [3]). Yet, its use is often limited due to general lack of understanding of local knowledge and how it can be explored [4], and to a subjective sense of inequity between formal science and farmers’ knowledge [5]. Local soil knowledge has been defined as “the knowledge people living in a particular environment for some period of time have of soil properties and soil” [6]. Many studies have compared local farmers’ perceptions of soil fertility and/or perception of soil classification with scientifically determined soil parameters [7–13]. Other studies have highlighted the potential of local soil knowledge

∗ Corresponding author. Tel.: +55 53 32757268; fax: +55 53 32757267. E-mail address: [email protected] (A.C.R. Lima).

for sustainable soil management [3,14–20]. One study examined how farmers assess soil quality [2]. In general, such studies provide good information for particular soils and land management practices. Besides, they reveal that a worldwide consensus of standardized soil quality indicators is difficult to reach because local knowledge is location specific. With regard to the production of irrigated rice in the south of Brazil, the relevance of local soil knowledge has not been documented. Rice is the predominant crop in the southern lowlands producing approximately 5.5 million Mg rice per year, equivalent to 52% of total Brazilian rice production [21]. Production levels are high, but there is clear evidence that the threat to soil quality in terms of physical, chemical and biological degradation due to intensive rice production also is high [22–26]. As a first step in reversing this trend, researchers need to understand what local farmers know about soil quality. However, this information is only valid when the potential use of this knowledge for maintaining soil quality and developing sustainable land management is assessed and put in the context of decision-making [27,28]. The objective of the study presented here was to answer the following questions: (1) Which soil quality perceptions do rice farmers have? (2) Which soil quality indicators are most important to them? (3) Do rice farmers use their local knowledge about soil quality indicators as a tool for guiding soil management decisions and developing sustainable land management?

1573-5214/$ – see front matter © 2011 Royal Netherlands Society for Agricultural Sciences. Published by Elsevier B.V. All rights reserved. doi:10.1016/j.njas.2010.08.002

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A.C.R. Lima et al. / NJAS - Wageningen Journal of Life Sciences 58 (2011) 31–38

Table 1 Time table of management activities for the three rice production systems studied in Camaquã, and mean monthly rainfall in the region.

Production system

Semi-direct

May

Jun

Jul

Aug

- - - - - Fallow/cattle - - - - -

Sep

Oct

Nov

Soil preparationa

Soil preparationa

- - Fallow/cattle - -

Mar

Apr

- - Harvest - -

- - - Sowingc - - -

- - Harvest - -

-------------------------- - Fallow/cattle - -

Inundation

Mean rainfall (mm)

Feb

-------------------

Inundation Pre-germinated

Jan

Chemical weed control and sowing c

Inundation*

Conventional

Dec

b

- - Soil preparation - -

- - Harvest - -

c

- - - - Sowing - - - -

-------------------------------------------------------------------------------------56

108

92

136

113

125

157

94

172

172

82

120

a

Ploughing and harrowing. Ploughing, harrowing and levelling. Drained field is required for sowing operation. * Period of inundation.

b c

2. Study context 2.1. Study area The community of our study was ‘Banhado do Colégio’, which is located in the municipality of Camaquã (between latitude 30◦ 48 and 31◦ 32 S, and longitude 51◦ 47 and 52◦ 19 W); in the state of Rio Grande do Sul, southern Brazil. Rice production is the most important agricultural activity in the region. According to IRGA [29], in the period 2007–2008 the Camaquã region produced 186,664 Mg of rice on 31,375 ha (5.95 Mg/ha), which ranks the region as the 10th most important production area of the state. Besides its economic importance for revenue generation, rice production also contributes to the social equilibrium given the large number of farmers (small and large) involved. The study area was chosen because the farmers from ‘Banhado do Colégio’ use the main irrigated rice production systems of Rio Grande do Sul. Furthermore, there is a large variation in farm size (2–500 ha), with size related to the type of production system and to the social production format adopted by each farm. As shown in earlier studies [30], these relationships are the key to the analysis of farmers’ knowledge. Similarly, in this study we assume that farm size, production system and the social organizational type of production are elements strongly related to farmers’ conceptual understanding of soil quality and sustainability.

2.2. Social aspects of production In the area of Camaquã, irrigated rice is important for both large and small farmers. Rice production fits well into the climate and the soils of the region and has become a traditional agricultural activity. Even on small farms, rice is of great importance because of the restrictions to grow other crops imposed by difficult soil drainage conditions. According to INCRA FAO [31], of all farms (about 2500) in Camaquã, 92% can be classified as small family farms, while the rest are considered large-scale farm enterprises, classified as patronal agriculture [31]. Patronal agriculture is mostly found on medium-sized and large farms, and is mainly characterized by the types of production rela-

tions established on the farm: relying on paid labour, these farms show a capitalist rationality with maximizing profits as their main objective. In Camaquã the patronal type of farm represents 66% of the total area, but contributes to no more than 57% of the net value generated by agriculture. These farms have access to financial credit, which is a prerequisite for applying state-of-the-art technology in terms of machinery and irrigation systems. With these technologies these patronal types of farm are more flexible than small farms, because they offer better opportunities for growing other crops (e.g., soya bean) in the rotation, better weed control and better soil drainage. Rice production under the patronal type of agriculture is mainly based on two production systems: semidirect and conventional. These systems are described in the next section. The family farm type of agriculture (peasant farming) is mainly practised on small farms. In contrast to patronal agriculture, the family farm’s primary objective of production is subsistence. The work force is basically the family and all responsibilities in the production processes are taken by the family members. Additionally, the land is both a production factor and a symbol of farm history. In Camaquã, the pre-germinated system is commonly associated with family farming. 2.3. Rice production systems A calendar of the three main production systems and the average monthly rainfall are presented in Table 1. Table 2 lists relative importance, farm size and grain yield for the three production systems. The growing period of rice is from sowing between late September and early December up to harvesting in March–April. Table 2 Relative importance, farm size and grain yield for the three rice production systems in Camaquã. Production system

Relative importance (%)

Farm size (ha)

Grain yield (t ha−1 )

Semi-direct Conventional Pre-germinated

65 25 10

5–200 200–500 2–30

5.7 8.4 6.3

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The three main production systems differ as follows with respect to intensity and timing of soil tillage and water use: (a) Semi-direct: soil preparation is done in September or October (45–60 days before sowing) when the soil is not inundated. This early soil preparation with a disc plough and disc harrow permits the incorporation of the rice straw and the germination of weeds. A herbicide is used to kill these weeds, and rice is sown without seedbed preparation to prevent regrowth of weeds. Fields are inundated after emergence of the rice seedlings, as in the case of the conventional system. (b) Conventional: just before sowing, the fields are prepared when the soil is not yet inundated. Deep tillage is employed using a disc plough followed by superficial operations with a disc harrow with the aim to level the soil and prepare a seedbed with a fine tilth. Sowing (drilling) is done with a conventional sowing machine. Water is let onto the field after the rice seedlings have reached a height of approximately 10 cm. (c) Pre-germinated: the fields are inundated (early August) before tillage operations start. Tillage is done in September and October. Usually, the same disc implements are used as in the conventional system, often complemented with a pass of a special leveller to smoothen and level the wet surface layer. Seeds are pre-germinated by soaking until the coleoptile is 2–3 mm long. The seed is broadcast in the shallow (5–10 cm) water layer, either by hand or sowing machine, depending on the size of the farm. The water layer allows a more precise levelling of the field and controls weeds. 2.4. Community history The community of Banhado do Colégio started during the first Brazilian land reform in 1959. The community was founded in the early sixties on the dry land reclaimed from the marshes and approximately 200 families started farming. The lots (10–25 ha each) were gradually distributed among landless family farmers. These families were mainly descendants of German and Polish settlers who emigrated to Brazil at the end of the 19th century [32,33]. Research by Fernandes [34] involving small farmers (‘peasants’) revealed reasons why they are an important feature of Brazilian agriculture, especially in the rural reality of the state of Rio Grande do Sul. According to this author, small farmers generally are able to achieve high land productivity despite having less support and resources than large farmers. Belonging to a land reform settlement the farmers are accustomed to being subject of study. This type of settlement generally consists of small farmers who are open to changes and are willing to exchange experiences in order to achieve better living (or even survival) conditions. During the time of settlement the soil in the region was classified as one of richest in organic matter in Brazil. The predominant soil types are Albaqualfs and Humaquepts [35]. The main difference between these soil types is the clay content in the topsoil [36]. Some topsoil (0–10 cm) properties for these two soil types are listed in Table 3.

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The total area of the community is 4900 ha, mostly characterized by fields that were not suited to crops other than irrigated rice. Indeed, pushed by rural extension services, rice production was started soon after the community was founded. The inherent fertility of the soils was also a reason to attract farmers to the new community, although they hardly had any experience with growing rice. Since then, the same fields are still used for agricultural production, but with increased use of external inputs (seeds, pesticides, fertilizers, etc.), and increased intensification in soil preparation and use of water [36]. As a result, the rice production level can reach records of 9 Mg ha–1 . Not all original farmers and their descendants are better off today than when the community was founded. About one third of the original farmers and their descendants no longer live in the community. The majority of those still living in the community (small farmers) have difficulty with earning a reasonable income and economically depend on the production of rice or on their pensions. A few, however, have prospered by producing rice in larger areas. They have good infrastructure, such as farm storage facilities and machinery and are better positioned in obtaining financial support from banks than the small farmers and bought neighbouring lots. They now possess large farms and use conventional or semidirect rice production systems. The majority of the small farmers use the pre-germinated rice production system, mainly because of lower costs, easier weed control and less dependence on the weather for soil preparation and sowing activities. The natural and effective weed control by the intensive use of water in pregerminated systems allows rice production year after year. Besides, their fields are generally located in lowland areas where a rotation of rice with soya bean is not profitable. 3. Methodology 3.1. Study design Semi-structured interviews alternated with discussion groups were chosen as research methods in order to accurately assess farmers’ knowledge at the individual and group level and to identify if differences in soil quality perception occur between farmers who use different production systems (for further explanations of this methodological rationale see [37]). All interviews and discussions were recorded on tape for analysis. 3.1.1. Initial individual interviews Semi-structured interviews were used for gathering information on perceptions of soil quality indicators. These interviews took place at the farmer’s house or in his field. Out of the 200 active rice farmers, 50 were chosen to be interviewed based on the following criteria: (a) farmers should own and work the fields themselves in order to minimize misunderstandings due to limited knowledge of the soil and the production systems; and (b) the three production systems had to be represented among the farmers. After contacting these potential farmers, only 32 of them were interviewed (3 using the conventional production system, 13 using the pre-germinated

Table 3 Mean values and standard deviation (SD) of some topsoil (0–10 cm) properties for the two great soil groups used for rice production in Camaquã region (values from soil samples collected at harvest time). Soil great group

Colour

Albaqualfs White Endoaqualfs Black

Organic mater

Clay

pH

(%)

SD

(%)

SD

2.6 7.7

1.1 2.6

26.5 59.8

14.2 12.9

4.9 5.0

Bulk density

Total porosity

Total N

P

K

SD

(g cm−3 )

SD

(%)

SD

(%)

SD

(mg dm−3 )

SD

(mg dm−3 )

SD

0.2 0.3

1.5 0.9

0.2 0.2

0.4 0.6

0.1 0.1

0.1 0.5

0.1 0.3

8.4 10.8

5.4 6.2

36.0 41.6

19.5 29.5

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system, and 16 using the semi-direct system; Table 3) because not all farmers were prepared to spend the necessary time or were interested in participation in the study. This first round of individual interviews was held in November and December 2003. The farmers were presented two open and broad questions: (1) “What do you think is a good soil?” and (2) “How do you recognize a good soil?” This resulted in an inventory of farmers’ perceptions of soil quality and of the soil quality indicators they use. 3.1.2. Discussion group meeting A discussion group meeting was held in January 2004. Out of the 32 farmers who participated in the individual interviews, 18 farmers responded to the invitation (1 using the conventional production system, 9 using the pre-germinated system, and 8 using the semi-direct system). First, participants were divided into three groups to start a discussion about the list of soil quality indicators that emerged from the individual interviews. This step served as a warming up and to acquaint the farmers with the topic of soil quality. Next, the whole group was brought together for a final discussion. During this meeting farmers were given several opportunities to discuss their own perceptions of soil quality indicators. The main purpose of this meeting was to rank the list of soil quality indicators collected from the individual interviews and to reach consensus about the most important indicators. Two facilitators were involved in guiding and documenting the discussion. The meeting lasted 3 h. 3.1.3. Further individual interviews For the third objective (Do farmers use their knowledge in soil quality management) we interviewed 24 farmers from the original group of 32, in June and July 2005. It was not possible to interview the other farmers. However, all three production systems were represented in the sample (2 farmers using the conventional production system, 8 farmers using the pre-germinated system, and 14 farmers using the semi-direct system). The following open questions were asked: Do you use soil quality indicators in your day-to-day decisions? If so, which indicator is the most important

one for guiding soil management decisions? and “Why, when and how do you use it?” 4. Results 4.1. Rice farmers’ perceptions of soil quality The rice farmers of Camaquã region distinguished soil quality primarily on the basis of three classes of soil colour: black (preto), mixed (misturado) and white (branco). The list and classification of the farmers’ soil quality indicators is presented in Table 4. The farmers considered soil colour as a proxy for soil quality. According to their perception black soil is found in lower areas and is the best soil because it contains more clay, is rich in organic matter, is softer, has better infiltration, is more fertile, has more soil organisms and nutrients, and thus produces more. During the interviews, each farmer valued his own lot by using terms such as ‘good’,’ rich’ and ‘strong’ for black soils, ‘moderate’ for mixed soils, and ‘bad’, ‘poor’ and ‘weak’ for white soils. The perception of soil quality was not only closely related to environmental factors but also to economic factors. The farmers emphasized that a good soil has to be flat (level) and low-lying because this saves costs for soil preparation and water management of the irrigated rice. This view is supported by the fact that lower areas are more expensive to buy or rent. The farmers frequently addressed properties of the topsoil rather than subsoil features to assess whether the soil was recovering from previous cropping. This is probably because topsoil is influenced more by tillage and plant growth than subsoil and also because they rarely see the subsoil. Farmers also pointed to visual features while walking in the field (e.g., spontaneous vegetation, soil colour). Many indicators related to rice crop performance (e.g., yield, rice plant and root development) were mentioned as soil quality indicators. Most farmers also touched and felt the soil for assessment of its quality (rubbing soil between fingers to feel its quality), as stated by a farmer: “Soil is like cloth: we really see what is good when we touch it.” (Hélio Duarte).

Table 4 Classification of the farmers’ soil quality indicators. Indicator

% of farmers who named the indicator

Farmers’ statements

Biological Earthworms

97

“Where there is strong soil we can find earthworms”

Intrinsic soil characteristics Soil colour

87

“The darker the soil, the better soil quality”

Chemical Organic matter

57

“A good soil is a black soil, which has more fat (organic matter) in it.” “If the soil has fat it means a stronger soil, with more nutrients, so it is more fertile”

Physical Friability

43

“A soft soil better allows the development of the roots” “We can feel if the soil is hard or not by just walking”

Plant performance Yield Spontaneous vegetation

67 63

Root development

53

Rice plant development Rice plant colour

43 16

Number of rice tillers

16

“Good soil is one that produces a lot” “Good soil can be seen through its own vegetation. It has to be strong, vigorous, well developed, have beautiful green colour, fast growth.” “If there is vegetation, any crop can grow on that field” “A plant that has more roots finds more food (nutrients)” “If a soil permits the growth of the roots, this means a soft soil” “Short roots: low yield” “The quality of a soil can be seen during rice plant development” “The gold yellow of the rice flower and the dark green of the rice plant tell us that the soil is good, so the colour of the rice plant can give us information about how the soil is” “The higher the number of rice tillers, the better the soil”

10

“If a field has beautiful cattle (fat), it means strong natural vegetation from a good soil”

Other Healthy and good-looking cattle

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In the initial individual interviews, 11 soil quality indicators were named. Indicators were considered higher in importance if they were named by more farmers (Table 4). 4.2. Important soil quality indicators From the group discussions it appeared that out of the 11 soil quality indicators named in the first individual interviews, only soil colour, earthworms, soil organic matter and soil friability were unanimously considered by farmers as significant indicators of soil quality, with soil colour as the most important one. Farmers could not decide on the order of importance of these four indicators because they considered all to be interrelated. According to farmers’ comments, if the soil is darker it will contain more clay, more organic matter, produces a more abundant spontaneous vegetation, contains more earthworms and other organisms. Consequently, friability and root development would be better and yields higher. However, to get to know which indicators are important in decision-making, a second round of individual interviews was made. Farmers were (again individually) asked which of the 11 soil quality indicators named by all farmers involved in the study was useful to their management decisions. Out of the four indicators mentioned earlier, only soil colour was considered important for decisionmaking, while two other ones were now highlighted: spontaneous vegetation and rice plant development. Additionally, they stated that their usefulness depended on the production system used, and on the type of decision to be made, i.e., day-to-day management or buying and renting land, as explained below. 4.2.1. Spontaneous vegetation For farmers who applied semi-direct and conventional production systems, the appearance of spontaneous vegetation during the fallow period was the most important soil quality indicator, because the soil can get ‘natural benefits’ from the vegetation. More spontaneous vegetation results in a reduced use of inorganic fertilizer because the biomass is considered a natural organic fertilizer. Besides, the farmers believe that the decomposing vegetation increases the ‘fat’ of the soil (organic matter), maintains soil friability and soil water content, promotes earthworms and micro-organisms, and provides protection against erosion. Looking at the appearance of spontaneous vegetation, farmers decide (each year) to apply supplemental inorganic fertilizer (usually based on nitrogen) or to postpone this action until the next annual cropping season. If they decide to apply inorganic fertilizer, they base this on soil chemical analysis. According to the farmers, if the spontaneous vegetation is dark, green and well developed in terms of plant height they assume their fields to be good for the following crop without needing soil chemical analysis to determine if additional fertilization is necessary. Thus, spontaneous vegetation is considered to contribute to soil quality and, consequently, to sustainable farming. As commented by a farmer in the second round of individual interviews: “If a field can always sustain much spontaneous vegetation during the fallow period, it means that the soil is going to keep its own life for my grandchildren.” (Reinaldo Zaikowisk). A second farmer added: “The soil health of tomorrow is like the health of a person; it depends on today’s eating habits.” (Adolfo Westphal). 4.2.2. Development of the rice plant Farmers who practice the pre-germinated system cannot evaluate the quality of their soils by looking at the spontaneous vegetation during the fallow period as their soils are too degraded (because, as they perceive it, the soil’s ‘fat’ is lost by soil preparation) to support much growth of the spontaneous vegetation and also because the fallow is shorter as they start to prepare the soil earlier. So these farmers have no idea of soil quality before soil preparation and planting rice. Soil quality is only assessed by observing develop-

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ment of the rice plant in terms of colour, height, root development and numbers of tillers. 4.2.3. Soil colour If farmers want to buy or rent land, soil colour is the most important indicator. They assume that black soil has a high potential production because of the characteristics (qualities) mentioned earlier and, therefore the soil has a high economic value. 4.3. The use of local soil knowledge in (development of sustainable) land management Farmers are conscious of the fact that soil quality varies from field to field because of inherent soil characteristics and the strong influence of management. Farmers are also aware of soil degradation and its association with land management. Most soil degradation in the region is observed in the pre-germinated production system. Farmers believe that rotation of irrigated rice with soya bean increases soil fertility, ‘softens’ the soil and results in better weed control.1 To improve soil quality, some farmers use fallowing and cattle grazing for 2–3 years. Many farmers said that grazing cattle adds manure to the field, crop residues add organic matter to the soil, roots that remain in the field increase water-holding capacity of the soil and, as a result, soil life is diversified. However, they consider that these options are limited to only a small part of the farmers, i.e., those who have relatively much land or money. The majority of these farmers adopt the conventional production system and some of them use the semi-direct system. They do not depend on just one plot of land for survival; they can divide their land in order to produce rice, soya bean or keep a field under fallow. So they spread the risk of crop failure and at the same time maintain soil fertility for rice production. Most of the small farmers are located on poor soils, in low-lying areas, where it is almost impossible to produce soya bean because of poor drainage. For rice, they are bound to use the pre-germinated system with long periods of inundation. Farmers observe that because of this, soil quality decreases, making it much more acid, and leading to iron toxicity, compaction and reduction of soil life. 5. Discussion 5.1. Soil colour as quality indicator Although farmers described their own soils as sandy and clayey, they mainly used soil colour as a criterion for soil quality. They related soil colour to soil fertility (organic matter) and consequently to quality. The use of colour as a major descriptor of soils has also been reported by Saito et al. [38] for different ethnic groups in northern Laos. Rice farmers in Laos preferred black soils over red, white and yellow soils, and preferred clayey and loamy soils over sandy and stony soils. Darker soils were considered to contain high levels of organic matter, to have a high water-holding capacity, to be inhabited by earthworms and to produce high rice yields. Such soils were commonly considered more fertile than soils of other colours. This was also the case in our study: black soil (terra preta) was considered the most fertile because of its high clay and organic matter content, whereas white soil (terra branca) was considered the least fertile because of its low clay and organic matter content. A comparison of these local farmers’ responses with the formal values presented in Table 2 supports farmers’ understanding of soil quality. Similar findings [3,7,12,14,17] show that soil colour is the

1

Red and black rice; other spontaneous vegetation is not considered weeds.

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most widely used indicator for classifying soils in other parts of the world and for different crops as well. 5.2. Farmers’ holistic view on soil quality The interviews showed that farmers have a holistic view of their soils. Farmers see soil quality as a dynamic asset, integrating the chemical, physical and biological characteristics. As a farmer commented: “I cannot separate what happens in the soil . . . for me everything is related . . . it is alive . . . it is a living system . . . and the things happen in cycles.” (Bruno Ritter). The Camaquã farmers are interested in soil productivity and appropriate management practices. Their view tends to be that a good soil is a ‘productive’ soil. They associate good soils with productive crops, as was also found by Bruyn and Abbey [39]. However, it was admitted that the relationship between yield (a measurement of soil productivity) and soil quality is complex. As farmers said: “Yield does not indicate a good soil. Any well-treated soil produces!” (Antônio Bartz). “The yield depends on the weather rather than other factors.” (Adelino Oswaldt). These statements reveal that in the eyes of the farmers yield does not indicate good soil because they know they can manipulate their soils in order to get high yields. Thus, some of the potential indicators those farmers would use as ‘natural’ indicators of soil quality, they could not use it nowadays because of the intensive use of external inputs and/or modified seeds. 5.3. Farm size and soil quality It is important to state that there are two main farmer groups in the region: small and large farmers. They live together in the regional landscape. Local soil knowledge is not related to farm size, but the opportunities to use it are farm-size related. Farmers pointed out that soil quality could be changed in time because soil fertility can be manipulated. Potentially, fallowing or rotating rice with soya bean could improve the quality of small farmers’ soils and might raise additional income just as in the case of large farmers. However, small farmers (mainly those who use the pre-germinated rice management system) cannot risk their own sustenance by growing soya bean instead of rice because their low land is likely to flood during the growing season, which is fatal for soya bean. The risk of flooding on the small farms is also related to the water management systems of their neighbours (if these grow rice). Furthermore, agrochemical (such as herbicides) applications by the neighbours can damage their crops. On the other hand, large farmers (who mainly use the conventional and in some cases semi-direct rice production systems), can plant soya bean because they own larger and higher-lying pieces of land, and have better infrastructure for drainage and, therefore, are less vulnerable to weather extremes and are hardly affected by their neighbours’ land management. 5.4. Socio-economic aspects of soil quality So as also shown by Scoones and Toulmin [40], socio-economic issues are key driving forces of day-to-day and long-term decisions about specific practices, such as rice–soya bean rotation, irrigation, the use of inorganic fertilizer, the rice varieties and the machines to prepare the soil. This can be illustrated by the following farmer’s statement: “We already know our lands very well . . . we do not have surprises after all . . . we know that sometimes we are doing something wrong but it is not because we do not have knowledge, it is because we do not have economic resources to do the right thing.” (Ederaldo Dumer). This statement shows the reality of the regional farmers. Indeed, farmers know what would be the best way to treat their land

sustainably, but they do not have the resources to manage the soil properly. Therefore, implementation of measures leading to sustainability is impaired. This is crucial in the situation of small farmers who practice the pre-germinated production system, and who see that the adoption of better agricultural practices is out of reach. It should be stressed that what appears to be unsustainable management for the scientist (the conventional production system) in fact is a system that leads to a natural recovery of soil quality during a longer fallow period or by applying a rotation with soya bean. But this is affordable only to the large farms. This result is in contrast with some other local soil knowledge studies, such as on farms in Central Honduras, where Ericksen and Ardón [19] found that the farmers prefer, as a primary solution, to apply more inorganic fertilizer instead of using a soya bean rotation or fallowing to recuperate soil quality.

5.5. Multiple indicators for soil quality The responses of farmers to our questions showed that to them the concept of soil quality is complex with no single indicator making a soil good or bad. Organic matter is something most farmers acknowledge. They know that it results from decomposing crop residues, which supply what the soil ‘needs’ and correct what is ‘missing’ (nutrients). Contrary to the study of Barrios and Trejo [3], the farmers in this study did not distinguish between types of spontaneous vegetation growing on their soil. Barrios and Trejo [3] provide lists of native plants as important local soil quality indicators associated with modifiable soil properties from different regions in Latin America. They show that traditional farmers use associations of native plants as indicators of soil quality, and native plants as indicators of locations where crops should not be grown. In our case, farmers were more interested to know if any vegetation grows vigorously or not. They do not investigate the relationship between different natural vegetations and regional soil fertility, although this might help them in taking management decisions. Farmers of Camaquã know that soil organic matter content can be influenced by land management practices. One farmer who used the pre-germinated system explained: “Because we prepare the soil under water our soils are too much washed (impoverished) . . . all fat (organic matter) of the soil goes out from the fields to the drainage channels.” (Álvaro Bueno). Besides, the farmers also acknowledged that most of the soil degradation in the region is observed in the pre-germinated production system. This is consistent with findings of Pedrotti et al. [41] and Lima et al. [42], who studied similar irrigated rice systems on lowland experimental sites in Pelotas, Rio Grande do Sul. These authors showed that rice production on Albaqualfs under less intensive tillage practices was accompanied by the lowest bulk density values. Under these conditions, a decrease in bulk density, can only be expected as a result of an increase in soil organic matter content [24], which is difficult to achieve in the pre-germinated production system. In flooded soil, typical for the pre-germinated production system, soil chemical degradation only started to become significant under reduced conditions. Redox potentials decrease under anaerobic conditions in the presence of organic matter, which may lead to toxic Fe levels in the soil solution after a few weeks of flooding [43]. In this study, farmers observed that soil quality decreases: the soils become more acid, leading to iron toxicity, increasing soil compaction and reducing soil life. This is in line with research findings from countries in Africa and from Sri Lanka [44,45] where low pH values and iron toxicity were found in valley bottoms. Problems were also associated with poor nutrient condition, which was also found in our case.

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To avoid this problem and also save water, instead of keeping fields flooded all the time, some regions (i.e., Philippines) choose to keep the soil near saturation, or apply alternate wetting and drying regimes using intermittent irrigation [46,47]. However, it is necessary to differentiate between environments in which rice is grown under flooded conditions. According to Dobermann [48], in relatively fertile lowland environments, growing rice under flooded condition is more sustainable, whereas periodic oxygenation is mainly recommendable on marginal soils that need aeration to improve oxygen supply to the roots so as to avoid toxic concentrations of reduced substances such as ferrous iron (Fe2+ ) or hydrogen sulfide (H2 S) and, consequently, increase yields. This practice would be desirable, but is hardly possible in the lowland soils in the region studied, as the peasants only have a small piece of land to survive and, hence, little potential for applying alternatives for the pre-germinated system. In addition, they have little quantitative information and, therefore, cannot be certain about the effectiveness of the measures they (might) take. However, this problem is not representative for most rice soils in the world. In the case of Asia, for example, more than 75% of the rice is grown on 79 million ha of irrigated land [49] with almost year-long flooding. According to Tuong et al. [49] most irrigated lowland rice ecosystems in Asia have the rainy season as an advantage, when climatic conditions are much more favourable for rice production than for other crops. In conclusion, the yield and performance of flooded rice planted in different countries appear to vary widely due to site-specific characteristics such as climate, soil, water supply, farming practices and socio-economic conditions [48]. 5.6. Limited observations Another factor to be considered is that farmers in this study generally only take the topsoil or the plough layer into account. So their perceptions rely on soil indicators that they can see and/or experience directly. Farmers’ interpretations then are not necessarily based on sufficient information because of their limited observations. For example, although the majority of farmers (97%) identified earthworms as an indicator of soil quality, the presence or absence of earthworms in the soil was not important in their decision-making. A possible explanation is that they hardly see earthworms in their own fields because of the effects of management systems, particularly tillage, water management and pesticide use. Farmers said: “Our lands are under the water most of the time, so there is no time for the earthworm to appear . . . besides, the earthworm does not like inundated soil . . . they cannot survive in that.” (Orzeli Reinard) or “Because of the herbicides the soil is dead!” (Antônio Kila Neto). Earthworm species that may occur in deeper layers or semiaquatic earthworms did not concern the regional farmers. In a recent publication, Lima and Rodriguez [50] highlighted the presence of a number of earthworm species in irrigated rice fields in the region of this study. The fact that farmers recognize that the presence of earthworms is an indicator of soil quality is remarkable, but their incapability of using this in their decision-making is not surprising. Farmers have experience with cropping dry soils (most of farmers still have their own vegetable gardens and orchards around their houses, where earthworms are easily visible) and therefore promptly associate earthworms with good soils. But as it is more difficult to observe earthworms in flooded rice fields, they become doubtful about their utility when assessing soil quality. From the scientist’s point of view, therefore, the farmers do not use an indicator that they consider important to its full potential. On the other hand, scientists often underestimate the importance of socio-economic factors in farmers’ management decisions, as shown above when the farmers

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have to decide about some specific practices (e.g., rice–soya bean rotation). 6. Conclusions Rice farmers from Camaquã showed to have detailed knowledge of the soil they are cultivating. The holistic farmers’ view of soil quality is based on dynamic processes integrating chemical, physical and biological soil characteristics. They know what indicates soil quality best, but nowadays they can hardly use the best indicators due to limitations set by their management practices. Nevertheless, conventional and semi-direct management systems (larger farms) better allow application of farmers’ knowledge than the pre-germinated production system (small farms). The results of this study provide a better understanding of the importance of farmers’ knowledge of the soil in the context of sustainability of farming systems. Researchers must continue to face the challenge to provide a base for bridge-building between the best (largely holistic) farmers’ and (largely reductionist) scientists’ knowledge. In doing so, they will help to develop mutually acceptable indicators of soil quality [2,14] for sustainable land management. This study shows that farmers also use indicators that are part of a standard soil description routine already used by soil scientists, but that they have this kind of information for all their fields whereas scientists will only have it for a few points. Farmers are the principal actors in agriculture, and their knowledge should be considered one of the most important assets in striving towards sustainability. Therefore, an important role for scientists in formal soil quality research is to strengthen the capacity of farmers to make informed management decisions and to evaluate the feasibility of alternative production systems in terms of longterm soil quality. Our study shows that this is particularly true for the rice production systems we investigated. Acknowledgements The authors acknowledge the financial support of CAPES (Fundac¸ão Coordenac¸ão de Aperfeic¸oamento de Pessoal de Nível Superior – Federal Agency for Post-Graduate Education), Brazil. We wish to thank Prof. Dr. Leontine Visser (Wageningen University) for the useful comments on an earlier version of the manuscript, and the farmers from the community of ‘Banhado do Colégio’ in Camaquã, Rio Grande do Sul state of Brazil who participated in this study. References [1] E.G. Gregorich, M.R. Carter, D.A. Angers, C.M. Monreal, B.H. Elert, Towards a minimum data set to assess soil organic matter quality in agricultural soils, Canadian Journal of Soil Science 74 (1994) 367–385. [2] D.E. Roming, M.J. Garlynd, R.F. Harris, K. McSweeney, How farmers assess soil health and quality, Journal of Soil and Water Conservation 50 (1995) 229–236. [3] E. Barrios, M.T. Trejo, Implications of local knowledge for integrated soil management in Latin America, Geoderma 111 (2003) 217–231. [4] N. Oudwater, A. Martin, Methods and issues in exploring local knowledge of soil, Geoderma 111 (2003) 387–401. [5] R. Ellen, P. Parkes, A. Bicker, Indigenous environmental knowledge and its transformations, critical anthropological perspectives, University of Kent at Canterbury, UK, 2001, 337 pp. [6] A.M.G.A. Winklerprins, Local soil knowledge: a tool for sustainable land management, Society and Natural Resources 12 (1999) 151–161. [7] M. Corbeels, A. Shiferaw, M. Haile, Farmers’ knowledge of soil fertility and local management strategies in Tigray, Ethiopia, in: Managing Africa’s Soil. No. 10, International Institute for Environment and Development (IIED), Drylands Programme, London, 2000, 23 pp. [8] L.C. Gray, P. Morant, Reconciling indigenous knowledge with scientific assessment of soil fertility changes in southwestern Burkina Faso, Geoderma 111 (2003) 425–437. [9] H. Osbahr, C. Allan, Indigenous knowledge of soil fertility management in southwest Nigerm, Geoderma 111 (2003) 457–479.

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