Strategies to Improve Biodiversity in Rice Paddy Fields

There are measures that can be taken to improve biodiversity in rice paddy fields, such as continuous application of organic fertilizers. Alternatively, biofertilizers can be applied to introduce microorganisms that benefit nutrient cycles and energy supply. Farmers can also undertake crop rotation to cut the life cycles of pests.

Fig. 5.2 Populations of phosphate solubilizing microorganisms (PSM) as a result of conversion from conventional to organic paddy fields by applying bokashi continuously in the Pagelaran subdistrict. Bars indicate standard error (P = 0.95) (Dermiyati et al. 2008)

Application of Organic Matter and Biofertilizers

In theory, addition of organic matter promotes biological and microbial activities that accelerate the breakdown of organic substances in the organic matter. The use of organic materials such as animal manure, crop residues, green manure, and bokashi compost as alternative sources is promising.

Soil microbial biomass comprises living plant roots and organisms, and the living portion of soil organic matter. It acts as the agent of biochemical changes in soil and as a repository of plant nutrients such as nitrogen (N) and P in agricultural ecosystems (Jenkinson and Ladd 1981). Lower microbial biomass in soils from conventional agro-ecosystems is often caused by reduced organic carbon content in the soil (Fliebach and Mader 2000). The quantity and quality of organic inputs are the most important factors affecting microbial biomass and community structure (Peacock et al. 2001). Continuous cultivation with frequent tillage results in rapid loss of organic matter through increased microbial activity (Shepherd et al. 2001).

Nakhro and Dkhar (2010) observed that the application of organic fertilizers increased fungal and bacterial populations as well as microbial biomass carbon compared to the application of inorganic fertilizers or a control. The increases were found both at surface soil depth (0–15 cm) and at sub-surface soil depth (15–30 cm); however, the increases were greater at sub-surface soil depth. This could be due to the addition of organic amendments that might have a large impact on soil microbial activity (Elliot and Lynch 1994), microbial diversity (Girvan et al. 2004), and bacteria density (Bruggen-van and Semenov 2000).

Crop Rotation

The main components of organic farming systems are soil protection, bio-control, nutrient cycles, and biodiversity. So far, farmers' efforts have been limited to replacing the use of agrochemicals (fertilizers and pesticides) with organic fertilizers (such as compost) and pesticides. However, this approach primarily addresses soil protection, and only partly influences bio-control and nutrient cycles, while no attention has yet been focused on biodiversity. Although monoculture is part of the “Green Revolution,” or conventional, farming systems, it still prevails in paddy fields that have been declared organic. In order to improve biodiversity, therefore, crop rotation is necessary in these paddy fields.

Crop rotation affects microbial populations. Research in the Pagelaran district showed that there were differences in the populations of phosphate solubilizing microbes in paddy fields where bokashi compost was continuously applied. Crop rotation from paddy to legumes caused a decrease in the population of phosphate solubilizing microbes (Dermiyati et al. 2009). It was likely that the cultivation of legumes increased the nitrogen-fixing bacteria rhizobium. These bacteria have an ability to fix nitrogen from the air and make it available for the plant by cooperation with legume roots. Moreover, it was observed that the activity of phosphate solubilizing bacteria in the rhizosphere was affected by the presence of nitrogenfixing bacteria like rhizobium (Widawati 1999).

Conclusions

As mentioned previously, improvements are necessary in rice paddy fields where heavy chemicals have been applied so that biodiversity can be maintained and sustainability in wetland rice growing is achieved. Shifting from conventional to organic farming needs a strong policy from the government to make organic fertilizers available at prices farmers can afford, or to subsidize their prices for the farmers. Government policy has to encourage and incentivize farmers who conduct organic farming and support high prices for organic products. Meanwhile, the farmers themselves must change their habits and culture with regard to paddy field cultivation to increase yields for food security. In relation to food security, production of organic fertilizers that contain high levels of nutrients is recommended. In addition, agricultural extension must teach the farmers simple technologies such as how to make bokashi or compost using local materials available in the villages.

To establish organic agriculture as an important tool in sustainable food production, assessments of the many social, environmental, and economic benefits of organic farming systems need to be complemented by a fuller understanding of the factors limiting organic yields. Agro-ecologists and conservation biologists should work together to formulate strategies based on biodiversity as an organizing principle in the sustainable management of rice field agro-ecosystems.

Open Access This article is distributed under the terms of the Creative Commons Attribution Noncommercial License which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and source are credited.

 
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