Effects on Water Organisms in Paddy Fields

Aquatic biodiversity in rice fields is endangered as a result of the expansion of human populations. It has led to increasing pressure on living aquatic resources in rice fields due to agrochemical use and runoff, sedimentation, habitat loss, destruction of fish breeding grounds, and unsustainable fishing methods (Halwart 2004).

Information about the types of organism living in paddy fields is necessary because they can serve as indicators for environmental risks. Niswati and Purnomo (2007) studied how the community structure, diversity, and population density of aquatic organisms in Lampung Province was affected by whether paddy fields were conventional or organic (Table 5.1). Their study found 22 types of water organism

with a size of 50 μm to 1 cm in the four types of study site. The study sites were categorized according to farming system and location, as follows: (1) Conventional,

Taman Bogo; (2) Organic, Pagelaran; (3) Conventional, Pagelaran; and (4) Organic, Greenhouse. Organisms from the groups of Cladocera, Cyclopoida, Ploimida, Zygnemetales, Nematoda, Diptera, Podocopida, Volvocida, and Archipora were found in all locations. However, Anostraca, Ephemeraptera, Closterium, Bdelloida, and Haplatoxida were found only in the conventional paddy fields in Taman Bogo, while a greater total number of organisms was found in Taman Bogo's flooded paddy fields than in Pagelaran. In Pagelaran there were a greater variety of organism types in the organic paddy fields than in the conventional fields. Meanwhile, organism populations in the organic paddy field inside the greenhouse were higher than in the external paddy fields but the organisms were more homogenous.

Organism population changes in the conventional paddy fields in Taman Bogo and Pagelaran, as well as the organic paddy fields in Pagelaran showed that Cladocera, Cyclopoida, Ploimida, and Volvocida are found throughout the duration of plant growth, while other organisms are not. Some organisms, namely Nematodes, Ephemeraptera, and Chlorococcum, are found only at the beginning of plant growth; on the other hand, Bdelloida, Turbellaria, and Archipora are found only at the end

Table 5.1 Types of water organisms in Lampung Province and their abundances (individual m−2) (Niswati and Purnomo 2007)

Farming system types/locations

Taxonomic groups

Conventional, Taman Bogoa

Organic, Pagelaranb

Conventional, Pagelaranb

Organic, Greenhousec

Cladocera

56,608

27,520

1,152

142,500

Cyclopoida

127,384

93,824

33,856

3,500

Ploimida

24,192

33,600

21,88

25,250

Zygnemetales

12,416

6,400

3,392

14,750

Anostraca

824

0

0

0

Nematoda

752

6,080

13,632

2,250

Algae spyrogira

1,288

768

448

0

Diptera

360

1,600

1,472

4,000

Podocopida

2,496

2,880

2,688

6,000

Ephemeraptera

280

0

0

0

Closterium

688

0

0

0

Bugs

1,064

64

0

0

Isopoda

584

0

192

0

Chlorococcum

1,240

0

0

11,500

Volvocida

5,280

640

1,344

19,500

Bdelloida

200

0

0

0

Haplatoxida

216

0

0

0

Turbellaria

480

3,328

1,088

10,750

Paramecium

0

128

576

40,750

Euglenida

0

256

1,408

82,500

Archipora

1,158

1,280

0

0

Sessilida

0

192

128

0

a Seven observations

b Five observations

c Ten observations

of plant growth. Meanwhile, Podocopida, Algae Spyrogira, Zygnemetales, Diptera, Closterium, Bugs, and Haplatoxida were found inconsistently. This type of succession was similar to that reported by Yamazaki et al. (2004).

In comparison, surveys conducted in Sri Lanka on biodiversity in wetland rice field ecosystems documented 494 species of invertebrates belonging to 10 phyla, and 103 species of vertebrates, while the flora included 89 species of macrophytes, 39 genera of microphytes, and 3 species of macrofungi (Bambaradeniya et al. 2004).

Moreover, changes affecting dominant protozoa and algae populations in conventional and organic paddy field flooding water in Lampung Province were also studied (Niswati et al. 2008). There were two genera of protozoa (Euglena sp. and Pleodorina sp.) and two genera of algae (Volvox sp. and Diatom) that were dominant in the paddy fields where bokashi was continuously applied (Fig. 5.1). Among dominant protozoa, the population of Volvox sp. was significantly influenced by the continuous application of bokashi. The populations of protozoa and algae were higher under continuous bokashi application (for 2–4 years) than under the control.

Fig. 5.1 Abundance of dominant protozoa and algae in paddy field water where bokashi was applied continuously. Bars indicate standard error (P = 0.95) (Niswati et al. 2008)

Fluctuation in numbers of protozoa and total algae in organic paddy fields was higher than under conventional cultivation systems, the highest being after 4 years of bokashi application. Meanwhile, other protozoa and algae were also found, namely Chlorococcum, Archipora, Bdelloida, Algae Spyrogira, and Ploimida, but they were not dominant.

Populations of dominant protozoa and algae were likely to increase, starting 30 days after planting and continuing steadily until harvesting time (data not shown). This is because continuous application of bokashi compost may increase the populations of bacteria and fungi in the soil (Labidi et al. 2007) as well as increasing carbon biomass, nitrogen, phosphorus, and sulfur. Bacteria and fungi can act as food sources for protozoa, so continuous application of bokashi may increase microbial activity in the soil, which may increase the protozoa population. The decreases in protozoa and algae populations that occurred at 30 and 60 days after planting time were due to organic paddy field management involving weed cutting, wetting by irrigation, and drying out of the water in the paddy fields.

The biodiversity index for protozoa and algae was the same for both conventional and organic paddy fields. It is likely that the application of bokashi compost affected all organisms in the flooding water of the paddy fields so that the food chain was not yet affected.

In separate research, Roger et al. (1991) summarized some studies from multiple countries about species abundance in traditional rice fields. They reported that based on a 1975 study in Thailand the species abundance in one traditional rice field in 1 year was 590 species (excluding fungi) (Heckman 1979). Moreover, about 39 taxa of aquatic invertebrates were reported following a 2-year study of pesticide application on Malaysian rice fields (Lim 1980). Across 18 sites in the Philippines and India the highest number of aquatic invertebrate taxa reported was 26 and the lowest was 2 by single sampling at individual sites (Roger et al. 1987). Based on these data recorded from 1975 to the present, they stated that crop intensification had a tendency to decrease the values for total number of species; however, it cannot be accepted as a general concept that crop intensification decreases biodiversity in rice fields (Simpson et al. 1994).

Effects on Soil Microorganisms in Paddy Fields

The soil microbial community is involved in numerous ecosystem functions, such as nutrient cycling and organic matter decomposition, and plays a crucial role in the terrestrial carbon cycle (Schimel 1995). Changes in populations of phosphate solubilizing microorganisms in conventional and organic paddy fields were also studied (Dermiyati et al. 2009). Although the populations of phosphate solubilizing microorganisms were not affected by continuous application of bokashi and the contribution to soil P from bokashi was relatively low, the microorganisms did play a role in the availability of soil available-P from residual P fertilizers that were applied intensively for long periods. Figure 5.2 shows the changes in phosphate solubilizing microorganism populations as a result of converting from conventional to organic paddy fields by applying bokashi continuously.

Roger et al. (1991) also reviewed effects of crop intensification on soil and water microbial populations. The impacts of crop intensification on the rice field microflora due to pesticide use are: (1) alteration of activities related to soil fertility, and (2) reduction of pesticide efficiency because of shifts in microbial populations toward organisms more efficient in their degradation.

 
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