Intensive Rice Farming Research Articles

Absence of domestic triatomine colonies in an area of the coastal region of Ecuador where Chagas disease is endemic

Rhodnius ecuadoriensis is considered the second most important vector of Chagas disease in Ecuador. It is distributed across six of the 24 provinces and occupies intradomiciliary, peridomiciliary and sylvatic habitats. This study was conducted in six communities within the coastal province of Guayas. Triatomine searches were conducted in domestic and peridomestic habitats and bird nests using manual searches, live-bait traps and sensor boxes. Synantrhopic mammals were captured in the domestic and peridomestic habitats. Household searches (n = 429) and randomly placed sensor boxes (n = 360) produced no live triatomine adults or nymphs. In contrast, eight nymphs were found in two out of six searched Campylorhynchus fasciatus (Troglodytidae) nests. Finally, Trypanosoma cruzi DNA was amplified from the blood of 10% of the 115 examined mammals. Environmental changes in land use (intensive rice farming), mosquito control interventions and lack of intradomestic adaptation are suggested among the possible reasons for the lack of domestic triatomine colonies.

Yield potential and water use efficiency of aerobic rice ( Oryza sativa L.) in Japan

Intensive rice farming in aerobic soil, referred to herein as aerobic rice, can greatly reduce the water input compared to that of flooded rice cultivation. The objective of this study was to compare the potential productivity of aerobic rice and flooded rice using high-yielding varieties at two locations in Japan in two successive years. In aerobic fields, the total amount of water supplied (irrigation plus rainfall) was 800–1300 mm. The soil water potential at 20-cm depth averaged between −15 and −30 kPa each growing season, but frequently reached −60 kPa. The average yield under aerobic conditions was similar to or even higher than that achieved with flooded conditions (7.9 t ha −1 in 2007 and 9.4 t ha −1 in 2008 for aerobic versus 8.2 t ha −1 for flooded). The average water productivity under aerobic conditions was 0.8–1.0 kg grain m −3 water, slightly higher than common values in the literature. The super-high-yielding cultivar Takanari achieved yields greater than 10 t ha −1 with no yield penalty under aerobic conditions in 3 out of 4 experiments. The favorable agronomic characteristic of Takanari was its ample sink capacity (grain number × grain weight). In conclusion, high-productivity rice cultivation in aerobic soil is a promising technology for water conservation. With continued breeding, future aerobic rice varieties will possess large numbers of spikelets and sufficient adaptation to aerobic conditions such that they will consistently achieve yields comparable to the potential yield of flooded rice.

The Taim Wetland Conflict: A Compromise Between Environment Conservation and Irrigation

The Taim federal environmental protection area was created in 1978 to promote conservation of this subtropical wetland, one of the last existing ecosystems of this kind in southern Brazil. However, the protected area does not include lake Mangueira, the Taim's main water source, which is surrounded by intensive rice farming. Rice irrigation demands a large proportion of water during the dry season (40,000 m3/year out of 50,000 m3/year inflow to the lake). A severe drought (1989-1991) almost dried the Taim wetland, resulting in legal actions to enforce the conservation status. As a consequence, several studies were undertaken to elucidate the Taim's hydrological behavior, and to determine adequate water resources management policies. Results show that the ecosystem cannot withstand the present rate of water extraction. The two problems are: (i) defining a suitable plan to manage water extraction, and (ii) ensuring that the farmers respect it. A plan has been proposed, which includes forecasting the available volume and the complementary use of water from the nearby lake Mirim. The final form of the regulations, and their enforcement procedures, are under discussion with federal law enforcement officers, federal and state environmental and water resources agencies, and farmers.