Reducing non-point DOC and nitrogen exports from rice fields: A pilot study and quantitative survey to determine the effects of different hydrologic management practices : Deliverable 15.3 Final Report

Rice cultivation at any level in the Sacramento–San Joaquin Delta (existing or expanded) compels the need to quantify surface and subsurface loads of dissolved organic carbon (DOC), disinfection byproduct precursors (DBPPs) and nitrogen. This information can be used to develop Best Management Practices (BMPs) to reduce export of these constituents in order to improve drinking water quality. Although rice cultivation in the Delta is relatively limited, several factors outside of this research could contribute to increased rice acreage in the Delta: • Recently developed rice varieties seem more suitable for the Delta climate than earlier varieties which required warmer conditions; • Previous economic analyses (Appendix A.10) suggest rice is more profitable than corn, a dominant land use in the Delta; • Recent studies on wetlands at Twitchell Island suggest rice production can help mitigate oxidative subsidence (Miller et al. 2000); • The different oxidative states that result from flooding in rice as compared to those found in crops that require drained soils may help control crop specific weeds and nematodes when rice is incorporated into a crop rotation; and • Providing flooded conditions during a greater part of the year than other crops may benefit water birds. ... (PDF contains 249 pages)

Integrating fish into seasonally flooded rice fields: on-farm trials in Assam, India

In the State of Assam, floodplains cover 2.6 million ha of area that is traditionally rice growing. The ecosystem in the rice-growing areas has undergone major changes as a result of various developmental activities and adoption of modern farming technology. Rice fields were once the major source of fish for the rural farmers. There has been a sharp decline in fish population in rice field leading to a chronic shortage of fish in the State and a deterioration of the rice ecosystem. This paper describes two on-farm experiments for integrating rice cultivation and fish production with the intent of contributing to the understanding of how raising fish can improve rice yields, riceecosystems and farm incomes.

Stocking of eggs versus hatchlings in rice fields: a comparison of survival and growth of common carp (Cyprinus carpio) fingerlings

The study assesses the relative profitability of stocking eggs versus hatchlings of common carp (Cyprinus carpio) in the rice-fish systems in Bangladesh. Results showed that although stocking eggs-covered water hyacinths directly into rice fields is a simple low cost option, the yields and profits are much higher from incubating eggs in cloth hapas and nursing hatchlings before stocking them into rice fields.

Land surface hydrology in a general circulation model: global and regional fields needed for validation

For the last two decades most general circulation models (GCMs) have included some kind of surface hydrology submodel. The content of these submodels is becoming increasingly complex and realistic. It is still easy to identify defects in present treatments. Yet, to improve our ability to model the contribution of land hydrology to climate and climate change, we must be concerned not with just the surface hydrology submodel per se, but also with how it works in the overall context of the GCM.

Growth and yield of GIFT (Oreochromis niloticus) and Thai silver barb (Barbodes gonionotus Bleeker) in rice fields and their effects on the yield of rice

(GIFT) (Oreochromis niloticus) and Silver barb (Barbodes gonionotus) in rice fields and their effects on the yield of rice was carried out in nine experimental rice plots. Three treatments viz., treatment-1 with 0. niloticus (T1), treatment-2 with B. gonionotus (T2) and treatment- 3 was kept as control (T3, without fish) were used in this study. Fertilizers such as, Urea (178 kg ha-1), T.S.P (125 kg ha-1) and M.P. (67 kg ha-1) were applied in each treatment. The fishes were stocked @ 6250 ha·1 and the experiment was continued for a period of 107 days. The values of water quality parameters such as, water temperature, dissolved oxygen, pH and chlorophyll-a were found within suitable level. Between the two species, higher specific growth rate was recorded in 0. niloticus than that of B. gonionotus. But B. gonionotus showed much higher survival (72%) than that of 0. niloticus (35%). Similar to survival, higher production (244 kg ha-1) and income (Tk. 6399 ha-1) were recorded in B. gonionotus than those of 0. niloticus (142.8 kg ha'1 and Tk. 2137 ha-1). Significant differences (p

Culture of Amblypharyngodon mola in rice fields alone and in combination with Barbodes gonionotus and Cyprinus carpio

A rice-fish culture experiment with four treatments viz., T 1 with Amblyphmyngadan mala alone, T 2 with A. mala and Barbodes gonionotus, T3 with A. mala and Cyprinis carpio and T4 as control (without fish) was carried out in the rice fields during April through August1999. The recovery rate of A. mala were 42%, 37% and 42% in treatments 1, 2 and 3 respectively and the same recorded for B. gonionotus and C. cmpio were 62% and 55% respectively. Among the three species of fish, B. gonionotus showed much higher recovery rate than both of A. mala and C. carpio. The production of A. nwla was 12.50 kg/ha/3 months in monoculture, and 7.92 kglha/3 months and 8.86 kglha/3 months in combination with B. gonionotus and C. carpio, respectively. The production of B. gonionotus in T2 was 169.29 kg/ha/3 months and C. cmpio in T 3 was 252.92 kg/ha/3 months. The total fish production was 12.50 kg/ha/3 months, 175.21 kg/ha/3 months and 261.88 kg/ha/3 months in Tp T2 and T3, respectively. The highest yields of rice grain (5.78 ton/ha) and straw (7.83 ton/ha) were recorded in T3 and the lowest of the same was in T4 (grain 4.96 ton/ha and straw 6.62 ton/ha). Rice yield increased by about 12.10% in T1, 13.30% in T2 and 16.33% in T3 in context to T4, rice-alone culture. The results demonstrated that the culture of fish in rice fields had profound beneficial impact on the production of rice grain and straw.

Effects of fish and prawn culture on physico-chemical parameters of water and rice yield in rice fields

An experiment was conducted with five treatments i.e. rice combined with fish having regular urea fertilization (T1), rice combined with prawn having regular urea fertilization (T2), rice combined with fish with supplementary feeding (T3), rice combined with prawn with supplementary feeding (T4) and without fish and prawn (T5) was kept as control. The dissolved oxygen values obtained in treatments with fish both in morning and afternoon were lower than the values of prawn containing treatments and control. The values of nitrate-N, ammonia-N, phosphate-P and chlorophyll-a were higher in fish containing treatments than the prawn containing treatments and control. Between the two fish containing treatments the higher gross (539.44 kg/ha) and net (440.14 kg/ha) yield were obtained in T3 with supplementary feeding and the lower gross (424.88 kg/ha) and net (314.32 kg/ha) yield were recorded in T1 without supplementary feeding. Again, between two prawn containing treatments the higher gross (108.69 kg/ha) and net (81.92 kg/ha) yield were obtained in T4 with supplementary feeding and lower gross (64.32 kg/ha) and net (30.98 kg/ha) yield were recorded in T2 without supplementary feeding. The highest yield of rice grain (3.45 mt/ha) and straw (6.37 mt/ha) were obtained in T1 with fish having urea fertilization without feeding.