Upland Rice Fields Research Articles

Reducing soil CO2 emission and improving upland rice yield with no-tillage, straw mulch and nitrogen fertilization in northern Benin

To explore effective ways to decrease soil CO2 emission and increase grain yield, field experiments were conducted on two upland rice soils (Lixisols and Gleyic Luvisols) in northern Benin in West Africa. The treatments were two tillage systems (no-tillage, and manual tillage), two rice straw managements (no rice straw, and rice straw mulch at 3 Mgha−1) and three nitrogen fertilizers levels (no nitrogen, recommended level of nitrogen: 60kgha−1, and high level of nitrogen: 120kgha−1). Potassium and phosphorus fertilizers were applied to be non-limiting at 40kg K2Oha−1 and 40kg P2O5ha−1. Four replications of the twelve treatment combinations were arranged in a randomized complete block design. Soil CO2 emission, soil moisture and soil temperature were measured at 5cm depth in 6–10 days intervals during the rainy season and every two weeks during the dry season. Soil moisture was the main factor explaining the seasonal variability of soil CO2 emission. Much larger soil CO2 emissions were found in rainy than dry season. No-tillage significantly reduced soil CO2 emissions compared with manual tillage. Higher soil CO2 emissions were recorded in the mulched treatments. Soil CO2 emissions were higher in fertilized treatments compared with non-fertilized treatments. Rice biomass and yield were not significantly different as a function of tillage systems. On the contrary, rice biomass and yield significantly increased with application of rice straw mulch and nitrogen fertilizer. The highest response of rice yield to nitrogen fertilizer addition was obtained for 60kg Nha−1 in combination with 3 Mgha−1 of rice straw for the two tillage systems. Soil CO2 emission per unit grain yield was lower under no-tillage, rice straw mulch and nitrogen fertilizer treatments. No-tillage combined with rice straw mulch and 60kg Nha−1 could be used by smallholder farmers to achieve higher grain yield and lower soil CO2 emission in upland rice fields in northern Benin.

Integrated rodent management in outbreak-prone upland rice growing areas of Northern Laos

An integrated rodent management program was tested in outbreak-prone areas in three provinces of the Northern uplands of Laos (Luangprabang, Phongsaly, Houaphanh). In each province, it was replicated in six villages and associated upland rice fields; six neighboring villages served as negative controls. The program started end of 2010 and aimed at protecting the wet season rice harvest of 2011 against rodent damage. Rodent control techniques included sustained trapping, rodent-proofing of grain stores, rodent hunts and village sanitation campaigns, and biological rodent control using the protozoan parasite Sarcocystis singaporensis. The measures were embedded in a community approach, which was coordinated by provincial and district agricultural officers. Compared to the control villages, which showed on average 10.9% rat damage to ripening upland rice before harvest in 2011, and to the situation of the previous year (12.8%), rat damage was significantly reduced to an average of 4.3% in rice fields of the treatment villages. The incidence of rat-infested rice storage huts dropped significantly from an average of 86% in 2010 to 3.5% in 2011 in the treatment villages. Villagers from Houaphanh culled a total of 73,088 rodents over a period of about nine months, which included mainly black rats (Rattus rattus). Because the program phased out before harvest in 2011, potential losses due to rodents were predicted based on yield-damage relationships of the crop year 2010. The predicted average reduction of yield loss for 2011 was 55%, or 417.6 kg ha−1, in the treatment villages when compared to the controls. The program implemented principles of ecologically-based rodent management (EBRM), the components of which are discussed. In conclusion, EBRM could be helpful in stemming as what was observed as high chronic rodent populations in the uplands of Laos. True outbreaks will require development of a suitable forecast system.

Net primary production of major plant functional types in China: Vegetation classification and ecosystem simulation

The characteristics and distribution of vegetation are essential information for understanding the structure and functioning of terrestrial ecosystems across a large region. In this study, we developed the contemporary and potential vegetation maps of China with a spatial resolution of 1 km × 1 km. The vegetation classification scheme includes 17 types of vegetation and 3 non-vegetated land cover types. For cropland, we further provide spatial information on three major cropping systems across China, i.e., single, double and triple cropping system. In addition, we further evaluate the accuracy of this classification against field survey. As a case study, we used this vegetation data set combined with other environmental factors (climate, atmospheric CO2 and nitrogen deposition) to drive the Dynamic Land Ecosystem Model (DLEM) for estimating terrestrial net primary production at both plant functional type and national levels. DLEM simulations indicate that net primary productivity (NPP) in China's terrestrial ecosystem has substantially increased by 51%, from 2.50 Pg C y−1 in the 1900s to 3.79 Pg C y−1 during the first decade of the 21st century. Among major plant functional types across China, cropland shows the largest NPP increase by nearly 3–4 fold during 1901–2010 primarily due to cropland expansion as well as increased nitrogen fertilizer use and irrigation. The NPP increase is estimated to be 480 and 692 gC m−2 y−1 for upland crops and rice fields, respectively. This vegetation distribution data set was originally developed for driving the Dynamic Land Ecosystem model (DLEM), but it can be used for other purposes such as driving hydrological and climate models.

Aboveground Arthropod Composition, Abundance and Guild Structure in Upland Rice Agro-ecosystem at Matalam, North Cotabato, Philippines

With the recent innovations in the field of ecological pest management,conservation and enhancement of biological diversity at any rice agro-ecosystemshas received considerable attention. The composition and abundance ofaboveground arthropods was assessed on upland rice fields in Matalam, NorthCotabato, Southern Mindanao, Philippines. Sampling and monitoring was doneusing malaise trapping, sweep netting and direct counting techniques. A total of29 arthropod species belonging to 21 families in nine orders were documented.The collected samples were comprised of 40% insect pests, 53% predators and7% parasitoids. The three most abundant insect pests were rice bug (Leptocorisaoratorius), rice seedling maggot (Atherigona oryzae), and pink stemborer (Sesamia inferens). The predators are dominated by lady bird beetle (Micraspis spp.), social wasp (unknown) and long-jawed spider (Tetragnatha maxillosa). Ichneumonids,Braconids and Tachinids, though in smaller numbers, were present throughoutthe cropping season. More importantly, the study reported the presence of four rice stem borer species – Scirpophaga innotta, Scirpophaga incertulas, Sesamia infere and Chilo suppressalis and two rice grain bug species – Paraeucosmetuspallicornis and Elasmolomus sordidus in Matalam. The occurrence, compositionand abundance of insect pests and associated natural enemies vary with ricegrowth and developmental stages. The negative Pearson’s correlation coefficient (r= -0.31) between the insect pests and natural enemies was attributed to effectivecultural management practices which have been developed through decades ofsubsistence upland rice farming.Keywords: Ecology, aboveground arthropods, upland rice agro-ecosystem, sampling andmonitoring, Philippines

Effect of Arbuscular Mycorrizhal Fungi Inoculation on Glomalin, Growth and Rice Yield

TITLE : EFFECT OF ARBUSCULAR MYCORRIZHAL FUNGI INOCULATION ON GLOMALIN, GROWTH AND RICE YIELD. The aim of this study was to measure the glomalin production, growth and yield of rice in upland rice fields. The research used Completely Randomized Design with four treatments: two sterilization levels (no sterilisatio and with sterilization) and two levels of mycorrhizae inoculation ( no mycorrhizae and with mycorrhizae). Mycorrhizae (5 g/pot) was inoculated before planting rice seeds. The results showed that Glomalin Total (GT) and Glomalin easily extracted (GEE) were higher in mycorrhizae inoculation, increased by 16% and 20% in non-sterile soil and 25% and 11% in sterile soil compared to non-mycorrhizae inoculation. The content of the GT ranged from 4.95 to 9.74 mg/g soil and GEE 0.99 to 2.78 mg/g soil. Plant height, tillers number and the grain yield was increased by mycorrhizae inoculation significantly. Soil sterilization could reduce the effectiveness of mycorrhizae inoculated.

SHORT- TO MID-TERM IMPACT OF CONSERVATION AGRICULTURE ON YIELD VARIABILITY OF UPLAND RICE: EVIDENCE FROM FARMER’S FIELDS IN MADAGASCAR

SUMMARYFamily farming in the tropics suffers from low crop productivity mainly due to a combination of poor soil fertility, low investment capacity, and a variable climate. The Lake Alaotra region of Madagascar is no exception and rainfed production is particularly hard hit. To evaluate the agronomic benefits of conservation agriculture (CA) in a region of erratic rainfall, we analysed four years of yield, management and climatic data from 3803 upland rice fields cultivated by farmers and monitored by researchers. Fields located on rainfed lowlands and hillsides were cultivated with sole rice using conventional tillage (Cv) or rice sown with no-tillage on dead organic mulch and rotated with other cereal/legume combinations (CA) from 2006 to 2011. A first global comparison across seasons, locations and years of adoption showed significantly higher average yields under CA, with no change in variance (on lowland: 2.6 ± 0.9 t ha–1 Cv, 2.8 ± 0.9 t ha–1 CA; on hillside: 2.1 ± 0.8 t ha–1 Cv, 2.4 ± 0.8 t ha–1 CA). Grouping fields according to the number of years under CA (first to fourth) revealed that CA gradually increased average yields and reduced the coefficient of variation in the short and mid-term (on lowland: +0.2 t ha–1 and –6% coefficient of variation; on hillside: +0.7 t ha–1 and –13% coefficient of variation, over four to six years of successive CA cropping). The average yield increase under CA was not associated with an increase in mineral fertiliser use, as farmers used the same amounts of fertilisers (or none) under Cv and CA. The comparison Cv versus CA also highlighted a major benefit of CA regarding climate: it widened the window of possible sowing dates. A classification and regression tree analysis of the entire dataset revealed that rice yield was more affected by agro-environmental factors than management factors (fertilisation, Cv or CA), and extreme climate variability such as the severe drought of 2007–2008 could not be offset by CA. The hypothesis of yield penalties during the first years of implementation of CA cannot be verified with the evidence presented in this study.

The Last Swiddens of Sarawak, Malaysia

Swidden cultivation was observed to be under pressure but still persisting in many areas in Sarawak, Malaysia around 2000–2003. Since then rapid development of smallholder oil palm and rubber, continuing urbanization and rural to urban migration appear to have considerably reduced the area under swidden cultivation. With the aim of understanding the extent and impacts of this development, 55 households in three communities that were interviewed in 2002–2003 were re-interviewed in 2011. In an area with rapid oil palm development, the households engaged in smallholder oil palm production have experienced considerable improvements in income and wealth whereas the other households have experienced more limited wealth increases or even a decline in income. Many households have decreased or abandoned cultivation of upland rice, which used to be the core of the swidden cultivation system, and the upland soils in the area are now dominated by oil palm. In another area, where no oil palm development has taken place because of a hydroelectric dam, upland rice fields under swidden cultivation have also decreased and new high yielding rubber is now being planted because of the favorable rubber prices. Moreover, tourism has in this area gained further economic importance and overtaken agriculture as the main economic activity of households. The demise of swidden has not yet occurred in Sarawak, but a continued decline has been observed. However, there is a possibility that the new smallholder oil palm and rubber may provide an opportunity for a new type of ‘productive fallow’ that will allow continued cultivation of upland rice on a small scale.

Meloidogyne graminicola and Sclerotium rolfsii interaction in rice

Rice root-knot nematode Meloidogyne graminicola causes yield losses of up to 18% in rainfed upland rice in eastern India, and seedling blight disease of rice, caused by Sclerotium rolfsii , is seen to be associated with it (Mathur 1973). This observation led to the investigation of the nature and type of association among rice cultivar IR8, M. graminicola , and S. rolfsii . Samples of IR8 plants with an intact root system and rhizosphere soil collected from the 0-5-cm depth of a rainfed upland rice field served as a source of inoculum for the greenhouse experiments.

Influence of Soil Amendments on Mitigating Methane Emissions and Sustaining Rice Productivity in Paddy Soil Ecosystems of Bangladesh

Two field experiments were conducted at two different rice ecosystems, one in the upland rice field of Bangladesh Agricultural University farm, Mymensingh and the another one in the low lying area of Bhaluka, Mymensingh to investigate the effects of soil amendments on mitigation of methane emissions and sustaining rice productivity. The experimental treatments were urea (250 kg ha-1), urea plus coal ash (1t ha-1), urea plus phosphogypsum (90 kg ha-1), urea plus silicate fertilizer (150 kg ha-1), ammonium sulphate 400 kg ha-1, ammonium sulphate plus silicate fertilizer (150 kg ha-1), urea (25% less than the recommended doze) plus cyanobacteria plus azolla (1t ha-1). In case of BAU upland rice field, the total seasonal CH4 emission was decreased by 12-21% and rice grain yield was increased by 4.0- 18.0% respectively, whereas 11.0-26.0% reduction in total CH4 emission and 4.5-24.0% increase in rice grain yield was recorded from the low lying rice field of Bhaluka with the application of soil amendments. Among the amendments silicate fertilization with urea and silicate in combination with ammonium sulphate reduced total CH4 flux by 18- 23% and 21-26% respectively, whereas rice grain yield was increased by 18-24% and 16-18%, respectively in both ecosystems. Although maximum reduction in total seasonal CH4 flux was recorded with silicate and sulfate of ammonia amendment in paddy soil, however soil acidity was developed which might affect soil fertility and rice productivity in the future. Therefore, silicate fertilizer could be introduced with the nitrogenous fertilizer sources, preferably with 50% urea plus 50% ammonium sulphate for reducing CH4 emissions and increasing rice productivity under both irrigated upland and lowland rice field ecosystems. DOI: http://dx.doi.org/10.3329/jesnr.v5i1.11574 J. Environ. Sci. & Natural Resources, 5(1): 179 - 185, 2012

Effect of cowpea residue incorporation and nitrogen application rates on the productivity of upland rice

3 Abstract: A trial was conducted in 2009 and 2010 at the upland rice field of the Teaching and Research Farms of the University of Agriculture, Abeokuta (Latitude 7°2 N and 21°E) to investigate effects of cowpea residue incorporation and nitrogen application rates on the productivity of upland rice. The experiment was laid out in Randomized Complete Block Design in split- split plot arrangement and replicated three times. The main plots were incorporated cowpea residue and no cowpea residue incorporated, sub plot were the nitrogen rates (0, 20, 40 and 60 Kg N ha ) while the sub-sub plot were the rice varieties (NERICA 2 and ITA 150). Results 1 obtained were subjected to analysis of variance (ANOVA) and significant treatments means were separated using Least Significant Difference (LSD). The yield and yield components of rice measured were significantly (P < 0.01) influenced by the incorporated cowpea residue, while nitrogen rates had significant (P < 0.01) influence on yield of rice in 2009 and 2010. Rice varieties showed significant (P < 0.01) difference on all traits measured. It is concluded that the incorporation of grain cowpea with nitrogen fertilizer significantly (P <0.01) enhanced the performance of upland NERICA rice.

How different or similar are nematode communities between a paddy and an upland rice fields across a flooding–drainage cycle?

The paddy field is being recognised as a biodiversity hotspot fostering a variety of organisms. However, there are few studies on the ecology of paddy field nematodes. We characterised nematode communities in rice paddy fields by comparing them with upland fields of rice or soybean. We examined nematode communities of the top (0–15 mm) and second (15–50 mm) soil layers before flooding (March or April), during flooding (June or July) and during the draining period (October) 2007–2009. We found that the nematode community in the paddy was different than that in the upland fields during all periods. Rhabdolaimus, Tobrilus, Mesodorylaims and Monhysteridae characterised the top of the paddy and Hirschmanniella characterised the second layer of the paddy. Total nematode density was generally lower in the paddy than in the upland field. However, the density in the paddy top layer increased with time from the flooding period to the draining period, during which time it was about the same as (or even greater than) the peak density in the upland fields. The density in the second layer of the paddy remained lower than that in the top layer of the paddy throughout the time course. Community diversity values were generally greater in the paddy top layer than in the paddy second layer across the six sampling periods, but periodic differences between the paddy and upland fields or between soil layers were not significant. During the flooding period, the F/(F + B) (13–37) and Enrichment Index (17–38) values were lower in the paddy than in the upland fields (32–47, 37–74, respectively) to reflect that bacteria dominate over fungi with slow decomposition due to anaerobic conditions in the flooded paddy field. In addition, particularly in the top layer, the Maturity (2.0–2.4) and Structure Index (23–72) values were greater in the paddy than in the upland fields (1.7–2.1, 9–15, respectively), indicating a well-developed ecosystem under water. These unique nematode communities persisted during the draining period, but there was a rapid increase in opportunistic bacterivores, which increased the EI values. We suggest that bactivorous nematodes in the families Cephalobidae and Chronogasteridae, herbivores in the genus Hirschmanniella, and fungivores in the genus Filenchus may be specific to paddy field soil rather than to pond and lake sediments.

Agronomic and socio-economic constraints to high yield of upland rice in Tanzania

A field survey was conducted in March 2009 in upland rice growing agro-ecosystem of four districts in Tanzania namely Ulanga, Kyela, Morogoro and Korogwe to investigate the agronomic and socio-economic factors which influence rice productivity and suitability of these areas for NERICA cultivation so as to increase rice productivity. Questionnaire was used to gather primary information from ten farmers from each district. Secondary information was obtained from district agricultural offices and weather data from Tanzania Meteorological Agency. A composite soil sample was collected from upland rice fields of sampled farmers and analyzed for complete soil fertility. The findings showed that rice is the most important crop in all areas as both food and cash crop. However, rice yield is as low as 1 tha-1. Low yields are attributed to diseases and pests, poor inputs, insufficient water, poor soil fertility, short supply of fertilizers and use of low yielding traditional varieties, among other factors. The soils are potentially low in nitrogen and phosphorus and therefore N and P fertilization is recommended. Rainfall and temperature pattern is adequate for NERICA cultivation which gives higher yields compared to traditional upland varieties under stress-prone environments such as poor soil fertility, disease and pests and moisture stress which characterize the upland agro-ecosystem. Key words: NERICA, adaptability, soil fertility, upland rice agro-ecosystems, productivity.

Molecular Characterization of Fungal Communities in Non-Tilled, Cover-Cropped Upland Rice Field Soils

This study aimed to characterize soil fungal communities in upland rice fields managed with tillage/non-tillage and winter cover-cropping (hairy vetch and cereal rye) practices, using PCR-based molecular methods. The study plots were maintained as upland fields for 5 years and the soils sampled in the second and fifth years were analyzed using T-RFLP (terminal restriction fragment length polymorphism) profiling and clone libraries with the internal transcribed spacer (ITS) region and domain 1 (D1) of the fungal large-subunit (fLSU) rRNA (D1(fLSU)) as the target DNA sequence. From the 2nd-year-sample, 372 cloned sequences of fungal ITS-D1(fLSU) were obtained and clustered into 80 nonredundant fungal OTUs (operational taxonomic units) in 4 fungal phyla. The T-RFLP profiling was performed with the 2nd- and 5th-year-samples and the major T-RFs (terminal restriction fragments) were identified using a theoretical fragment analysis of the ITS-D1(fLSU) clones. These molecular analyses showed that the fungal community was influenced more strongly by the cover-cropping than tillage practices. Moreover, the non-tilled, cover-cropped soil was characterized by a predominance of Cryptococcus sp. in the phylum Basidiomycota. We provided a genetic database of the fungal ITS-D1(fLSU)s in the differently managed soils of upland rice fields.

Endo- and ectoparasites of the Philippine rice field rat, &lt;i&gt;Rattus tanezumi&lt;/i&gt; Temminck, on PhilRice farms

The Philippine rice field rat, Rattus tanezumi Temminck, is one of the principal pre- and postharvest pests of rice and other agricultural crops. This species usually thrives in lowland and upland rice fields but can also be found in or near places of human habitation. They damage agricultural crops and also serve as reservoir hosts for diseases of certain human and domestic animals caused by helminths, protozoans, and microbes. Many endoparasites infecting the different viscera of R. tanezumi belong to taxonomic groups Nematoda (roundworms), Cestoda (tapeworms), and Trematoda (flukes). The more important ones are those that are transmissible to humans. In contrast, there have been few reports on the ectoparasites that infest these rats. These are the mites, ticks, and fleas, some of which may serve as vectors of microbial infections to humans and domestic animals. Rattus tanezumi is an alternative meat source for the rural folk. Rat meat is a favorite accompaniment to alcoholic beverages during drinking sprees. Unknowingly, some zoonotic infections can be transmitted to humans through improperly cooked rat meat and viscera, accidental wound contamination with rat urine, or rat bites during handling and precooking preparations

Soil erosion from shifting cultivation and other smallholder land use in Sarawak, Malaysia

The sustainability of shifting cultivation systems and their impact on soil quality continues to be debated, and although a growing body of literature shows a limited impact on, e.g. soil carbon stocks, shifting cultivation still has a reputation as detrimental to the environment. We wished to compare soil erosion from three land use types in a shifting cultivation system, namely upland rice, pepper gardens and native forest. We used two sample sites within the humid tropical lowland zone in Sarawak, Malaysia. Both areas had steep slopes between 25° and 50°, and were characterised by a mosaic land use of native forest, secondary re-growth, upland rice fields and pepper gardens. Soil samples were collected to 90 cm depth from all three land use types, and analysed for various chemical parameters, including texture, total organic matter and 137Cs content. 137Cs is a radioactive isotope derived from nuclear fallout, and was used to estimate the retention of topsoil in the profiles. Soil chemical parameters in upland rice fields, such as extractable cations, pH and conductivity, indicated limited soil transportation downslope, and depletion of cations from upslope samples are most likely caused by leaching and losses via ashes after clearing and burning. The position on slope had no significant effect on soil texture, carbon or P content, indicating very limited physical movement of soil downslope. A soil carbon inventory to 90 cm depth on the three land uses only showed a higher carbon concentration in the top 5 cm of forest and upland rice plots. When corrected for soil density, there was no effect of land use on the carbon inventory. Moreover, the carbon content in the top 30 cm contributed <50% of the total carbon inventory, hence even significant effects of land use on carbon content in the upper soil layers, are unlikely to change the carbon inventory dramatically. 137Cs content in the soil profile indicated largest retention of original topsoil in the native forest plots, and a loss of 18 and 35% of topsoil from upland rice and pepper gardens, respectively, over the past 40 years. When comparing to 30 cm depth, soil loss was 30% from both upland rice and pepper fields. Low 137Cs activity in deeper soil layers rendered a total profile inventory impossible. It is concluded that shifting cultivation of upland rice in the current system is not leading to degradation of soil chemical and physical quality. The soil carbon inventory is not affected by land use in this analysis, due to the contribution from the deeper soil layers.

Archaeal Diversity of Upland Rice Field Soils Assessed by the Terminal Restriction Fragment Length Polymorphism Method Combined with Real Time Quantitative-PCR and a Clone Library Analysis

The PCR amplification-based analysis of microbial diversity is subject to potential problems. In this study, to minimize the bias toward a 1:1 ratio in multitemplate PCR, a real-time PCR assay was carried out using a quenching fluorescence dye primer and amplification efficiency was monitored. Then terminal-restriction fragment length polymorphism (T-RFLP) profiling was performed using the PCR product with minimized PCR bias. This method was applied to an analysis of the diversity of the archaeal community in an upland rice field under different tillage systems and winter cover cropping. Terminal restriction fragments (T-RFs) of PCR-amplified archaeal 16S rRNA genes were assigned to the gene sequences recovered from the same soil by using an archaeal 16S rRNA gene clone library. Our results indicated that soil archaeal members were not influenced but the relative abundance of archaeal species particularly those belonging to Crenarchaeota which changed between the tillage and non-tillage treatments.

Effects of land uses on solid-phase distribution of micronutrients in selected vertisols of the Mississippi River Delta

The Mississippi River Delta (U.S.A.) is the major agricultural and aquacultural base where many crops and fishes are sensitive to micronutrients (Zn, Cu, Mn). Zinc is a common yield-limiting factor for rice and was reported to increase rice yields grown on some Delta soils. Soil/sediments in fish ponds of the Delta are drained and disposed for improving the conditions of bottoms. Bioavailability of micronutrients in soils is controlled by distribution between solution and solid-phase and further among various solid-phase compounds. The effects of land uses on distribution and bioavailability of micronutrients (Cu, Zn, Mn) in Mississippi River Delta have not been studied. The objectives of this study were to determine effects of land uses on solid-phase distribution of micronutrients (Cu, Zn, Mn) and Fe in selected vertisols of the Mississippi River Delta alluvial plain. Land uses include upland forest, rice fields and short- and long-term of catfish production. Micronutrients Cu and Zn and Fe and Mn in fresh soils were fractionated into seven operationally defined solid-phase components. Iron and Zn were mainly present in the stable residual fraction (60–70% of the total Zn and 50–60% of the total Fe), Mn mainly in labile fractions (70–80% of the total Mn, including soluble plus exchangeable, carbonate bound, Mn oxide bound, and organically bound fractions), and Cu in the potentially labile fractions (40–50% of the total Cu in amorphous and crystalline Fe oxide bound fractions). Partitioning of these elements into solid-phase fractions varied with land uses. Mn, Fe and Zn in catfish pond soils were higher in labile fractions and lower in potential labile fractions than paddy and forest soils. Paddy and forest soils had higher Fe, Mn and Zn in potential labile fractions. Drying caused redistribution of metals in solid-phase components with possibably lower potential bioavailability and mobility. In conclusion, land uses strongly affect micronutrient distribution in solid-phase components in the selected vertisols of the Mississippi River Delat alluvial plain. The results of the present study may be applicable to other river delta areas of the world.

Numerical response of predatory ladybirds (Coccinellidae) to aphid outbreaks and their diversity in major rice ecosystems of Cameroon

Field study conducted on upland rice fields in North Cameroon showed that Rhopalosiphum rufiabdominalis (Sasaki) and Hysteroneura setariae (Thomas) are the most important aphid species feeding on rice crops compared with Rhopalosiphum maidis (Fitch) and Schizaphis minuta (van der Goot) in term of numbers. The investigations also revealed the occurrence of 13 species of predatory coccinellids dominated by Xanthadalia effusa ssp. rufescens (Mulsant) and the Scymnus spp. The dynamics of the individual species was different according to growing seasons. The aphid H. setariae and Scymnus spp. were the most numerous during the rice early growing season, whereas during the mid- to late growing period high occurrence of R. rufiabdominalis and X. effusa rufescens was recorded. In both growing seasons synchronization between the development of aphids and coccinellids was observed. Significant positive correlation was found between aphids and ladybirds during the second half growing season. Species richness and the Shannon indexes fluctuated from year to year in rice irrigated plots.

Household Differentiation and On-farm Conservation of Biodiversity by Indigenous Households in Xishuangbanna, China

With diversification of field type among households in same eco-environment and social situation, even in the same ecosystem, merging household socio-economics with biodiversity initiative values to determine incentives and optimum strategy of on-farm conservation of biodiversity. Botany survey of agroecosystems at landscape level in Daka and Baka, Xishuangbanna, Yunnan, China, as well as household differentiation of biodiversity in agroecosystem and on-farm conservation strategy merging household socio-economic characters were studied. There were 73 families 179 species distributed in 0.1 ha of different agroecosystems in Daka, and 70 families 166 species distributed in 0.08 ha different agroecosystems of Baka respectively. The cosmopolitan families, such as Gramineae and Compositae decreased the percentage of tropical families and subtropical families. Botany survey among 12 random selected households from Daka in 46 sampling plots of different agroecosystems showed significant differentiation of the species richness indices of natural biodiversity and agrobiodiversity as there were differences of cognition and utilization of plant species besides management practices among households. Dengrogram using the Ward method of hierarchical cluster analysis based on annual questionnaire interview of 60% household from 1998 to 2001 in Daka showed disparity among different households’ socio-economics which underpins management diversity. There were significant correlation coefficients between household socio-economics and species richness indices of different agroecosystems. Fallow size had significant positive correlation coefficients with species richness index of rubber plantation. By contraries, production input had negative correlation coefficients with species richness index of upland rice field. Meanwhile, cereal crop income had significant positive correlation coefficient with agro-species richness index of rubber plantation. By contraries, other income such as off-farm income had negative correlation coefficients with agro-species richness index of rubber plantation. Innovations of the expert farmer on agrobiodiversity on farm conservation were admiration.

Predatory ground-dwelling beetles (Carabidae and Staphylinidae) in upland rice fields in North Cameroon

Indicators of diversity (population density, relative number of species and evenness) in ground beetles (Carabidae) and rove beetles (Staphylinidae) in upland rice fields were assessed between 1995 and 1999 at Garoua in the Benue valley in North Cameroon. A total of 4369 beetles belonging to 45 carabid species and 2109 beetles belonging to 31 staphylinid species were caught in pitfall traps. Among the carabid beetles, five species Scarites (Orientolobus) lucidus strigiceps Quedenfeldt, Chlaeniostenus denticulatus elatus (Erichson), Lissauchenius venator (LaFerte), Pheropsophus marginatus (Dejean) and Abacetus crenulatus Dejean, in decreasing order, were dominant. In the staphylinid group, Paederus sabaeus Erichson was the most common, followed by Stenus ravus Puthz and Stenus (Mendicus) senegalensis Bernhauer. The Shannon–Weiner and evenness indices varied slightly from year to year. Diversity values remained relatively low among the staphylinid beetles, revealing that rice fields were underpopulated by this group of polyphagous predators. The features of predatory soil-surface beetles and the role they play as an IPM component in West African rice ecosystems are discussed.