|Publisher||Springer Berlin / Heidelberg|
|ISSN||1611-2490 (Print) 1611-2504 (Online)|
|Subject Collection||Biomedical and Life Sciences|
|Subject||Earth and Environmental Science, Life Sciences, Agriculture, Hydrogeology, Geoecology/Natural Processes, Monitoring/Environmental Analysis/Environmental Ecotoxicology, Soil Science & Conservation and Waste Water Technology / Water Pollution Control / Water Management / Aquatic Pollution|
|SpringerLink Date||Sunday, July 13, 2003|
Abstracts of Recent Papers
The acidic condition of soil intervened crop growth, especially for rice crop. This research aimed to examine whether application of SRI method on saline soil can improve the productivity of rice. This research applied SRI method in the hinterland of mangrove forest areas around Segara Anakan Lagoon of Indonesia through modified irrigation to reduce saline water intrusion. SRI along with deep furrows in this first implementation had reduced the use of synthetic fertilizers by 40%, reduced variable costs by 8.35%, increased the B/C ratio by 95% and crop productivity by 76% compared to the control methods and increased the B/C ratio by 161% and crop productivity by 133% compared to conventional methods. The farmer’s motivation to apply SRI along with deep furrows for both N-Ach and N-Aff majority was distributed from moderate to high.
For soil water and solute transport research, time domain reflectometry (TDR) has been commonly used since its introduction to soil research in 1980 by Topp and his colleagues. Although TDR seems to be very versatile for laboratory and field experiments, it requires modest user skills for accurate measurements and the instrument itself is still expensive. A new soil moisture and electrical conductivity (EC) sensor was recently developed at a reduced cost. The new sensor independently measures soil water content, and soil bulk electrical conductivity using frequency phase-shift techniques, and soil temperatures using a thermistor. We evaluated the new sensor for measurements of water content, and EC using three different sensors in variably saturated soils. There was little deviation among the units for water content measurement except at near saturation. Separate exponential curves provided good calibrations for all the soils used in the full range of water content between air-dry and saturation. In saline water up to 54 mS m−1, the mV output in the EC measurement mode was linearly related to solution EC. Although slopes were quite similar among the three sensors, the intercepts differed from the manufacturer’s calibration. The calibrations for volumetric water content and electrical conductivity provided by the manufacturer were not good enough for any use. The temperature effect on volumetric water content could be negligible or easily compensated with a simple formula. Little EC dependency of the sensor on volumetric water content was observed.
Water logging and salinity often occur together because rising water table brings salt to the surface. We studied the effects of a range of low soil matric suctions (or nearly paddy condition) (2–33 kPa) and salinity (EC = 0.7–8 dS m−1 for bean and 2–20 dS m−1 for wheat) on the root respiration (Rr) in two sandy loam and clay loam soils at greenhouse condition. Results showed that the aeration porosity mainly controls Rr especially at 2 kPa matric suction. As matric suction increases, soil aeration rises and consequently the Rr reaches maximum values (7.9 μmol m−3 s−1 for bean and wheat) at 6 and 10 kPa suctions in clay loam and sandy loam soils, respectively. Using a mechanistic soil respiration model reveals that these matric suctions, h, are corresponded to the aeration porosities of 0.18 m3 m−3 in sandy loam and 0.16 m3 m−3 in clay loam soils. Bean and wheat Rr remains nearly constant at higher suctions (h > 10 kPa) in sandy loam and decreases slightly in clay loam soil. Gas diffusivity and the root surface area may explain the variation of the Rr between the sandy loam and the clay loam soils. Results showed that the salinity (EC = 6–8 dS m−1 for bean and EC = 16–20 dS m−1 for wheat) amplifies the effect of aeration stress at 2 kPa matric suction in both soils. We also observed a strong correlation between root surface area, Rs, and the Rr for all experiments. We concluded that the aeration deficit is not only major factor determining differential plant respiration under adverse stress conditions, and the salinity has a pronounced impact on differences in crop physiological responses.
This study investigated the effect of extracts with time (a range of extraction periods: 0.2 days to maximum 150 days) of rice and rye straw on the growth of Microcystis aeruginosa (a cyanobacterium). The effect was assessed by an effective concentration 50 (EC50) of extracts measured by a carbon (C) content, when 50% normalized maximum growth yield (50% inhibition effect) of M. aeruginosa occurred. We found that extracts of rice and rye straw inhibited the growth of M. aeruginosa. Extracts from the earliest incubation phase (0.2 days) for rice straw and the 40-day extract for rye straw showed the most inhibitive EC50 value of 28.0 mg C L−1 and 18.9 mg C L−1, respectively. The inhibition effect was positively related to the extraction period of the rye straw, but inversely of the rice straw. Our results suggested that the long-term decomposition of extracts during straw extraction be linked with the formation of allelochemicals. These results provided information on how allelochemicals derived from agricultural by-products affect algal growth in aquatic ecosystems.
Paddy fields converted into winter wheat fields in Hokkaido, Japan, receive extremely high snowfall, creating a risk of flood damage to crops in spring due to waterlogging of snowmelt runoff and poor drainage. Meanwhile, in June there is relatively little rainfall, and a lack of moisture inhibits winter wheat growth. Therefore, we developed a method involving a series of 30-cm-deep ditches in agricultural fields to be used for drainage during the flood-prone period and for furrow irrigation during the dry period using water drawn from the canals that feed the paddy fields. The ditches are called ‘hybrid ditches’ as they are able to perform both drainage and irrigation functions. In this study, we investigated the optimal construction timing and spacing for hybrid ditches. We also evaluated their ability to improve the drainage and irrigation of winter wheat. We found that the optimal timing for digging hybrid ditches is immediately after sowing, and the inter-ditch spacing for irrigation should be 15 m or less. The hybrid ditches promoted increased soil temperature and healthy development of wheat plants by improving drainage during the flood-prone period. In addition, water was successfully supplied via the hybrid ditches to irrigate the fields in June. Under experimental conditions in which rainfall was excluded, grain yield was 10% higher and percent protein content was more than 1% point greater in the irrigated plot compared with the non-irrigated plot. Grain yield was also observed to increase by 3–29% in demonstration tests conducted at local farms. From these results, we conclude that hybrid ditches are capable of improving the growth and yield of winter wheat by improving drainage and providing irrigation in converted paddy fields in Hokkaido.
Manganese (Mn) deficiency is prevalent in rice-growing regions resulting in poor paddy yield and human health. In this study, role of Mn, applied through various methods, in improving the productivity and grain biofortification of fine grain aromatic rice was evaluated. Manganese was delivered as soil application (SA) (0.5 kg ha−1), foliar spray (FA) (0.02 M Mn), seed priming (SP) (0.1 M Mn) and seed coating (SC) (2 g Mn kg−1 seed) in conventional (puddled transplanted flooded rice) and conservation (direct seeded aerobic rice) production systems at two different sites (Faisalabad, Sheikhupura) in Punjab, Pakistan. Manganese application, through either method, improved the grain yield and grain Mn contents of fine grain aromatic rice grown in both production systems at both sites. However, Mn application as SC and FA was the most beneficial and cost effective in improving the productivity and grain biofortification in this regard. Overall, order of improvement in grain yield was SC (3.85 t ha−1) > FA (3.72 t ha−1) > SP (3.61 t ha−1) > SA (3.36 t ha−1). Maximum net benefits and benefit–cost ratio were obtained through Mn SC in flooded field at Faisalabad, which was followed by Mn SP in direct seeded aerobic rice at the same site. However, maximum marginal rate of return was noted with Mn SC in direct seeded aerobic rice at both sites. In crux, Mn nutrition improved the productivity and grain biofortification of fine grain aromatic rice grown in both conventional and conservation production systems. However, Mn application as seed treatment (SC or SP) was the most cost effective and economical.
The aim of this study was to evaluate virtual water export through five crops (barley, rice, maize, soybeans, and wheat) in terms of the external virtual water rate, within and outside of Asia from 2000 to 2012, and in comparison with that within and outside the European Union (EU). The external virtual water rate indicates the proportion of virtual water export outside of a boundary. Approximately 46.9% of the green water exports and 40.9% of the blue water exports were discharged from Asia to non-Asian countries. For example, Thailand, which is the main exporter in Asia, exported 55.5% of the total virtual water exported to non-Asian countries, and Kazakhstan exported 63.8% of the total virtual water exported to European countries. In comparison, the external virtual water rate for the EU was 30.2% (green water) and 25.2% (blue water). The virtual water trade is also important to the main importers in Asia. We evaluated the virtual water dependency on exporters in East Asia of Japan, Korea, and Taiwan. These three countries have a high dependency on virtual water imported from only a few exporters; thus, they should extend their virtual water trade boundary to include additional exporters. These results provide information necessary for the development of an integrated water strategy in Asia, and could convince the main Asian importers of the risks of serious dependency on foreign water resources.