|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 consumption of energy inputs in agricultural production has been increasing rapidly during the past decades. However, given the limitations and costs of non-renewable energy, increasing production while using the least energy possible has become a major concern of most nations. Prompted by this concern, we conducted a face-to-face survey of 90 farming households in Thai Nguyen Province, Vietnam, to find out how energy is being used in agriculture and, specifically, in their rice production. Through analysis of energy input–output balances, combined with economic efficiency analysis, a comparison was made of conventional and SRI methods of rice production. The study found that applying the SRI method can save around 23% of energy inputs, while increasing energy outputs by 11%. Economic benefits per hectare also rise by more than 8 million dong (USD 364) compared to those under the conventional cultivation system. The study also showed conflicts between the energy and economic balances for manual compared with machine ploughing operations. This study contributes to providing an overview of energy consumption in rice cultivation at the household level. Its findings can help stakeholders to assess current policies and make better decisions on the uses of energy in agricultural production. In addition, the comprehensive approach taken here to analysing energy use and efficiency could expand the analysis and comparison of energy uses at sectoral or activity level—still a new field in Vietnam and many other countries.
Land application of animal manure has been accepted as an effective method and disposal option, which has economic, environmental and social benefits, while also sometimes exists questions about its impact on soil and water quality and crop yields. This paper presents a field-scale study in Chongming Island, Shanghai, China, where land application of digested swine liquid manure with chemical fertilizer supplement in paddy field (SMC field) was conducted to study the short-term effect on soil quality in different depth, pollutant losses by surface runoff, pollutant concentrations in groundwater and crop yields, compared to conventional paddy field with land application of pure chemical fertilizer (CKC field). The results indicated that: (1) in groundwater, the concentrations of chemical oxygen demand (COD), nitrate nitrogen (Nitrate-N), total phosphorus (TP) and dissolved phosphorus (DP) were significantly increased by 24.69, 17.04, 11.76 and 21.05%, respectively, in the SMC field; (2) in surface runoff, the loss loading of COD, TP and DP was significantly increased by 32.18, 15.46 and 28.13%, respectively, while the ammonia nitrogen (Ammonia-N) was significantly decreased by 31.81%, in the SMC field; (3) in the different depth of soil, the contents of total nitrogen presented a greater decrease in the SMC field, while the contents of TP presented a greater decrease in the CKC field, compared to the properties of original soil; (4) for the crop yields, there was no significant difference between the SMC and CKC field. These practices had proved the feasibility for land application of swine liquid manure in the paddy field, and this approach could be extended after being rate modified to concern the nutrient utilization and pollution risk to water environment.
Application of control release fertilizer in rice cultivation is a smart way to reduce the environmental nitrogen contamination and enhance the nitrogen use efficiency. The effect of coating thickness and radius of urea granule on nitrogen release rate was modelled, but their effect on nitrogen transformation in soil was not modelled for any crop. In this study, a simple rice water and nitrogen balance model was integrated with a nitrogen release rate model and the effect of coated urea on nitrogen transformations was studied in the CRF-applied flooded rice. The simulated nitrogen release during urea hydrolysis was verified with literature data for uncoated, polymer-coated and mix urea (polymer-coated + uncoated) cases. The integrated model successfully predicted the lag, linear and decay periods of nitrogen release, and peak nitrogen concentration during urea hydrolysis and declining trend during nitrogen transformations. The integrated model could be used as a management tool for determining optimum coating thickness and urea radius for which the nitrogen loss to environment is minimum.
The Nilwala Ganga Basin of Sri Lanka includes important natural wetlands that are habitat for vulnerable animal and plant species. Flood protection and intensive rice production in the Basin have resulted in degraded acid soils and declining rice yields. However, traditional ‘maavee’ rice production outside the flood protection scheme has continued to generate a high-value rice product. This study reports on interviews conducted with farmers and other stakeholders to document the production practices and the potential environmental and economic benefits associated with maavee rice paddies. The maavee production system has prevailed for at least several decades. Farmers apply no chemicals to their paddies, relying instead on alluvial deposits as a source of nutrients, and on the natural pest and disease resistance of their traditional varieties. The maavee rice product can attain three times the selling price of rice from conventional farms making it more economically viable than conventional rice production. However, much of maavee production is for home consumption and the system is threatened by increasing labour costs, an ageing farming population and pressures to increase rice yields. Non-invasive production practices and the proximity of maavee paddies to regenerating wetlands in the Kirala Kele Sanctuary suggest that traditional paddies may constitute an important habitat for vulnerable wildlife; however, maavee farmers also perceive wetland birds as potentially damaging to rice. Based on a SWOT (strengths, weaknesses, opportunities and threats) analysis, we make recommendations for future research needs and potential management actions to safeguard the environmental and economic sustainability of the maavee system.
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.