多变量自回归模型在三江平原井灌水稻需水量预测中的应用

应用多变量自回归模型ARV(n), 利用三江平原腹地-富锦市1985～1999年气象资料, 按水稻生育期划分6个生育阶段, 建立了井灌水稻生育期内需水量预测模型. 经模型拟合与预测, 效果良好, 可以为该地区开展节水灌溉、灌溉用水管理、合理开发利用地下水资源, 缓解地下水危机提供参考依据.     

Electricity generation from rice husk in Indian rice mills: Potential and financial viability

Rice husk generated as a by-product of rice processing is an important energy resource. The availability of this resource in India has been assessed and the technologies for exploitation of its energy potential in rice processing industry discussed. Nomographs have been developed for estimation of the husk required to meet the energy demand of parboiling, drying and milling operations. The unit cost of electricity using rice husk gasifier-based power generation systems has been calculated and its financial feasibility assessed in comparison with utility-supplied and diesel-generated electricity. With the cost and efficiency data assumed here, the unit cost of electricity produced by rice husk gasifier-dual fuel engine-generator system varies between Rs 2/kWh and Rs 7/kWh. (Note: 35 Rs approximates to $US 1.)     

氯化钙-腐殖酸活化作用下土壤Cd的电动脱除性能

为了提高稻田土壤Cd的去除率,同时减小对土壤pH值的影响,采用氯化钙-腐殖酸复合活化液增强土壤Cd的可移动性,基于电动土工合成材料(EKG)电动排水脱除土壤Cd,重点考察了不同活化剂浓度和活化时间下,土壤有效态Cd含量以及土壤pH值的变化,研究了活化-电动排水后土壤Cd的电动脱除量、土壤全Cd含量、有效态Cd含量、土壤pH值的变化。研究结果表明:0.5%氯化钙-1%腐殖酸对土壤Cd的活化效果最佳,土壤有效态Cd含量可从0.30 mg/kg提高至0.44 mg/kg,而活化处理后的土壤pH值仅降低约0.4;排尽上覆水后,通过电动排水可进一步脱除土壤Cd,土壤Cd的电动脱除量为上覆水中Cd含量的3倍左右;活化-电动排水后,土壤全Cd含量从1.72 mg/kg降低至1.20 mg/kg左右,土壤有效态Cd含量降至0.27~0.31 mg/kg,各截面土壤pH值较为均一且变化不明显,介于5.45~6.30之间。研究所提出的方法可最大限度地脱除土壤Cd,提高稻田土壤Cd的去除率,同时减小对土壤pH值的影响,一定程度上保证了农作物的安全生产。     

Scientific basis for establishing country greenhouse gas estimates for rice-based agriculture: An Indian case study

A comprehensive scientific assessment of CH₄ budget estimation for Indian rice paddies, based on a decade of measurements in India, is presented. Indian paddy cultivation areas contain soils that have low to medium levels of soil organic carbon. The average seasonally integrated CH₄ flux (E _sif) values calculated from these measurements were 15.3 ± 2.6 g m^–2 for continuously flooded (CF), 6.9 ± 4.3 g m^–2 for intermittently flooded (IF) single aeration (SA) and 2.2 ± 1.5 g m^–2 for IF multiple aeration (MA) rice ecosystems. For CF and IF (MA) rice ecosystems having high soil organic carbon, without organic amendments, the CH₄ flux (E _sif) may be increased by 1.7 times relative to low soil organic carbon, whereas it may enhance by 5.3 for CF if amended organically. Organic amendment and high soil organic carbon paddy areas do not alter the methane budget estimates for India (3.6±1.4 TgY^–1) much, due to their small paddy harvested area. Methane estimated using average emission factors (E _sif) for all paddy water regimes, which include harvested areas having soils with high organic carbon and organic amendments, may give a budget of 5 TgY^–1 for India.     

Ammonium transformation in paddy soils affected by the presence of nitrate

Coupled nitrification and denitrification is considered as one of the main pathways of nitrogen losses in paddy soils. The effect of NO₃ ^– on NH₄ ⁺ transformation was investigated by using the ¹⁵N technique. The paddy soils were collected from Wuxi (soil pH 5.84) and Yingtan (soil pH 5.02), China. The soils were added with either urea (18.57 mol urea-N enriched with 60 atom% ¹⁵N excess) plus 2.14 mol KNO₃-N (natural abundance) per gram soil (U+NO₃) or urea alone (U). The KNO₃ was added 6 days after urea addition. The incubation was carried out under flooded condition in either air or N₂ gas headspace at 25°C. The results showed that in air headspace, ¹⁵NH₄ ⁺ oxidization was so fast that about 10% and 8% of added ¹⁵N in the treatment U could be oxidized during the incubation period of 73 hours after KNO₃ addition in Wuxi and Yingtan soil, respectively. The addition of KNO₃ significantly inhibited ¹⁵NH₄ ⁺ oxidation (p<0.01) in air headspace, while it stimulated ¹⁵NH₄ ⁺ oxidation in N₂ gas headspace, although the oxidation was depressed by the N₂ gas headspace itself. Therefore, the accumulation of NO₃ ^– would inhibit further nitrification of NH₄ ⁺ at micro-aerobic sites in paddy soils, especially in paddy soils with a low denitrification rate. On the other hand, NO₃ ^– would lead to oxidation of NH₄ ⁺in anaerobic bulk soils.     

Field Validation of DNDC Model for Methane and Nitrous Oxide Emissions from Rice-based Production Systems of India

The DNDC (DeNitrification and DeComposition) model was tested against experimental data on CH₄ and N₂O emissions from rice fields at different geographical locations in India. There was a good agreement between the simulated and observed values of CH₄ and N₂O emissions. The difference between observed and simulated CH₄ emissions in all sites ranged from −11.6 to 62.5 kg C ha⁻¹ season⁻¹. Most discrepancies between simulated and observed seasonal fluxes were less than 20% of the field estimate of the seasonal flux. The relative deviation between observed and simulated cumulative N₂O emissions ranged from −237.8 to 28.6%. However, some discrepancies existed between observed and simulated seasonal patterns of CH₄ and N₂O emissions. The model simulated zero N₂O emissions from continuously flooded rice fields and poorly simulated CH₄ emissions from Allahabad site. For all other simulated cases, the model satisfactorily simulated the seasonal variations in greenhouse gas emission from paddy fields with different land management. The model also simulated the C and N balances in all the sites, including other gas fluxes, viz. CO₂, NO, NO₂, N₂ and NH₃ emissions. Sensitivity tests for CH₄ indicate that soil texture and pH significantly influenced the CH₄ emission. Changes in organic C content had a moderate influence on CH₄ emission on these sites. Introducing the mid-season drainage reduced CH₄ emissions significantly. Process-based biogeochemical modeling, as with DNDC, can help in identifying strategies for optimizing resource use, increasing productivity, closing yield gaps and reducing adverse environmental impacts.     

Laboratory study of methane oxidation in paddy soils

Methane oxidation in paddy soils was investigated under laboratory conditions. Paddy soils collected before early rice transplanting could not oxidize atmospheric CH₄ but could oxidize CH₄ when the concentration exceeded 10 μl l^-1. Initial CH₄ oxidation rate increased with the increase of initial CH₄ concentration. Soil with the maximum potential to produce CH₄, also had the maximum CH₄ oxidation activity and the maximum emission flux from paddy soil. High CH₄ concentration stimulated the oxidation of CH₄. After 10 days' incubation under atmosphere containing 1000 μl^-1 or 10⁴ μl l^-1 CH₄, the soil which could not oxidize atmospheric CH₄ was able to oxidize it. This revised version was published online in August 2006 with corrections to the Cover Date.     

不同灌溉模式下太湖流域稻田土对氨氮的吸附特性

为了考察灌溉模式对稻田土吸附氨氮的影响,本文采集太湖流域不同灌溉模式下的稻田土,在室内开展氨氮的等温吸附试验。结果表明:氨氮在两种稻田土上的吸附动力学过程均可分为明显的快、慢两个阶段,且均以准二级吸附动力学方程的拟合结果最佳;控制灌溉模式下稻田土氨氮的理论平衡吸附量、试验平衡吸附量分别为454.5mg/kg和446.2mg/kg,均高于漫水灌溉模式。Freundlich方程对等温吸附数据的拟合结果最好。控制灌溉模式下稻田土的不均匀性、吸附氨氮的反应强度以及对氨氮的吸附容量均升高。     

Cadmium in agricultural soils,vegetables and rice and potential health risk in vicinity of Dabaoshan Mine in Shaoguan,China

Soil cadmium （Cd） contamination resulted from mining and smelting is a major environmental concern,and health risk associated with Cd exposure to multi-media through muti-pathway is increasing.Cd concentrations in soils,vegetables and paddy rice were investigated,and potential non-carcinogenic and carcinogenic health risks exposure to Cd were estimated at six villages around the Dabaoshan Mine,South China.A total of 87 soil samples were found to exceed the China＇s maximum permission level （MPL） for Cd,while the highest value of 4.42 mg/kg was found near irrigation ditch associated with Hengshi River in Xinyi （XY） Village.Cd contents in vegetables and rice exceeded the maximum permissible concentration by more than five times in every village.Cadmium accumulation in plants is in the order of celery 〉 lactuca sativa L 〉 Chinese cabbage 〉 Romaine lettuce 〉 asparagus lettuce 〉 mustard 〉 cabbage mustard 〉 cabbage.The mean hazard quotient （HQ） of all villages is in the range of [5.29,25.75],and the mean values of cancer risk for investigated areas are more than 10 times greater than the USEPA （2009） threshold limit value of 10-4.Moreover,human non-carcinogenic and carcinogenic risks are mainly attributable to paddy rice intake,followed by vegetables intake,soil ingestion,inhalation,and dermal contact.The results indicate that Cd has a huge potential risk on human health for the local residents.     

A new method using feature extraction for identifying paddy rice species for quality seed selection

The purpose of this work was to explore a new feature extraction method for classifying paddy seeds using a feature extraction algorithm to achieve the area ratio, horizontal–slant and front–rear angles and find whether the proposed features have high discriminating power. Another objective was to find the smallest feature set that can ensure highly accurate recognition of seeds. A total of a 100 image features were extracted, and features having significant discriminating power were identified based on the analysis of variance (ANOVA). From the 100 features, 14 features were found to have high discriminating power and from these features, six were selected as the proposed features. Experimental results show that the proposed features and removal of redundant features enhanced the discriminating power of the feature set, and that the proposed features have an excellent discriminating property for seeds. The presented features resulted in the highest classification accuracy (98.8%) when compared to other methods.