覆膜旱作稻田土壤有效N、P、K及盐分分层变化研究

以常规水作和裸地旱作作对照,对覆膜旱作栽培条件下稻田各土层(0～60cm)土壤有效N、P、K和盐分含量变化作了比较研究。结果表明:与常规水作相比,覆膜旱作稻田10～15cm土层的碱解氮与有效磷含量显著增加,其余差异不大。与裸地旱作相比,覆膜旱作稻田5～15cm土层的碱解氮含量及5～20cm土层的有效磷含量显著增加,其余差异不大。与常规水作和裸地旱作相比,覆膜旱作稻田土壤速效钾含量在20cm以上土层增加明显。当地下水位较高时,覆膜旱作稻田0～5cm表层土壤表现积盐,地下水位较低时表层表现脱盐。     

施用钢渣对水稻土pH、水溶态硅动态及水稻产量的影响

测定了盆栽水稻生育期土壤淋滤液pH和水溶态硅浓度 ,探讨了其变化规律。结果表明 ,与对照相比施用钢渣提高了土壤 pH ,且这种影响随钢渣施用量的增加和粒度变细而加强。在水稻生育期内各处理土壤水溶态硅都经历了一个先上升达到高峰 ,然后逐渐下降 ,最终趋于稳定的过程 ;施用钢渣各处理土壤水溶态硅浓度在插秧后 3～ 4周内低于对照 ,以后则高于对照 ,这种情况随钢渣施用量的增加或粒度变细而更为显著。试验结果还表明 ,施用钢渣可以明显提高水稻产量。     

Enhancement of paddy straw digestibility and biogas production by sodium hydroxide-microwave pretreatment

Biogas has become a promising energy substitute to fossil fuels. Lignocellulosics, being cheap and renewable resource, could be very well used as a feedstock for biogas generation. Paddy straw is an abundant lignocellulose which is rich in organic matter like cellulose, hemi-cellulose and lignin. It is generally disposed off by burning causing environmental pollution whilst it can be used for biofuel generation. The digestibility of paddy straw is low due to high lignin and silica content. The present study was carried out to enhance paddy straw digestibility and biogas production through sodium hydroxide (NaOH) pretreatment. The paddy straw was pretreated with NaOH by soaking (24 h) in different concentrations of NaOH (2, 4, 6, 8 and 10%) and supplementing with microwave irradiations (30 min, 720 W, 180 °C). 4% NaOH-30 min microwave was found to be the best pretreatment which resulted in 65.0% decrease in lignin content and 88.7% reduction in silica content. This increased digestibility due to reduced lignin and silica content resulted in 54.7% increase in biogas production. Scanning Electron Microscopy of pretreated paddy straw revealed breakdown of lignocellulose structure resulted from the tearing of different layers of cell wall of paddy straw.     

Optimising indoor phosphine fumigation of paddy rice bag-stacks under sheeting for control of resistant insects

Three indoor, sheeted bag-stack fumigations of paddy rice using aluminium phosphide were undertaken in Guangdong Province, southern China. We measured the effect of two types of sheeting (polyvinylchloride [PVC] or polyethylene [PE]) and two types of floor sealing (clips or fixing into a slot with a rubber pipe) on phosphine concentration and retention. The aim was to test the feasibility of retaining fumigant at a sufficient concentration for long enough to control known resistant insect pests. Each stack was pressure tested and phosphine concentrations measured daily during the fumigation. Cages of test insects in culture medium, including resistant and susceptible strains, were placed inside each stack and could be observed through the clear sheeting. Highest concentrations for the longest period were obtained in a PVC-covered stack that included a ground sheet and wall sheets sealed to the floor with rubber pipes. A similar PVC-covered stack sealed to the floor with clips instead of pipe did not retain gas as efficiently and required re-dosing. A PE-covered stack, with no ground sheet but also with wall sheets sealed to the floor with pipe, produced an acceptable fumigation. Susceptible Rhyzopertha dominica were controlled in 2 days and the most resistant strain in 15 days. Resistant Cryptolestes ferrugineus survived until day 21. The paddy was still free of insect infestation 7 months later when the bag-stack was opened to mill the rice. Pressure half-lives correlated with gas concentration and retention. Sorption appeared to be a major limiting factor, reducing potential fumigant dosage by about 50%. The trials demonstrated the feasibility of sealing bag-stacks to a standard high enough to control all known resistant strains.     

潜育化作用对水稻土磷素形态与供磷能力的影响

本文对江汉平原四湖地区几个不同潜育度水稻土剖面的磷素状况及其有效性进行了研究 ,并用张守敬—Jakson无机磷分级法做无机磷分级。结果表明 ,土壤潜育化程度对土壤全磷没有明显的影响 ,对土壤磷素形态及其有效性有明显的影响。随着土壤潜育化程度加重 ,无机磷中的O—P含量有增加趋势 ,其占土壤无机磷的百分数增大 ;土壤有机磷也随之增加 ;但有效磷含量减少。潜育化状况对土壤磷素形态与有效性的影响与土壤有机质和还原状况有关     

Toxicity of heavy metals to some fungi

The comparative toxicity of heavy metals such as Cu, Co, Ni and Zn to some plant pathogenic and non‐pathogenic fungi has been assessed. The growth of mycelia in substrate treated with metals remained dose‐dependent, and at higher concentrations total inhibition was noticed. Sporulation was delayed in all the cases, although there occurred a vigorous growth of mycelia after a few days of incubation. The possibility of using fungi to monitor heavy metal pollution has been discussed.     

Impact of model uncertainty on soil quality standards for cadmium in rice paddy fields

At present, soil quality standards used for agriculture do not consider the influence of pH and CEC on the uptake of pollutants by crops. A database with 750 selected paired samples of cadmium (Cd) in soil and paddy rice was used to calibrate soil to plant transfer models using the soil metal content, pH, and CEC or soil Cd and Zn extracted by 0.01 M CaCl₂ as explanatory variables. The models were validated against a set of 2300 data points not used in the calibration. These models were then used inversely to derive soil quality standards for Japonica and Indica rice cultivars based on the food quality standards for rice. To account for model uncertainty, strict soil quality standards were derived considering a maximum probability that rice exceeds the food quality standard equal to 10 or 5%. Model derived soil standards based on Aqua Regia ranged from less than 0.3 mg kg^− 1 for Indica at pH 4.5 to more than 6 mg kg^− 1 for Japonica-type cultivars in clay soils at pH 7. Based on the CaCl₂ extract, standards ranged from 0.03 mg kg^− 1 Cd for Indica cultivars to 0.1 mg kg^− 1 Cd for Japonica cultivars. For both Japonica and Indica-type cultivars, the soil quality standards must be reduced by a factor of 2 to 3 to obtain the strict standards. The strong impact of pH and CEC on soil quality standards implies that it is essential to correct for soil type when deriving national or local standards. Validation on the remaining 2300 samples indicated that both types of models were able to accurately predict (> 92%) whether rice grown on a specific soil will meet the food quality standard used in Taiwan.     

基于NDVI与LAI的水稻生长状况研究

在水稻反射光谱特性与水稻生物参数关系的支持下,以吉林省德惠市夏家店镇为研究区,探讨了一条基于TM遥感影像反演得到的归一化植被指数(NDVI)与地面观测数据叶面积指数(LAI)的水稻生长状况的研究途径,并利用NDVI和LAI对该区2000年和2001年的水稻生长状况进行了分析研究。     

Development of a micrometeorological model for the estimation of methane flux from paddy fields: Validation with standard direct measurements

This work has focussed on the development of an indirect method for estimating methane fluxes from paddy fields and wetlands. A micrometeorological model, based on an analytical solution of the Eulerian advection–diffusion equation for vertical diffusion, has been used; model parameters include the location of the methane analyser and standard surface layer scaling factors. Flux chambers, which are commonly used for measuring methane fluxes from agricultural sources, are usually mechanically operated with a rated induced-draft fan and as such cannot replicate the real world atmospheric conditions. The results are not very reliable due to leakages along the piping and at fittings, especially when these chambers are used over a relatively rough surface like an agricultural field or a wetland. The results of the model have been compared with those from the direct method. The seasonal average methane flux calculated by the indirect method, for the cultivar type “Sundari”, is 7.13E+05 g/ha, while cultivar type “Shatabdi” gives a little lower value of 5.22E+05 g/ha. In case of the direct chamber method also, the seasonal average methane flux for the cultivar type “Sundari” (6.20E+05 g/ha) is more than cultivar type “Shatabdi” (4.84E+05 g/ha). When the two methods of assessment were compared, season September–December 2004 gave r² = 0.91, RMSE = 0.16 and MNB = 0.13 while we got r² = 0.94, RMSE = 1.22 and MNB = 0.06 for the season September–December 2005.In very few experiments we could cover a huge aerial plot instead of a huge number of experiments necessary for the direct chamber method.     

施用化肥对下辽河平原稻田土壤线虫群落产生的影响

通过田间小区试验,研究了施用化肥对下辽河平原稻田土壤线虫群落组成产生的影响。结果表明,共获得15科、19属,其中绕线属、小杆属、垫刃属为优势属。线虫总数、食细菌线虫、植物寄生线虫和杂食-捕食线虫数量在不同处理之间存在极显著差别(p<0.01),三个施肥处理中的线虫总数显著高于无肥处理(对照)。在水稻收获后土壤线虫数量变化对不同种类肥料具有不同的响应。