同位素载体对青菜吸收~(141)Ce的影响

运用模拟污染物的同位素示踪技术探索了稳定同位素载体对青菜吸收１４１Ｃｅ 的影响, 结果表明,青菜植株及其各部位中１４１Ｃｅ 浓度与载体引入量间均呈线性负相关;青菜各部位中１４１Ｃｅ 浓度的大小顺序是：根＞ 地上部, 而地上部的枯黄叶＞ 老叶＞ 嫩叶⒚     

氮钾配比对莴笋品质的效应研究

[目的]为生产优质、高产叶菜类蔬菜提供理论依据。[方法]采用盆栽试验,设4个施肥处理,收获后,测定每盆产量和莴笋的硝酸盐、维生素C、氨基酸和可溶性糖含量。[结果]不同施肥处理间莴笋产量有极显著差异,增施氮肥、钾肥莴笋产量增加13.9%~51.0%,以200 mg/kg N和100 mg/kg K处理增加幅度最大(51.0%)。增施氮肥使莴笋的Vc含量降低6.7%~10.1%,氨基酸含量增加24.9%~44.8%,对硝酸盐和可溶性糖的含量作用不一致,而增施钾莴笋硝酸盐含量增加22.7%,氨基酸和可溶性糖的含量分别降低15.2%和19.9%,对Vc的含量影响不大。[结论]从莴笋产量和品质来看,200 mg/kg N和100 mg/kg K处理对莴笋的综合效应最好,为最佳处理。     

In vitro digestibility and calculated PER as rapid methods for the nutritional evaluation of potato protein

Protein Efficiency Ratios (PER) have been determined for hybrid potato selections by feeding flake diets to rats; more rapid and inexpensive tests are required by breeding programs which select for improved potato protein. Two more recent methods, in vitro digestibility (IVD) and calculated PER utilizing discriminant computed PER (DC-PER) and computed PER (C-PER), were studied for their potential in evaluation of the nutritional quality of potato. Albumin (A) and two subfractions, acid soluble and insoluble (ASA and AIA), were studied, as well as flakes. The average IVD for albumin was 68.9%, for ASA was 67.5% and for AIA was 77.5%. Digested proteins were identified by electrophoresis before and after enzyme treatment. The higher IVD values for AIA were probably due to the presence of protease inhibitors among the ASA proteins. IVD differences among groups of hybrids were found and a reasonable correlation (r=0.71*) of these values with flake PER values was observed. The DC-PER values ranged from 2.64 to 2.79, these values were larger than those observed in feeding trials; additional genotypes need to be studied before this method can be proposed for potato evaluation. The presence of protease inhibitors in the albumin samples is indicated, because the average IVD value of 68 increased to about 84 after the albumins were heated prior to IVD determinations.Scientific Journal Article 12,095 of the Minnesota Agricultural Experiment Station. This research was supported by a USDA/SEA Grant.     

Effects of forest cover type and ratio changes on runoff and its components

Changes in forest cover can affect not only the total runoff from a watershed, but also the runoff components (e.g., surface runoff, interflow, groundwater flow). In this study, based on the WetSpa model simulation method and the recursive digital filtering (RDF) method, the Banchengzi watershed in the mountainous region of Beijing, China, was selected to investigate how changes in forest cover type and cover percentage affect total runoff, surface runoff, interflow, and groundwater flow through scenario settings. Our results show that the difference between the WetSpa model and the RDF method for separating runoff components is small, with only 4.7% and 0.4% difference between the calibration and validation periods. Total runoff in different forest types followed the order shrub forest > coniferous forest > mixed forest > broadleaf forest. Regarding runoff components, the proportions of baseflow (sum of interflow and groundwater flow) to total runoff were 61.1% and 60.8% for broadleaf and mixed forests, which was significantly higher than those of 53.0% and 43.1% for coniferous and shrub forests. However, the proportion of shrub forest baseflow was high in wet years, and that of broadleaf forest baseflow was high in normal and dry years. The proportions of interflow and groundwater flow from various forest cover types to total runoff continued to increase with increasing forest cover rate. Our results have important implications for the implementation of afforestation projects and forest conservation programs, contributing to water resource regulation and ecosystem protection in watersheds.     

Manure Phosphorus Fractions: Development of Analytical Methods and Variation with Manure Types

Abstract

Manure phosphorus (P) extraction and storage procedures were evaluated, and manure types were characterized for extractable P. The objectives of this research were to evaluate manure P extraction and sample storage procedures and to characterize manure types for water‐extractable P (WEP) and NaHCO₃ P (BiEP). Manure P was extracted at dry matter–to–water extraction ratios of 0.5 g/200 mL, 2 g/200 mL, 2 g/20 mL, and 20 g/200 mL. Shaking times of 0.5 h, 1 h, or 2 h were evaluated along with filter paper types (Whatman No. 42, Whatman No. 40, and 0.45‐µm). Single or sequential extractions and repeated extractions with water or NaHCO₃ were also compared on various manure sources. Manure types were treated as replications in the analysis of variance to reduce the probability of making a Type I error in applying the results to diverse manure types. Dry matter–to–water extraction ratios more concentrated than 1 g/100 mL removed less P than extraction at 1 g/200 mL, which removed a similar percentage of total P (TP) as 0.5 g/200 mL ratio. A single extraction with a 1 g/200 mL or more dilute ratio with 1 h of shaking time was found to give a good estimate of extractible P. Extracted manure P was similar for three sequential extractions of 1 g/100 mL dilution ratio compared to one extraction with 1 g/300 mL. Filter paper type did not affect the amount of P extracted. Phosphorus extraction was more consistent with samples stored dry as compared to refrigerated or frozen conditions. Extractible P in swine manure, as a percentage of TP, was more than for other manure types.     

Potential net soil N mineralization and decomposition of glycine-C in forest soils along an elevation gradient

The objective of this research was to better understand patterns of soil nitrogen (N) availability and soil organic matter (SOM) decomposition in forest soils across an elevation gradient (235-1670 m) in the southern Appalachian Mountains. Laboratory studies were used to determine the potential rate of net soil N mineralization and in situ studies of ¹³C-labelled glycine were used to infer differences in decomposition rates. Nitrogen stocks, surface soil (0-5 cm) N concentrations, and the pool of potentially mineralizable surface soil N tended to increase from low to high elevations. Rates of potential net soil N mineralization were not significantly correlated with elevation. Increasing soil N availability with elevation is primarily due to greater soil N stocks and lower substrate C-to-N ratios, rather than differences in potential net soil N mineralization rates. The loss rate of ¹³C from labelled soils (0-20 cm) was inversely related to study site elevation (r=−0.85; P<0.05) and directly related to mean annual temperature (+0.86; P<0.05). The results indicated different patterns of potential net soil N mineralization and ¹³C loss along the elevation gradient. The different patterns can be explained within a framework of climate, substrate chemistry, and coupled soil C and N stocks. Although less SOM decomposition is indicated at cool, high-elevation sites, low substrate C-to-N ratios in these N-rich systems result in more N release (N mineralization) for each unit of C converted to CO₂ by soil microorganisms.     

Ranges of nutrient concentrations in Quercus ilex leaves at natural and urban sites

The leaf nutrient concentrations and the N‐to‐nutrient ratios were analyzed to evaluate the nutritional status of holm oaks (Quercus ilex L.) experiencing various anthropogenic pressures. Leaves (1 year old) of Q. ilex and surface soil (0–5 cm) surrounding the trees were collected at seven natural and seven urban sites in Campania Region (Southern Italy) and analyzed for the concentrations of macro (C, N, P, S) and micronutrients (Mn, K, Na, Cu, Mg, Ca, Fe, Zn). The available soil fraction of micronutrients was also evaluated. The nutrients showed different concentration ranges for the natural and the urban sites in the soil (total and available) and in the leaves, that we reported separately. Organic‐matter content and macronutrient concentrations were higher in the natural soils, while the highest leaf N, S, and P concentrations were found at some urban sites. Concentrations of Cu, Na and Zn both in leaves and soil, and Mg and Fe in leaves from the urban sites appeared to be affected by air depositions. Manganese was the only micronutrient to show higher concentrations at the natural than at the urban sites, both in soil and leaves. For this nutrient, in addition, a relationship between leaf and available soil concentrations was found at the natural sites. The ratios between the concentrations of N and each studied nutrient in the leaves highlighted a different nutritional status between the plants from the natural and urban sites.     

秸秆的微贮及喂牛试验

为充分利用当地秸秆资料,１９９５～１９９６年作者在山西吕梁地区用微贮饲料（黄干玉米秸）饲喂６０头试验牛;对照组６０头牛所喂黄干玉米秸未作任何处理,育肥９０天。精料由玉米粉５６．１％、麸皮２１．４％、棉籽饼２０％、食盐０．５％、矿物质及其它添加剂０．３％组成,两组牛精料日喂量均按平均体重的１％分两次饲喂。试验结果表明：试验组日增重为０．８９３ｋｇ,对照组为０．６５ｋｇ,试验组增重提高７２．８％。两组牛的料重比分别为８．１６％和１０．４１％,即对照组比试验组多消耗精料２７．５７ｋｇ。试验组头均盈利１１７．１元,对照为１３．４元,试验组比对照牛多盈利１０．３７元。     

Maize growth and yield responses to seed‐inoculated N2‐fixing bacteria under Dryland production conditions

Maize (Zea Mays L.) seeds were inoculated with the N₂‐fixing bacteria, Azospirillum brasilense and Azorhizobium caulinodans. Shoot growth, shoot nitrogen (N) concentration, and grain yield was determined under dryland production conditions in a silt loam. Fertilizer N was applied according to soil test recommendations at either 0, 50, 75, or 100% of the recommended N requirements for a 7,500 kg ha^‐1 yield goal. Both A. brasilense and A. caulinodans increased shoot dry matter production, shoot N concentration, and grain yield somewhat at the lower N recommended rates. There was no agronomic benefit with either A. brasilense and A. caulinodans inoculations under dryland conditions for high N fertility soils under dryland production conditions in a subhumid or semi‐arid moisture regime.     

不同比例红蓝光对奶油生菜生长、光合特性及品质的影响

选用奶油生菜为试验材料,研究了白光(CK)、红光(R)、蓝光(B)、不同比例红蓝光等6种光质对生菜生长发育、叶片光合特性及品质的影响。结果显示:不同光质对生菜生长的影响不同,R处理下生菜的地上部分干、鲜质量及叶面积最大,R︰B=1︰1、R︰B=1︰2次之;R︰B=1︰2处理下生菜叶片中叶绿素a/b最大,R︰B=2︰1、R︰B=1︰1、R︰B=1︰2处理均可提高生菜叶片的净光合速率;R处理有利于生菜叶片中糖分的积累,R︰B=2︰1、R︰B=1︰1、R︰B=1︰2处理下生菜可溶性蛋白含量提高,R︰B=1︰2处理更有利于生菜VC含量的增加。综合各项指标,R︰B=1︰2处理下生菜的产量及品质最佳。