Effects of cropping history and phosphorus source on yield and nitrogen fixation in sole and intercropped cowpea–maize systems

Symbiotic N₂-fixation, N uptake efficiency, biomass- and crop production of cowpea and maize as affected by P source, sole- and intercropped, and introduction of break crops were studied on a farmer’s fields in semi-arid Tanzania. Cowpea fixed around 60% of its N from the atmosphere amounting to 70 kg N ha⁻¹ under sole and 36 kg N ha⁻¹ under intercropping as estimated by the ¹⁵N isotope dilution method around peak biomass production. The amount of N₂-fixed was 30–40% higher when P was applied as either TSP or MRP whereas cowpea yield were unaffected. Intercropped maize with 19,000 plant ha⁻¹ accumulated the same amount of N as 38,000 sole cropped maize plants although intercropping reduced the dry matter accumulation by 25%. The N uptake efficiency of the applied ¹⁵N labelled fertiliser was 26%, which equal a total pool of early available plant N of 158 kg N ha⁻¹. Under the N deficient conditions, P application did not increase the grain yield of maize. The LER indicate that sole cropping required 18% more area than intercropping in order to produce the same grain yield, and 35% more land when LER was based on N uptakes. Introduction of break crops in the maize systems, more than doubled accumulation of dry matter and N in the grain compared to continuous maize cropping. During maturation sole crop cowpea shedded leaves containing 41 kg N ha⁻¹. The current findings underline the importance of crop diversity in Sub Saharan Africa agriculture and emphasise the need for including all residues, including shedded leaves, in nutrient balance studies.     

Net N immobilisation during the biodegradation of mucilage in soil as affected by repeated mineral and organic fertilisation

Repeated fertilisation of crops with manure commonly increases both the amount and the quality of soil organic matter, the mineralisation of which strongly determines the availability of N to plants. In the rhizosphere, the microbial mineralisation/immobilisation of N is enhanced due to rhizodeposition (release of organic compounds from roots). In this work, we studied N transformations during incubation of maize root mucilage in soils that had been previously fertilized with composted pig manure or with ammonium nitrate for 7 years. Our work revealed mucilage was rapidly mineralised (average half-life of 3 days), inducing a rapid N immobilisation of 94 mg N g⁻¹ of mucilage C, followed by a slow remineralisation. Fertilisation with manure induced a persistent stimulation of the soil organic matter mineralisation, leading to an enhanced content of soil inorganic N (+23% in 58 days of incubation). Due to this stimulation of microbial activity in the soil fertilized with manure, the decrease in inorganic N during the biodegradation of mucilage lasted a shorter time as compared to the mineral fertilisation. However, the type of fertilisation did not significantly change the amount of N immobilised.     

Soil nutrient evaluation from swine effluent application to five forage-system practices

Many contract swine producers are located in the southeastern U.S. In this region almost all of the swine effluent from swine production is applied to warm-season perennial species such as bermudagrass [Cynodon dactylon (L.) Pers.] which is widely grown for summer grazing and hay production. A 3-yr study was conducted to investigate the impact of forage double-cropping on nutrient accumulation and leaching in Mantachie fine loam soil fertilized with swine (Sus scrofa domesticus) lagoon effluent as the source of plant nutrients. Plots of previously established Tifton 44 bermudagrass were overseeded in the fall with one of four winter annuals: berseem clover (Trifolium alexandrinum L.); crimson clover (T. incarnatum L.); ryegrass (Lolium multiflorum L.); or wheat (Triticum aestivum L.). Four plots of bermudagrass were not overseeded and considered as control. Plots were harvested in spring for cool-season annual hay and in summer for bermudagrass hay. Swine effluent was applied during spring and summer on a need base. Suction lysimeters were installed in selected plots at two depths to monitor nutrient leaching. Surface soil samples were taken to determine baseline nutrient contents, followed by three other sampling dates during the study. Bermudagrass dry matter production (3-yr average = 9.8 Mg ha⁻¹) was not adversely affected by the overseeding treatments. Greatest dry matter production was achieved with bermudagrass overseeded with ryegrass (3-yr average  = 11.3 Mg ha⁻¹). Soil pH decreased by almost one unit by the end of the study. While total P (TP) did not change much, Mehlich-3 P (M3-P), K, Cu, and Zn increased significantly, Mg and Mn concentrations decreased by 2002 compared to the baseline levels. Soil P, Mg, K, Fe, Mn, and Zn accumulation were greater under bermudagrass/wheat combination. In general, the influence of double cropping on soil nutrient accumulation was not conclusive, however, this practice provides the year-round green forage for grazing and haying. Nutrient concentrations in soil and lysimeter leachate were directly related to the quantity of effluent applied. Results also demonstrated that effluent application must be coordinated with the nutrient requirements of the growing forages in order to minimize accumulation and leaching.     

原油中含氮化合物参数在储层连通性评价中的应用

油藏连通性研究是油藏地球化学研究的重点之一。其最重要的作用在于证明不同井（或一个特定层位）、不同井段（或地区）油层的连通性，为勘探和开发提供科学依据。在油田的后期开发中，为了有效地提高油田采收率，较详细了解储层连通性十分重要。     

中国煤中硫氮的赋存状态研究

煤中的硫、氮在煤利用转化过程中的释放对环境和生物健康影响巨大。笔者从煤中硫、氮的分布、结构,同位素研究等几方面对中国煤中硫、氮的赋存状态研究进行了总结,并提出了今后的研究方向和热点问题。     

Factors controlling ammonia loss from trash covered sugarcane fields fertilized with urea

Ammonia losses following surface applications of urea to trash covered sugar cane fields were investigated in four climatic zones of tropical Queensland. Volatilization of ammonia and evaporation of water were determined by micrometeorological techniques. The results showed that the pattern, rate and extent of ammonia loss were controlled by the availability of water in the trash and its evaporation. Water added by dewfall, rainfall or condensation of evaporated soil moisture dissolved some of the urea and allowed it to be hydrolyzed to ammonia by the urease enzyme in the sugarcane residues; when the water evaporated, ammonia was lost to the atmosphere.In the dry climatic zone, where no rain or dew fell, water addition to the trash by condensation of evaporated soil moisture was not sufficient to dissolve much urea so very little ammonia was lost. In the cool and warm moist zones, small additions of water to the trash from dew, light rain and condensation maintained a slow but steady pattern of ammonia loss over a period of six weeks and resulted in losses of 32% and 39% of the applied nitrogen. At the site in the wet zone, heavy rainfall apparently washed the urea from the trash layer into the soil and limited ammonia loss to 17% of the applied nitrogen.Substitution of ammonium sulfate for urea reduced ammonia loss to less than 1.8% of the applied nitrogen.     

用MH-81′状态方程模拟液氮洗涤塔

本文采用MH-81′状态方程和与密度无关的局部组成型混合法则,从二元汽-液平衡数据得到的二元相互作用参数,预测了部分液氮洗过程中的二元体系的混合焓,结果满意。采用三对角矩阵方法,对两种不同工况的液氮洗涤塔进行了模拟,计算结果与设计值和实测值符合较好。     

Synthesis and characterization of carbonaceous replicas of multilayered vesicular siliceous materials

Synthesis of novel, carbon porous replicas of vesicular siliceous materials has been described. The original siliceous materials consist of small, spherical structures resembling onions, known in the literature as multilamellar vesicles (MLVs). They have been characterized with a number of analytical methods that allow one to determine its 3-D structure and basic parameters of the pore system. Carbonaceous materials, made similarly of onion-like porous structures, have been obtained using a standard procedure to form replicas. They have been characterized by the same methods as those applied to the parent materials.     

保护气氛井式快速退火炉的研制及其在"白带钢"生产中的应用

在普通井式电阻炉的基础上,采用保护气氛加热,配套循环冷却系统进行快速冷却,在“白带钢”的再结晶退火生产中取得了理想的效果。