Direct and Residual Contributions of Symbiotic Nitrogen Fixation by Legumes to the Yield and Nitrogen Uptake of Maize (Zea mays L.) in the Nigerian Savannah

Field experiments were conducted to determine the direct and residual contributions of legumes to the yield and nitrogen (N) uptake of maize during the wet seasons of 1994 and 1995 at the University Farm, Abubakar Tafawa Balewa University, Bauchi, Nigeria, located in the Northern Guinea savannah of Nigeria. Nodulating soybean, lablab, green gram and black gram contributed to the yield and N uptake of maize either intercropped with the legumes or grown after legumes as a sole crop. Direct transfer of N from the nodulating soybean, lablab, green gram and black gram to the intercropped maize was 24.9–28.1, 23.8–29.2, 19.7–22.1 and 18.4–18.6 kg N ha^–1, respectively. However, the transfer of residual N from these legumes to the succeeding maize crop was 18.4–20.0, 19.5–29.9, 12.0–13.7 and 9.3–10.3 kg N ha^–1, respectively. Four years of continuous lablab cropping resulted in yields and N uptake of the succeeding maize crop grown without fertilizer N that were comparable to the yields and N uptake of the succeeding maize crop supplied with 40–45 kg N ha^–1 and grown after 4 years of continuous sorghum cropping. It may therefore be concluded that nodulating soybean, lablab, green gram and black gram may be either intercropped or grown in rotation with cereals in order to economize the use of fertilizer N for maize production in the Nigerian savannah.     

城镇化水平计算方法比较分析

城镇化是社会经济发展的必然趋势，与小城镇人口、经济实力、社会发展和环境保护等方面密切相关。城镇化判别指标归纳起来分两大类：一类是单一指标法或称主要指标法；另一类是多项指标法、复合指标法或称综合指标法。在常用的、单一指标法的城镇化水平计算方法中，城镇人口比重指标法和带眷系数法两种方法能够比较准确地反映小城镇的城镇化水平，尤其以城镇人口比重指标法计算结果最符合实际。     

An evaluation of the Olsen test as a measure of plant-available phosphorus in grassland soils derived from basalt parent material

Abstract. Anecdotal and circumstantial evidence have suggested that the Olsen test underestimates plant-available phosphorus (P) in basaltic soils in Northern Ireland. Therefore, the ability of this test to predict plant-available P in basaltic (and non-basaltic) soils was investigated by regressing Olsen-P data against herbage P indices calculated from plant tissue test data using the diagnosis and recommendation integrated system. The average Olsen-P concentration for a range of fields situated on basaltic soils was considerably lower than the average Olsen-P concentration for a range of fields situated on non-basaltic soils, and yet mean sward P status, as given by the herbage P indices, was similar for both groups of fields. Herbage P indices were also much better correlated with Olsen-P measurements in non-basaltic soils than in basaltic soils. Furthermore, at low Olsen-P values (≶9mgPL⁻¹) some swards on basaltic soils were genuinely deficient in P, while others were sufficient or even in surplus for this nutrient. The results confirm that Olsen-P is inadequate as a predictor of plant-available P in basaltic soils. It is concluded that an alternative soil test is needed to provide a reliable assessment of plant-available P in basaltic soils, to prevent overuse of fertilizer and manure P and to minimize the amounts of P entering local watercourses.     

高校公寓文化建设的几点思考

从校园文化、学风建设、素质教育、思想教育等方面，阐述公寓文化的作用和意义，提出理顺管理机制、发挥学生主体作用、加强制度建设，开展公寓文化活动等几点建议。     

浅谈国有林场森林分类经营

本文结合大兴安岭地区加格达奇林业局国有林场的实际经营情况，论述了国有林场实行森林分类经营的必要性、并对经营管理体制与措施进行了探讨。     

Long-term variation in brown trout, Salmo trutta L., stocking success in a large lake: interplay between availability of suitable prey and size at release

Abstract –  Factors affecting long-term variation in brown trout, Salmo trutta L., stocking success were examined in a large lake, Lake Oulujärvi, in central Finland. Brown trout were stocked in spring (late May to early June) in 1974–1991 and in summer (late June to early July) in 1992–2001. The biomass of the vendace, Coregonus albula (L.), population (prey) at release time had the largest positive effect on stocking success within both periods: biomass of adult vendace in spring and both 0+ and adult vendace in summer. Increasing the size of stocked fish had a positive effect if the vendace available at release were only adults. The increasing trend of predator-catch-per-unit-effort (CPUE) [combined CPUE of northern pike Esox lucius L., burbot Lota lota (L.), and pike-perch Stizostedion lucioperca (L.)] through the study period and its negative effect on trout stocking success suggested an increasing effect of predation within the entire time series.     

广东山区开发的理论与实践：—广东山区开发理论与实践研讨会综述

本文述了“广东山区开发理论与实践研讨会”所达成共识的观点：广东山区开发具有重要的战略意义，广东山区开发必须走可持续肆展，农业产业化经营、工业化道路，同时必须搞好基础设施建设，组织好商品流通工作，优化资源配置。     

Grouped, stacked rods and tapeta lucida in the retina of Japanese anchovy Engraulis japonicus

ABSTRACT: Morphology of the photoreceptor cells and tapetum of the Japanese anchovy Engraulis japonicus was studied by histologically and by chemical analysis. The Japanese anchovy has a duplex retina. The cones form parallel rows consisting of alternately placed long cones and bifid cones. Both types of cones are intimately associated and form triple units that are regularly spaced along the row of cones. The rods are grouped and stacked. This fish has a retinal tapetum lucidum composed of guanine and hypoxanthine. Three structures of the tapetum lucidum were recognized: platelet, diamond and rod types. Photomechanical changes include movements of the photoreceptor cells and the retinal tapetum. The retina of the Japanese anchovy is thought to be highly sensitive and well adapted to a dim light environment.     

Analysis of the Impact of Alfalfa Forage Production under Summer Water-Limiting Circumstances on Productivity, Agricultural and Growers Returns and Plant Stand

The trade-off between summer water conservation from alfalfa production and the effects on plant growth, agricultural crop value, and grower returns in the low desert area (Imperial, Palo Verde, Parker and Yuma Valleys of California and Arizona) was analysed using an experimental plot in the Palo Verde Valley. The purpose was to provide a basis for evaluating water conservation decisions and policies. Four summer dry-down periods (withdrawing water for a predetermined period) of 0 days (control), 35 days, 70 days, and 105 days were analysed. Our results show that whereas the various dry-down periods would provide water conservation ranging from 254 to 944 million m³, the region would experience agricultural income decline by US $16 to US $73 million. For growers, benefits of dry-down would be effective only if the water price exceeds US $0.045 m⁻³ in California and US $0.036 m⁻³ in Arizona. Also dry-down would have possible adverse effects in the following areas including declines in plant stand density, long-term productivity, service industry sales, employment and biological benefits of soil fertility and organic matter that is attributed by the alfalfa plant in which case agriculture's and growers monetary losses could increase.