Disease incidence and severity on beans in alleys between Leucaena hedgerows in Kenya

The effects of inter-row spacing of Leucaena leucocephala in an alley cropping system on the incidence and severity of diseases on intercropped beans (Phaseolus vulgaris L.) and their yield were examined over two years (1993 and 1994) at Chepkoilel Campus in Kenya. Each experiment consisted of three randomized blocks with treatments of three alley widths (2 m,4 m and 8 m) and a treeless control with two intra-row spacings of Leucaena (0.5 m and 1.0 m). Hedgerows were coppiced at 1.0 m height and pruned subsequently at two-to-three months intervals. No fertilizer was applied but Leucaena loppings were incorporated as green leaf manure. Incidence of angular leaf spot (Phaeoisariopsis griseola) and anthracnose (Colletotrichum lindemuthianum) on beans were assessed at three growth stages in each season, using the Centro International de Agricultura Tropical (CIAT) scales. Microclimate was monitored in treatments, in 1994. Angular leaf spot and anthracnose decreased with increasing alley width and were more severe in bean rows adjacent to hedgerows. Light availability and diurnal temperaturereaching the bean canopy increased with alley width but relative humidity and leaf wetness duration decreased. Proximity to hedgerows also had markedly reduced light levels, lower temperatures and higher relative humidity. Higher incidence and severity of angular leaf spot and anthracnose on beans in alleys than on beans in treeless plots were examined in relation to microclimate, inoculum survival and dispersal. The pattern of the diseases was best explained by microclimate changes induced by Leucaena hedgerows, especially effects of humidity. This revised version was published online in June 2006 with corrections to the Cover Date.     

Quantifying soil displacement and tillage erosion rate by different tillage systems in dryland northwestern Iran

Redistribution of soil particles by the force applied by tillage is a major factor in soil degradation of agricultural land. Decreasing tillage intensity can reduce the amount of soil displaced and the distance moved and hence may reduce rates of erosion. To understand the relative importance of erosion, we tabulated machine, soil and landform properties likely to be involved. We compared soil displacement and tillage erosion rates under different systems, including mouldboard ploughing (conventional tillage), chisel ploughing (reduced tillage), stubble cultivator (minimum tillage) and no‐tillage under dryland agriculture in northwestern Iran. The area was undulating and so all tillage took place along contours. Metallic tracers were buried in the soil at known locations and depths and their recovery after tillage provided a measure of soil displacement and tillage erosion. Conventional tillage along a contour line caused significantly greater soil displacement (≃57 cm) in the direction of tillage than reduced and minimum tillage systems (~20 and ~15 cm, respectively). Conventional tillage also caused more lateral soil displacement (downwards in the main direction of slope, the tillage erosion rate) than reduced or minimum tillage systems (48 cm or 152 kg/m vs. 5 and 4 cm or 16 and 7 kg/m, respectively). Although a range of factors contribute to the tillage systems used by farmers, our results suggest that under dryland conditions, similar to those found in our study area, adoption of noninversion, reduced tillage along the contour, for example by chisel ploughing can substantially limit tillage erosion relative to conventional tillage.     

Trees,grasses, and weeds: species choices in farmed-developed contour hedgerows

Innovations intended to conserve soils and improve soil nutrient cycling have not been widely adopted because of technical problems and lack of fit with farmers' cricumstances. Research in Claveria, the Philippines, facilitated and monitored farmers' adaptation of contour hedgerows to fit their particular needs. Farmers tested different establishment methods and many hedgerow species. They initially planted a combination ofGliricidia sepium (a legume tree) andPennisetum purpureum. (grass). Later adoptors chose fodder grasses (especiallySetaria spp.) or naturally occuring vegetation in their hedgerows-either solely or in combination with other species, including weeds such asRottboellia cochinchinensis identified as crop problems. Upland rice and maize farmers who adopted contour hedgerows from 1987 through 1991 were interviewed in 1992. Although hedgerow-crop competition, grazing by neighbors' cattle, and added labor were problems, farmers viewed hedgerows as a way to reduce soil erosion and provide fodder. Farmers planting mulberry were disappointed after a silkworm project folded. Farmers now face the problem of soil nutrient depletion, leading to fallowing of fields with hedgerows and shifting to other parcels. A farmer decision tree model of the minimum necessary criteria for sustainable adoption of contour hedgerows is hypothesized.     

不同农艺措施组合对云南红壤坡耕地氮素平衡和流失的影响

通过对野外坡度为26．05％的径流小区实地观测，研究种植方式、施肥方式和等高植物篱条带3种农艺措施不同组合对云南红壤坡耕地氮素投入、带走平衡的影响。结果表明，在等高种植＋平衡施肥＋等高植物篱条带组合农艺措施条件下，收获玉米带走的氮为177．24kg·hm^-2，占水土流失和收获玉米带走氮总量的99．42％，水土流失带走1．03kg·hm^-2的氮，占水土流失和收获玉米带走氮总量的0．58％；顺坡种植＋农民习惯施肥收获玉米带走的氮仅为120.31kg·hm^-2，占水土流失和收获玉米带走氮总量的79．36％，而水土流失带走31．29kg·hm^-2的氮，占带走氮总量的20．64％。等高种植比顺坡种植增加收获玉米带走氮素13．36kg·hm^-2，减少水土流失带走氮素18．53kg·hm^-2；等高种植和平衡施肥条件下，等高植物篱条带因占用少量土地而减少收获玉米带走氮素6．09kg·hm^-2，减少水土流失带走氮素5．73kg·hm^-2；顺坡种植和习惯施肥条件下，等高植物篱条带减少收获玉米带走氮素5．39kg·hm^-2，减少水土流失带走氮素29．97kg·hm^-2；平衡施肥比习惯施肥增加收获玉米带走氮素49．66kg·hm^-2，减少水土流失带走氮素6．00kg·hm^-2。云南红壤坡耕地氮素的平衡主要与氮肥、钾肥施用量和玉米籽粒、秸秆产量有密切关系，施氮量高，氮素投入高于带走；平衡施肥玉米籽粒、秸秆产量高，氮带走总量较多，氮素带走略高于投入；习惯施肥玉米籽粒、秸秆产量低，氮素投入高，带走较少。     

埃塞俄比亚中部Angacha地区树篱鸟类多样性、对树篱类型的偏好及其保护(英文)

本文旨在研究埃塞俄比亚中部Angacha地区树篱中的鸟类多样性。采用样线法及样点法调查了五个子地点的鸟类多样性、丰富度、相似度及对生境的偏好等指标。树篱中鸟类多样性及其对树篱类型的偏好因其植被组成及结构的不同而有所差异。在树篱生境中记录到5个特有鸟种,即卢氏歌 (Cossyfa semirufa)、白颊蕉鹃(Tauraco leucotis)、横斑拟鴷(Lybius undatus)、黑头林鹂(Oriolus monacha)及肉垂鹮(Bostrychia carucullatta)。树篱的稠密度、高度及宽度影响到鸟类的多样性、丰富度及相似度。较密的树篱常常拥有较高的鸟类物种多样性、丰富度和相似性。组成树篱的植物多样性及其鸟类多样性之间呈高度相关,并与生境质量直接相关。树篱中鸟类多样性较高,并且一些鸟类对某些类型的树篱有明显的偏好,这就对当地树篱优先保护与管理提出了要求。     

Optimization of the contour ridge system for controlling nitrogen and phosphorus losses under seepage condition

Contour ridging can enhance the occurrence of deep seepage because more rainwater concentrates in the low areas along furrows when soil is saturated. Greater seepage could significantly increase nonpoint source pollution. To optimize the contour ridge system to effectively control nutrient losses under seepage condition, 23 treatments with three variables (row grade, field slope and ridge height) in five levels were arranged in a quadratic orthogonal rotation combination design. Results showed that field slope and interactions between the three factors did not significantly influence NO₃‐N and PO₄‐P losses. The dominant factor that controlled NO₃‐N loss was ridge height, followed by row grade. The smallest NO₃‐N loss was obtained at a ridge height of 8.72 cm and a row grade of 7.05°. The dominant factor that controlled PO₄‐P loss was ridge height. The optimal ridge height for efficiently controlling PO₄‐P loss was 9.79 cm. For simultaneously maximally controlling NO₃‐N and PO₄‐P losses, a ridge height of 9.26 cm, a row grade of 7.05° and a field slope of 5° were optimum. This study provides guidance for implementing the contour ridge system.     

Morphologic,morphometric and contour shape variations of sagittal otoliths of Lepidorhombus spp. in the Aegean Sea

Otoliths are calcareous anatomical structures in the inner ear of fishes, and they can be used in the discrimination of fish species and stocks due to their species-specific shape. Sagittal otoliths in the Lepidorhombus whiffiagonis and Lepidorhombus boscii, two flatfish species of the same genus distributed in the Aegean Sea, were compared using morphology, morphometry and contour shape analyses. Blind and eyed side otoliths of Lepidorhombus species were evaluated separately due to their morphological features and statistical differences in morphometric measurements (p < 0.05). Four analysis groups were formed: blind side otolith of L. whiffiagonis, eyed side otolith of L. whiffiagonis, blind side otolith of L. boscii and eyed side otolith of L. boscii. Morphometric differences in otolith shape were performed by canonical discriminant analysis, and the first discriminant axis explained 97.4% (Wilks λ = 0.270) of the variance between the groups, and the second axis explained 2.3% (Wilks λ = 0.620). Classification success between Lepidorhombus species based on CDA is 100%, and the overall CDA classification score between groups is 76.5%. The wavelet functions obtained in the contour analysis showed high variability in the anterior, posterior-dorsal, antero-dorsal and ventral regions of the otoliths among these four analysis groups. Consequently, it is thought that this study will contribute to the taxonomic classification of fish with the morphological and morphometric differences in the blind and eyed side otoliths and the analyses made with the high discrimination success obtained in Lepidorhombus species.     

DEM在低山丘陵区综合治理中的应用

随着低山丘陵区水土流失日益严重,基于多角度、新方法的综合治理迫在眉睫。DEM模型能准确快速地反映区域的地形地貌特征,在低丘的治理中有着多层次的应用。笔者提出了应用DEM模型进行低山丘陵区气温和降水的空间模拟方法,划分区域作物优生区、适宜区的操作流程以及土地利用分区的确定,并把理论应用到小流域的具体实践中,数字化地形图建立样区的DEM模型,根据DEM数据监测样区内各种土地利用类型的坡度等级分布,提取坡度>25°的耕地,为小流域进一步的退耕还林做数据支持。实验结果表明:应用DEM模型能形象地表达区域的地形因子及流域特征,在低山丘陵区的综合治理中有广泛的应用前景。