Occurrence and treatment of cracked-skull disease affecting Clarias spp. in homestead ponds in Nigeria

Abstract. Cracked-skull disease, previously unrecorded in Nigeria, affected fish in 80% of the homestead ponds investigated in this study. It was peculiar to mud catfish, Clarias spp., under intensive culture in urban Lagos, Nigeria. Male and female fish that were more than 10cm in length were equally vulnerable. The accessory respiratory structures were involved, but the liver, kidney, heart and the other internal organs were not. At its peak, the infection was characterized by a lateral crack in the skull, which resulted in death. Dip treatment in either 2-0ppm potassium permanganate or 0-5ppm formalin (with alcohol) for 30s day ¹resulted in 65-0 and 41-3% full recovery in 7 days, respectively. The implications of the disease for homestead fish culture are discussed.     

III. Buchbesprechungen

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Transgression und Heterofis bei Populus-Kreuzungen

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III. Buchbesprechungen

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Die Mitzweisung der Magnetnadel

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Home garden system dynamics in Southern Ethiopia

Home gardens in southern Ethiopia are regarded as efficient farming systems, allowing interactions and synergies between crop, tree and livestock components. However, these age-old traditional home gardens are evolving rapidly in response to changes in both the socio-economic and biophysical environment. Altered cropping patterns, farm size and component interactions may affect the systems’ sustainability. Home gardens exhibit a huge diversity in farms and farming systems, which needs to be understood in order to design interventions for improvement. Dynamics of home gardens were studied over two-decades (1991–2013) based on a survey of 240 farm households and focus group discussions. Farms were grouped into five types: Khat-based, Enset-cereal-vegetable, Enset-based, Enset-coffee and Enset-livestock. Farm trajectories revealed a shift from food-oriented Enset-based and Enset-livestock systems to (1) cash crop oriented khat-based systems, and (2) combined food and cash crop oriented Enset-cereal-vegetable systems. In densely populated, market proximate areas a major trend was expansion of khat, from 6 to 35% of the area share per farm, while the combined area share of enset and coffee decreased from 45 to 25%. Concurrently, the cattle herd size fell from 5.8 TLU to 3.9 TLU per household. In medium populated, less accessible areas the trend was consolidation of combined production of food and cash crops. Enset and coffee together maintained a share of over 45%. Easy transport and marketing of the perishable cash-generating khat compared with traditional crops favoured its cultivation among smallholders located close to markets. The insights in home garden change in response to increasing population pressure, decreasing farm size and market development may help to design interventions to increase system sustainability.     

Defining competition vectors in a temperate alley cropping system in the midwestern USA: 1. Production physiology

With renewed interest in the use of ecologically-designed, sustainable agricultural systems for temperate regions of the world, agroforestry is being proposed as an alternative to intensive production of crops in monocultures. However, the knowledge-base for understanding and managing complex, multi-strata systems worldwide is limited, particularly so for temperate regions. We examined an alley cropping system in the midwestern US where maize (Zea mays L.) is grown in alleys between tree rows of either black walnut (Juglans nigra L.) or red oak (Quercus rubra L.). During a course of ten years, crop yields in rows adjacent to tree rows declined by 50% or more. With the experimental introduction of barriers to separate tree and crop root systems, yields in the rows near trees were equal to those of the center row (and monoculture). Irrespective of a high correlation between photosynthetically active radiation and net photosynthesis, shading did not have a major influence on crop yield. At this stage of system development (11 year old trees), influence of incident PAR on crop yield seems to be minimal. Subsequent papers in this series examine the sharing of belowground resources between trees and crops to quantify the competitive interactions that impact crop yields and their implications for economic return to the farmer.This revised version was published online in November 2005 with corrections to the Cover Date.     

Factors influencing stump sprouting by pondcypress (Taxodium distichum var. nutans (Ait.) Sweet)

Sprouting can be an important mechanism of regeneration in harvested cypress (Taxodium sp.) wetlands; however, limited information exists on factors influencing sprouting. We examined the influence of harvesting practices, tree size, and site conditions on stump sprouting in eight pondcypress (Taxodium distichum var. nutans (Ait.) Sweet) wetlands in Florida, USA. Stumps were cut at three heights: 20 cm below high water level, at high water, and 40 cm above high water. Half of each site was harvested using a sawhead feller and the other half using shearhead. We monitored sprouting for 2 years post-harvest. Stump height affected first year sprouting, but the effect disappeared during year 2. Felling equipment did not affect sprouting; however, the shearhead caused greater stump damage. Sprouting declined with increasing parent tree size; percentage of stumps with sprouts after 2 years was 68% for trees 10–14 cm dbh and 28% for trees 20–24 cm dbh. Stump sprouting ranged among sites from 23 to 54% after 2 years. Results indicate that sprouting may be an important, but inadequate, form of regeneration. At sites with short hydroperiods, dense understories, and/or predominance of trees greater than 20 cm dbh, reduced sprouting may occur, and planting seedlings may be beneficial.