Length-weight relationships of fishes from tributaries of the Volta River, Ghana Part 1: Analysis of pooled data sets

The parameters a and b of length-weight relationships of the form W = a L super(b) were estimated for 45 fish species sampled in the Oti, Pru and Black Volta rivers, Ghana. Also, the slope and intercepts of regressional enabling standard to total length conversions were estimated for each of these same species. The estimates of b, which ranged from 2.35 to 3.27 have a mean of 2.98, with a s.e. of 0.036. These results are complemented with a brief discussion of the need for data summaries such as presented in this article

Length-weight relationships of fishes from tributaries of the Volta River, Ghana: Part II and Conclusion

Slopes and intercepts of length-weight relationships obtained from 37 populations from the rivers Oti, Pru and Black Volta in Ghana were compared using a one way analysis of covariance with fixed effects. Although no significant differences were obtained from this analysis, an ANOVA comparing the magnitudes of mean condition factors (Wx100/SL3) found 9 out of 37 populations significantly different at the 0.05 level. A two-way nested ANOVA using all populations combined, however, did not yield any significant differences between the three rivers. Thus, pooling the data to obtain the results presented in Part I (see Entsua-Mensah et al. Naga 1995) is justified here

Climate Smart Agriculture: Threshold Number of Trees in Agroforestry Parkland for Better Land Management to Climate Adaptation and Mitigation in West Africa Burkina Faso

Agroforestry system is the most climate smart agriculture practices in West Africa. Because perennials are generally more resistant to climate extremes, such as drought, flood, and heat, than annual crops. Park land may appear to be competitive with crop on farm. To elucidate that, trees number and their canopy cover on farming system were assessed through tree inventory in three municipalities and compared with normal trees canopy cover. More than 3000 trees which spreading was 1154 in Bouroum-Bourom, 884 in Ouahigouya, and 1054 in Sapouy were used. Trees density and mean tree canopy cover in farms were calculated. Trees density on farm were about the double of trees threshold number in Soudanian zone, one and half both in Soudan Sahel and Sahel strict zones. Tree canopy cover were 66.25, 59.92, and 42.1 m2, respectively in Bouroum-Bourom, Sapouy, and Ouahigouya. The average tree cover was 23.99, 18.23, and 14.88%, respectively, the Municipality. Agroforestry system as more trees that it should be, to optimize the positive impact of agroforestry system to increase crop yield and restore land fertility the number of trees on parkland system should be 15, 17, and 24 trees/ha, respectively in Bouroum-Bouroum, Sapouy, and Ouahigouya

Mapping the drivers of parasitic weed abundance at a national scale : a new approach applied to Striga asiatica in the mid‐west of Madagascar

The parasitic weed genus Striga causes huge losses to crop production in sub‐Saharan Africa, estimated to be in excess of $7 billion per year. There is a paucity of reliable distribution data for Striga ; however, such data are urgently needed to understand current drivers, better target control efforts, as well as to predict future risks. To address this, we developed a methodology to enable rapid, large‐scale monitoring of Striga populations. We used this approach to uncover the factors that currently drive the abundance and distribution of Striga asiatica in Madagascar. Two long‐distance transects were established across the middle‐west region of Madagascar in which S. asiatica abundance in fields adjacent to the road was estimated. Management, crop structure and soil data were also collected. Analysis of the data suggests that crop variety, companion crop and previous crop were correlated with Striga density. A positive relationship between within‐field Striga density and the density of the nearest neighbouring fields indicates that spatial configuration and connectivity of suitable habitats is also important in determining Striga spread. Our results demonstrate that we are able to capture distribution and management data for Striga density at a landscape scale and use this to understand the ecological and agronomic drivers of abundance. The importance of crop varieties and cropping patterns is significant, as these are key socio‐economic elements of Malagasy cropping practices. Therefore, they have the potential to be promoted as readily available control options, rather than novel technologies requiring introduction

Rubber and plantain intercropping: Effects of different planting densities on soil characteristics

Two field experiments were conducted at Ellembelle and Jomoro districts in the Western region of Ghana where rubber cultivation is a predominant farming activity. The objective of the study was to assess the effect of rubber and plantain intercropping systems on selected soil properties. The experiment was arranged in a randomized complete block design (RCBD) with 3 replications. The treatments were the sole crop rubber (R), sole crop plantain (P) and three intercrop systems comprising an additive series of plantain: one row of plantain to one row of rubber (PR), two rows of plantain to one row of rubber (PPR) and three rows of plantain to one row of rubber (PPPR). Generally, agroforestry systems improved the soil hydraulic properties considerably, with the highest cumulative infiltration rates of 5.16 and 8.68 cm/min observed under the PPPR systems at the Ellembelle and Jomoro sites, respectively. Microbial biomass C (Cmic), N (Nmic) and P (Pmic) was significantly improved (P < 0.05) under the agroforestry than the monocrop systems. The Cmic, Nmic and Pmic values were highest under the PPPR system at both Ellembelle (Cmic, = 139.9 mg/kg; Nmic = 36.26 mg/kg and Pmic = 87.6 mg/kg) and Jomoro (Cmic = 78.7 mg/kg; Nmic = 80.3 mg/kg and Pmic = 3.45 mg/kg) sites

A Genotyping Array for the Globally Invasive Vector Mosquito, Aedes albopictus

BACKGROUND: Although whole-genome sequencing (WGS) is the preferred genotyping method for most genomic analyses, limitations are often experienced when studying genomes characterized by a high percentage of repetitive elements, high linkage, and recombination deserts. The Asian tiger mosquito (Aedes albopictus), for example, has a genome comprising up to 72% repetitive elements, and therefore we set out to develop a single-nucleotide polymorphism (SNP) chip to be more cost-effective. Aedes albopictus is an invasive species originating from Southeast Asia that has recently spread around the world and is a vector for many human diseases. Developing an accessible genotyping platform is essential in advancing biological control methods and understanding the population dynamics of this pest species, with significant implications for public health. METHODS: We designed a SNP chip for Ae. albopictus (Aealbo chip) based on approximately 2.7 million SNPs identified using WGS data from 819 worldwide samples. We validated the chip using laboratory single-pair crosses, comparing technical replicates, and comparing genotypes of samples genotyped by WGS and the SNP chip. We then used the chip for a population genomic analysis of 237 samples from 28 sites in the native range to evaluate its usefulness in describing patterns of genomic variation and tracing the origins of invasions. RESULTS: Probes on the Aealbo chip targeted 175,396 SNPs in coding and non-coding regions across all three chromosomes, with a density of 102 SNPs per 1 Mb window, and at least one SNP in each of the 17,461 protein-coding genes. Overall, 70% of the probes captured the genetic variation. Segregation analysis found that 98% of the SNPs followed expectations of single-copy Mendelian genes. Comparisons with WGS indicated that sites with genotype disagreements were mostly heterozygotes at loci with WGS read depth \u3c 20, while there was near complete agreement with WGS read depths \u3e 20, indicating that the chip more accurately detects heterozygotes than low-coverage WGS. Sample sizes did not affect the accuracy of the SNP chip genotype calls. Ancestry analyses identified four to five genetic clusters in the native range with various levels of admixture. CONCLUSIONS: The Aealbo chip is highly accurate, is concordant with genotypes from WGS with high sequence coverage, and may be more accurate than low-coverage WGS

Efficient Utilization of Water and Nitrogen Resources for Grain Sorghum under Rainfed Conditions

Grain sorghum (Sorghum bicolor L. Moench) is the fifth world leading cereal after maize, wheat, rice and barley. The crop can yield reasonably well under adverse conditions of low soil water and high temperature. A three year field study was conducted in a transect across Nebraska where annual mean precipitation ranges from 300 to 900 mm yr-1 to evaluate management practices to optimize yield potential under water limiting conditions. Loss in grain yield due to planting configurations ranged from 20 to 30% with skip-row configurations compared to conventional planting configuration (s0) at the site with greatest precipitation. At a site with moderate precipitation, grain yield was reduced by 18% with plant two skip two configurations (s2) and was not significantly affected with plant one skip one configuration (s1). At sites with the lowest precipitation and significant soil water deficits, grain yield increased with s1 and s2 ranging between 5 and 123% over s0. Considering yield across all sites, s0 yield was greater than skip-row configurations when average yield was above 4.5 Mg ha-1. Water use efficiency was highest with skip-row configuration at low to medium in-season precipitation sites but lower at sites where the mean in-season daily precipitation was greater than 2.5 mm. Increased N rate resulted in increased grain yield with s0 but there were no significant response to N application after 100 kg N ha-1. With skip-row planting, raising N rate above 50 kg N ha-1 did not significantly increase grain yield. Conventional planting (s0) had significantly higher agronomic N use efficiency (AEN) and partial factor productivity of N applied (PFPN) than skip-row configurations. Water and nitrogen stress both resulted in significant increase of leaf and canopy reflectance. A model calibrated in a greenhouse study using a reciprocal index in the green and red edge and in the NIR ranges predicted chlorophyll content with RMSE ranging between 52 and 56 mg m-2

Fertilizer phosphorus fractions and their available to maize on different landforms on a vertisol in the coastal Savanna zone of Ghana

No Abstract

Grain sorghum leaf reflectance and nitrogen status

Nitrogen deficiency is a common but readily managed constraint to grain yield. A quick and nondestructive detection of crop N status using remote sensing could be a means to increased N use efficiency. Research was conducted in a greenhouse in 2006 at the University of Nebraska-Lincoln to establish the relationship of spectral reflectance with N status in leaves of grain sorghum, to develop indices for interpretation of the results and to predict chlorophyll content. Nitrogen stress decreased chlorophyll meter reading and leaf N content, but increased leaf and canopy reflectance. The SPAD values were significantly increased by both water and N stress. Reciprocal reflectance in the green range (549 to 560 nm), and red edge range (710 to 718 nm) wavelength of the spectrum were good indicators of N stress. The best fit regression between leaf chlorophyll content and the indices in the green and red edge wavebands were linear with an R2 of 0.76 to 0.79. A model calibrated using these wavelengths minus reciprocal reflectance of NIR (750 nm), predicted leaf chlorophyll content with root mean square error (RMSE) ranging between 52 and 56 mg m-2, and reduced the intercept of the model from 312 to 35 mg m-2 in the green range and 486 to 21 mg m-2 in the red edge. Future studies will be conducted to evaluate the effectiveness of the indices at the canopy level of grain sorghum

Antibiotic Use in Animal Production: Environmental Concerns

Introduction Antibiotic1 use in animal production has led to improved feed use efficiency and increased growth rates. In turn, these resulted in reduced food production costs and reduced excrement of manure nutrients which may cause pollution problems. On the other hand, antibiotic use leads to antibiotic resistance and a possible reduction in effectiveness of treatment options for both animals and humans. This publication addresses these issues. Disease-causing microorganisms2, including bacteria,are the most diverse and numerous organisms on earth. Diverse in their habitat, environmental adaptation, and mechanisms of reproduction, they have short generations with high multiplication rates. Such characteristics help develop antibiotic resistance. Resistance has developed to antibiotics used for human treatment but very limited evidence is shown for development of antibiotic resistance because of its use in animal production