Effectiveness of indigenous soyabean rhizobial isolates to fix nitrogen under field conditions of Zimbabwe

Ten promiscuous soyabean isolates that proved superior in nitrogen fixation effectiveness to commercial inoculant strains under greenhouse studies were evaluated for their symbiotic potential under field conditions. The promiscuous soyabean variety, Magoye and the specific variety Solitaire were used as test hosts. Five of the isolates were obtained from the nodules of Magoye and coded M1 to M5 while the other five were isolated from the promiscuous soyabean variety Hernon 147 and coded H1 to H5. Two commercial inoculant strains, MAR 1491 and 1495 were included for comparison. Parameters tested included nodulation effectiveness, yield, nitrogen content and nitrogen fixation effectiveness. Isolate M3 gave significantly higher nitrogen contents and N2 fixation effectiveness in Magoye than the reference strains, while H1, H3 and H5 gave better nitrogen contents and N2 fixation effectiveness with Solitaire. Nodule numbers and yields obtained were highly variable and not reliable indicators of effectiveness. There were strong harvest index effects of different rhizobial isolates, which closely followed the trend for grain yield. Isolates M3, H1, H3 and H5 were concluded to be potential commercial inoculants, while the other six need to be retested over many sites and seasons before they can be recommended

Manure and soil properties affect survival and persistence of soyabean nodulating rhizobia in smallholder soils of Zimbabwe

Persistence of the soyabean rhizobial inoculant strain MAR 1491 was assessed in 52 soils from Guruve, Hurungwe and Goromonzi districts of Zimbabwe, which had been inoculated 1¿4 or 6 years previously. Most probable number estimates of rhizobia in the soils showed that population sizes decreased with increasing time since the last inoculation. Rhizobial populations of up to 102 cells g¿1 soil were found in Guruve soils inoculated 3 years before, while persistence in Hurungwe and Goromonzi soils was significant for soils inoculated 2 years before. The greater rhizobial persistence in Guruve soils was attributed to their higher clay (>20%) and organic C (>1%) compared with the sandier, relatively less fertile Hurungwe and Goromonzi soils. Farmers with favourable soils such as those in Guruve can grow soyabean for at least 3 years without the need for repeat inoculation. Manure application led to increased indigenous rhizobial numbers at two smallholder sites and larger numbers of rhizobia in inoculated plots in sandy soils from Goromonzi. Inoculation and manure addition increased rhizobial numbers and soyabean yields in field experiments; soyabean yields varied from 0.5 t ha¿1 in uninoculated, unmanured plots to 1.1 t ha¿1 in inoculated plots receiving 10 t manure ha¿1. Increases in numbers closely followed the progress of the wet season. The highest rhizobial population of 105 cells g¿1 soil was obtained in plots that had received 10 t ha¿1 manure when a high soil moisture (15%, w/w) was recorded during the cropping season, while the lowest population of 101 cells g¿1 soil was recorded in treatments during the dry season when soil moisture was low

Variability in decomposition rate of sorghum cultivar residues linked to lignin content

International audienc

Crop residues differ in their decomposition dynamics: Review of available data from world literature

International audienc

Variance components and heritability of traits related to root : shoot biomass allocation and drought tolerance in wheat

Enhanced root growth in plants is fundamental to improve soil water exploration and drought tolerance. Understanding of the variance components and heritability of root biomass allocation is key to design suitable breeding strategies and to enhance the response to selection. This study aimed to determine variance components and heritability of biomass allocation and related traits in 99 genotypes of wheat (Triticum aestivum L.) and one triticale (X. Triticosecale Wittmack) under drought-stressed and non-stressed conditions in the field and greenhouse using a 10x10 alpha lattice design. Days to heading (DTH), days to maturity (DTM), number of tillers (NPT), plant height (PH), spike length (SL),shoot and root biomass (SB, RB), root to shoot ratio (RS), thousand kernel weight (TKW) and yield (GY) were recorded. Analyses of variance, variance components, heritability and genetic correlations were computed. Significant (p70%) for RS observed in this population constitute several bottlenecks for improving yield and root mass simultaneously. However, indirect selection for DTH, PH, RB, and TKW, could help optimize RS and simultaneously improve drought tolerance and yield under drought-stressed conditions

A cross-sectional study among detergent workers exposed to liquid detergent enzymes.

Objectives: To investigate sensitisation and respiratory health among workers who produce liquid detergent products and handle liquid detergent enzymes. Methods: We performed a cross-sectional study among 109 eligible workers of a detergent products plant. 108 were interviewed for respiratory and allergic symptoms and 106 blood samples were taken from them to examine sensitisation to enzymes. Those sensitised to >=1 enzymes were referred for clinical evaluation. Workers and representatives were interviewed to characterise exposure qualitatively and estimate exposure semi-quantitatively. Workers were classified into three exposure groups with varying exposure profiles to enzymes, based on frequency, duration, and level of exposure. Results: Workers were exposed to proteases, {alpha}-amylase, lipase and cellulase. The highest exposures occurred in the mixing area. Liquid spills with concentrated enzyme preparations and leakage of enzymes during weighing, transportation and filling were causing workplace contaminations and subsequently leading to both dermal and inhalation exposure for workers. Workers with the highest exposures reported significantly more work-related symptoms of itching nose (prevalence ratio (PR) = 4.2, 95% CI 1.5 to 12.0) and sneezing (PR = 4.0, 95% CI 1.5 to 10.8) and marginally significant more symptoms of wheezing (PR = 2.9, 95% CI 0.9 to 8.7) compared with the least exposed group. Fifteen workers (14.2%) were sensitised to >=1 enzymes. A marginally statistically significant gradient in sensitisation across the exposure categories was found (p = 0.09). There was a clinical case of occupational asthma and two others with probable occupational rhinitis. Conclusions: Workers exposed to liquid detergent enzymes are at risk of developing sensitisation (14%) and respiratory allergy

A cross-sectional study of exposures, lung function and respiratory symptoms among aluminium cast-house workers

Objectives To investigate exposures, respiratory symptoms, lung function and exposure-response relationships among aluminium cast-house workers. Methods A cross-sectional study was conducted among 182 workers. Exposure data were used to model exposure to irritants. Lung function and questionnaire data on respiratory symptoms were compared to a general population sample and an internal reference group. Blood samples were taken from 156 workers to examine total IgE, eosinophils and sensitisation to common allergens. Results Average daily mean exposure to inhalable dust, metals, hydrogen fluoride, fluoride salts and sulphur dioxide was relatively low compared to reference values. Airflow patterns in the hall were disturbed regularly and resulted in pot emissions with high concentrations of fluorides. Peak exposures to chlorine gas occurred intermittently due to production process disturbances. Workers reported significantly more respiratory symptoms (continuous trouble with breathing (prevalence ratio (PR) 2.5; 95% CI 1.2 to 5.3), repeated trouble with breathing (PR 1.8; 95% CI 1.1 to 3.0), wheezing (PR 1.4; 95% CI 1.1 to 1.8), asthma attack (ever) (PR 2.8; 95% CI 1.7 to 4.6) and doctor diagnosed asthma (PR 2.6; 95% CI 1.5 to 4.4). Regression analysis showed significantly lower FEV(1) values (-195 ml) and FVC values (-142 ml) compared to a general population sample. Lung function did not differ between groups. Conclusion This epidemiological study suggests cast-house workers in the aluminium industry are exposed to respiratory hazards. Exposure-response relationships could not be demonstrated but this study supports preventive measures in the work environment with a focus on (peak) exposures to irritants