Modelling the effects of bioturbation on the re-distribution of 137Cs in an undisturbed grassland soil

Under favourable conditions, soil ingestion by earthworm populations can be equivalent to approximately 5–10% of the topsoil mass per year. This suggests that for contaminants that are strongly bound to soil, earthworm ‘bioturbation’ may be a more important transport mechanism than water‐borne advection dispersion. It is therefore quite surprising that few modelling studies to date have explicitly considered the effects of biological processes on contaminant transport in soil. In this study, we present a general model that incorporates the effects of both ‘local’ and ‘non‐local’ biological mixing into the framework of the standard physical (advective‐dispersive) transport model. The model is tested against measurements of the redistribution of caesium‐137 (¹³⁷Cs) derived from the Chernobyl accident, in a grassland soil during 21 years after fallout. Three model parameters related to biological transport were calibrated within ranges defined by measured data and literature information on earthworm biomasses and feeding rates. Other parameters such as decay half‐life and sorption constant were set to known or measured values. A physical advective‐dispersive transport model based on measured sorption strongly underestimated the downward displacement of ¹³⁷Cs. A dye‐tracing experiment suggested the occurrence of physical non‐equilibrium transport in soil macropores, but this was inadequate to explain the extent of the deep penetration of ¹³⁷Cs observed at the site. A simple bio‐diffusion model representing ‘local’ mixing worked reasonably well, but failed to reproduce the deep penetration of Cs as well as a dilution observed close to the soil surface. A comprehensive model including physical advective‐dispersive transport, and both ‘local’ and ‘non‐local’ mixing caused by the activities of both endogeic and anecic earthworms, gave an excellent match to the measured depth profiles of ¹³⁷Cs, with predictions mostly lying within confidence intervals for the means of measured data and model efficiencies exceeding 0.9 on all sampling occasions but the first.     

Condensed tannins from Sesbania sesban and Desmodium intortum as a means of Haemonchus contortus control in goats

Two experiments were conducted to determine whether the proanthocyanidin (condensed tannin)-containing forage legumes Desmodium intortum cv Greenleaf and Sesbania sesban (accession 15019) could be integrated into a feeding management strategy as a means of Haemonchus contortus control in goats. The anthelmintic effects of condensed tannin extracts from the two legumes on H. contortus L₃ larvae were studied in an in vitro larval migration inhibition system. The extracts inhibited larval migration in a dose-dependent manner, and at concentrations from 1,000???g/ml condensed tannin, the extract from D. intortum caused a significantly higher inhibition of larval migration than did the corresponding concentrations of the S. sesban extract (P?<?0.01). Prolonged feeding of tanniniferous forage legumes showed that animals receiving D. intortum had the lowest total worm burden, the lowest female to male parasite ratio, the lowest number of eggs in the uterus of each female worm and the lowest per capita fecundity (P?<?0.01). However, there was no change in the performance (weight gain) of parasite-infected goats probably due to incomplete removal of the parasite or prolonged confinement of goats in small pens, which calls for further investigation. However, since there is no single efficient method in control of parasites, based on the obtained data from this experiment, integrated feeding of D. intortum with other suitable method of parasite control is thus suggested.     

Structure liming enhances aggregate stability and gives varying crop responses on clayey soils

It has been suggested that liming can improve soil structure and thereby decrease losses of particles and associated nutrients. In this study, two types of structure lime, slaked lime (Ca(OH)₂) and a mixed product of calcium carbonate (CaCO₃) and slaked lime (Ca(OH)₂), were applied at three different rates in field trials on clayey soils (23%–40% clay). A combination of primary tillage and structure liming was also studied, in a split-plot trial on a clayey soil (25% clay). Aggregate (2–5?mm) stability, measured as reduction in turbidity (which is strongly correlated with losses of particulate phosphorus), was significantly increased with the highest application rates of both structure lime products. Aggregate size distribution was also improved with structure lime, creating a finer tilth in the seedbed. Yield response to structure lime was not consistent, with both negative and positive responses over the four-year study period. Positive yield responses can possibly be attributed to the finer tilth preventing evaporation in two dry growing seasons. Negative yield responses were probably an effect of impaired phosphorus availability associated with limited precipitation in May-July in 2011 and 2013. Two years after liming, soil pH levels were significantly elevated in plots with the highest application rate of structure lime, whereas no significant increases were found three years after liming. However, a lingering effect of liming was still detectable, as manganese concentration in barley grain was significantly lower in plots with the highest application rates of both structure lime products in the fourth study year. These results indicate that structure liming can be used as a measure to mitigate phosphorus losses from clayey soils, thereby preventing eutrophication of nearby waters. However, the yield response was varying and unpredictable and thus further investigations are needed to determine the circumstances in which field liming can act efficiently not only to prevent phosphorus losses, but also to ensure consistent yield increases.     

Occurrence of mastitis and associated risk factors in lactating goats under pastoral management in Borana,Southern Ethiopia

Mastitis prevalence and related risk factors were studied in 1,072 udder halves of 536 lactating goats from October, 2008 to February, 2009. Clinical and subclinical mastitis were prevalent in 4.3% (95% CI = 2.8, 6.5) and 11.2% (95% CI = 8.7, 14.3) of the studied animals, respectively, resulting in an overall prevalence of 15.5% (95% CI = 12.6, 18.9). Univariate analysis of the potential risk factors has depicted that mastitis was more prevalent in does with previous mastitis history, increased parity, poor body conditions, increased milk production, late lactation stage, long teat, and housed goats. Furthermore, prevalence was significantly higher (p < 0.05) during the wet period of October to November than the dry periods of January to February. No significant variations (p > 0.05) were observed in mastitis prevalence with udder tick infestation, mixing goat with sheep and flock size. With multivariable analysis, lactation stage, teat length, body condition, and season (wet months) have showed significant association with mastitis prevalence, and these factors maintained significant in the stepwise elimination of multivariable logistic regression model. As a result, does in late stage of lactation (OR = 4.3, 1.8, 10.4), poor body condition (OR = 5.0, 1.7, 10.0), long teats (OR = 2.2, 95% CI = 1.1, 4.2) and does examined in wet period were at higher risk of udder infections than early lactation, good body condition, short teat, and examined in dry period, respectively. The study showed occurrence of mastitis and associated risk factors in studied goats, which suggests the need for control intervention. Further investigations into pathogens involved in goat mastitis will optimize our knowledge of causative agents and control interventions.     

Phosphorus leaching from clay soils can be counteracted by structure liming

Two field experiments with drained plots on clay soils (60% and 25% clay) demonstrated a significant reduction in leaching of total phosphorus after application of structure lime. Aggregate stability was significantly improved. Phosphorus leaching in particulate form was significantly reduced following structure liming at the site with a very high clay content. Sites representing low (50 mg kg^?1) and high (140 mg kg^?1) levels of phosphorus extractable with acid ammonium lactate in topsoil displayed differing effects on leaching of dissolved reactive P (DRP). This form of phosphorus was only significantly reduced compared with the control at one site with high topsoil phosphorus status and relatively high (17–18%) degree of phosphorus saturation in the subsoil. Laboratory experiments with simulated rain events applied to topsoil lysimeters from the same site also demonstrated a significant reduction in leaching of DRP. These findings indicate that structure liming is an appropriate leaching mitigation measure on soils with both a high clay content and high soil phosphorus status.     

Nutritive value of botanical fractions of Moringa oleifera and Moringa stenopetala grown in the mid-Rift Valley of southern Ethiopia

Nutritive value of botanical fractions (leaves, twigs, pods and whole forage) of Moringa oleifera and Moringa stenopetala were evaluated based on chemical composition, in sacco dry matter (DM) degradability, in vitro gas production and in vitro organic matter digestibility. The objective was to characterize the nutritive value of the different morphological fractions in order to determine their potential as alternative sources of livestock feed. The crude protein content (g/kg DM) was highest (P < 0.05) in M. oleifera leaves (361.2) followed by M. stenopetala leaves (334.4) and lowest in M. oleifera twigs (79.1) and M. stenopetala pods (89.2). The fiber (NDF, ADF and ADL) contents were higher (P < 0.05) in the twigs and pods than the leaves and whole forage in both species. The different morphological fractions of both species had high mineral content, although the Na content was low or marginal in most fractions except whole forage and green pods of M. stenopetala. The in sacco DM degradability ranked the morphological fractions in the order of leaves > whole forage = pods > twigs after 24 h of incubation time. The potential degradability (A + B) was highest (P < 0.05) in M. oleifera twigs (97.9 %) and M. stenopetala leaves (98.5 %) and lowest in the pods of both species (64.4–69.5 %) with intermediate values in all other fractions. No significant differences were observed in the instantly fermentable fraction (a) and rate of gas production (c), whereas lower (P > 0.05) insoluble but slowly fermentable (b) and potential gas production (a + b) were recorded in the pods than in the other morphological fractions of both species. The study showed that the different morphological fractions of the two Moringa species are good source of nutrients with high degradability which could be used as potential supplements to low quality tropical roughages.     

Ingestion of indigestible foreign materials by free grazing ruminants in Amhara Region, Ethiopia

Ruminants slaughtered in Bahir-Dar, northern Ethiopia, were studied to estimate the prevalence and types of foreign bodies in the rumen and reticulum. Of the 400 cattle, 320 sheep, and 320 goats examined between November 2011 and May 2012, 41.8, 20.6 and 11.9 %, respectively, contained one or more types of foreign bodies. The prevalence of foreign bodies was significantly (P?<?0.05) higher (i) in cattle than in sheep and goats, (ii) in cattle in poor body condition than those in good condition, and (iii) in the rumen than in the reticulum. The most commonly encountered materials were plastics, which resulted from the widespread use of plastic bags and improper waste disposal. Other materials found were cloth, rope, metal, and leather. The study demonstrated that ruminants in the area are ingesting various types of indigestible foreign bodies, which can hamper their health and productivity. To avert the problem, collaborative intervention schemes need to be applied involving professionals, policy makers, livestock keepers, and environmental activists.     

Soil and crop responses to controlled traffic farming in reduced tillage and no-till: some experiences from field experiments and on-farm studies in Sweden

ABSTRACT

The purpose of this study was to investigate the impact of controlled traffic farming (CTF) with respect to soil physical properties and crop yield for Swedish conditions. Three field trials were conducted for six growing seasons in central and southern Sweden. In two of the trials, we compared CTF with random traffic farming (RTF) in deep chiseling (DC, 15–20?cm), shallow cultivation (SC, 5–10?cm) and no-till. The third trial was on farm study by using the existing CTF module at the farm. In the tracks of CTF (traffic zone) dry bulk density was increased and water movement was decreased. Soil penetration resistance was greater in the traffic zone than in the crop zone in some of the trials but the difference was not statistically significant. On average, crop yield was similar between CTF and RTF for all trials. Yield in the traffic zone was significantly less than that in the crop zone in the on-farm trial, but the yield in both zones were similar in the field trial at Lönnstorp, south Sweden. On the contrary, in the field trial at Säby 1 in Uppsala, central Sweden, crop zone produced less yield than traffic zone probably because of too loose soil, which impaired the uptake of nutrients and water. We conclude that if vehicle weight is not very high and the soil is not vulnerable to compaction, dual wheels and CTF are equal options.     

Herbicide sorption, degradation, and leaching in three Swedish soils under long-term conventional and reduced tillage

Soil tillage has the potential to influence water flow and solute transport through the soil by cutting continuous macropores which connect the soil surface to the subsoil. Tillage also affects soil organic carbon sequestration which may lead to different sorption and degradation properties depending on the long-term tillage practices. The objective of this study was to quantify the differences in sorption, degradation and leaching of the herbicides bentazone and isoproturon between conventional tillage (CT) and reduced tillage (RT) under Swedish conditions. Three sites, Ultuna (silty clay), Säby (loam), and Lönnstorp (sandy loam moraine till), where replicate plots had been under either CT or RT for at least 9 years, were included in the study. A higher organic carbon content had developed in the top 5 cm of RT plots compared to the 10–20 cm depth and CT plots since the establishment of the experimental treatments. Adsorption and degradation were studied in laboratory experiments and solute transport was studied in undisturbed column experiments using non-reactive tracers and herbicides. The results from the column experiments were not significantly different between tillage treatments for Säby and Lönnstorp. For Ultuna, RT resulted in a more pronounced preferential tracer transport pattern and isoproturon leaching was twelve times larger compared to CT columns. This indicates that the tillage treatment had affected the macropore connectivity only at Ultuna. Freundlich adsorption coefficients for both bentazone and isoproturon were larger (though not always significantly) in the top 5 cm of RT soil compared to the 10–20 cm depth and to CT, reflecting the higher organic carbon content. The degradation rate was also generally larger (though not always significantly) in the top 5 cm of RT soil. These results show that RT has the potential to reduce pesticide leaching. However, any such reduction may be counter-balanced by enhanced preferential flow for soils where RT results in improved macropore connectivity.     

Department of Animal Production and Rangeland Management,Awassa College of Agriculture,P.O. Box 5, Awassa,Sidamo, Ethiopia

Samples were collected from clinically infected carthorses in Awassa. Fungus species affecting the carthorses were identified. Eight genera of fungal groups were isolated from swabs and skin scrapes taken from symptomatic horses. These included Aspergillus spp., Histoplasma spp., Penicillinum spp., Microsporum spp., Trichophyton spp., yeast cells of Candida spp., Cryptococcus spp. and Geotrichum spp. The most frequent isolates were from the genera Aspergillus (48 %), Penicillium (39.2 %) and Trichophyton (31.6 %). Clinical findings are reported, the economic, zoonotic and pathogenetic importance of fungi causing dermatomycoses is discussed, and further studies are recommended.