Nutrient flows and balances in intensively managed vegetable production of two West African cities

This study reports and analyzes nutrient balances in experimental vegetable production systems of the two West African cities of Tamale (Ghana) and Ouagadougou (Burkina Faso) over a two‐year period comprising thirteen and eleven crops, respectively. Nutrient‐use efficiency was also calculated. In Tamale and Ouagadougou, up to 2% (8 and 80 kg N ha^?1) of annually applied fertilizer nitrogen were leached. While biochar application or wastewater irrigation on fertilized plots did not influence N leaching in both cities, P and K leaching, as determined with ion‐absorbing resin cartridges, were reduced on biochar‐amended plots in Tamale. Annual nutrient balances amounted to +362 kg N ha^?1, +217 kg P ha^?1, and –125 kg K ha^?1 in Tamale, while Ouagadougou had balances of up to +692 kg N ha^?1, +166 kg P ha^?1, and –175 kg K ha^?1 y^?1. Under farmers' practice of fertilization, agronomic nutrient‐use efficiencies were generally higher in Tamale than in Ouagadougou, but declined in both cities during the last season. This was the result of the higher nutrient inputs in Ouagadougou compared to Tamale and relatively lower outputs. The high N and P surpluses and K deficits call for adjustments in local fertilization practices to enhance nutrient‐use efficiency and prevent risks of eutrophication.     

Interactive influence of livestock grazing and manipulated rainfall on soil properties in a humid tropical savanna

Purpose

The effect of uncontrolled grazing and unpredictable rainfall pattern on future changes in soil properties and processes of savanna ecosystems is poorly understood. This study investigated how rainfall amount at a gradient of 50%, 100%, and 150% would influence soil bulk density (ρ), volumetric water content (θ_v), carbon (C), and nitrogen (N) contents in grazed (G) and ungrazed (U) areas.

Materials and methods

Rainfall was manipulated by 50% reduction (simulating drought—50%) and 50% increase (simulating abundance—150%) from the ambient (100%) in both G and U areas. Plots were named by combining the first letter of the area followed by rainfall amount, i.e., G150%. Samples for soil ρ, C, and N analysis were extracted using soil corer (8 cm diameter and 10 cm height). Real-time θ_v was measured using 5TE soil probes (20 cm depth). The EA2400CHNS/O and EA2410 analyzers were used to estimate soil C and N contents respectively.

Results and discussion

The interaction between grazing and rainfall manipulation increased θ_v and C but decreased N with no effect on ρ and C:N ratio. Rainfall reduction (50%) strongly affected most soil properties compared to an increase (150%). The highest (1.241?±?0.10 g cm^?3) and lowest (1.099?±?0.05 g cm^?3) ρ were in the G50% and U150% plots respectively. Soil θ_v decreased by 34.0% (grazed) and 25.8% (ungrazed) due to drought after rainfall cessation. Soil ρ increased with grazing due to trampling effect, therefore reducing infiltration of rainwater and soil moisture availability. Consequently, soil C content (11.45%) and C:N ratio (24.68%) decreased, whereas N increased (7.8%) in the grazed plots due to reduced C input and decomposition rate.

Conclusions

The combined effect of grazing and rainfall variability will likely increase soil θ_v, thereby enhancing C and N input. Grazing during drought will induce water stress that will destabilize soil C and N contents therefore affecting other soil properties. Such changes are important in predicting the response of soil properties to extreme rainfall pattern and uncontrolled livestock grazing that currently characterize most savanna ecosystems.

     

How relevant is recalcitrance for the stabilization of organic matter in soils?

Traditionally, the selective preservation of certain recalcitrant organic compounds and the formation of recalcitrant humic substances have been regarded as an important mechanism for soil organic matter (SOM) stabilization. Based on a critical overview of available methods and on results from a cooperative research program, this paper evaluates how relevant recalcitrance is for the long‐term stabilization of SOM or its fractions. Methodologically, recalcitrance is difficult to assess, since the persistence of certain SOM fractions or specific compounds may also be caused by other stabilization mechanisms, such as physical protection or chemical interactions with mineral surfaces. If only free particulate SOM obtained from density fractionation is considered, it rarely reaches ages exceeding 50 y. Older light particles have often been identified as charred plant residues or as fossil C. The degradability of the readily bioavailable dissolved or water‐extractable OM fraction is often negatively correlated with its content in aromatic compounds, which therefore has been associated with recalcitrance. But in subsoils, dissolved organic matter aromaticity and biodegradability both are very low, indicating that other factors or compounds limit its degradation. Among the investigated specific compounds, lignin, lipids, and their derivatives have mean turnover times faster or similar as that of bulk SOM. Only a small fraction of the lignin inputs seems to persist in soils and is mainly found in the fine textural size fraction (<20 µm), indicating physico‐chemical stabilization. Compound‐specific analysis of ¹³C : ¹²C ratios of SOM pyrolysis products in soils with C3‐C4 crop changes revealed no compounds with mean residence times of > 40–50 y, unless fossil C was present in substantial amounts, as at a site exposed to lignite inputs in the past. Here, turnover of pyrolysis products seemed to be much longer, even for those attributed to carbohydrates or proteins. Apparently, fossil C from lignite coal is also utilized by soil organisms, which is further evidenced by low ¹⁴C concentrations in microbial phospholipid fatty acids from this site. Also, black C from charred plant materials was susceptible to microbial degradation in a short‐term (60 d) and a long‐term (2 y) incubation experiment. This degradation was enhanced, when glucose was supplied as an easily available microbial substrate. Similarly, SOM mineralization in many soils generally increased after addition of carbohydrates, amino acids, or simple organic acids, thus indicating that stability may also be caused by substrate limitations. It is concluded that the presented results do not provide much evidence that the selective preservation of recalcitrant primary biogenic compounds is a major SOM‐stabilization mechanism. Old SOM fractions with slow turnover rates were generally only found in association with soil minerals. The only not mineral‐associated SOM components that may be persistent in soils appear to be black and fossil C.     

The Use of Positron Emission Tomography in Soft Tissue Sarcoma Patients under Therapy with Trabectedin

Background

We used 2-deoxy-2-[¹⁸F] fluoro-D-glucose (FDG) positron emission tomography (PET) to evaluate the FDG uptake in patients with advanced and/or metastatic soft tissue sarcoma (STS) undergoing therapy with Ecteinascidin-743 (ET-743, Trabectedin, Yondelis™).

Patients and Methods

The pilot study included nine patients with metastatic STS receiving a minimum of one cycle of treatment with trabectedin. Patients were examined using PET prior to onset of therapy and after completion of one or three cycles of trabectedin. Restaging according to Response Evaluation Criteria in Solid Tumours (RECIST) was performed in parallel using computed tomography (CT) and/or magnetic resonance imaging (MRI) and served for reference.

Results

Clinical outcome of nine evaluable patients was as follows: one patient with partial remission (PR), three patients with stable disease (SD), and five patients with progressive disease (PD). A more than 40% decrease of the standardized uptake value (SUV) of sequential PET examination could be demonstrated for the responding patient (PR), whereas patients with SD or PD showed a stable SUV, but no increase in SUV.

Conclusion

To our knowledge, this is the first small series of patients being treated with trabectedin and monitored using sequential PET imaging demonstrating SUV stabilization in nearly all monitored patients.     

Apple proliferation resistance of <Emphasis Type="Italic">Malus sieboldii</Emphasis>-based rootstocks in comparison to rootstocks derived from other <Emphasis Type="Italic">Malus</Emphasis> species

In three trials carried out over a period of 24 years, open-pollinated seedlings of Malus sieboldii and M. sargentii and 22 apomictic rootstock selections with either M. sieboldii, M. sargentii or M. hupehensis in their parentage were examined for apple proliferation (AP) resistance in comparison to clonal M. x domestica-based rootstocks M 9, M 11, M 13, stocks of the B (Budagovski) and the Polish P series and M. robusta seedlings. Following experimental inoculation or natural infection the Golden Delicious-grafted trees on most of the M. sieboldii-derived progenies showed a high level of AP resistance expressed by low cumulative disease indices, a high percentage of non or little affected trees, low incidence of the small fruit symptom and non or little effect on vigour. Trees on M 9 and M 11, B 118 and M. robusta seedlings were moderately susceptible while trees on progenies with M. sargentii and M. hupehensis parentage, rootstocks of the P series, B 9, B 490 and M 13 proved highly susceptible. The screening also showed that rootstocks with M. sieboldii and M. sargentii parentage are often highly susceptible to latent apple viruses. Trees on most of the M. sieboldii-based progenies were more vigorous than trees on standard stock M 9, whereas the vigour of some progenies from selections with M. sargentii parentage was in the range of M 9 or even lower. Productivity was often correlated with the vigour.     

Herbage yield,essential oil content and composition of three oregano (Origanum vulgare L.) populations as affected by soil moisture regimes and nitrogen supply

To compare the response of oregano (Origanum vulgare L.) populations to soil moisture regimes and nitrogen fertilization, a greenhouse experiment with three populations of oregano cultivated in Germany (O. vulgare var. creticum, O. vulgare ssp. hirtum, O. vulgare var. samothrake) was conducted during 2006–2007 at the research station Rauischholzhausen of Justus Liebig University in Germany. A completely randomized experimental design with three soil moisture regimes (optimal, consistent water deficiency and water deficiency from the beginning of flowering) and two nitrogen fertilization levels with six replications was realized. Dry matter production of population O. vulgare var. samothrake was stable for two experiment years, whereas those of the populations O. vulgare var. creticum and O. vulgare ssp. hirtum were higher in 2007 than in 2006. Among tested populations O. vulgare var. samothrake showed the highest essential oil content in both experiment years. Consistent water deficiency caused reduction of dry matter, but not essential oil content. Water deficiency in flowering stage reduced also dry matter production, but increased essential oil content, resulting in the highest essential oil yield in 2006 and a comparable essential oil yield as control in 2007. Higher nitrogen levels caused an increase in dry matter production of oregano for both experiment years and a decrease in essential oil content in 2007, which can be explained in terms of dilution effect. Totally, 42 compounds were identified in essential oils of three populations by means of GC–MS. Carvacrol was the dominant compound (70.0–77.4%) for all essential oil samples, followed by γ-terpinene (8.1–9.5%) and p-cymene (4.5–5.3%). The composition of essential oil of oregano populations was independent of cultivation conditions. In conclusion, the population of O. vulgare var. samothrake showed a stable dry matter yield with higher essential oil content than the populations of O. vulgare var. creticum and O. vulgare ssp. hirtum. Water deficiency after beginning of blooming (folded flowers) can induce an increase in essential oil content and thus result in higher quality of oregano herbage and higher water use efficiency of oregano plants.     

Spontaneous outcrossing in tomato depends on cultivar and environment and varies between individual flowers

Knowledge about the degree of spontaneous outcrossing of diverse genotypes is essential for breeding programmes, maintenance breeding, and seed production. For tomato (Lycopersicon esculentum Mill.), very limited scientific evidence for genotypic differences is available and evidence from Europe is scarce. To close this knowledge gap, six cultivars were investigated in three Central European locations as part of the Organic Outdoor Tomato Project. To determine outcrossing rates, the monogenetic “cut‐leaf” trait, which is dominant over the “potato‐leaf” trait, was used as morphological marker. The observed range of outcrossing was 0.0%–5.2%. Outcrossing was significantly influenced by cultivar and environment. The outcrossing rate of individual flowers varied within cultivars ranging from 0% to 37%. The potential of newly opened flowers to accept foreign pollen varied largely with the cultivar. Genotypic differences could partly be linked to flower morphology traits. The potential for recombination between tomato genotypes is generally very low but can be a source for new variation in on‐farm management.     

Impact of highly varying seeding densities on grain yield and yield stability of winter rye cultivars under the influence of delayed sowing under sandy soil conditions

The objective of this study was to determine how to establish high and stable yields of winter rye under the impact of highly varying seeding densities and delayed sowing date. A field trial with three winter rye cultivars (two population cultivars and one F1 hybrid) was conducted on a sandy site over a period of three years. The results showed that seeding density, cultivar choice, and annual weather conditions are important factors impacting the yield variability of winter rye. Higher seeding densities led to higher and slightly more stable yields of winter rye. Moreover, a cultivar-adapted seeding date seemed to exploit yield potential advantageously. Interestingly, all three cultivars showed better yield stability with a two-week delay in seeding date. This study suggests that cultivar choice and management practices such as modulation of seeding date and seeding density play an important role in improving the grain yield and yield stability of winter rye.     

Cover Image,Volume 73, Issue 7

The cover image, by Reinhold Siede et al., is based on the Research Article Performance of honey bee colonies under a long‐lasting dietary exposure to sublethal concentrations of the neonicotinoid insecticide thiacloprid ^?, DOI: 10.1002/ps.4547 .