Effects of soil physics,chemistry, and microbiology on soil carbon sequestration in infertile red soils after long-term cultivation of perennial grasses

Determining the effect of perennial energy crop (PEC) cultivation on soil organic carbon (SOC) in marginal land soil is vital for carbon neutrality and bioeconomy development. However, a comprehensive and systematic evaluation of the response of SOC content to different PECs and its underlying drivers is still lacking. We used soil data collected from infertile red topsoil (0–20 cm) after 10 years of cultivation with Miscanthus (MS), Panicum virgatum (SG), and Saccharum arundinaceum (SA) to explore the changes in SOC stock induced by PEC. The roles of physical, chemical, and microbiological factors driving the increase in the SOC stock were investigated. Results revealed that SA and MS enhanced SOC stock by 87.97% and 27.52% relative to the uncultivated control. Conversely, PEC increased the percentage of soil mega-aggregates, geometric mean diameters, soil chelate iron (Fe), and aluminum (Al) oxides, and reduced soil acidity for the infertile red soils. In addition, fungal richness and diversity for PEC soils were enhanced compared to the unplanted soil. It is possible that PEC cultivation reduced the relative abundance of copiotrophic fungi but increased the relative abundance of oligotrophic fungi. Furthermore, variance partitioning analysis revealed that chemical and microbiological factors accounted for 80.54% of the total variation for the SOC stock. The partial least squares path model showed that PEC cultivation enhanced soil carbon (C) stock via soil deacidification and increased soil bacterial function. In conclusion, this study confirms the SOC sequestration potential of PEC cultivation in marginal land and the underlying mechanism driving SOC stock. The main positive factors controlling soil C sequestration included “pH,” while the negative factors were “bacterial community,” “fungal community,” and “bacterial function.” Our research may help encourage and support decision-makers of wasted marginal land conversion to PEC cultivation.     

Effect of aluminum sulfate on litter composition and ammonia emission in a single flock of broilers up to 42 days of age

New alternatives are necessary if the environmental impact linked to intensive poultry production is to be reduced, and different litter handling methods should be explored. Among these, acidifying amendments added to poultry litters has been suggested as a management practice to help reduce the potential environmental effect involved in multiple flock cycles. There have been several studies on the use of aluminum sulfate (alum) and its benefits, but almost no data are available under farm conditions in Europe. An experiment with Ross 308 broilers from 1 to 42 days of age was conducted to evaluate the effect of alum on litter composition, the solubility of some mineral elements and NH₃ emission during a single flock-rearing period in commercial houses located in southeast Spain. Broilers were placed on clean wood shavings in four commercial houses, containing 20 000 broilers each. Before filling, alum was applied at a rate of 0.25 kg/m² to the wood shavings of two poultry houses, whereas the remaining two were used as control. Litter from each poultry house was sampled every 3 to 5 days. Ammonia emissions from the poultry houses were monitored from 37 to 42 days of age. In comparison with the control group, alum treatment significantly reduced the pH level of the litter (P < 0.001) with an average difference of 1.32 ± 0.24 units. Alum-treated litter showed, on average, a higher electrical conductivity than the control litter (5.52 v. 3.63 dS/m). The dry matter (DM) and total N and P contents did not show differences between the treatments (P > 0.05). Regarding the NH₄⁺-N content, alum-treated litter showed a higher value than the untreated litter, with an average difference of 0.16 ± 0.07% (on a DM basis). On average, alum-treated litter had lower water-soluble P, Zn and Cu contents than the untreated litter. Alum noticeably reduced the in-house ammonia concentration (P < 0.001), with an average of 4.8 ppm at 42 days of age (62.9% lower than the control), and ammonia emissions from 37 to 42 days of age were significantly reduced by the alum treatment (P < 0.001), representing a reduction of 73.3%. The lower pH values might have reduced ammonia volatilization from the litter, with a corresponding positive effect on the building environment and poultry health. For these reasons, litter amendment with alum could be recommended as a way of reducing the pollution potential of European broiler facilities during a single flock cycle.     

Effect of soil K, Ca and Mg saturation and endomycorrhization on growth and nutrient uptake of sugar maple seedlings

Nutrient imbalances of declining sugar maple (Acer saccharum Marsh.) stands in southeastern Quebec have been associated with high exchangeable Mg levels in soils relative to soil K and Ca. A greenhouse experiment was set up to test the hypothesis that the equilibrium between soil exchangeable K, Ca, and Mg ions influences the growth and nutrient status of sugar maple seedlings. Also tested was whether endomycorrhization can alter nutrient acquisition under various soil exchangeable basic cations ratios. Treatments consisted of seven ratios of soil exchangeable K, Ca, and Mg making up a total base saturation of 58%, and a soil inoculation treatment with the endomycorrhizal fungus Glomus versiforme (control and inoculated), in a complete factorial design. Sugar maple seedlings were grown for 3 months in the treated soils. Plant shoot elongation rate, dry biomass and nutrient concentrations in foliage were influenced by the various ratios of soil cations. The predicted plant biomass and foliar K concentration were highest at a soil Ca saturation of 38%, a soil K saturation of 12%, and a soil Mg saturation of 8%. Potassium concentration in foliage was dependent on the level of Ca and Mg saturation in the soil when soil K saturation was close to 12%. Foliar Ca and Mg levels were more dependent on their corresponding levels in soil than foliar K. Colonization by G. versiforme did not influence seedling growth and macronutrient uptake. The results confirm that growth and nutrition of sugar maple are negatively affected by imbalances in exchangeable basic cations in soils.     

Seasonal variation of dissolved aluminum concentration in harmonic-type Lake Biwa, Japan

Monthly observations performed on a typical harmonic-type lake, Lake Biwa (latitude 35°15′ N, longitude 136°05′ E, Japan), showed that the particulate aluminum concentration varied around a mean value of 0.8 μM, with occasional extraordinarily high values, whereas the dissolved aluminum concentration varied, in the surface layer of the whole lake, between a minimum of 0.01 μM and a maximum of 0.30 μM, depending on the season. Although the variation in dissolved aluminum paralleled the variation in the pH of the lake water, the variation in dissolved aluminum lagged behind the variation in pH by approximately 1 month. A series of laboratory incubation experiments suggested that the supply of dissolved aluminum from, and its removal by, the suspended particulate matter involved a slow, pH-dependent reaction. The stoichiometry and the apparent equilibrium constant of this reaction were evaluated by adopting a zeolite-like structure for the surfaces of the suspended particulates. Received: December 28, 2000 / Accepted: August 22, 2001     

Soil phosphorus fractions,aluminum, and water retention as affected by microbial activity in an Ultisol

Increased organic matter input into weathered and infertile soils through agricultural techniques such as minimum tillage or agroforestry can improve P availability to crops. Organic matter is an energy source for microbes, and their activity may be responsible in part for increased levels of labile P. The objective of the work reported here was to examine, in a highly weathered Ultisol, the influence of microbial activity in mobilizing P, maintaining it in a plant-available state, and preventing its fixation, and the effect of N and biocides on these processes. Exchangeable aluminum and soil moisture were also determined, since they interact with microbes and soil P.Results showed that increased microbial activity reduced sorption of dissolved and organic P by soil, maintained inorganic P in soluble and labile pools, increased microbial P, decreased mineral P, increased exchangeable Al, and increased water retention. Additions of N and biocides had variable effects, probably due to complex interactions between N, degrading biocides, and microbial populations.