Climate change will alter precipitation patterns with consequences for soil C cycling. An understanding of how fluctuating soil moisture affects microbial processes is therefore critical to predict ...responses to future global change. We investigated how long‐term experimental field drought influences microbial tolerance to lower moisture levels (“resistance”) and ability to recover when rewetted after drought (“resilience”), using soils from a heathland which had been subjected to experimental precipitation reduction during the summer for 18 years. We tested whether drought could induce increased resistance, resilience, and changes in the balance between respiration and bacterial growth during perturbation events, by following a two‐tiered approach. We first evaluated the effects of the long‐term summer drought on microbial community functioning to drought and drying–rewetting (D/RW), and second tested the ability to alter resistance and resilience through additional perturbation cycles. A history of summer drought in the field selected for increased resilience but not resistance, suggesting that rewetting after drought, rather than low moisture levels during drought, was the selective pressure shaping the microbial community functions. Laboratory D/RW cycles also selected for communities with a higher resilience rather than increased resistance. The ratio of respiration to bacterial growth during D/RW perturbation was lower for the field drought‐exposed communities and decreased for both field treatments during the D/RW cycles. This suggests that cycles of D/RW also structure microbial communities to respond quickly and efficiently to rewetting after drought. Our findings imply that microbial communities can adapt to changing climatic conditions and that this might slow the rate of soil C loss predicted to be induced by future cyclic drought.
Climate change will increase the intensity of drought and rainfall events. We investigated whether a history of drought affected the ability of soil microorganisms to withstand low moisture availability during drought (“resistance”) and recover quickly when soil was rewetted again (“resilience”). Using soils which had been exposed to an experimental summer drought for 18 years, we found that a history of drought did not affect microbial resistance to low moisture, but did lead to a faster recovery upon rewetting. These findings suggest that historical climate will be important in shaping microbial responses to future climate change.
•Yield responses to biochar persisted for 10 years, or 20 growing seasons.•Variability in grain yield decreased when biochar and fertiliser were combined.•Maximum recovery of carbon from biochar in ...the top 20 cm was 60% after 10 years.•Biochar can be a valuable component of integrated soil fertility management.
Application of biochar has been shown to increase soil fertility and enable soil carbon sequestration, indicating potential for agricultural and environmental benefits from using locally produced biochar on African smallholder farms. However, previous studies have been rather short-term and little is known about the longer-term effects of biochar application on crop yields. Biochar contains ash, but the potential liming effect and nutrient release from ash may be short-lasting. To investigate long-term effects, we set up a series of field trials replicated at three sites in Kenya in 2006. The trials are still on-going and are possibly the longest biochar trials in sub-Saharan Africa. Here, we report effects on crop yield and soil properties over 10 years after applying biochar, produced mainly from Acacia spp., at a rate of 50 + 50 Mg ha−1 during the first two seasons. Maize (Zea mays) and soybean (Glycine max) were grown in rotation, with or without inorganic fertiliser, and crop yield was monitored. For comparison of soil properties, additional plots were kept in bare fallow. Biochar addition slightly increased soil porosity, pH, plant-available phosphorus and soil water-holding capacity. Crop yield responded positively to biochar at all sites and yield responses were similar with and without mineral fertiliser, i.e., the effects of biochar and mineral fertiliser were additive. The seasonal yield increase due to biochar application was in average around 1.2 Mg ha−1 for maize and 0.4 Mg for soybean, independently of fertilisation, over seasons and sites. Application of mineral fertiliser to maize increased maize yield by 1.6 Mg ha−1 and the subsequent, unfertilized soybean yield by 0.6 Mg ha−1, illustrating a carry-over effect. Most importantly, the effect on maize and soybean yield of adding biochar to soil persisted over the whole 10-year period. Analysis of the carbon (C) balance in topsoil indicated that about 40% of biochar C was apparently lost through mineralization, erosion or vertical translocation. Moreover, changes in soil carbon/nitrogen ratios indicated that biochar application increased nitrogen mineralization from native soil organic matter.
Fertilized agricultural soils can be a major source of soil nitrous oxide (N2O) emissions to the atmosphere. Conservative soil management may have the ability to reduce N2O emissions through ...affecting a number of N-cycling-related soil biophysical properties. Using in situ N2O measurements combined with the techniques of quantitative polymerase chain reaction (qPCR), amplicon sequencing, and metagenomic sequencing, we aimed to understand the effects of long-term (>10 y) conservation tillage (i.e., zero- and chisel-till vs. conventional plow-till) on soil N2O production and associated microbial guilds following inorganic N fertilizer application in maize. Between 2017 and 2019, continuous in situ measurements of N2O fluxes indicated that both zero- and chisel-till significantly lowered cumulative emissions within the growing season, compared to plow-till, mainly through shortening the duration and reducing the magnitude of post-fertilization emission events. Conservative soil management, in particular zero-till, consistently increased the Shannon diversity index of bacterial community over the growing season, compared with plow-till. High-frequency qPCR analyses further revealed a clear tillage-induced niche differentiation between nosZI- and nosZII-N2O reducers, as evidenced by the dominant gene abundance of nosZII compared to nosZI in the conservation tillage soil, which eventually probably contributed to the transformation of N2O to N2. Moreover, compared to plow-till, zero-till significantly decreased gene abundances involved in N2O production including the nirS, nirK, and narG genes, but increased abundances of N2O reduction genes such as nosZ during peak N2O emissions. Critically, the abundances of detected species involved in denitrification, such as Deltaproteobacteria_bacterium spp. and Alphaproteobacteria_bacterium spp. were clearly inhibited by zero-till. Overall, the reduced soil N2O emissions under reduced tillage positively and strongly depended on the nosZI-to-nosZII ratio, while increased emissions due to conventional tillage were positively associated with intensified denitrification. Such improvements in understanding of the responses of N-cycling gene abundances to tillage intensity can certainly help in the development of updated soil management practices and adaptative N application strategies to reduce reactive N emissions in agricultural ecosystems.
•Conservation tillage shortened the duration and lowered the magnitude of post-fertilization N2O emissions.•nosZI, and nosZII genes suggested a tillage-induced niche differentiation among N2O reducers.•Conservation tillage decreased abundance of genes involved in N2O production.•The reduced N2O emissions were mainly attributed to the low nosZI-to-nosZII ratio.•Intensified denitrification resulted in higher emissions of N2O under conventional tillage soil.
Unsustainable agricultural management practices such as non-conservationist tillage and overuse of fertilizers result in soil acidity and, in turn, soil degradation due to reduced carbon (C) ...concentrations and nutrient availability and increased aluminum toxicity. Application of lime (L) and phosphogypsum (PG) can overcome these constraints and improve soil quality, but the long-term effects of these amendments on both abiotic and biotic soil properties are not known, particularly when applied in combination. Here, we evaluated the effects of L (acidity corrective), PG (soil conditioner), and their combination (LPG) on soil organic matter (SOM) transformations, soil chemical and physical properties, and microbiome assembly in a long-term experiment under a no-till crop rotation system in a tropical soil. The Ca-based soil amendments increased C concentrations (labile and stable fractions), improved soil physicochemical properties, and changed the associations between several bacterial and fungal groups. Contrary to expectations, the acidic soil amended with PG exhibited greater number of significant shifts in the bacterial community than soil amended with L or LPG, as well as higher soil bulk density. By contrast, the fungal community underwent greater shifts in soil amended with L or LPG, which had higher macroporosity. L and LPG amendment shaped the fungal community and rearranged the SOM fractions at similar rates, suggesting an essential role of the altered fungi in SOM transformation. In addition, combining L with PG increased the relevance of many low-abundance microorganisms, especially fungi, compared with the control, indicating an increase in their ecological role in the soil. Finally, by applying general joint attribute modeling and sensitivity analysis, we determined that soil fertility increased most in LPG-amended soil, as the ensuing changes in the bacterial and fungal communities resulted in improved SOM fractions, soil physical characteristics and, ultimately, soil quality.
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•Lime + Phosphogypsum (LPG) increased labile and stable C fractions.•LPG synergistically changed soil quality in long-term no-till intercropping system.•LPG increases soil fertility promoting changes in the soil microbiome.•The changed microbiome improves SOM fractions and soil physical characteristics.•LPG legacy increases the abundance of rare fungi.
Optimizing irrigation strategies to increase water utilization efficiency and achieve higher yield is vital for balancing groundwater use and improving food security during water shortage in the ...North China Plain (NCP). Based on a 16-year field experiment (2003–2018) using seven irrigation schedules from W0M0 to W4M3 (numbers are irrigation times in wheat (W) and maize (M) season, 75 mm each) in the winter wheat–summer maize double cropping system, we analyzed annual total water consumption (ETa) and groundwater table change in terms of net groundwater depletion, annual total grain yield, water productivity (WP), irrigation water productivity (IWP) and marginal benefit of the whole wheat–maize system. Relationship between yield or WP and irrigation or ETa were also revealed. Results showed that (1) total ETa increased as irrigation input increased, ranging from 427.3 mm (Rainfed, W0M0) to 891.0 mm (W4M3). Soil water storage contributed nearly 30% to ETa for winter wheat under water deficit conditions. Pre-sowing soil water storage played an important role in improving the annual yield and WP of both wheat and maize by promoting germination, seedling emergence and root growth; (2) the rainfed treatment (W0M0) was best for mitigating the groundwater table decline (0.1 m yr-1), followed by W1M1 (0.5 m yr-1) and W2M1 (0.8 m yr-1). Groundwater table decline in M2W2 almost overlapped the observed data at the station (1.1 m yr-1). In W3M2, the farmers’ traditional practice, the groundwater table declined by 1.4 m yr-1, obviously over exploitation, while W4M2 and W4M3 declined by almost 2.0 m yr-1; (3) the relationship between total annual yield and irrigation (or ETa) followed a quadratic curve. Total annual yield significantly increased from W0M0 to M1W1 (25%) to M2M1 (5%) and then kept stable. Average annual WP decreased as irrigation increased, from 2.4 kg m-3 (W0M0) to 1.6 kg m-3 (W4M3). Average annual IWP and marginal benefit also declined as irrigation increased. These results over 16 years indicated that the W2M1 is the most balanced irrigation regime for wheat– maize rotation to mitigate groundwater decline, maintain grain production, and improve water use efficiency in the NCP.
●A 16-year field experiment of seven irrigation regimes for wheat-maize was conducted.●ETa increased and water productivity decreased with increasing irrigation amount.●W2M1 was the best optimized irrigation regime for balancing groundwater use and yield.
Mid‐term (MTEs, 5–20 years) and long‐term (LTEs, 20+ years) field experiments are key sources of information to design future climate‐smart agriculture. Within the European Joint Program SOIL (EJP ...SOIL), we built the EJP SOIL‐MTE/LTE metadataset that contains metadata from 240 MTEs/LTEs across Europe. Metadata collected included precise descriptions of the treatments (combination of factors such as tillage, crop type/rotation, amendments/fertilizers, grazing and pest/weed management), soil and crop measurements and pedo‐climatic information. Using different figures and dashboards, an overview of those MTEs/LTEs is presented and specific research themes (tillage systems, residue management, amendment type and cover crops) are further analysed within their pedo‐climatic context. An interactive web portal developed in collaboration with the BonaRes project (https://lte.bonares.de), enables users to explore the metadataset and find relevant MTEs/LTEs for specific combinations of practices (e.g. all MTEs/LTEs that investigate cover crops on a Cambisol in no‐tillage system). Finally, a SWOT (Strengths, Weaknesses, Opportunities, Threats) analysis of the metadataset was carried out to highlight the potential contribution of MTEs/LTEs to a harmonized European soil observation and monitoring approach. We propose that the metadataset could be elaborated with metadata from other existing MTEs/LTEs in Europe or even worldwide.
Biochar is produced from a wide range of organic materials by pyrolysis, specifically for improvement of poor quality soils. One of the main issues nowadays in studying biochar as soil amendment is ...to upscale experiments and move from short-term, laboratory conditions to long-term field trials.
This paper presents a long-term field study, being the final step of a scale-up technology development, on grain husk and paper fibre sludge biochar application for soil improvement with focus on two degraded soil types of a temperate region. The effects of biochar on an acidic and a calcareous sandy agricultural soil were studied applying a complex approach including physico-chemical, biological and ecotoxicological methods. Our study demonstrated that the applied biochar had positive direct and indirect influences on the acidic sandy soil, but these effects were different in terms of extent and time. 30 t/ha biochar addition improved the pH of the acidic sandy soil by 24% and also increased significantly the nutrient concentrations (P2O5 by 68%, K2O by 11% and organic matter by 33%), and the water-holding capacity after 30 months. Furthermore, biochar addition improved also the microbiological activity and diversity in the acidic sandy soil. Biochar application did not induce any negative effects. Biochar had no toxic effect on the plants and the biochar-treated soil provided a more liveable habitat for soil living animals than the untreated acidic sandy soil.
The favourable biochar-mediated influences on soil properties were manifested mainly in the acidic sandy soil, proving that the biochar-related advantages have to be verified for different soil types. The benefits of grain husk and paper fibre sludge biochar application in an acidic sandy soil were confirmed on the long term by the applied tiered approach.
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•Long-term positive effects of grain husk and paper fibre sludge biochar was proved.•Effect of biochar in soils was dependent on soil pH, OM and carbonate content.•0.5% and 1% biochar addition had favourable effects mainly in the acidic sandy soil.•Long-term positive effect of biochar on the availability of P and K was revealed.•Biochar increased microbiological activity and provided good habitat for white worm.
•Higher mineral N fertilisation led to more stable wheat yields.•Mineral P and K supply resulted in minor effects on yield stability of wheat.•Additional application of manure has a stabilising ...effect on wheat yields.
It is well known that a balanced nutrient supply ensures high crop yields and stable cropping systems. In comparison, little is known about the influence of different fertilisation regimes on the yield stability of crops. Therefore, the objective of this study was to identify the impact of mineral and organic fertilisation supplied in different combinations (P + K/N + P/N + K/N + P + K) and levels (50%/100%/100% + manure) on the stability of the winter wheat grain yield. A long-term fertilisation field experiment at Giessen University (Germany, temperate climate, silty clay), established in 1956 with a multifactorial set up, was used. For an accurate stability analysis that matches the experimental design, we subjected the data to a mixed model analysis based on the restricted maximum likelihood (REML) method calculating Shukla‘s stability variance and Finlay–Wilkinson regression and performing Eskridge's risk analysis. It was found that without any nutrient supply, the wheat yields exhibited high annual variability and only modest stability. A similar pattern was identified for the fertiliser combination of the minerals P + K. The combinations containing mineral N showed a significant improvement in yield stability in which N + P and N + K are almost identical. In all fertilisation variants, the additional supply of manure stabilised the wheat yields. The mineral supply of N + P + K with additional manure provided the best yield stability and lowest agronomic risk for yield failure.
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•30 t ha−1 of biochar decreased native SOC, but inverse in 60 t ha−1 and 90 t ha−1.•Biochar content was higher in aggregates with larger size.•Increase in biochar rate increased ...proportion of aggregates of 2000–1000 μm.•Changed wheat-derived SOC accounted for native SOC content variation in aggregates.
Soil aggregates play an important function in soil carbon sequestration because larger aggregates have higher soil organic carbon contents. A field experiment was set up in 2009 that included four treatments, i.e., B0, B30, B60, and B90 representing biochar application rates of 0, 30, 60, and 90 t ha−1, respectively. In 2017, we investigated the soil aggregate distribution, biochar and n-SOC contents in soil and different aggregate sizes using the ignition method, as well as the contribution of wheat and maize residues to n-SOC content in each aggregate by isotopic analysis. The results showed that, relative to B0, the n-SOC content presented an 14.0% decrease in B30, compared with an 18.8% and 8.2% increase in B60 and B90 (p < 0.05), respectively. Furthermore, the decreased n-SOC content in B30 was due to the decreased proportions of < 53 μm and 1000–250 μm aggregates. The increased n-SOC content in B60 was due to the significantly enhanced proportion of 2000–1000 μm and 1000–250 μm aggregates because the n-SOC contents of these two aggregates size classes were not changed by biochar. However, in B90, the increased n-SOC content was ascribed to the enhanced proportions of 2000–1000 μm and < 53 μm aggregates, although the n-SOC content in 2000–1000 μm aggregate was significantly decreased by biochar. Further analysis showed that the decreased n-SOC content in 2000–1000 μm aggregates was associated with decreased wheat-derived n-SOC content. In synthesis, our study showed a long-term effect of biochar on the n-SOC content by mainly changing soil aggregation and native organic carbon derived from wheat residue, and this effect was dependent on the applied amount. The biochar rate of 60 t ha−1 is recommended for carbon sequestration in terms of the more pronounced negative priming of native SOC, while the feasible combination between other biochars and soils needs further clarification.
Global climate change and decreases in available land are significant challenges that humans are currently facing. Alternative management approaches for sugarcane fields have great potential to help ...mitigate these problems in China. We hypothesized that soybean intercropping with reduced nitrogen input could increase crop productivity and reduce the carbon footprint (CF) of sugarcane fields in China. Therefore, a long-term field experiment from 2009 to 2017 in the Pearl River Delta of China was chosen to test this hypothesis. The results showed that the energy yields of sugarcane/soybean intercropping systems were 17.8%–39.4% higher than those of sugarcane monocropping systems. The energy yields of the same cropping systems using conventional and reduced N inputs (525 kg ha−1 and 300 kg ha−1) did not show a significant difference. Additionally, the CF values of the unit yield (CFY) for sugarcane/soybean intercropping were 3.2%–30.4% lower than those of the monocropping systems, showing the higher CF efficiency of the intercropping pattern, although the difference was not significant. The CF of the unit area (CFA) and the CFY of all the cropping patterns at the conventional N level were 19.5%–62.0% higher than that at the reduced N level, demonstrating that reducing the nitrogen input could significantly lower the CF of the sugarcane fields. In addition, the high N level cased negative effects in terms of increasing the crop productivity and reducing the CF of the soybean/sugarcane intercropping pattern. In conclusion, sugarcane/soybean intercropping with reduced N input improved crop productivity while lowering the CF of sugarcane fields in China. The sugarcane/soybean (1:2) intercropping with 300 kg N ha−1 system showed the best benefits in the Pearl River Delta of China. These advanced agricultural practices contributed to improved farmland use efficiency and clean production in an agricultural system.
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•Yield and CF of soybean/sugarcane intercropping with two N levels are analyzed.•A field experiment carried out for 9 years in China was studied.•Soybean/sugarcane intercropping significantly improves crop productivity.•Reduced N practice significantly decreases CF of sugarcane field.
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