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The agronomic use of compost and biochar as soil amendments may exhibit contrasting results in terms of soil fertility and plant nutrition. The effects of the biennial application of biochar, compost and a blend of compost:biochar (90:10; % dw:dw) on the agronomical performance of an organically managed and well established 25-year-old olive orchard was assessed 5 years after the initial application. The agronomical evaluation was based on the assessment of the soil physical, chemical, and biological characteristics, and the assessment of the soil fertility by both crop production and nutritional status of the orchard, and the bioassay with olive plantlets. Biochar mainly benefited the physical properties (bulk density, total porosity, aeration, water retention capacity) of soil, especially in the top 0–5 cm. Compost and its blend with biochar improved microbial activity, soil nutritional status (increasing the content of soluble organic C, N, and P) and favoured the formation of aggregates in soil. The bioassay conducted with young plantlets confirmed the enhanced soil fertility status in the three amended treatments, particularly in the case of biochar and its blend with compost. However, this effect was not significantly observed in the adult plants after 5 years of application, reflecting the slow response of adult olive trees to changes in fertilization. Based on these results, alongside the desirable long-residence time of biochar in soil and the ready availability of compost, the blend of biochar with compost assayed in this study is defined as a valid strategy for preparing high quality soil organic amendments. [ABSTRACT FROM AUTHOR]

Purpose: Improving crop yields by increasing fertilizer-use-efficiency is essential to minimizing agriculture's environmental impact. Water-dispersible carbon nanomaterials (CNM) have emerged as an innovative material to improve crop yields by increasing nutrient utilization and enhancing crop physiological processes. However, the optimum dose of CNM, performance on crop growth, and impact on soil biochemical properties remain poorly understood. Methods: A greenhouse pot experiment (55 days) was conducted to evaluate the effect of three CNM rates, applied basally as a soil drench amendment, on the growth of two lettuce varieties and soil biochemical properties. We compared three CNM rates (200, 400 & 800 mg kg−1; C200F, C400F & C800F) along with a negative control (C0F0; no fertilizer or CNM) and a positive control (C0F; fertilizer at recommended doses like CNM treatments, no CNM applied). Results: We found that nitrogen (N), phosphorus and potassium (K) accumulation by lettuce and availability in soil were enhanced with CNM application, with 31% (C200F) and 34% (C400F) increases in shoot N accumulation compared to C0F, and K accumulation peaking at C800F (230% increase over C0F). Compared to C0F, soil microbial biomass carbon was 67–180% (C200F) or 42–150% (CF400) higher, phosphatase enzyme activity was 29–32% higher with C200F, and urease enzyme activity was 37–38% higher at C400F, indicating greater soil biological activity at lower application rates. Conclusion: Overall, CNM (200–400 mgkg−1 soil) promoted lettuce growth, enhanced soil fertility and soil biological activity, elucidating that water-dispersible CNM can be an alternative soil amendment to improve crop growth and soil biochemical quality. [ABSTRACT FROM AUTHOR]

Manure composts can improve soil health and crop production, but their application with Trichoderma species has not been well evaluated in amaranth cultivation. This study aimed to determine the effects of manure compost (MC) and MC supplemented with Trichoderma asperellum CHF 78 (MC+CHF 78) on the yield and nutrient uptake of amaranth, as well as on soil properties, under field conditions. Four fertilization treatments, including a control without fertilization, chemical fertilization (CF), MC, and MC+CHF 78, were arranged in a randomized complete block design with six replications in the experimental field. MC and MC+CHF 78 significantly increased the yield of amaranth by 96.2–102% in comparison with CF. In addition, MC and MC+CHF 78 significantly increased the soil pH, soil organic matter, soil available P and exchangeable K, and soil microbial activity compared with those in the control and CF treatments. However, only amaranth plants applied with MC+CHF 78 showed a significantly greater P uptake than those with the control and CF treatments, which may be attributed to the phosphate-solubilizing ability of T. asperellum CHF 78. In conclusion, manure compost fortified with T. asperellum CHF 78 can be used as an alternative to chemical fertilizers for amaranth cultivation. [ABSTRACT FROM AUTHOR]

Modern temperate alley-cropping systems combine rows of trees with rows of crops (agroforestry), which allows for diverse interspecific interactions such as the complementary and competitive use of resources. The complementary use of resources between trees and crops is considered the main advantage of these multifunctional land use systems over cropland monocultures. Moreover, several studies demonstrated that agroforestry systems are environmentally more sustainable than cropland monocultures. Over two decades of research on soil microorganisms in temperate alley-cropping systems are characterized by a variety of different methodological approaches and study designs to investigate the impact of agroforestry on the soil microbiome. Here, we review the available literature on the abundance, diversity, and functionality of soil microorganisms in temperate alley-cropping systems. Further, we identify current knowledge gaps as well as important experimental factors to consider in future studies. Overall, we found that temperate alley-cropping systems increase soil microbial abundance, diversity, and functions as compared to cropland monocultures, which is expected to contribute to enhanced biological soil fertility in these systems. [ABSTRACT FROM AUTHOR]

A 6-year field experiment was conducted to assess the effects of biogas slurry (BS) application on rice yield, soil nutrients, soil microbial activity (MicroResp™) and community composition (16S rRNA gene sequencing) in paddy field in southeast China. The experiment included five treatments: (1) 270 kg N ha−1 from urea (mineral fertilizers only, MF); (2) 135 kg N ha−1 from urea and 135 kg N ha−1 from BS (BS1); (3) 270 kg N ha−1 from BS (BS2); (4) 405 kg N ha−1 from BS (BS3) and (5) 540 kg N ha−1 from BS (BS4). Results showed that no significant differences were found in average rice yield between the MF and BS treatments (BS1–BS4). Both soil available phosphorus (AP) and soil available potassium (AK) increased with an increasing application rate of BS. The average substrate-induced respiration was significantly higher in the treatment with lower rate of BS (BS1 and BS2) than in other treatments and then decreased with increasing application rate of BS. Soil microbial communities were affected by BS application. Chloroflexi, Proteobacteria and Acidobacteria were the dominant bacterial phyla across all soil samples. The BS application resulted in a relative abundance of Nitrospirae 2.6–3.7 times than that in MF. Our results also indicated that AP and AK were the two main factors affecting soil microbial activity and community. Overall, the results suggest that the replacement of chemical fertilizer with BS may be an alternative management practice for improving soil quality, soil fertility and nutrient balance in paddy field. [ABSTRACT FROM AUTHOR]

ABSTRACT The Seridó Desertification Region is a result of inadequate management of the native Caatinga vegetation, which generated degraded areas with little or no capacity for plant production. The area has experienced a succession of different land uses, but little is known about the impact of these changes. The present study tested the hypothesis that the intense degradation of the Caatinga drastically decreased vegetal biomass production, which favored direct soil exposure and resulted in a lower abundance and diversity of species and groups of vegetation as well as microorganisms. This study aimed to quantify some of the main physical, chemical, and microbiological properties of Alfisol ( Luvissolo Crômico órtico lítico ) and Entisol ( Neossolo Litólico eutrófico típico ) under different plant covers in the Seridó Desertification Region, in the municipality of Parelhas, in the state of Rio Grande do Norte (RN), Brazil. Three different areas were studied: an area of preserved Caatinga, a recovery area with jurema [ Mimosa tenuiflora (Willd.) Poir.], and a degraded area. Soil samples were collected from the 0.00-0.10 m soil layer and later characterized in terms of their physical and chemical properties. The microbiological characteristics analyzed were microbial activity (microbial biomass carbon and microbial respiration) and glomalin. The soil under the Caatinga vegetation exhibited better properties than the other analyzed soils. Aggregate stability was the physical property with the highest potential for differentiating between areas. Glomalin, which is associated with the presence of mycorrhizae, and which, in turn, is related to the uptake of P, which is often deficient in these soils, was the most discriminating microbiological variable according to an analysis of canonical variables. The total of Ca2+ and Mg2+ was the most discriminating chemical properties, and played a positive role in soil aggregation, especially Ca2+.

Disposal of ashes from agro-industrial waste has become an important issue that can cause serious environmental problems. These materials may be used in agriculture for soil fertility improvement and carbon sequestration. The effect of applying bagasse ash (BA), rice husk ash (RHA), and RHA mixed with fly ash (MA) to wheat was evaluated on soil organic carbon (SOC) and microbial activity in a loamy sand soil after four years of wheat-rice cropping. BA application resulted in C accrual at 525 kg ha−1y−1in soil, whereas RHA and MA did not have a significant effect. BA increased coarse particulate (cPOC) and mineral-associated organic matter (MinOC) and extractable C pools viz. hot water soluble, potassium permanganate (KMnO4)-oxidizable, easily oxidizable, non-oxidizable, and microbial biomass C. BA application also improved overall microbial and oxidative activity and stimulated fluorescein diacetate (FDA), dehydrogenase, and cellulase enzyme activities in soil. Application of RHA though did not lead to net C sequestration, yet it increased dehydrogenase and cellulase activities. Compared to unamended soil, MA application increased MinOC and FDA activity in soil. After 4 years of their application, none of the ashes adversely influenced soil biological activity expressed in terms of enzyme activities suggesting that these ashes can be disposed to agricultural soils. However, effects of their long-term application on soil biological processes need to be further investigated. [ABSTRACT FROM AUTHOR]

The aim of this study was to evaluate the usefulness of protein hydrolysate (Hemozym) for fertilization purposes used in unpolluted and cadmium-polluted soil. Three levels of Hemozym (0, 0.1, and 0.2 cm3 kg−1dry weight [DW] soil) and cadmium (Cd) rate 5 mg kg−1DW soil were used. The fertilizer value of Hemozym was evaluated based on characteristics of the sorptive complex and soil respiratory activity as well as based on the soil and plant heavy-metal content. Increased soil fertility due to the beneficial effect of Hemozym on the improvement in the physicochemical properties of the soil and its microbial activity. However, they do not allow us to determine unambiguously the effect of this fertilizer on solubility vs. binding of heavy metals that occur naturally in the soil (zinc [Zn], copper [Cu], and lead [Pb]) and of intentionally introduced Cd, in spite of an indicative tendency towards the conversion of metals into poorly soluble forms. [ABSTRACT FROM AUTHOR]

Abstract: Biochar is known to enhance soil fertility and C sequestration, but relatively little information is currently available about its effect on soil microbial community, a component of terrestrial ecosystems that plays a key role in nutrient cycling. This study tested the effects of soil amendment with two loads of wood-derived biochar (30 and 60 t ha−1) in a wheat crop in Tuscany (Italy). Soil samples were collected 3 and 14 months after treatments over two successive growing seasons, and analysed for pH, total organic C (Corg), extractable C (Cext), microbial biomass-C (Cmic), 25 specific microbial activities, mean substrate-induced respiration (mSIR) for 25 substrates, functional microbial diversity and bacterial genetic diversity. No significant effect of biochar treatment was observed on Corg, Cext, Cmic, microbial quotient (Cmic % Corg) or genetic diversity. An increase in mSIR, some specific microbial activities and soil pH, and a significant change in functional diversity were observed 3 months after treatment. In contrast, no effect of biochar was detected 14 months after treatment for the parameters considered, except for a small but significant increase in pH. Our data suggest that biochar addition stimulated soil microbial activity without causing any apparent disturbance, but this positive effect was very short-lived. [Copyright &y& Elsevier]

Abstract: There are plans to vegetate soil of the former lake Texcoco and use wastewater sludge to provide nutrients. However, the Texcoco soil is N depleted, so the amount of N available to the vegetation might be limited and the dynamics of C and N affected. We investigated how emissions of CO2, N2O and N2, and dynamics of mineral N were affected when different types of N fertilizer, i.e. NH4 +, NO3 −, or unsterilized or sterilized wastewater sludge, were added to the Texcoco soil. An agricultural soil served as control. Sewage sludge added to an alkaline saline soil (Texcoco soil) induced a decrease in concentrations of NH4 + and NO3 −. Addition of sewage sludge increased the CO2 emission rate>two times compared to soil amended with sterilized sludge. The NH4 + concentration was lower when sludge was added to an agricultural soil for the first 28 days and in the Texcoco soil for 56 days compared to soil amended with sterilized sludge. Production of N2O in the agricultural soil was mainly due to nitrification, even when sludge was added, but denitrification was the main source of N2O in the Texcoco soil. Microorganisms in the sludge reduced N2O to N2, but not the soil microorganisms. It was found that microorganisms added with the sludge accelerated organic material decomposition, increased NH4 + immobilization, and induced immobilization of NO3 − (in Texcoco soil). These results suggest that wastewater sludge improves soil fertility at Otumba (an agricultural soil) and would favour the vegetation of the Texcoco soil (alkaline saline). [Copyright &y& Elsevier]

The forest-steppe ecotone in NW Patagonia is a semiarid ecosystem affected by natural and anthropogenic fires, and overgrazing by sheep. Following a wild fire in the driest portion of this ecotone, a 3-year study was conducted to assess the impacts of a single application of inorganic and organic fertilizers on soil and vegetation recovery. Organic fertilizers were composts derived from biosolids and municipal solid wastes. Six treatments were evaluated: screened and unscreened biosolids compost and municipal solid wastes compost (40 Mg ha−1), inorganic fertilizer (100 kg N and 35 kg P ha−1), and no application. Soils were chemically characterized, and soil microbial activity was assessed as potential respiration and N-mineralization. Vegetation responses included plant cover, composition, phytomass, and N resorption prior to abscission, and leaf litter quality of the dominant species. Organic fertilizers increased soil organic matter, nutrients and microbial activity. Plant cover and aboveground phytomass, dominated by the native perennial tussock grass Poa ligularis, showed a higher increase with inorganic than with organic fertilization. While vegetation responded more to inorganic fertilizer, due to its higher initial pulse of available N, organic fertilizers had a positive impact on soil chemical and biological properties. [ABSTRACT FROM AUTHOR]

An incubation test was conducted to study the effects of antibiotics oxytetracycline on the μbial number and activity in three soils varied with fertility level under the conditions with or without pig manure application. The soils were injected with six concentrations (0, 0.1, 1, 10, 100, and 1000 mg×kg-1) oxytetracycline, and incubated for 30 d at 25 degrees C. Soil samples were collected on the 1st, 4th, and 30th day of incubation to measure the bacterial number, respiratory activity, and enzyme activity. Under no pig manure application, oxytetracycline had little effects on the soil bacterial number and activity. The EC10 values of oxytetracycline based on a 10% decrement of bacterial number, respiratory activity, enzyme activity, and NO3--N concentration in treatment without pig manure were 36-1000 mg×kg-1, 20-1000 mg×kg-1, and 4-1000 mg×kg-1 for S1, S2 and S3, while those in treatment with pig manure application were 2-656 mg×kg-1, 2-81 mg×kg-1, and 1-42 mg×kg-1 for S1, S2 and S3, respectively. Soil fertility level had obvious effects on the dose-response relations between oxytetracycline and soil μbial number and activity. The effects of oxytetracycline on soil μbial number and activity increased with increasing soil fertility level, and the effects on μbial number and respiratory activity were higher than those on enzyme activity and NO3--N concentration. The effects of oxytetracycline on soil μbial number and activity were time-depending, being the greatest on the 4th day of incubation. Overall speaking, oxytetracycline could exert temporary inhibition on soil μbes. [ABSTRACT FROM AUTHOR]

Abstract: Microcalorimetric technique was used to investigate the effects of balanced versus nutrient-deficiency fertilization on soil microbial activity in a long-term (19-year) fertilizer experiment. The number of microorganisms in soils was measured by viable cell count, and the power-time curves were recorded for soil samples supplemented with glucose and ammonium sulphate, also with or without sodium dihydrogen phosphate for P-deficiency fertilization. Both the bacterial and the fungal populations were significantly higher (P < 0.05) under balanced fertilization than under nutrient-deficiency fertilization. The microbial activity presented by heat dissipation per cell unit indicated that microorganisms under balanced fertilizer treatments had more efficient metabolism, while decreased microbial activity under nutrient-deficiency treatments was firstly due to soil available P, followed by N and K (P < 0.05). In addition, microbial growth in soils under P-deficiency fertilization was stimulated by adding available P, while the lower growth rate, less peak heat, and longer peak time all indicated the low activity of soil microorganisms. We emphasize the importance of balanced fertilization, as well as the role of available P, in maintaining and promoting soil microbial activity. [Copyright &y& Elsevier]

In agriculture, the use of soil biodegradable mulch films could represent an eco-friendly alternative to conventional plastic films. However, soil biodegradable mulch films incorporated into the soil through tillage, being not only a physical but also a biogeochemical input, is expected to influence the soil quality by affecting its functions. Therefore, the eco-compatibility of these biodegradable plastics needs to be evaluated for their impact on different soil functions. To understand the effect of biodegradable plastics on soil quality (i.e. microbial biomass, nitrogen cycle, and activity of soil enzymes involved in the biochemical processes of carbon and nitrogen), we added increasing quantities of biodegradable plastics in two different soils: a loamy (Cambisol) and sandy (Arenosol) soil. The results highlight that the carbon added through the biodegradable plastics influenced the processes linked to carbon and nitrogen cycles. Significant effects were observed mainly with the highest dose of biodegradable plastics added (1%), resulting in a higher growth of microbial biomass, increased carbon mineralisation, and increased immobilisation of available nitrogen. The results also underline the importance of evaluating the impact of biodegradable plastics in different soils because all the processes considered are also influenced also by soil physicochemical characteristics. [Display omitted] • Biodegradable mulch films as eco-friendly alternative in agriculture • Biodegradable mulch films incorporation could affect soil functionality. • Significant impact of biodegradable plastics on soil microbial biomass and activity • Biodegradable plastics influenced the processes linked to soil C, N and P cycles. • Importance of considering soils with distinct characteristics [ABSTRACT FROM AUTHOR]

The measurement of soil carbon dioxide (CO2) respiration is a means to gauge biological soil fertility. Test methods for respiration employed in the laboratory vary somewhat, and to date the equipment and labor required have limited more widespread adoption of such methodologies. A new method to measure soil respiration was tested along with the traditional alkali trap and titration method. The new method involves the Solvita gel system, which was originally designed for CO2 respiration from compost but has been applied in this research to soils with treatments of increasing dairy manure compost. The objectives of this research are to (1) examine the relationship between the CO2 release after 1 day of incubation from soils amended with dairy manure compost that have been dried and rewetted as determined using the titration method and the Solvita gel system, and (2) compare water-soluble organic nitrogen (N), as well as carbon (C), N, and phosphorus (P) mineralization after 28 days of incubation with 1-day CO2 release from the titration method and Solvita gel system. One-day CO2 from both titration and the Solvita gel system were highly correlated with cumulative 28-day CO2 as well as the basal rate from 7-28 days of incubation. Both methods were also highly correlated with 28-day N and P mineralization as well as the initial water-extractable organic N and C concentration. The data suggest that the Solvita gel system for soil CO2 analysis could be a simple and easily used method to quantify soil microbial activity and possibly provide an estimate of potential mineralizable N and P. Once standardized soil sampling and laboratory analysis protocols are established, the Solvita method could be easily adapted to commercial soil testing laboratories as an index of soil microbial activity. [ABSTRACT FROM AUTHOR]

Abstract: Conservation tillage (no-till and reduced tillage) brings many benefits with respect to soil fertility and energy use, but it also has drawbacks regarding the need for synthetic fertilizers and herbicides. Our objective was to adapt reduced tillage to organic farming by quantifying effects of tillage (plough versus chisel), fertilization (slurry versus manure compost) and biodynamic preparations (with versus without) on soil fertility indicators and crop yield. The experiment was initiated in 2002 on a Stagnic Eutric Cambisol (45% clay content) near Frick (Switzerland) where the average annual precipitation is 1000mm. This report focuses on the conversion period and examines changes as tillage intensity was reduced. Soil samples were taken from the 0–10 and 10–20cm depths and analysed for soil organic carbon (C org), microbial biomass (C mic), dehydrogenase activity (DHA) and earthworm density and biomass. Among the components tested, only tillage had any influence on these soil fertility indicators. C org in the 0–10cm soil layer increased by 7.4% (1.5g C org kg−1 soil, p <0.001) with reduced tillage between 2002 and 2005, but remained constant with conventional tillage. Similarly, C mic was 28% higher and DHA 27% (p <0.001) higher with reduced than with conventional tillage in the soil layer 0–10cm. In the 10–20cm layer, there were no significant differences for these soil parameters between the tillage treatments. Tillage had no significant effect on total earthworm density and biomass. The abundance of endogeic, horizontally burrowing adult earthworms was 70% higher under reduced than conventional tillage but their biomass was 53% lower with reduced tillage. Wheat (Triticum aestivum L.) and spelt (Triticum spelta L.) yield decreased by 14% (p <0.001) and 8% (p <0.05), respectively, with reduced tillage, but sunflower (Helianthus annuus L.) yield was slightly higher with reduced tillage. Slurry fertilization enhanced wheat yield by 5% (p <0.001) compared to compost fertilization. Overall, C org, C mic, and DHA improved and yields showed only a small reduction with reduced tillage under organic management, but long-term effects such as weed competition remain unknown. [Copyright &y& Elsevier]

Temperate pastures are often managed with P fertilizers and N2-fixing legumes to maintain and increase pasture productivity which may lead to greater nitrous oxide (N2O) emissions and reduced methane (CH4) uptake. However, the diel and inter-daily variation in N2O and CH4 flux in pastures is poorly understood, especially in relation to key environmental drivers. We investigated the effect of pasture productivity, rainfall, and changing soil moisture and temperature upon short-term soil N2O and CH4 flux dynamics during spring in sheep grazed pasture systems in southeastern Australia. N2O and CH4 flux was measured continuously in a High P (23 kg P ha−1 yr−1) and No P pasture treatment and in a sheep camp area in a Low P (4 kg P ha−1 yr−1) pasture for a four week period in spring 2005 using an automated trace gas system. Although pasture productivity was three-fold greater in the High P than No P treatment, mean CH4 uptake was similar (−6.3 ± SE 0.3 to −8.6 ± 0.4 μg C m−2 hr−1) as were mean N2O emissions (6.5 to 7.9 ± 0.8 μg N m−2 hr−1), although N2O flux in the No P pasture did not respond to changing soil water conditions. N2O emissions were greatest in the Low P sheep camp (12.4 μg ± 1.1 N m−2 hr−1) where there were also net CH4 emissions of 5.2 ± 0.5 μg C m−2 hr−1. There were significant, but weak, relationships between soil water and N2O emissions, but not between soil water and CH4 flux. The diel temperature cycle strongly influenced CH4 and N2O emissions, but this was often masked by the confounding covariate effects of changing soil water content. There were no consistently significant differences in soil mineral N or gross N transformation rates, however, measurements of substrate induced respiration (SIR) indicated that soil microbial processes in the highly productive pasture are more N limited than P limited after >20 years of P fertilizer addition. Increased productivity, through P fertilizer and legume management, did not significantly increase N2O emissions, or reduce CH4 uptake, during this 4 week measurement period, but the lack of an N2O response to rainfall in the No P pasture suggests this may be evident over a longer measurement period. This study also suggests that small compacted and nutrient enriched areas of grazed pastures may contribute greatly to the overall N2O and CH4 trace gas balance. [ABSTRACT FROM AUTHOR]