Search

Digestate, a by-product of biogas production, is widely recognized as a promising renewable nitrogen (N) source with high potential to replace synthetic fertilizers. Yet, inefficient digestate use can lead to pollutant N losses as ammonia (NH 3) volatilization, nitrous oxide (N 2O) emissions and nitrate ((Figure presented.)) leaching. Cover crops (CCs) may reduce some of these losses and recycle the N back into the soil after incorporation, but the effect on the N balance depends on the CC species. In a one-year field study, we tested two application methods (i.e., surface broadcasting, BDC; and shallow injection, INJ) of the liquid fraction of separated co-digested cattle slurry (digestate liquid fraction [DLF]), combined with different winter cover crop (CC) options (i.e., rye, white mustard or bare fallow), as starter fertilizer for maize. Later, side-dressing with urea was required to fulfil maize N-requirements. We tested treatment effects on yield, N-uptake, N-use efficiency parameters, and N-losses in the form of N 2O emissions and (Figure presented.) leaching. CC development and biomass production were strongly affected by their contrasting frost tolerance, with spring-regrowth for rye, while mustard was winter killed. After the CCs, injection of DLF increased N 2O emissions significantly compared with BDC (emission factor of 2.69% vs. 1.66%). Nitrous oxide emissions accounted for a small part (11%–13%) of the overall yield-scaled N losses (0.46–0.97 kg N Mg grain −1). The adoption of CCs reduced fall (Figure presented.) leaching, being 51% and 64% lower for mustard and rye than under bare soil. In addition, rye reduced (Figure presented.) leaching during spring and summer after termination by promoting N immobilization, thus leading to −57% lower annual leaching losses compared with mustard. DLF application method modified N-loss pathways, but not the cumulative yield-scaled N losses. Overall, these insights contribute to inform an evidence-based design of cropping systems in which nutrients are recycled more efficiently.

Organic and mineral fertilizers are important sources of ammonia (NH3 ) emissions from agricultural fields. The objectives of this study were (a) to evaluate how different cover crop (CC) residues (i.e., rye [Secale cereale L.], white mustard [Sinapis alba L.], and bare soil as control) in combination with different application methods of digestate (surface broadcast vs. shallow injection) affect NH3 volatilization before planting maize (Zea mays L.) and (b) to assess the residual effect of previous CCs on NH3 volatilization after urea top-dress application at the V5-V6 phonological stage of maize. Ammonia volatilization was measured using semi-static chambers for 14 d (335 h) after planting and for 6 d (150 h) at the V5-V6 stage. Overall, NH3 emissions decreased by 67-77% with digestate injection compared with surface broadcasting. However, the reduction in NH3 volatilization using the injection method was significantly lower with mustard residue (6.72 kg NH3 -N ha-1 ) than with rye residue (14.15 kg NH3 -N ha-1 ), which allowed for more volatilization by increasing the exposure of digestate to the air. Broadcast digestate method did not affect the cumulative NH3 -N losses obtained with different CC types. After urea top-dressing at the V5-V6 stage of maize, the cumulative losses of NH3 (during 150 h) were 2.99 kg NH3 -N ha-1 with rye as previous CC and 2.49 kg NH3 -N ha-1 with mustard. Our study shows that digestate injection before maize planting and urea top-dressing application followed immediately by irrigation (15 mm) could be considered as useful strategies to mitigate NH3 volatilization and increase N use efficiency in maize.

Co-inoculation of arbuscular mycorrhizal fungi (AMF) and bacteria can synergically and potentially increase nitrogen use efficiency (NUE) in plants, thus, reducing nitrogen (N) fertilizers use and their environmental impact. However, limited research is available on AMF-bacteria interaction, and the definition of synergisms or antagonistic effects is unexplored. In this study, we adopted a response surface methodology (RSM) to assess the optimal combination of AMF (

Plant Biostimulants (BSs) are a valid supplement to be considered for the integration of conventional fertilization practices. Research in the BS field keeps providing alternative products of various origin, which can be employed in organic and conventional agriculture. In this study, we investigated the biostimulant activity of the eluate obtained as a by-product from the industrial production of lactic acid bacteria on bare agricultural soil. Eluates utilization is in line with the circular economy principle, creating economical value for an industrial waste product. The research focused on the study of physical, chemical, biochemical, and microbiological changes occurring in agricultural soil treated with the biowaste eluate, applied at three different dosages. The final aim was to demonstrate if, and to what extent, the application of the eluate improved soil quality parameters and enhanced the presence of beneficial soil-borne microbial communities. Results indicate that a single application at the two lower dosages does not have a pronounced effect on the soil chemical parameters tested, and neither on the biochemical proprieties. Only the higher dosage applied reported an improvement in the enzymatic activities of β-glucosidase and urease and in the chemical composition, showing a higher content of total, nitric and ammonia N, total K, and higher humification rate. On the other hand, microbial communities were strongly influenced at all dosages, showing a decrease in the bacterial biodiversity and an increase in the fungal biodiversity. Bioinformatic analysis revealed that some Operative Taxonomic Units (OTUs) promoted by the eluate application, belong to known plant growth promoting microbes. Some other OTUs, negatively influenced were attributed to known plant pathogens, mainly Fusarium spp. Finally, the ecotoxicological parameters were also determined and allowed to establish that no toxic effect occurred upon eluate applications onto soil.

Seed inoculation with beneficial microorganisms has gained importance as it has been proven to show biostimulant activity in plants, especially in terms of abiotic/biotic stress tolerance and plant growth promotion, representing a sustainable way to ensure yield stability under low input sustainable agriculture. Nevertheless, limited knowledge is available concerning the molecular and physiological processes underlying the root-inoculant symbiosis or plant response at the root system level. Our work aimed to integrate the interrelationship between agronomic traits, rhizosphere microbial population and metabolic processes in roots, following seed treatment with either arbuscular mycorrhizal fungi (AMF) or Plant Growth-Promoting Rhizobacteria (PGPR). To this aim, maize was grown under open field conditions with either optimal or reduced nitrogen availability. Both seed treatments increased nitrogen uptake efficiency under reduced nitrogen supply revealed some microbial community changes among treatments at root microbiome level and limited yield increases, while significant changes could be observed at metabolome level. Amino acid, lipid, flavone, lignan, and phenylpropanoid concentrations were mostly modulated. Integrative analysis of multi-omics datasets (Multiple Co-Inertia Analysis) highlighted a strong correlation between the metagenomics and the untargeted metabolomics datasets, suggesting a coordinate modulation of root physiological traits.

The application of microbial biostimulants to plants has revealed positive effects related to nutrients uptake, stress tolerance, root development and phenological growth. However, little information is available exploiting the potential synergistic biostimulant action of microbes on the functional quality of the yields. The current research elucidated the effect of single or coupled action of biostimulants, associated with either optimal or reduced nitrogen application, on the functional quality of tomato fruits. Chemical assays and untargeted metabolomics were applied to investigate Rhizoglomus irregulare and Funneliformis mosseae administration (both being arbuscular mycorrhiza, AMF), under optimal or low N input conditions, alone or coupled to Trichoderma atroviride application. The coupling of AMF and Trichoderma fungal inoculations resulted in a synergistic biostimulant effect on tomato fruits under sub-optimal fertility, revealing improved concentrations of carotenoid compounds—B-carotene (0.647 ± 0.243 mg/100 g), Z-carotene (0.021 ± 0.021 mg/100 g), 13-z-lycopene (0.145 ± 0.052 mg/100 g) and all-trans-lycopene (12.586 ± 1.511 mg/100 g), and increased values for total phenolic content (12.9 ± 2.9 mgGAE/g), total antioxidant activity (phosphomolybdenum, 0.9 ± 0.2 mmolTE/g), radical scavenging activity (DPPH, 3.4 ± 3.7 mgTE/g), reducing power (FRAP, 23.6 ± 6.3 mgTE/g and CUPRAC, 37.4 ± 7.6 mg TE/g), and enzyme inhibitory activity (AChE, 2.4 ± 0.1 mg GALAE/g), when compared to control. However, evidence of carotenoid and bioactive compounds were exclusively observed under the sub-optimal fertility and no significant differences could be observed between the biostimulant treatment and control under optimal fertility.

Abutilon theophrasti Medik. (velvetleaf) is a problematic annual weed in field crops which has invaded many temperate parts of the world. Since the loss of crop yields can be extensive, approaches to manage the weed include not only conventional methods, but also biological methods, for instance by microorganisms releasing phytotoxins and plant-derived allelochemicals. Additionally, benzoxazinoid-rich rye mulches effective in managing common weeds like Amaranthus retroflexus L. have been tested for this purpose. However, recent methods for biological control are still unreliable in terms of intensity and duration. Rye mulches were also ineffective in managing velvetleaf. In this review, we present the attempts to reduce velvetleaf infestation by biological methods and discuss possible reasons for the failure. The resilience of velvetleaf may be due to the extraordinary capacity of the plant to collect, for its own survival, the most suitable microorganisms from a given farming site, genetic and epigenetic adaptations, and a high stress memory. Such properties may have developed together with other advantageous abilities during selection by humans when the plant was used as a crop. Rewilding could be responsible for improving the microbiomes of A. theophrasti.

An evaluation of the effect of the conservation agriculture (CA) on agro-environmental aspects is needed at the farm scale in intensive production systems, which are likely prone to reduce soil fertility. Here, as part of the HelpSoil LIFE+ Project and involving 20 farms in the Po valley (Northern Italy), we have estimated the soil organic carbon (SOC) content, SOC stock, crop yield, biological fertility, soil biodiversity, and economic efficiency under different agricultural systems (CA and conventional, CvtA) at the beginning (March 2014) and end (October 2016) of the experimental period. CA was mostly represented by no-till practice (NT) coupled with the cultivation of winter cover crops. Minimum tillage (MT) was considered as CA or CvtA practice according to the farm design. The CA practices have been implemented on the monitored farms at different times (Long-term = before 2006, Medium-term = between 2006 and 2013, Short-term = after 2013). A direct comparison between CA and CvtA of soil-related variables, yields, and costs was performed on 14 out of the 20 farms; data were statistically treated with a linear mixed model. Overall, CA resulted in significantly higher SOC content, SOC stock, biological fertility, QBS-ar, and earthworms for the Medium-term group. Considering the effect of tillage practices observed on the 20 farms, SOC content was the highest in NT for the Long-term group. The biological fertility index was higher in NT and MT compared to CvtA within the Long-term and Medium-term groups in 2016. QBS-ar was the higher in MT and NT than CvtA for the Long-term and Medium-Term groups. The number of earthworms was the highest under NT for the Long-term group. Maize, winter wheat, and soybeans yields were generally 1 t ha−1 higher in CvtA than in CA, but this did not reach statistical significance. The cost for herbicides was 18% more expensive in NT, whereas the fuel consumption and total costs for weeding operations did not differ between NT and CvtA. The overall outcome of the analysis was that CA is a viable solution for intensive farms in the monitored area, but further skills need still to be acquired in to enhance its economic feasibility.

No-till (NT) has repeatedly been reported to result in several environmental advantages, including the reduction of soil erosion, sequestration of carbon from the atmosphere and increase of water retention in soils. However, experimental evidences to date show negative effects of NT on soil physical parameters (i.e., increasing penetration resistance and soil bulk density) and root development of plants, thus reducing crop yield. A three-year field study (2014–2016) was conducted to assess the effects of NT vs conventional tillage (CT) on root growth in maize, soybean, and winter wheat, on a silty clay soil in the Northern Italy. Root length density (RLD), diameter class length (DCL), root dry weight (RDW) and roots composition (C and N) in the top 60 cm of soil were measured. The total amount of root C (TRC) was calculated by multiplying RDW by root C content. Relationships among root traits, soil bulk density (BD) and penetration resistance (PR) were investigated using the non-parametric Spearman rank coefficient. RLD was significantly increased under NT compared to CT in the topsoil (0–5 cm) in maize (6.37 vs. 2.03 mg cm−3) and winter wheat (5.38 vs. 2.90 cm cm−3), while it was lower in NT than in CT in the deeper soil (5–15 cm) only in maize (3.19 vs. 4.53 cm cm−3). RDW was increased under NT compared to CT in the 0–5 cm layer in maize (3.86 vs.0.50 mg cm−3), soybean (4.33 vs. 0.43 mg cm−3), and winter wheat (0.96 vs. 0.38 mg cm−3). NT significantly reduced root C:N ratio of maize (-9%), increased C:N ratio of soybean (+14%), and did not affect C:N ratio of winter wheat. This was mainly related to the effect of NT on coarse roots, which decreased average roots N content. A negative correlation between root traits (RLD, RDW) and soil physical parameters (BD, PR) was found in this study under NT while no correlation occurred for CT. This corroborates the hypothesis that when tillage is abandoned roots are major drivers and detectors of soil physical conditions, which in turn affects roots growth again. Moreover, these results showed that BD did not always represent the main factor affecting root development and the increase of soil strength and particle density under NT did not reduce downwards root growth, which suggests that stability of continuous biopores as induced by NT in well-structured soils is probably much more relevant than the total amount of pores to affect root traits.

Introducing smart and sustainable tools for climate change adaptation and mitigation is a major need to support agriculture’s productivity potential. We assessed the effects of the processed gypsum seed dressing SOP® COCUS MAIZE+ (SCM), combined with a gradient of N fertilization rates (i.e. 0 %, 70 % equal to 160 kg N ha-1, and 100 % equal to 230 kg N ha-1) in maize (Zea mays L.), on: (i) grain yield, (ii) root length density (RLD) and diameter class length (DCL), (iii) biodiversity of soil bacteria and fungi, and (iv) Greenhouse Gases (GHGs, i.e. N2O, CO2, and CH4) emission. Grain yield increased with SCM by 1 Mg ha-1 (+8 %). The same occurred for overall RLD (+12 %) and DCL of very fine, fine, and medium root classes. At anthesis, soil microbial biodiversity was not affected by treatments, suggesting earlier plant-rhizosphere interactions. Soil GHGs showed that (i) the main driver of N losses as N2O is the N-fertilization level, and (ii) decreasing N-fertilization in maize from 100 % to 70 % decreased N2O emissions by 509 mg N-N2O m-2 y-1. Since maize grain yield under SCM with 70 % N-fertilization was similar to that under Control with 100 % N-fertilization, we concluded that under our experimental conditions SCM may be used for reducing N input (-30 %) and N2O emissions (-23 %), while contemporarily maintaining maize yield. Hence, SCM can be considered an available tool to improve agriculture’s alignment to the United Nation Sustainable Development Goals (UN SDGs) and to comply with Europe’s Farm to Fork strategy for reducing N-fertilizer inputs.

An environmental Life Cycle Assessment (LCA) was performed to compare four typical milk production systems of the Po Valley: drinking milk (A); Parmigiano-Reggiano more intensive (B); Parmigiano-Reggiano less intensive (C) and Grana Padano (D). The input and output data were collected directly from the farmers by way of questionnaires. The results indicated that the total GHG emissions from the analysed farms, with biological allocation, were: 1.47, 1.35, 1.49 and 1.50 kg CO2 eq. kg−1 FPCM (Fat Protein Corrected Milk) for farm A, B, C and D respectively. Excluding Land Use Change (LUC) emissions and Soil Organic Carbon (SOC) sequestration, total GHG emissions were reduced to 1.02, 1.11, 1.26 and 1.20 kg CO2 eq. kg−1 FPCM for farm A, B, C and D respectively. These reductions were mostly due to the GHG emissions associated to the LUC from imported soybean meal, while the contribution of SOC sequestration to the total GHG emissions was found to be negligible. When LUC emissions from imported soybean meal were not included in the analysis, lower GHG emissions were associated to higher milk yield, feed self-sufficiency and feed efficiency. However, when LUC emissions were included in the analysis, the highest level of these parameters did not always lead to a reduction of the total GHG emissions because the higher use of maize silage was associated with an increase in the use of imported soymeal. The results of this LCA also indicated that marine eutrophication, freshwater eutrophication, non-renewable energy use, land occupation and total biodiversity loss decreased as the level of intensification of the production system increased. Conversely, local biodiversity loss, instead, increased if the milk yield per cow increased. We can conclude that, in the specific context analysed, the increase in productivity may lead to a trade-off between global impacts (such as GHG emissions) and local impacts (e.g. local biodiversity and eutrophication).

Conventional agricultural practices (CAP) highly impacted soil functions involved in the provision of multiple ecosystem services. No-till (NT) has been repeatedly indicated as a key way to enhance soil fertility and biodiversity, while having a positive effect on the environment and climate change. However, experimental evidence to date shows contrasting effects of NT on physical parameters of soil fertility, as well as on soil organic carbon (SOC) storage and soil biodiversity especially if different soil types and cropping systems are considered. The objectives of the present 7-year field study were: (i) to unravel the effect of NT on SOC, soil bulk density, and water stability index (WSI) of soil aggregates across five different soil types (Silty Clay, Silty Clay Loam, Clay Loam, Silt Loam, and Sandy Loam) and cropping systems (silage vs grain production), (ii) to examine how soil fauna (i.e. microarthropods and earthworms) is affected by NT practices under those soil-crop conditions, and (iii) to assess relationships among responses of soil physical indicators (i.e. soil bulk density and WSI), SOC, and soil fauna. Our results showed that soil bulk density was generally not affected by 7-year NT across all soil types. At the same time, NT increased WSI. It follows that NT may increase stable rather than artificial tillage-derived porosity due to reduced soil disturbance, and increased SOC and biological activity. However, reduced importance for boosting aggregates stability should be attributed to NT where initial SOC is high, clay and silt are predominant soil fractions, and the rate of crop residue is low. Our findings suggest that NT may enhance SOC stock (on average 0.66 Mg C ha−1 year−1) in the 0–30 cm soil layer. However, we found (i) a tendency of NT to decrease SOC concentration in the 15–30 cm soil layer (on average −1.18 g C kg−1), and (ii) no SOC increase induced by NT if crop residues were not left onto the soil surface. Nevertheless, NT practices promoted (i) the microarthropods adaptation measured with the QBS-ar index (105.5 vs 64.7), and (ii) the increase of earthworm abundance (412 vs 123 individuals m−2), which are fundamental for enhancing nutrient cycling and soil porosity. Correlations among soil fauna (i.e. QBS-ar and earthworm density), soil physical parameters (i.e. soil bulk density and WSI), and SOC (i.e. concentration and stock) corroborates the hypothesis that soil fauna adaptation and proliferation are main detectors of soil quality and sensitive indicators of changes in soil tillage.

A facultative, microbial micro-community colonizing roots of Abutilon theophrasti Medik. supports the plant in detoxifying hydroxylated benzoxazolinones. The root micro-community is composed of several fungi and bacteria with Actinomucor elegans as a dominant species. The yeast Papiliotrema baii and the bacterium Pantoea ananatis are actively involved in the detoxification of hydroxylated benzoxazolinones by generating H2O2. At the root surface, laccases, peroxidases and polyphenol oxidases cooperate for initiating polymerization reactions, whereby enzyme combinations seem to differ depending on the hydroxylation position of BOA-OHs. A glucosyltransferase, able to glucosylate the natural benzoxazolinone detoxification intermediates BOA-5- and BOA-6-OH, is thought to reduce oxidative overshoots by damping BOA-OH induced H2O2 generation. Due to this detoxification network, growth of Abutilon theophrasti seedlings is not suppressed by BOA-OHs. Polymer coats have no negative influence. Alternatively, quickly degradable 6-hydroxy-5-nitrobenzo[d]oxazol-2(3H)-one can be produced by the micro-community member Pantoea ananatis at the root surfaces. The results indicate that Abutilon theophrasti has evolved an efficient strategy by recruiting soil microorganisms with special abilities for different detoxification reactions which are variable and may be triggered by the allelochemical´s structure and by environmental conditions.

BACKGROUND:Fusarium ear rot and fumonisin contamination are serious problems for maize growers. The lack of maize genotypes highly resistant to fumonisin contamination emphasises the need for management strategies to prevent contamination by this mycotoxin. There are conflicting reports regarding no-till and nitrogen (N) fertilisation practices in relation to the incidence of fumonisins. In this study the effect of no-till compared with conventional tillage and of N fertilisation rates on fumonisin occurrence was investigated over three years in Northern Italy. RESULTS: The average contamination of grain by fumonisins B1 and B2 over the three years was significantly different, with a lower value in 2000 (516 µg kg−1) than in the other years (5846 and 3269 µg kg−1 in 2001 and 2002 respectively). Conventional tillage and no-till treatments had no significant effect on the incidence of fumonisins. This finding suggests that above-ground residues infected by Fusarium would not lead to an increase in fumonisin incidence. However, N fertilisation significantly increased fumonisin levels, by 99 and 70% in 2000 and 2001 respectively. CONCLUSION: Maize monoculture does not show a cumulative effect on the occurrence of fumonisins, while high rates of N fertiliser consistently result in elevated fumonisin levels. Both these effects can be influenced by annual meteorological fluctuations. Copyright © 2008 Society of Chemical Industry

Abutilon theophrasti Medik., previously found to be rather insensitive to benzoxazinoid containing rye mulch and the allelochemical benzoxazolin-2(3H)-one (BOA), can be associated with the zygomycete Actinomucor elegans, whereby the fungus colonizes the root relatively superficially and mainly in the maturation zone. The fungus mitigates necrosis of the cotyledons when seedlings are incubated with 2 mM BOA, in contrast to those that lack the fungus. In liquid cultures of the fungus, tryptophan was identified. The accumulation of tryptophan is increased in presence of BOA. This amino acid seems to be important in protecting Abutilon against BOA and its derivatives since it suppressed the accumulation of BOA derived, highly toxic 2-aminophen-oxazin-3-one (APO) in the medium and on the root surface during BOA incubations of Abutilon seedlings. Although A. elegans is insensitive to BOA and APO, the fungus is not able to protect the plant against harmful effects of APO, when seedlings are treated with the compound. Abutilon can detoxify BOA via BOA-6-OH glucosylation probably by a cell wall associated glucosyltransferase, but only low amounts of the product accumulate. Low tryptophan concentrations can contribute to a degradation of the toxic intermediate BOA-6-OH by Fenton reactions, whereby the amino acid is oxidized. One of the oxidation products was identified as 4(1H)-quinolinone, which is the core substructure of the quorum sensing molecule 2-heptyl-3-hydroxy-4-quinolone. The mutualistic association of Abutilon theophrasti with Actinomucor elegans is considered as opportunistic and facultative. Such plant-fungus associations depend rather likely on environmental conditions, such as the mode of fertilization.

The allelopathic potency of rye (Secale cereale L.) is due mainly to the presence of phytotoxic benzoxazinones— compounds whose biosynthesis is developmentally regulated, with the highest accumulation in young tissue and a dependency on cultivar and environmental influences. Benzoxazinones can be released from residues of greenhouse-grown rye at levels between 12 and 20 kg/ha, with lower amounts exuded by living plants. In soil, benzoxazinones are subject to a cascade of transformation reactions, and levels in the range 0.5–5 kg/ha have been reported. Starting with the accumulation of less toxic benzoxazolinones, the transformation reactions in soil primarily lead to the production of phenoxazinones, acetamides, and malonamic acids. These reactions are associated with microbial activity in the soil. In addition to benzoxazinones, benzoxazolin-2(3H)-one (BOA) has been investigated for phytotoxic effects in weeds and crops. Exposure to BOA affects transcriptome, proteome, and metabolome patterns of the seedlings, inhibits germination and growth, and can induce death of sensitive species. Differences in the sensitivity of cultivars and ecotypes are due to different species-dependent strategies that have evolved to cope with BOA. These strategies include the rapid activation of detoxification reactions and extrusion of detoxified compounds. In contrast to sensitive ecotypes, tolerant ecotypes are less affected by exposure to BOA. Like the original compounds BOA and MBOA, all exuded detoxification products are converted to phenoxazinones, which can be degraded by several specialized fungi via the Fenton reaction. Because of their selectivity, specific activity, and presumably limited persistence in the soil, benzoxazinoids or rye residues are suitablemeans for weed control. In fact, rye is one of the best cool season cover crops and widely used because of its excellent weed suppressive potential. Breeding of benzoxazinoid resistant crops and of rye with high benzoxazinoid contents, as well as a better understanding of the soil persistence of phenoxazinones, of the weed resistance against benzoxazinoids, and of how allelopathic interactions are influenced by cultural practices, would provide the means to include allelopathic rye varieties in organic cropping systems for weed control.

The allelopathic potential of rye ( Secale cereale L.) is mainly due to phytotoxic benzoxazinones, compounds that are produced and accumulated in young tissues to different degrees depending on cultivar and environmental influences. Living rye plants exude low levels of benzoxazinones, while cover crop residues can release from 12 to 20 kg ha –1 . This paper summarizes the results obtained from several experiments performed in both controlled and field environments, in which rye was used as a cover crop to control summer weeds in a following maize crop. Significant differences in benzoxazinoid content were detected between rye cultivars. In controlled environments, rye mulches significantly reduced germination of some broadleaf weeds. Germination and seedling growth of Amaranthus retroflexus and Portulaca oleracea were particularly affected by the application of rye mulches, while Chenopodium album was hardly influenced and Abutilon theophrasti was advantaged by the presence of the mulch. With reference to the influence of agronomic factors on the production of benzoxazinoids, nitrogen fertilization increased the content of allelochemicals, although proportionally less than dry matter. The field trial established on no-till maize confirmed the significant weed suppressiveness of rye mulch, both for grass and broadleaf weeds. A significant positive interaction between nitrogen (N) fertilization and notillage resulting in the suppression of broadleaf weeds was observed. The different behavior of the weeds in the presence of allelochemicals was explained in terms of differential uptake and translocation capabilities. The four summer weeds tested were able to grow in the presence of low amounts of benzoxazolin-2(3H)-one (BOA), between 0.3 and 20 mmol g –1 fresh weight. Although there were considerable differences in their sensitivity to higher BOA concentrations, P. oleracea , A. retroflexus , and Ch. album represented a group of species with a consistent absorption capability. The insensitivity of A . theophrasti to BOA was due to reduced accumulation in seedlings. Overall, results confirm that the use of a rye cover crop in a suitable crop rotation represents a sustainable weed management practice permitting a reduction in the amount of herbicides used in agroecosystems, thus limiting the environmental risks of intensive agriculture.

The likelihood of a strong seasonal effect on the analytical results of soil chemical tests has been substantiated by several findings. The occurrence of such a trouble would heavily affect the routine work of chemical laboratories dealing with hundreds or thousands of soil samples every year and would possibly interfere even with current timing of soil sampling and testing in agronomical research. Soils from four different experimental fields were sampled and analyzed for Olsen P test through the growing season of both spring-summer crops (maize) and autumn-spring crops (soft wheat). To avoid the cross effect of recent P applications, samples were collected only from the control plots, with no P applied. In a first long-time experiment the level of Olsen P was followed in three soils during two years, while in a second experiment the study considered two different soils for a couple of years each. The amount of extractable (available) Olsen P showed significant fluctuations-with-time in four years out of six. The observed variations seems entirely due to P absorption by crops, as they appeared in the final samplings during the cropping season. The amount of decrease was nearly always small, less than 1-1.5 mg kg-1 soil, and consistent with the reduction of the available pool which is to be expected as crops gradually take up nutrients. As far as Olsen P is concerned, no evidence was found for the occurrence of erratic seasonal variations such as those previously reported. As soil samples for advisory purposes are usually taken at different times of the year, it seems reassuring that no complications are to be expected about information needed to interpret the results of chemical tests.

Planting maize under no-tillage is an increasing farming practice for sustainable agriculture and sound environmental management. Although several studies on yield of no-till maize have been done, there is few information about the effect of tillage on fumonisin contamination. The present study was done to determine the effect of notillage and conventional tillage with two rates of nitrogen on fumonisin content in kernels of continuous maize. Average grain contamination with fumonisins B1 and B2 over the years 2004-06 was not significantly different, with mean values of 1682, 1984 and 2504 μg kg-1, respectively. Fumonisin B1 was the most abundant toxin found in the samples. No-tillage significantly affected the incidence of fumonisins during the first year of the trial, in which fumonisin content was significantly higher with no-till (2008 μg kg-1) compared with conventional tillage (1355 μg kg-1). However, no-tillage did not significantly affect the incidence of fumonisins in the second and third years of the study. Fumonisin content at the rate of 300 kg N ha-1 was not statistically different compared to that obtained without N fertilization. The interaction between the soil management system and the rate of applied nitrogen was only evident in the second year. Our results indicate that fumonisin contamination was affected by no-tillage only in the first year. Nitrogen fertilization had no significant effect on fumonisin content in any year. The weather conditions during susceptible stages of maize development have probably overridden the effect of nitrogen fertilization.

An experimental trial was carried out over three years at Cavacurta (Po valley, Italy) on continuous barley. The soil was a coarse-loamy over sandy, mixed, mesic Fluventic Ustochrept. The experimental design was a split-plot with four replicates; the main factor was the soil management system (conventional tillage, CT, and no-tillage, NT), while the secondary factor was the nitrogen fertilization (N0 = 0, N1 = 50 and N2 = 90 kg N ha-1 year-1). At the end of the third year soil samples were taken in all plots at four depths (0-5, 5-10, 10-15 and 15-20 cm). For these samples, pH, organic matter, total N, available P and cation exchange capacity were determined. On the contrary, water aggregate stability was determined for a single layer (0-20 cm depth), excluding the N1 level of fertilization. The biological indicator, QBS-ar index, was studied only in the layer 0-10 cm. Statistical analysis shows that no-till positively influenced all the indices except for CEC and QBS-ar. N fertilization had significant effects on CEC only; in the upper layer, the value in N2 subplots was of approx. 1 cmol+ kg-1 higher than in N0 and N1 subplots. There was no significant interaction for any of the indices. As regards only the 0-20 cm layer, the most important results are as follows. The organic matter content in NT plots was significantly higher than in CT plots (32.6 vs 29.8 g kg-1), as was the total N (2.11 vs 1.97 g kg-1). No-till also had a very clear effect on the Olsen-P (12.3 vs 9.3 mg kg-1). The most remarkable result was found for the water aggregate stability: for NT plots the value was 246% higher than for CT plots (34.3 vs 9.9%). As regards the microarthropod community, the value of the QBS-ar index was between 90 and 126, a typical range for soil under barley.