Cover crops and compost prevent weed seed bank buildup in herbicide‐free wheat–potato rotations under conservation tillage

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Faba bean grain yield, N2 fixation, and weed infestation in a long-term tillage experiment under rainfed Mediterranean conditions

Background and aims

Long-term experiments could provide valuable information to determine the effects of an agronomic practice on agro-ecosystem productivity and stability. This study evaluated the long-term (18-year) impact of different tillage systems on faba bean (Vicia faba L.) productivity, including weed and broomrape incidence, and N₂ fixation.

Methods

The experiment was carried out on a Vertisol under rainfed Mediterranean conditions. It was set up as a strip-plot design. The tillage systems were: conventional tillage (CT) with moldboard plow, reduced tillage (RT) with chisel plow, and no tillage (NT). Nitrogen fixation was estimated over 2?years in the final phase of the experiment using the ¹⁵N isotope dilution technique.

Results

On average, grain yield was 31?% and 23?% higher under NT than under CT and RT, respectively; however, the effect of tillage varied by year. The yield advantage of NT over CT was pronounced when rainfall was scarce. Average broomrape infestation was lower under NT than under CT, but a reduction in tillage intensity resulted in an increase in weed biomass. Tillage had no effect on weed richness, but the use of the NT technique progressively altered the weed composition by determining conditions conducive to the growth of a few weed species that are hard to control. Nitrogen fixation was strongly influenced by tillage, being higher under NT than under CT.

Conclusions

The results suggest that NT is a valuable option in the rainfed cereal–legume rotation systems of Mediterranean environments; however, the success of NT technique depends on the use of effective weed control strategies.     

Extending the host range of the bioherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene

Spore formulations of the bioherbicidal fungus Colletotrichum gloeosporioides f. sp. aeschynomene (ATCC No. 20358) (CGA) were evaluated for control of three weed species: northern jointvetch (Aeschynomene virginica), Indian jointvetch (A. indica), and hemp sesbania (Sesbania exaltata) in greenhouse experiments. Mortality, dry weight reduction, and plant height reduction of A. virginica seedlings ranged from 98% to 100%, 15 days after inoculation with CGA in water, in an invert emulsion, or in Silwet L-77 surfactant. However, CGA in water caused no effects of these parameters on S. exaltata, and only slight effects on A. indica. A. indica and S. exaltata were also severely injured (mortality, dry weight and plant height reduction, 98–100%) by CGA in the invert emulsion or in Silwet L-77. The CGA in Silwet formulation incited severe disease development more rapidly than the invert emulsion or water formulations of CGA in all species. These results suggest that the host range of CGA can be expanded though formulation modification to enable this bioherbicide to control multiple weeds, thus making this product more economically acceptable.     

Weed development in spring wheat after contrasting soil tillage and nitrogen management

Soil tillage and nitrogen (N) management effects on weed species composition were evaluated in 2013 and 2014 on a clayey soil after 5‐years of organic management at the Royal Agricultural University's Harnhill Manor Farm, UK. Three tillage systems – Conventional Tillage (CT), and High and Low Intensity Non‐inversion Tillage (HINiT & LINiT) – were compared at four N fertiliser rates of 0, 70, 140 and 210 kg N ha^?1. Broad‐spectrum herbicide was applied before soil operations across the site in both years. Previous organic management legacy of high weed biomass promoted greater weed prevalence in 2013 while 2‐years of herbicide inclusion reduced weed biomass. Contrasting weather conditions across the seasons affected weed incidence. In the 2014 wet season, early weed dry weight (DM) was higher under HINiT than CT and LINiT, while no differences were observed in the 2013 dry year. At midseason, weed DM was higher under HINiT than CT and LINiT in both years, which was related to higher DM of the dominant weeds Stellaria media (L.) Vill. and Sinapis arvensis L. Grass weed DM was higher under non‐inversion tillage than CT. N fertilisation increased midseason total weed DM and weed prevalence at harvest. Spring wheat yield was the highest under CT while LINiT produced 17% higher yields than HINiT. Despite higher but still tolerable weed prevalence under both non‐inversion tillage systems and with the application of N, weeds alone was not the only yield‐limiting factor. However, results show that CT is the most reliable option for weed control in changing weather, while N fertilisation rates needs to be considered.     

Tillage differentially affects the capture rate of pitfall traps for three species of carabid beetles

The influence of tillage, gender, and microclimate on capture rates of pitfall traps for the beetles Poecilus scitulus LeConte, Poecilus lucublandus (Say), and Pterostichus melanarius Illiger (Coleoptera: Carabidae) were assessed in mark–release–recapture experiments in spring pea and spring wheat. Experiments were conducted during June, July, and August of 2003 in the Palouse region of northern Idaho, USA. Rates of capture in pitfall traps for the three carabid species were differentially affected by crop‐tillage systems. Capture rates for P. scitulus and P. lucublandus were higher in no‐till (NT) than in conventional tillage (CT) peas, whereas capture rates for P. scitulus and Pt. melanarius were higher in CT than in NT wheat. Ground‐level temperatures and relative humidity (r.h.) differed little among tillage systems. Nevertheless, capture rates were generally positively correlated with ground‐level temperature and negatively correlated with r.h., with correlations more often significant in NT than in CT systems. The response of the thermophilic Poecilus spp. to temperature provides a possible mechanistic explanation for capture rate patterns in legumes during June, but not in other months for peas or any month in wheat during the experiments. Movement impedance due to residue could explain lower capture rates of P. scitulus and Pt. melanarius in NT than in CT spring wheat. These results suggest that researchers using pitfall trapping for carabid populations should take into account potential capture biases their treatments can introduce.     

Conservation agriculture for wheat-based cropping systems under gravity irrigation: increasing resilience through improved soil quality

A field experiment was conducted under furrow irrigation on a Vertisol in arid northwestern Mexico, to evaluate sustainable production alternatives for irrigated wheat systems. Treatments included: tillage (conventionally tilled raised beds where new beds are formed after disc ploughing before planting [CTB] and permanent raised beds [PB]) and irrigation regimes (full and reduced). Physical and chemical soil quality was compared among treatments. PB improved soil structure and direct infiltration, increased topsoil K concentrations (0–5 cm; 1.6 cmol kg^?1 in PB vs. 1.0–1.1 cmol kg^?1 in CTB) and reduced Na concentrations (0–5 cm; 1.3–1.4 cmol kg^?1 in PB vs. 1.9–2.2 cmol kg^?1 in CTB) compared to CTB. Crop growth dynamics were studied throughout the season with an optical handheld NDVI sensor. Crop growth was initially slower in PB compared to CTB, but this was compensated by increased crop growth in the later stages of the crop cycle which influenced final yield, especially under reduced irrigation. These results were reflected in the final grain yield: in the third year after conversion to PB, no difference in grain yield was found between tillage systems under full irrigation. However, under reduced irrigation the improved soil quality with PB resulted in a 19% and 26% increment in bread and durum wheat grain yields, respectively. As projected climatic scenarios forecast higher evapotranspiration, less reliable rainfall and increased drought, our results indicate that PB could contribute to maintaining and increasing wheat yields in a sustainable way.     

Effects of tillage systems on wheat and weed water relationships over time when growing together,in semiarid conditions

Water availability directly influences interactions and competition between weeds and crops. This article is based on the idea that relative water content (RWC) indicates the water uptake within plants and that it is possible to explain the water relationships between plants that are growing together. A field experiment carried out for 3 years (2013–2014, 2014–2015 and 2015–2016) compared the short-term effects of years and tillage systems on wheat grain yield, weed density, wheat-RWC, weed-RWC and soil water content (SWC), at tillering and flowering stages in a winter wheat monoculture system. The three tillage treatments were conventional tillage (CT), minimum tillage (MT) and no-tillage (NT). Wheat grain yield was low all years of study, because of low interannual rainfall, and we did not observe differences between tillage systems. Weed density was also affected by year and not by tillage systems. Lowest winter rainfall (73.4 mm from Nov to Feb) in the last year of the study (2015–2016), decreased the weed density in all tillage systems. Despite the rainfall variability over the 3 years of study, the NT system presented higher weed density (73 plants/m²) than MT and CT systems (39.83 and 46.33 plants/m²). We also observed a higher number of weed species for the NT system, facilitated by a high soil water storage in this system. The wheat-RWC, at tillering stage, varied with years and tillage systems; we found that high winter rainfall (2013–2014) led to higher values in CT (64.5%) compared with MT (52.9%) and NT plots (52.9%). Weed-RWC values did not vary and SWC was greater in NT than in CT and MT. At flowering stage, the year (2015–2016) with highest spring rainfall favoured higher wheat-RWC in NT (56.9%) compared with CT (48.3%). However, the lowest spring rainfall coincided with the lowest weed-RWC, (18% in NT plots) and SWC was always higher in NT soils. The results showed that climatic conditions affected the water competence dynamics between weeds and wheat in different ways. Seemingly, weeds can tolerate a lack of water availability until crop tillering stage independently of tillage system; however, the competition for water was not a problem as crops overcame the high weed density by flowering stage.     

The host specificity of Anomalococcus indicus Ayyar (Hemiptera: Lecanodiaspididae), a potential biological control agent for prickly acacia (Vachellia nilotica ssp. indica) in Australia

ABSTRACT

Prickly acacia, Vachellia nilotica ssp. indica (Benth.) Kyal. & Boatwr, is a significant weed of northern Australia and has been a target of weed biological control in Australia since the 1980s. Following native range surveys in India, the scale insect Anomalococcus indicus Ayyar was identified as the most promising agent and was imported into Australia for further research. A. indicus is a major pest of prickly acacia on the Indian subcontinent, where it causes shoot tip dieback and plant death. Despite field observations suggesting the species was specific to V. nilotica, A. indicus completed development on 17 of the 84 non-target plant species tested during no-choice host specificity trials under quarantine conditions. Of these, Acacia falcata, V. bidwillii, V. sutherlandii and Neptunia major supported high numbers of mature females in all replicates. All of these species were utilised in choice trials. Combined risk scores indicate that V. sutherlandii, N. major and A. falcata may be attacked in the field. Due to the limited ability of scale insects to disperse, only those non-target species that occur on the Mitchell grass downs (i.e. V. sutherlandii) are considered to be at risk. Nevertheless, in view of the disparity between quarantine test results and the observed field host specificity of A. indicus in India, field trials are currently being conducted in India using Australian native species on which complete development has occurred. The future of A. indicus as a biological control agent for prickly acacia in Australia will be determined once results from these field trials are known.     

Kinetics of net nitrification associated with soil aggregates under conventional and no-tillage in a subtropical rice soil

Tillage effects on soil nitrification kinetics at the aggregate scale were studied for a subtropical rice soil. Soil samples were separated into large aggregates (>2.0 mm), macro-aggregates (2.0–0.25 mm), micro-aggregates (0.25–0.053 mm) and silt + clay fractions (<0.053 mm) by wet-sieving. The net nitrification process was simulated by a zero- and first kinetics model. Conventional tillage (CT) increased the proportion of the silt + clay fraction by 60% and decreased large-aggregates by 35% compared to ridge with no-till (RNT). Regression analysis showed that the time-dependent kinetics of net nitrification were best fitted by a zero-order model for the large-aggregates and silt + clay fraction but a first-order kinetic model for macro- and microaggregates and whole soil, regardless of tillage regime. Both potential nitrification rates (V _p ) and net nitrification rates (V _a ) were higher for macroaggregates than microaggregates. The potential nitrification (N _p ) for whole soil under RNT was 38.7% higher than CT. The V _p and V _a for whole soil was 88.5% and 64.7% higher under RNT than CT, respectively. Although nitrification was stimulated under RNT, the kinetics model of nitrification was not affected by tillage. This inferred that the interaction between substrates and enzymes involved in nitrification associated with aggregates was not altered by tillage. For this soil, nitrifying microorganisms were mainly associated with macro- and microaggregates rather than large-aggregates and silt + clay fractions.     

Seasonality and species composition of Peristenus (Hymenoptera: Braconidae) species,and Lygus (Hemiptera: Miridae) species parasitism in southern Alberta,Canada

We report a long-term survey summarising the seasonal variation in species composition of Peristenus species, and their levels of parasitism in an assemblage of Lygus spp., over more than 10 years in southern Alberta in western Canada. Plants sampled include alfalfa (Medicago sativa L.), canola (Brassica napus L.), and stands of different weed and grass species commonly found on crop field edges. Three native Peristenus species (Peristenus dayi, Peristenus mellipes, and Peristenus howardi) were recorded in 2003–2011 and 2013–2015. In laboratory trials, P. mellipes emerged 13 days earlier than P. howardi. Degree-days for field-collected individuals suggested a sequential occurrence during the growing season: P. dayi appears early in the season, followed by P. mellipes, and later on by P. howardi. Studies of species composition and phenology of native parasitoids of insect pests provide valuable baseline information when considering introduction of exotic agents, and contribute to the management and improvement of conservation biological control by endemic natural enemies in agricultural systems.     

Assessment of carbon sustainability under different tillage systems in a double rice cropping system in Southern China

Purpose

Adoption of the carbon (C)-friendly and cleaner technology is an effective solution to offset some of the anthropogenic emissions. Conservation tillage is widely considered as an important sustainable technology and for the development of conservation agriculture (CA). Thus, the objective of this study was to assess the C sustainability of different tillage systems in a double rice (Oryza sativa L.) cropping system in southern China.

Methods

The experiment was established with no-till (NT), rotary tillage (RT), and conventional tillage (CT) treatments since 2005. Emission of greenhouse gasses (GHG), C footprint (CF), and ecosystem service through C sequestration in different tillage systems were compared.

Result and discussion

Emission of GHG from agricultural inputs (Mg CO₂-eq ha^?1 year^?1) ranged from 1.81 to 1.97 for the early rice, 1.82 to 1.98 for the late rice, and 3.63 to 3.95 for the whole growing season, respectively. The CF (kg CO₂-eq kg^?1 of rice year^?1) in the whole growing seasons were 1.27, 1.85, and 1.40 [excluding soil organic carbon (SOC) storage] and 0.54, 1.20, and 0.72 (including SOC storage) for NT, RT, and CT, respectively. The value of ecosystem services on C sequestration for the whole growing seasons ranged from ¥3,353 to 4,948 ha^?1 year^?1 and followed the order of NT > CT > RT. The C sustainability under NT was better than that under RT for the late, but reversed for the early rice. However, NT system had better C sustainability for the whole cropping system compared with CT.

Conclusions

Therefore, NT is a preferred technology to reduce GHG emissions, increase ecosystem service functions of C sequestration, and improve C sustainability in a double rice cropping region of Southern China.     

Seasonal abundance of hemipteran predators in relation to western flower thrips Frankliniella occidentalis (Thysanoptera: Thripidae) on weeds in the eastern Mediterranean region of Turkey

Generalist predators and the prey species Frankliniella occidentalis (Pergande) were periodically sampled from 64 weed species to determine their numerical interrelationships in three ecologically different locations in the eastern Mediterranean region of Turkey in 2002–2003. Adult and nymph stages of seven hemipteran predator species were recorded: Deraeocoris pallens Reuter, Geocoris arenarius (Jakovkev), Nabis punctatus Costa, Orius laevigatus Fieber, Orius majusculus (Reuter), Orius niger (Wolff) and Piocoris erythrocephalus (Peletie and Serville). The most common and abundant predator species was O. niger, which was found on 53 weed species in the winter–spring and summer–fall periods; the highest total numbers of O. niger adults per weed species were 139, 275, 266 and 325 on Urtica urens, Sinapis arvensis, Lamium amplexicaule and Mentha aquatica, respectively. Relatively higher numbers of Orius spp. nymphs were detected on the weed species Echium plantagineum, Cichorium intybus, Heliotropium europeum, Mentha aquatica and Polygonum aviculare. Orius spp. were attracted to flowers in significantly higher numbers than to leaves of the investigated weeds. No significant correlation was found between the numbers of Orius spp. and F. occidentalis on the major weed species, except E. plantagineum. These findings suggest that weeds may provide Orius spp. with resources other than prey, such as nectar and pollen, shelter, and breeding sites. The weed species on which relatively higher numbers of Orius adults and nymphs were found may be considered as candidates for studies aiming to include weeds to enhance integrated pest management of F. occidentalis on crops.     

Allelopathic interference of sweet potato with cogongrass and relevant species

Cogongrass (Imperata cylindria) is an invasive weed and harmful to ecological systems and agricultural production in many countries. It was found that plant extracts and root exudates of sweet potato (Ipomoea batatas) exhibit allelopathic potential and inhibit the growth of cogongrass to a greater extent than either barnyardgrass (Echinochloa crus-galli), Indian goose-grass (Eleushine indica), or lettuce (Lactuca sativa) in bioassays. Greenhouse trials indicated that sweet potato soil reduced the emergence of the noxious weed by 50 %, yet exhibited either weaker inhibition or the promotion of barnyardgrass, Bidens (Bidens pilosa), and Leucaena (Leucaena leucocephala), while the desired growth of upland rice (Oryza sativa) was not affected. In cogongrass fields, the incorporation of 1–2 tons aboveground parts and cultivation of sweet potato provided 80–85 % weed control. On the other hand, the reduction of congograss in fields may be offset by the alternate invasion of B. pilosa which multiplied its biomass by 2–6 times with sweet potato amended soils. The findings of this study indicate that sweet potato is an effective crop in the biologic management of the invasive cogongrass in agricultural fields, thus the interactive mechanism between sweet potato and the invasive weed demands further investigation. Ecologically, this study highlights the specificity of allelopathic interactions between cogongrass and sweet potato that is helpful to minimize the disturbance from infestation of this invasive weed against native species and crops.     

Conservation agriculture, increased organic carbon in the top-soil macro-aggregates and reduced soil CO2 emissions

Background and aims

Conservation agriculture, the combination of minimal soil movement (zero or reduced tillage), crop residue retention and crop rotation, might have the potential to increase soil organic C content and reduce emissions of CO₂.

Methods

Three management factors were analyzed: (1) tillage (zero tillage (ZT) or conventional tillage (CT)), (2) crop rotation (wheat monoculture (W), maize monoculture (M) and maize-wheat rotation (R)), and (3) residue management (with (+r), or without (?r) crop residues). Samples were taken from the 0–5 and 5–10?cm soil layers and separated in micro-aggregates (< 0.25?mm), small macro-aggregates (0.25 to 1?mm) and large macro-aggregates (1 to 8?mm). The carbon content of each aggregate fraction was determined.

Results

Zero tillage combined with crop rotation and crop residues retention resulted in a higher proportion of macro-aggregates. In the 0–5?cm layer, plots with a crop rotation and monoculture of maize and wheat in ZT+r had the greatest proportion of large stable macro-aggregates (40%) and highest mean weighted diameter (MWD) (1.7?mm). The plots with CT had the largest proportion of micro-aggregates (27%). In the 5–10?cm layer, plots with residue retention in both CT and ZT (maize 1?mm and wheat 1.5?mm) or with monoculture of wheat in plots under ZT without residues (1.4?mm) had the greatest MWD. The 0–10?cm soil layer had a greater proportion of small macroaggregates compared to large macro-aggregates and micro-aggregates. In the 0–10?cm layer of soil with residues retention and maize or wheat, the greatest C content was found in the small and large macro-aggregates. The small macro-aggregates contributed most C to the organic C of the sample. For soil cultivated with maize, the CT treatments had significantly higher CO₂ emissions than the ZT treatments. For soil cultivated with wheat, CTR-r had significantly higher CO₂ emissions than all other treatments.

Conclusion

Reduction in soil disturbance combined with residue retention increased the C retained in the small and large macro-aggregates of the top soil due to greater aggregate stability and reduced the emissions of CO₂ compared with conventional tillage without residues retention and maize monoculture (a cultivation system normally used in the central highlands of Mexico).     

Soil water content, maize yield and its stability as affected by tillage and crop residue management in rainfed semi-arid highlands

Rainfed crop management systems need to be optimized to provide more resilient options to cope with projected climatic scenarios forecasting a decrease in mean precipitation and more frequent extreme drought periods in Mexico. Soil water content (0?C60 cm) was measured during three crop cycles in maize plots with different agronomic management practices in a long-term rainfed experiment (established in 1991) in the highlands of Mexico. Maize yields of 1997?C2009 were reported. Crop management practices varied in (1) tillage (conventional [CT] vs. zero tillage [ZT]) and (2) residue management (full or partial retention and removal). ZT with residue retention had higher soil water content than management practices involving CT and ZT with residue removal which provided a buffer for drought periods during the growing seasons. In 2009, a cycle with a prolonged drought during vegetative growth, this resulted in yield differences of up to 4.7 Mg ha^?1 between ZT with (partial) residue retention and the other practices. Averaged over 1997?C2009, these practices had a yield advantage of approximately 1.5 Mg ha^?1 over practices involving CT and ZT with residue removal. ZT with (partial) residue retention used rainfall more efficiently and resulted in a more resilient agronomic system than practices involving either CT or ZT with residue removal.     

Species and functional responses of ants to inter-row tillage and vegetation in organic Mediterranean vineyards

Ants are arthropods providing crucial ecosystem services such as soil structuring, nutrient cycling, seed dispersal and pest predation. Thus, their abundance and diversity need to be considered in approaches to improve sustainability of land use such as Mediterranean viticulture. In our study, we tested whether (1) inter-row vegetation and the absence of tillage increase the species richness and/or functional diversity of ants in vineyards and (2) ground cover vegetation drives ant species composition. We included 23 Mediterranean organic vineyards in our analyses and distinguished three types of inter-row management: all inter-rows tilled, half of the inter-rows tilled, and all inter-rows are untilled and covered by vegetation. The occurrence of ant species was analysed in six pitfall traps per vineyard. Around each trap, the floristic composition of inter-row vegetation was analysed in 2 × 2 m² plots. We found that inter-row tillage significantly affected ant species richness, being higher in partially than in fully tilled vineyards whereas untilled vineyards were not different from the other tillage types. Grass cover and the perennial/annual rate were positively correlated with ant species richness. Ant functional diversity and the frequency of most predatory ants were not correlated neither with plant functional groups nor with tillage type. In conclusion, ant communities benefit from inter-row vegetation and/or absence of soil disturbance but partial inter-row tillage of vineyards may be tolerated and even benefit several species. In particular, grasses and perennial plant species favour ants in our system and need to be considered in inter-row sowing.     

Morphological development of larval and juvenile Alectis indica (Perciformes: Carangidae) reared in captivity

Larvae and juveniles of Alectis indica reared in captivity are described based on 47 specimens (3.2–32.0 mm in body length: BL). Development was typical for the tribe Carangini except for the presence of elongated fin filaments. Elongated dorsal-fin filaments were present at preflexion (3.2 mm BL). During flexion, the anal- and pelvic-fin rays elongated and the body deepened. The full complement of fin spines and rays was present by 7.1 mm BL. The larvae of A. indica could be differentiated from those of Alectis ciliaris, which also inhabits in the Indo-Pacific waters, by the presence of a ventral series of melanophores on the tail, elongated pelvic fins, and the timing of anal-fin spine migration. The rounded body and elongated fin rays of A. indica cause it to resemble venomous Cubomedusae.     

Effect of tillage system on the root growth of spring wheat

Little research has examined the influence of tillage system on root growth in wheat grown on rainfed Vertisols. A 3-year field study (2003, 2004 and 2005) was carried out on a typical Vertisol (southern Spain), to determine the effects of tillage system on root growth in spring wheat (Triticum aestivum L) grown in continuous rotation with faba bean (Vicia faba L), within the framework of the long-term “Malagón” experiment started in 1986. Tillage treatments were no-tillage (NT) and conventional tillage (CT), and the experiment was designed as a randomized complete block with three replications. The following parameters were measured: above-ground biomass, grain yield, root length density (RLD), root biomass (RB) and root N content. In the topmost 10 cm of soil, higher values were found under CT than under NT for RLD in the rainiest year (20.2 km m^?3 vs. 9.6 km m^?3 respectively) and for RB (512 kg ha^?1 vs. 261 kg ha^?1 respectively) in all study years. In deeper layers, no difference was recorded between the two tillage systems. Greater wheat root development in the upper soil layer under CT may reflect the greater soil penetration resistance found in the topmost 10 cm under NT. Root separation using a sieve with a 0.5 mm mesh screen led to a marked underestimation of RLD and RB, with values up to three times higher when using a 0.2 mm mesh screen. Mean wheat root N content in the topmost 30 cm of soil accounted for over 80% of total root N content. The highest grain yield was observed under NT, since this system provided greater water storage in the soil profile in the mostly dry study years.     

Tillage and herbicide reduction mitigate the gap between conventional and organic farming effects on foraging activity of insectivorous bats

The increased use of pesticides and tillage intensification is known to negatively affect biodiversity. Changes in these agricultural practices such as herbicide and tillage reduction have variable effects among taxa, especially at the top of the trophic network including insectivorous bats. Very few studies compared the effects of agricultural practices on such taxa, and overall, only as a comparison of conventional versus organic farming without accurately accounting for underlying practices, especially in conventional where many alternatives exist. Divergent results founded in these previous studies could be driven by this lack of clarification about some unconsidered practices inside both conventional and organic systems. We simultaneously compared, over whole nights, bat activity on contiguous wheat fields of one organic and three conventional farming systems located in an intensive agricultural landscape. The studied organic fields (OT) used tillage (i.e., inversion of soil) without chemical inputs. In studied conventional fields, differences consisted of the following: tillage using few herbicides (T), conservation tillage (i.e., no inversion of soil) using few herbicides (CT), and conservation tillage using more herbicide (CTH), to control weeds. Using 64 recording sites (OT = 12; T = 21; CT = 13; CTH = 18), we sampled several sites per system placed inside the fields each night. We showed that bat activity was always higher in OT than in T systems for two (Pipistrellus kuhlii and Pipistrellus pipistrellus) of three species and for one (Pipistrellus spp.) of two genera, as well as greater species richness. The same results were found for the CT versus T system comparison. CTH system showed higher activity than T for only one genus (Pipistrellus spp.). We did not detect any differences between OT and CT systems, and CT showed higher activity than CTH system for only one species (Pipistrellus kuhlii). Activity in OT of Pipistrellus spp. was overall 3.6 and 9.3 times higher than CTH and T systems, respectively, and 6.9 times higher in CT than T systems. Our results highlight an important benefit of organic farming and contrasted effects in conventional farming. That there were no differences detected between the organic and one conventional system is a major result. This demonstrates that even if organic farming is presently difficult to implement and requires a change of economic context for farmers, considerable and easy improvements in conventional farming are attainable, while maintaining yields and approaching the ecological benefits of organic methods.     

Corn Response to Subsoiling and Nematicide Application

A 2-year field study evaluated the influence of subsoiling and nematicide application, alone and in combination, on the growth and yield of field corn in a sandy soil in north-central Florida. The field had a 25-30-cm-deep tillage pan (plowpan) and was infested with Belonolaimus longicaudatus, Hoplolaimus galeatus, Trichodorus christei, and Pratylenchus spp. Subsoiling increased corn yield both years, and the residual effect of subsoiling in the first year increased yields in the second year. Preplant application of DD injected in-row increased yields and reduced nematode populations. At-planting applications of DD injected in-row and carbofuran in-furrow or in a band were less effective than subsoiling in increasing yields and reducing nematode numbers. Interactions between subsoiling and nematicide treatments occurred in the second year.