► Long term changes in soil quality and crop productivity with fertilizer and tillage. ► Soil Quality Index (SQI) developed using Principal Components Approach. ► Improved soil quality in No-till, ...Reduced Input compared to conventional management. ► Conservation management improves nutrient availability, soil stability and structure. ► Soil quality concord with microbial nitrogen processing, nitrogen use and leaching.
Intensively cropped agricultural production systems should be managed to improve soil quality and ecological processes and ultimately strengthen system capacity for sustained biological productivity. We examined the long-term changes (>20 years) in soil quality and productivity with incorporation of ecological management principles in a set of intensively managed row crop systems of the upper Midwest, USA. Replicated experimental treatments include corn (maize)–soybean–wheat cropping systems under four different management regimes: (a) conventional tillage and fertilizer/chemical inputs (
Conventional), (b) no tillage with conventional fertilizer/chemical inputs (
No-till), (c) conventional tillage with ∼30% of conventional fertilizer/chemical inputs and a leguminous cover crop (
Reduced Input), and (d) conventional tillage with no fertilizer/chemical input and a leguminous cover crop (
Organic). Effects of these treatments on soils were compared by developing a soil quality index (SQI) from 19 selected soil health indicators. An old field community maintained in early succession provided a benchmark for comparison. Reduction in tillage or fertilizer (
No-till,
Reduced Input and
Organic) resulted in increased SQI and improved crop production. The
No-till (SQI
=
1.02) and
Reduced Input (SQI
=
1.01) systems outperformed
Conventional management (SQI
=
0.92) in nitrogen availability and use efficiency, soil stability and structure improvement, and microbial nitrogen processing. Improvements in soil quality corresponded with increased primary production and crop yield in these systems, illustrating the value of an ecologically defined SQI for assessing the long-term effects of fertility and tillage management regimes in agricultural production systems.
Aim: To evaluate the efficiency of most effective trap among two types of sticky traps of, i.e., card or tray of two colours (yellow and blue) and their placement height within wheat crop for ...catching alate of R. maidis, the most abundant aphid species in selected locations. Methodology: Sticky card and tray traps of two colours; yellow and blue were placed at different heights within wheat crop and the effects of trap parameters (type, colour and height) were evaluated to determine the trapping efficiency of R. maidis alate. The traps were installed at two heights above ground level; 100 cm and 150 cm at Karnal and Ludhiana and at 60 cm and 120 cm above ground level at Niphad location. Alate aphid counts were recorded weekly to make comparisons. Results: The highest number of R. maidis alate were caught on yellow coloured sticky card traps placed within the crop canopy at 100 cm height above ground and the lowest on blue coloured sticky tray traps at 150 cm height above ground at Ludhiana and Karnal. At Niphad, the highest population was caught on yellow coloured sticky card traps placed at 60 cm height above ground and the lowest number on blue coloured sticky tray traps at 120 cm height above ground. Correlation analysis revealed that all three trap parameters (trap type, colour and placement height) were correlated with mean alate trap catches. Backward stepwise regression modelling indicated that trap type and placement height had a maximum influence on the R. maidis alate trapping. Interpretation: This study indicated that the yellow sticky card traps were most effective in catching R. maidis alate as compared to other tested traps. Key words: Aphids, Insect sampling, Trapping efficiency, Trap parameters, Triticum aestivum
Water and energy demands associated with bioenergy crop production on marginal lands are inextricably linked with land quality and land use history. To illustrate the effect of land marginality on ...bioenergy crop yield and associated water and energy footprints, we analyzed seven large‐scale sites (9–21 ha) converted from either Conservation Reserve Program (CRP) or conventional agricultural land use to no‐till soybean for biofuel production. Unmanaged CRP grassland at the same location was used as a reference site. Sites were rated using a land marginality index (LMI) based on land capability classes, slope, soil erodibility, soil hydraulic conductivity, and soil tolerance factors extracted from a soil survey (SSURGO) database. Principal components analysis was used to develop a soil quality index (SQI) for the study sites based on 12 soil physical and chemical properties. The water and energy footprints on these sites were estimated using eddy‐covariance flux techniques. Aboveground net primary productivity was inversely related to LMI and positively related to SQI. Water and energy footprints increased with LMI and decreased with SQI. The water footprints for grain, biomass and energy production were higher on lands converted from agricultural land use compared with those converted from the CRP land. The sites which were previously in the CRP had higher SQI than those under agricultural land use, showing that land management affects water footprints through soil quality effects. The analysis of biophysical characteristics of the sites in relation to water and energy use suggests that crops and management systems similar to CRP grasslands may provide a potential strategy to grow biofuels that would minimize environmental degradation while improving the productivity of marginal lands.
The present work aimed to determine the impact of nucleopolyhedrovirus (NPV) on the development of Eocanthecona furcellata Wolff and to measure the infectivity of NPV discharged through its faeces. ...Developmental time, survival rate, sex ratio and incubation period of the predator reared on different proportions of healthy and NPV infected S. litura larvae as lifetime meal did not vary significantly. However, when the proportion of infected prey in the predator’s lifetime meal exceeded 50 % significant reductions in body weight, fecundity, longevity and percent egg hatchability were noticed. The virus did not show detrimental effect on the developmental biology of the predator in the subsequent generations when offspring emerging from nymphs fed only on virus infected prey throughout their life were reared on 50 % of infected prey. Therefore, adverse effects on E. furcellata are unlikely in the field as the predator is not expected to consume more than 50 % of infected prey even if the virus application is done at recommended dose. Under field conditions, it was found that increased proportions of infected prey enhanced the dissemination of viral inoculum through the faeces of the predators and the subsequent infection in S. litura larvae ranged from 22 to 52 %.
The physiological age of adult males of seven mealybug species was measured in relation to the elongation of the male pair of the waxy caudal filaments. These filaments begin to emerge after eclosion ...and reached their maximum length from 29.4–46.6 h. The studied males were divided into three age groups, expressed as percentages of the total waxy caudal filaments length. Attraction to a sex pheromone source was significantly higher in the oldest male group (maximum filaments growth) compared with youngest one. Only the oldest male group copulated successfully; few of the younger males tested displayed 'courtship' behavior towards conspecific virgin females. The calculated duration of the sexually active phase of the adult male life cycle varied among species ranging from 34.4 to 46.6 h. There were marked variations in the strength of attraction to a pheromone source according to time of day. There was a continuous decrease in sexual activity from morning to evening. Our findings reveal clear maturation periods for adult males of the seven studied species. The long immature phase of the adult male mealybug is probably also related to several physiological processes that are needed to complete male maturation. The most noticeable change is the elongation of the waxy caudal filaments. However, mating may be performed at any time ambient conditions are suitable. Whereas male mealybug flight towards a pheromone source is restricted to a few hours, the male may continue mating activity throughout its sexually active period.
Over 13 million ha of former cropland are enrolled in the US Conservation Reserve Program (CRP), providing well-recognized biodiversity, water quality, and carbon (C) sequestration benefits that ...could be lost on conversion back to agricultural production. Here we provide measurements of the greenhouse gas consequences of converting CRP land to continuous corn, corn–soybean, or perennial grass for biofuel production. No-till soybeans preceded the annual crops and created an initial carbon debt of 10.6 Mg CO2 equivalents (CO2e)·ha–1 that included agronomic inputs, changes in C stocks, altered N2O and CH4 fluxes, and foregone C sequestration less a fossil fuel offset credit. Total debt, which includes future debt created by additional changes in soil C stocks and the loss of substantial future soil C sequestration, can be constrained to 68 Mg CO2e·ha–1 if subsequent crops are under permanent no-till management. If tilled, however, total debt triples to 222 Mg CO2e·ha–1 on account of further soil C loss. Projected C debt repayment periods under no-till management range from 29 to 40 y for corn–soybean and continuous corn, respectively. Under conventional tillage repayment periods are three times longer, from 89 to 123 y, respectively. Alternatively, the direct use of existing CRP grasslands for cellulosic feedstock production would avoid C debt entirely and provide modest climate change mitigation immediately. Incentives for permanent no till and especially permission to harvest CRP biomass for cellulosic biofuel would help to blunt the climate impact of future CRP conversion.
Infectivity of polyhedra of Spodoptera litura multiple nucleopolyhedrovirus before and after passage through the gut of the predatory stink bug, Eocanthecona furcellata Wolff (Hemiptera: ...Pentatomidae) was compared through field bioassay studies. Three sets of E. furcellata were used for bioassays and these were allowed to feed on a single meal of five third instar Oriental leaf worm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), that were infected with polyhedra before passage, after passage, and healthy (control) larvae 1 day prior to the trial. The predators were subsequently released on cabbage plants that were infested with 100 healthy S. litura larvae. The median lethal dose (LD50) and survival time (ST50) values before and after passage through the gut were not significantly different. Additional mortality due to virus infection increased 13- 17% before and after treatments but within these treatments the mortality did not vary significantly. It was concluded that E. furcellata disseminated the virus through their feces into the ecosystem and infectivity of the SpltMNPV was not altered after passage through the gut of the predator.
Infectivity of polyhedra of Spodoptera litura multiple nucleopolyhedrovirus before and after passage through the gut of the predatory stink bug, Eocanthecona furcellata Wolff (Hemiptera: ...Pentatomidae) was compared through field bioassay studies. Three sets of E. furcellata were used for bioassays and these were allowed to feed on a single meal of five third instar Oriental leaf worm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), that were infected with polyhedra before passage, after passage, and healthy (control) larvae 1 day prior to the trial. The predators were subsequently released on cabbage plants that were infested with 100 healthy S. litura larvae. The median lethal dose (LD50) and survival time (ST50) values before and after passage through the gut were not significantly different. Additional mortality due to virus infection increased 13–17% before and after treatments but within these treatments the mortality did not vary significantly. It was concluded that E. furcellata disseminated the virus through their feces into the ecosystem and infectivity of the SpltMNPV was not altered after passage through the gut of the predator.
Larvae that survived sublethal infection of
Spodoptera litura
granulovirus (
Sl
GV) as 4th and 5th instars led to an increase in the larval period of treated larvae when compared with control. While ...pupal period and pupal weight remained unaffected, a significant alteration in sex ratio was observed. Although survivor moths could mate successfully, there was a significant reduction in the proportion of ovipositing females in treated larvae as compared with control. A significant reduction in fecundity of moths emerging from treated larvae was also noticed, but the egg viability was never influenced by the treatment. However, there was a significant increase in progeny mortality in treated larvae over control. The offspring mortality in survivors increased up to three subsequent generations but not thereafter. Hence, repeated field applications of inoculum are required. The implication of the present findings in terms of reduced fecundity coupled with increased larval development indicates that vertical transmission can lead to increased virus dispersal, both of which would reduce the host's innate capacity for population increase. This is particularly important in
S. litura,
which is a migratory species and occurs sporadically in a particular agro-ecosystem.
PDF
