Changes in soil microbial communities after exposure to neonicotinoids: A systematic review.

Neonicotinoids are a group of nicotine-related chemicals widely used as insecticides in agriculture. Several studies have shown measurable quantities of neonicotinoids in the environment but little is known regarding their impact on soil microbial populations. The purpose of this systematic review was to clarify the effects of neonicotinoids on soil microbiology and to highlight any knowledge gaps. A formal systematic review was performed following PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyses) guidelines using keywords in PubMed, SCOPUS and Web of Science. This resulted in 29 peer-reviewed articles, whose findings diverged widely because of variable methodologies. Field-based studies were few (28%). Imidacloprid was the most widely used (66%) and soil microbial communities were most sensitive to it. Spray formulations were used in 83% of the studies and seed treatments in the rest. Diversity indices were the most frequently reported soil microbial parameter (62%). About 45% of the studies found that neonicotinoids had adverse impacts on soil microbial community structure, composition, diversity, functioning, enzymatic activity and nitrogen transformation. Interactions with soil physicochemical properties were poorly addressed in all studies. The need for more research, particularly field-based research on the effects of neonicotinoids on soil microorganisms was highlighted by this review.

Storage and initial processing of water samples for organic carbon analysis in runoff.

Runoff monitoring experiments are often conducted in remote sites. Sample collection and dispatch for analysis are often delayed due to sites' remoteness and limited local laboratory facilities. The standard method of dissolved organic carbon (DOC) and total organic carbon (TOC) analysis in water samples requires storage of the samples at 4 °C after collection and analysis with a minimum of delay. However, there is no freezing storage time limit specified to avoid degradation. To overcome the limitations of this approach, we investigated the method of storage, that is refrigeration (4 °C) versus freezing (-18 °C), and the effect of storage time on DOC and TOC fractions in runoff water. Storage of samples at 4 °C for more than a week resulted in a decline of TOC and DOC concentrations in runoff water.•Freezing unfiltered water samples immediately after collection minimized TOC losses during storage, however, it may lead to variable DOC results.•Filtering a subsample of runoff or irrigation water immediately after collection using a 0.45 µm filter and freezing both the filtered and unfiltered samples until analysis of DOC and TOC, respectively, can minimize losses during storage.

Influence of Crop Management and Environmental Factors on Wolf Spider Assemblages (Araneae: Lycosidae) in an Australian Cotton Cropping System.

Wolf spiders (Lycosidae) are the most abundant ground-hunting spiders in the Australian cotton (Gossypium hirsutum L.) agroecosystems. These spiders have potential in controlling pest bollworms, Helicoverpa spp. (Lepidoptera: Noctuidae) in minimum-tilled fields. A study was carried out during a wet growing season (2011-2012) in Narrabri, New South Wales, Australia, to determine how different crop rotations and tillage affect wolf spider assemblages in cotton fields. Spider abundance and species richness did not differ significantly between simple plots (no winter crop) and complex plots (cotton-wheat Triticum aestivum L.-vetch Vicia benghalensis L. rotation). However, the wolf spider biodiversity, as expressed by the Shannon-Weaver and Simpson's indices, was significantly higher in complex plots. Higher biodiversity reflected a more even distribution of the most dominant species (Venatrix konei Berland, Hogna crispipes Koch, and Tasmanicosa leuckartii Thorell) and the presence of more rare species in complex plots. T. leuckartii was more abundant in complex plots and appears to be sensitive to farming disturbances, whereas V. konei and H. crispipes were similarly abundant in the two plot types, suggesting higher resilience or recolonizing abilities. The demographic structure of these three species varied through the season, but not between plot types. Environmental variables had a significant effect on spider assemblage, but effects of environment and plot treatment were overshadowed by the seasonal progression of cotton stages. Maintaining a high density and even distribution of wolf spiders that prey on Helicoverpa spp. should be considered as a conservation biological control element when implementing agronomic and pest management strategies.

Organochlorine pesticides in soil under irrigated cotton farming systems in Vertisols of the Namoi Valley, north-western New South Wales, Australia.

Organochlorine pesticides (OCPs) such as DDT and DDE have been detected in the surface 0.2m of Vertisols in the lower Namoi Valley of north western New South Wales, Australia even though they have not been applied to crops since 1982. However, their presence in the deeper soil horizons has not been investigated. The objective of this study was to determine if OCPs were present to a depth of 1.2m in Vertisols under irrigated cotton farming systems in the lower Namoi Valley of New South Wales. Soil was sampled from the 0-1.2m depths in three sites, viz. the Australian Cotton Research Institute, ACRI, near Narrabri (149°36'E, 30°12'S), and two cotton farms near Wee Waa (149°27'E, 30°13'S) and Merah North (149°18'E, 30°12'S) in northern New South Wales, Australia. The OCPs detected and their metabolites were α-endosulfan, ß-endosulfan, endosulfan sulphate, DDD, DDE, DDT and endrin. The metabolite DDE, a breakdown product of DDT, was the most persistent OCP in all depths analysed. Endosulfan sulphate was the second most persistent followed by endrin>α-endosulfan>ß-endosulfan>DDT and DDD. DDT was sprayed extensively in the lower Namoi Valley up to the early 1980s and may explain the persistence of DDE in the majority of soil samples. Dicofol and Dieldrin, two OCPs previously undocumented in Vertisols were also detected. The movement of OCPs into the subsoil of Vertisols may occur when irrigation or rain transports soil colloids and organic matter via preferential flow systems into the deeper layers of a soil profile. Persistence of OCPs was closely correlated to soil organic carbon concentrations. The persistence in soil of OCP's applied to cotton crops grown more than two decades ago suggests that they could enter the food chain. Their presence at depths of 1.2m suggests that they could move into groundwater that may eventually be used for domestic and stock consumption.

Short-term effects of organic amendments on properties of a Vertisol.

Application of organic waste products as amendments has been proposed as a management option whereby soil quality of Vertisols could be improved. An incubation experiment was, therefore, conducted for 4 weeks under controlled temperature conditions (30 degrees C) to identify those potential organic amendments that might improve the quality of a Vertisol. Twelve organic amendments were investigated: cotton gin trash from three sources, cattle manure from two sources, green waste compost, chicken manure from three sources including a commercial product, biosolids and two commercial liquefied vermicomposts. Except for the biosolids, no other organic amendments had any effect on soil microbial biomass and respiration. Compared with NO3-N levels in the control, there was a 50% decrease in soil amended with 10 t ha(-1) green waste compost (65 microg g(-1)). The three different types of chicken manures increased the NO3-N concentration from 75% (228 microg g(-1)) to 226% (424 microg g(- 1)) over the control. Approximate recovery of P added by the amendment as resin-extractable soil P was 53% for cattle manure and 39% for chicken manure. Application of cattle manure resulted in a 22% increase in soil-exchangeable K over levels found in control. Organic amendments application also resulted in a significant increase in exchangeable Na concentration. Some of the organic wastes, viz. cotton gin trash (10 t ha(-1)), cattle manure (10 t ha(-1)), biosolids (10 t ha(-1)) and composted chicken manure (3 t ha(-1)) have value as a source of nutrients to soil and hence showed potential to improve Vertisol properties.