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Although farmers are the key actors in managing soil health, we have little understanding of what farmers know about soil health, how they define the term, and how they manage for it on their farms. Interviews with 34 farmers in Maritime Canada revealed their perceptions about soil health, their methods for assessing their own soils, and their reactions to a comprehensive soil health assessment based on the Cornell Soil Health Assessment (CSHA). Farmers primarily assessed soils using aboveground indicators such as plant health and yield, as well as physical indicators such as texture or water-holding capacity. Most farmers (91%) had heard of soil health, and their definitions focused on biological and productivity aspects of the soil. Organic farmers tended to be more open to the CSHA results and were more likely to give a holistic definition of soil health than conventional farmers. Depending on what frame is invoked about soil, farmers think of soil health differently. Despite differences between farmers' perceptions and CSHA results, most farmers found CSHA results useful (71%) and planned to undertake management changes (74%) based on them. Soil health could be an 'inclusive' common ground for farmers and soil scientists to think about and manage soils. [ABSTRACT FROM AUTHOR]

Phosphorus (P) is a limiting nutrient in many environments but plants and microbes have evolved with mechanisms for acquiring soil P, including the excretion of phosphatase enzymes. Molecular analysis of bacterial phosphatase genes can provide insight into biological P transformations and the contribution to soil P availability and plant uptake. To assess these relationships, soil and plant samples were collected from 12 organically-managed soybean fields varying in pH, labile P concentration, and potential phosphatase activity (pH 6.5) across Prince Edward Island, Canada. Real-time PCR was used to quantify bacterial phosphatase genes ( phoC and phoD ) in bulk and rhizosphere soil. Primers targeting class A ( phoC ) of the bacterial non-specific acid phosphatases (NSAPs) were designed and confirmed as effectively targeting phoC genes through sequencing, and phylogenetic comparison with acid phosphatase genes from Genbank. Across all sites, we found that labile P in bulk soil was negatively correlated with phoC and phoD gene abundance and phosphatase activity. In addition, phosphatase activity was consistently higher in rhizosphere compared to bulk soil and was significantly correlated with phoC (bulk soil only) and phoD (rhizosphere soil only) gene abundance. A positive relationship was observed between phosphatase activity, nodule weight, and plant P uptake. Quantification of bacterial genes involved in organic P transformations has been limited, with this study providing the first attempt at quantifying phoC genes in field soils. [ABSTRACT FROM AUTHOR]

Arbuscular mycorrhizal fungi (AMF) are considered to play a pivotal role in organic farming systems as they are known to enhance plant phosphorus (P) uptake from soils low in plant-available P. However, the structure and therefore function of AMF communities may be altered depending on environment and management conditions. Polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) and quantitative real-time PCR (qPCR) were used to explore AMF community structure in soils from perennial forages ( Medicago sativa—Phleum pratense ) on three pairs of long-term (>20 yr) organic and conventional dairy farm soils in Ontario, Canada. There were no significant differences in DGGE band numbers (indicative of species richness) among organic and conventionally managed soils. Analysis of Similarity revealed significant differences in AMF community composition with both farming system management and farm pair location having significant effects ( R = 0.71 and 0.91, respectively, P < 0.0001 for both). Real-time qPCR indicated greater abundance of Funneliformis mosseae under conventional management ( P = 0.036), while organic management tended to support greater abundance of Claroideoglomus claroideum ( P = 0.067). Such a compositional shift in AMF communities could have consequences for the growth and P-use efficiency of their host. The results of this study highlight that the structure of AMF community assemblages are co-determined by both local environmental conditions and farming system management, and importantly, demonstrate for the first time differences between organic and conventional management in dairy farm soils from mixed perennial forages. [ABSTRACT FROM AUTHOR]

Changes in land management practices may have significant implications for soil microbial communities important in organic P turnover. Soil bacteria can increase plant P availability by excreting phosphatase enzymes which catalyze the hydrolysis of ester-phosphate bonds. Examining the diversity and abundance of alkaline phosphatase gene harboring bacteria may provide valuable insight into alkaline phosphatase production in soils. This study examined the effect of 20 years of no input organic (ORG), organic with composted manure (ORG + M), conventional (CONV) and restored prairie (PRA) management on soil P bioavailability, alkaline phosphatase activity (ALP), and abundance and diversity of ALP gene ( phoD ) harboring bacteria in soils from the northern Great Plains of Canada. Management system influenced bioavailable P ( P < 0.001), but not total P, with the lowest concentrations in the ORG systems and the highest in PRA. Higher rates of ALP were observed in the ORG and ORG + M treatments with a significant negative correlation between bioavailable P and ALP in 2011 (r 2 = 0.71; P = 0.03) and 2012 (r 2 = 0.51; P = 0.02), suggesting that ALP activity increased under P limiting conditions. The phoD gene abundance was also highest in ORG and ORG + M resulting in a significant positive relationship between bacterial phoD abundance and ALP activity (r 2 = 0.71; P = 0.009). Analysis of phoD bacterial community fingerprints showed a higher number of species in CONV compared to ORG and ORG + M, contrary to what was expected considering greater ALP activity under ORG management. In 2012, banding profiles of ORG + M showed fewer phoD bacterial species following the second manure application, although ALP activity is higher than in 2011. This indicates that a few species may be producing more ALP and that quantitative gene analysis was a better indicator of activity than the number of species present. [ABSTRACT FROM AUTHOR]

Bacterial transformation of phosphorus (P) compounds in soil is largely dependent on soil microbial community function, and is therefore sensitive to anthropogenic disturbances such as fertilization or cropping systems. However, the effect of soil management on the transcription of bacterial genes that encode phosphatases, such as phoD, is largely unknown. This greenhouse study examined the effect of long-term management and P amendment on potential alkaline phosphatase (ALP) activity and phoD gene (DNA) and transcript (RNA) abundance. Soil samples (0-15 cm) were collected from the Glenlea Long-term Rotation near Winnipeg, Manitoba, to compare organic, conventional and prairie management systems. In the greenhouse, pots of soil from each management system were amended with P as either soluble mineral fertilizer or cattle manure and then planted with Italian ryegrass (Lolium multiforum). Soils from each pot were sampled for analysis immediately and after 30 and 106 days. Significant differences among the soil/P treatments were detected for inorganic P, but not the organic P in NaHCO3-extracts. At day 0, ALP activity was similar among the soil/P treatments, but was higher after 30 days for all P amendments in soil from organically managed plots. In contrast, ALP activity in soils under conventional and prairie management responded to increasing rates of manure only, with significant effects from medium and high manure application rates at 30 and 106 days. Differences in ALP activity at 30 days corresponded to the abundance of bacterial phoD genes, which were also significantly higher in soils under organic management. However, this correlation was not significant for transcript abundance. Next-generation sequencing allowed the identification of 199 unique phoD operational taxonomic units (OTUs) from the metagenome (soil DNA) and 35 unique OTUs from the metatranscriptome (soil RNA), indicating that a subset of phoD genes was being transcribed in all soils. [ABSTRACT FROM AUTHOR]

Minimizing nutrient surpluses and improving efficiency of nutrient use are key challenges for all dairy farming production systems, driven by economic, environmental and increasing regulatory constraints. Our study examined the efficiency of N, P and K use on a commercial dairy farm through an integrated approach that evaluated the nutrient status of all aspects of the production system of the case-study farm, a 75 lactating Holstein cow dairy in Kings County, Nova Scotia, Canada. During the decade after 1988, the farm owner implemented a series of changes in production practices, including diversification of the crop rotation, implementation of a management intensive grazing (MIG) regime and adoption of a systematic approach to soil and nutrient management. Milk production, and associated farm exports of N, P and K, increased by 666 kg cow[sup-1] between 1990 and 2000. Purchases of N-P-K fertilizers were eliminated in 1990 and feed nutrient imports were dramatically reduced. Feed costs per liter of milk declined from 14.3 cents (CDN) liter[sup-1] in 1990-92 to 11.6 cents liter[sup-1] in 1998-2000, even as feed prices increased regionally by 10-20% over the same period. Modeling of current whole farm mass N, P and K balance indicated that 25.0% of all N inputs are recovered in farm products, milk and meat. Non-legume-derived field N input (67kg N ha[sup-1] before losses) was close to optimum for the predominantly legume/grass-based forage cropping system. Model-determined annual farm nutrient surpluses (outputs-inputs)for P (9.0 kg ha[sup-1] yr[sup-1]) and K (8.2 kg ha[sup-1] yr[sup-1]) were significantly lower than those previously reported for regional confinement-based dairy farms, which were more reliant on corn production. However, data from 16 years of soil analysis (1985-2001) indicated an increase in soil-test P levels of approximately 2 mg kg[sup-1] yr[sup-1]. Recent refinements in dairy animal dietary P levels have further reduced the farm P surplus (2.6 [ABSTRACT FROM AUTHOR]

No-till green manure (Gmr) termination creates a unique situation compared to conventional no-till crop management due to the surface mulch generated. However, the impact this practice has on soil biota has been little researched, despite the important role soil biota play in soil ecosystem functions such as decomposition and pest control. This study examines how termination management of Gmr can affect soil biota and their population dynamics. Over two trials, Gmr tillage regimes of fall tilled, spring tilled, or no-till were applied to a spring planted Gmr of hairy vetch/oat (HVO) along with a typical regional practice of tilled red clover Gmr within a four-year grain rotation. Soil microbial biomass (SMB), earthworm density, and beetle and spider activity density were assessed up to three years following Gmr termination. SMB was greatest in the spring for no-till and fall tilled HVO Gmr treatments, but the effect was transient, disappearing after two months. Earthworm densities were negatively affected by tillage (88% and 86% less than no-till in Trial 1 and 2, respectively) but densities recovered three years after tillage to that of the no-till treatment. Beetle activity density was largely unaffected by Gmr termination. Spider captures were more numerous in no-till plots compared to spring tilled in one trial. Impacts of Gmr termination on soil organisms vary by taxa and earthworms were the most sensitive, taking two years to recover from tillage. No-till Gmr termination does not show clear benefits to soil biota. [ABSTRACT FROM AUTHOR]

Horticultural practices may impact invertebrates in agroecosystems, particularly natural enemies. Impacts can be better understood by grouping organisms functionally or using morphological traits in addition to taxonomic determinations., We compared the effects of mulch type (compost, pine needles, unmulched) and weeding strategy (weeded, unweeded) on beetle (Coleoptera) communities in highbush blueberries, focusing on early-season captures that reflected overwintering habitat., Beetle diversity was similar between plot types, although functional grouping revealed differences as a result of mulching but not weeding. Predatory and granivorous Carabidae were most abundant in unmulched plots, mycetophages were most abundant in pine needles, and saprophages were most abundant in compost. Predatory Staphylinidae were most diverse in compost plots, and the diversity of granivores was greatest in unmulched plots., Carabid biomass was greater in unmulched than compost mulched plots partly as a result of larger beetle size., Beetle communities in unmulched and pine needles mulched plots were more similar than those in compost mulched plots., A combination of compost mulched and unmulched areas should benefit all predatory taxa, although mulch use for pest control will need to be evaluated within the context of other production goals. [ABSTRACT FROM AUTHOR]

Recent studies exploring the soil P status of organic dairy farms in Canada report low concentrations of Olsen soil test P (STP), yet the impact on crop productivity is unclear. It has been suggested that soil biological activity, including organic P mineralization, may supply crops with P not measured by conventional soil P tests. Organic P (Po) mineralization depends on the forms of soil Po present; thus, the objective of this study was to compare soil P forms in perennial forage fields of three paired organic and conventional dairy farms in southwestern Ontario using solution 31P nuclear magnetic resonance (NMR) spectroscopy. Several methods to account for degradation of orthophosphate diesters during NMR analysis were also tested. Soils from conventional systems had greater proportions and concentrations of orthophosphate in NMR extracts than those from organic systems, while total Po was more abundant in organic systems. Proportions of diesters, thought to be readily mineralizable forms of Po, were high in all soils; this was especially true after accounting for diester degradation. The relative percentage of diesters was greater in soil extracts from organically managed systems than those from conventional fields when a moderate amount of diester degradation was assumed (26 vs. 19%). These results may in part explain why some organically managed perennial forage crops can maintain acceptable yields at low STP concentrations. [ABSTRACT FROM AUTHOR]

Recent studies exploring the soil P status of organic dairy farms in Canada report low concentrations of Olsen soil test P (STP), yet the impact on crop productivity is unclear. It has been suggested that soil biological activity, including organic P mineralization, may supply crops with P not measured by conventional soil P tests. Organic P (Po) mineralization depends on the forms of soil Po present; thus, the objective of this study was to compare soil P forms in perennial forage fields of three paired organic and conventional dairy farms in southwestern Ontario using solution 31P nuclear magnetic resonance (NMR) spectroscopy. Several methods to account for degradation of orthophosphate diesters during NMR analysis were also tested. Soils from conventional systems had greater proportions and concentrations of orthophosphate in NMR extracts than those from organic systems, while total Po was more abundant in organic systems. Proportions of diesters, thought to be readily mineralizable forms of Po, were high in all soils; this was especially true after accounting for diester degradation. The relative percentage of diesters was greater in soil extracts from organically managed systems than those from conventional fields when a moderate amount of diester degradation was assumed (26 vs. 19%). These results may in part explain why some organically managed perennial forage crops can maintain acceptable yields at low STP concentrations. [ABSTRACT FROM AUTHOR]

Soil phosphorus (P) tests are designed to indicate plant-available inorganic orthophosphate (P i ), but fail to account for P i that may become available through organic phosphorus (P o ) mineralization. This P source may be especially important in soils with low concentrations of solution and labile P i . We assessed gross P o mineralization and immobilization using labeling with 33 P in four calcareous Alfisols with varying concentrations of Olsen soil test P that were collected from forage fields of dairy farms in Ontario, Canada. Rapid microbial 33 P uptake during incubation was found for the soils with the lowest available P i as indicated by both Olsen soil test P and water-extractable P i . The tracer incorporation into microbial P after 8 days ranged from 7 to 44% of applied 33 P and was negatively related to water-extractable P i following a power-type relationship. As concentrations of microbial P were similar in all soils, this suggests faster turnover of P in the microbial biomass at water-extractable P i below 0.1 mg P kg −1 soil. Daily gross P o mineralization rates ranged from 0.2 to 2.8 mg P kg −1 soil d −1 and contributed 7–56% of the isotopically-exchangeable P in 8 days. Based on these findings, microbial processes have the potential to make a significant contribution to forage P nutrition. [ABSTRACT FROM AUTHOR]