Interseeded cover crops, soil health, and nitrogen supply for grain corn in Ontario

Non-Peer ReviewedInterseeded cover crops are a promising option for improving environmental sustainability in corn-based rotations. Field plots were established in 2015 under conventional tillage and regional corn N fertilization practices and repeated over two seasons at three sites in southern Ontario: Ridgetown, Elora, and Peterborough. The objectives were to evaluate the effects of interseeded annual ryegrass (ARG) and red clover (RCL) on grain corn yield and N uptake; soil mineral N (Nmin); and soil biological parameters. At each site, ARG, RCL, an ARG/RCl blend (MIX), and a no-cover control (BARE) were arranged in a RCBD replicated four times. The cover crops were seeded between the corn rows at the 5-leaf stage using an InterSeederTM drill. Cover crops accumulated 15 - 860 kg C ha-1 and 1.3 - 77 kg N ha-1 per season, and their yields were significantly correlated with soil microbial biomass, β-Glucosidase activity, and particulate organic matter. Community-level physiological profiling (BIOLOG EcoplatesTM) showed that microbial community diversity was significantly greater in ARG than BARE. Grain N concentration (10.8 - 11.2 g kg-1) and aboveground corn N uptake (100 - 154 kg ha-1) were not significantly reduced by cover crops at all sites. Although residual Nmin levels measured at grain corn harvest (0-30 cm) and the following spring (0-15 cm) were generally low (2.4 - 9.3 mg kg-1) at all sites, ARG had 48% lower Nmin than BARE. The effects of cover crops on soil health parameters, corn N uptake and Nmin were more affected by site and seasonal variability than by cover crop treatments. However, the results indicate the potential for improving soil health when there is successful establishment of interseeded annual ryegrass or red clover

Are current dynamic water quality models too complex? A comparison of a new parsimonious phosphorus model, SimplyP, and INCA-P

Catchment-scale water quality models are becoming increasingly popular tools for exploring the potential effects of land management, land use change and climate change on water quality. However, the dynamic, catchment-scale nutrient models in common usage are complex, with many uncertain parameters requiring calibration, limiting their usability and robustness. A key question is whether this complexity is justified. To explore this, we have developed a parsimonious P model, SimplyP, incorporating a coupled rainfall-runoff model and a biogeochemical model able to simulate streamflow, suspended sediment, particulate and dissolved P dynamics. The model’s complexity is compared in a small rural catchment in northeast Scotland. For three land use classes, less than six SimplyP model parameters must be determined through calibration alone, the rest may be based on measurements; INCA-P has around 40 unmeasurable parameters. Despite simpler process-representation, SimplyP produced a slightly better dissolved P simulation during both calibration and validation, and produced similar long-term projections in response to changes in land management. Results support the hypothesis that INCA-P is overly complex for the study catchment. We hope our findings will help prompt wider model comparison exercises, as well as debate amongst the water quality modelling community as to whether today's models are fit for purpose. Simpler models such as SimplyP have the potential to be useful management and research tools, building blocks for future model development (prototype code is freely available), or benchmarks against which more complex models could be evaluated

Decimetric-scale two-dimensional distribution of soil phosphorus after 20 years of tillage management and maintenance phosphorus fertilization

Improving soil test P assessment at plot scale is essential for productivity in conservation agriculture systems. We characterized the distribution of Mehlich-3 P (P-M3) concentrations at the decimetric scale with depth on either side of the sowing row in no-till (NT) and moldboard plow (MP) plots fertilized with 35 kg P ha(-1) every 2-yr in a corn-soybean rotation (20-yr). A total of 996 soil samples (83 samples x 2 depths [0-5 and 5-20 cm] x 6 plots [3 blocks each MP and NT]) were collected at corn harvest in 2012. The average PM3 concentrations in the 0-to 5-cm layer were 35.7 and 63.4 mg kg(-1) in MP and NT, respectively. The PM3 concentration in the 5-to 20-cm depth was similar between MP and NT and averaged 32.0 mg kg-1. The horizontal distribution of PM3 concentrations in these plots was less sensitive to extrinsic factors including tillage, P fertilization and soil depth. High coefficients of variation were associated with PM3 data in both MP (77 and 63% at 0-5 and 5-20 cm, respectively) and NT plots (46 and 66% at 0-5 and 5-20 cm, respectively). It is possible that this strong overall variability overshadowed any PM3 pattern that could have been introduced by NT management. Geostatistical semivariance analysis indicated a predominance of random spatial dependence in most plots, except two plots (one MP and one NT) with moderate spatial structures. The 2-D geospatial model related to tillage was not detected by the sampling grid used at this experimental site. Therefore, a similar sampling strategy would be appropriate and could be recommended for these two tillage systems in this long-term corn-soybean rotation

La collezione di marmi antichi del Museo di Mineralogia dell’Università di Pavia

A historic collection of polished squares of marbles has been analyzed for a awareness-raising project of the Mineralogical Museum, Pavia University. Seventy specimens were investigated for a petrographic classification and historical study. The collection setting refers to European fine art collections of the 19th century. The decorative stones were probably collected from Roman archaeological ruins and come from historical quarries of Greece, Turkey, Egypt and other localities of the Roman Empire. Rocks range from marbles to alabasters. Very little historical information is available: probably in the late 19th century the collection was given to the Mineralogical Museum but there is no written evidence of the original composition and number of marble samples. The aim of this work is to describe the marble collection, in order to plan a permanent exhibition for teaching purposes

Tillage practices of a clay loam soil affect soil aggregation and associated C and P concentrations

International audienceUnder long-term cultivation, greater accumulations of soil organic matter (SOM) and phosphorus (P) are found in the surface soil layer under no-till (NT) versus mouldboard ploughing (MP) practices. Our objective was to evaluate the effects of NT and MP practices on concomitant SOM and P distribution and sorption characteristics among water-stable aggregates and non-aggregated particles. The study was conducted in Quebec, Canada, as part of a long-term corn and soybean rotation experiment (established since 1992) on a clay loam soil of the St-Blaise series (Dark Grey Gleysol). Soil samples were collected in the fall of 2007 in the 0–5 cm layer from plots under NT and MP receiving 35 kg P ha–1 and 160 kg N ha–1. Samples were separated into three water-stable aggregate-sized classes (macro, 2000–250 μm; meso, 250–180 μm; micro, 180–53 μm) and (silt + clay)-sized particles (< 53 μm) using wet-sieving. Macro aggregates made up 60.2 and 48.5% of total soil weight under NT and MP, respectively. In wet-sieved soils from NT plots, water-extractable P (Pw) concentration increased in the order (silt + clay)-sized particles < micro- < meso- < macro-aggregates; under MP, micro-, meso-, and macro-aggregate fractions had the same Pw concentration, while the (silt + clay)-sized particles showed the lowest Pw concentration. The hierarchy observed among aggregate-sized classes under NT in relation to Pw concentration was also observed for carbon content, indicating that Pw is influenced by soil aggregation as driven by SOM accumulation. The lower Pw concentration in (silt + clay)-sized particles could be explained by a greater retention of P by reactive oxides and highly disordered alumino-silicates present on (silt + clay)-sized particles, thereby reducing the soluble P released from these particles. One important aspect of this study is the contrasting P sorption characteristics of solid particles under NT and MP. The P sorption maxima (Smax value) of the (silt + clay)-sized particles was twice that of the water-stable aggregates. Sorption characteristics reflect the hierarchy observed under NT for organic C and Pw, indicating a closer link between SOM and P dynamics within soil aggregates in contrast with MP