Potential Phosphorus Export in Snowmelt as Influenced by Fertilizer Placement Method in the Canadian Prairies.

Placement strategies for P fertilizer can affect P availability to crops and influence the amounts and forms of P removed from soil in runoff, contributing to eutrophication. On the Canadian prairies, most runoff occurs during snowmelt. Two adjacent farm fields in Saskatchewan, Canada, were used to assess the effects of spring P fertilizer placement on crop P uptake, residual soil P, and potential P export in simulated snowmelt. One was in conventional tillage (CT) with no history of P fertilization, and the other was in a no-till (NT) system with multiyear P fertilization at recommended rates. Fertilization (monoammonium phosphate) treatments were no P fertilizer (control); seed placed, deep banded, and broadcast and incorporated at 20 kg PO ha; and broadcast treatments at 20, 40, and 80 kg PO ha. Yield and P uptake were not affected by placement method. Water-extractable P at the soil surface after harvest was unaffected by placement or rate at either site but increased below the 5-cm depth at the NT site in 2016. Broadcast treatments increased P in runoff relative to in-soil P placement for the 20- and 80-kg PO ha treatments at the CT site and for the 80-kg PO ha treatment at the NT site. Thus, in-soil application of P fertilizer appears to be an effective strategy to reduce the risk of P export in snowmelt runoff.

Phosphorus speciation in a prairie soil amended with MBM and DDG ash: Sequential chemical extraction and synchrotron-based XANES spectroscopy investigations.

Sequential chemical extraction and synchrotron-based XANES spectroscopy techniques were used to identify P species in two ashes before and after addition to a prairie soil. The used ashes were: meat and bone meal ash (MBMA) and dried distillers grains ash (DDGA) plus mineral P fertilizer (MP) for comparison. Soil treated with MP contained higher content of resin-Pi and NaHCO3-Pi followed by DDGA and MBMA. The MBMA amended soil had the highest (47%) proportion of the soil P contained in recalcitrant HCl extractable fraction, reflecting more Ca-bound P present and being formed in soil after application. Analysis of both ashes with XANES spectroscopy before application to soil revealed that MBMA had strong spectral features consistent with hydroxyapatite (Ca5(PO4)3(OH)). DDGA exhibited spectral features consistent with a mixture of several Mg and K phosphate salts rather than a single mineral species. The distinctive features in the XANES spectra of both ashes largely disappeared after amendment to the soil, suggesting transformation to different P forms in the soil after application. It is also possible that the added amount of P to the studied soil via DDGS or MBMA was small enough so that P speciation is not different from the background P level.

Bioavailability of Metsulfuron and Sulfentrazone Herbicides in Soil as Affected by Amendment with Two Contrasting Willow Biochars.

This study investigated the effect of two willow (Salix spp.) biochars, produced using either fast- or slow-pyrolysis, on the bioavailability of metsulfuron and sulfentrazone herbicides in soil. Five rates (0%, 1%, 2%, 3%, and 4%; w/w) of each biochar were used, along with varying rates of metsulfuron (0-3.2 µg ai kg-1) and sulfentrazone (0-200 µg ai kg-1), followed by a sugar beet bioassay. The fast-pyrolysis biochar had minimal effect, while the slow-pyrolysis biochar decreased the bioavailability of both herbicides. Despite using the same feedstock, the two biochars had different physical and chemical properties, of which specific surface area was most contrasting (3.0 and 175 m2 g-1 for fast- and slow-pyrolysis biochar, respectively). Increased anionic herbicide adsorption associated with greater surface area of the slow-pyrolysis biochar is considered to be the primary mechanism responsible for reducing herbicide bioavailability with this biochar.

[Concepts and relative analytical techniques of soil organic matter].

The research of soil organic matter (SOM) has been highlighted in soil science. In the past 50 years, new perspectives in the relationship between SOM and sustainability of atmosphere and biomosphere, and strong motivation to find a vivid index for soil quality variation induced the transformation in concepts and analytical techniques of SOM: the curiousness to humic substances faded off since they were dull to anthropogenic activities, and interests were focused on the light fraction of organic matter (LFOM), organic carbon associated with different mineral particles in size, particulate and intra-particulate organic matter (POM and iPOM), water soluble organic matter (WSOM), and microbial biomass carbon (MB-C). The relative fractionation procedures have been developed, and the main research activities on SOM are transformed from the products of microorganisms (humus) to the organic matter comprised in plant residues at their various decomposition stages and the organic carbon in microorganisms, since they are biologically active and immediately respond to soil cultivation and tillage, crop rotation, and fertilizer application, etc.

[Soil particle size fractionation with centrifugation method].

According to the rotor size of Mandal RC5C and Stoks' law, a segregation procedure for soil particle size fractionation was designed, and used for the particle separation of Huangmian soil(Calcaric cambisols, FAO), Huihe soil (Haplic greyxems, FAO), and Helu soil(Calcic kastanozems, FAO) in the Loess Plateau of China, and of Orthic Brown Chernozem, and Orthic Black Chernozem in Canadian Prairie. The fractionation results of the 5 soils by using this procedure were in line with those of the standard pipette method.

[Influence of cultivation on organic carbon in three typical soils of China Loess Plateau and Canada Prairies].

The dynamics of organic carbon in 3 soils of China Loess Plateau and Canada Prairies was significantly different: in China, the Huangmian soil (Calcaric Cambisols, FAO) lost 77% of total organic carbon (0-20 cm) within 5 years of cultivation, with a decrease rate of 2.11 tons C.hm-2.yr-1, which was mainly caused by water erosion and tillage erosion; and the Huihe soil (haplic greyxems, FAO) lost 70% of total organic carbon (0-20 cm layer) at the rate of 0.961.06 tons C.hm-2.yr-1, because of water erosion and decomposition over 42 years. However, the orthic brown chernozem in Canada lost 11% and 44% of the total soil organic carbon (0-20 cm layer) after 40 and 80 years of cultivation, respectively, with a corresponding rate of 0.17 tons C hm-2.yr-1 and 0.45 tons C hm-2.yr-1. The improvement in tillage and rotation system, which prevented soil from wind erosion and increased current residues into soil, was responsible for the decrease of the loss rate. The dynamics of soil light fraction organic carbon (LFOC) was similar to that of total organic carbon: Huangmian and Heilu soil lost 73% and 90% of LFOC, while orthic brown chernozem lost 74% and 70% of LFOC after breaked in 1920 and 1960, respectively. Among the test soils, Huangmian and Huihe soil had the fast SOC depletion due to the difference in the allocation of organic carbon between LFOC and HFOC.