ABSTRACT
Understanding how extended excess soil moisture exacerbated by extreme weather events affects changes in iron (Fe) chemistry is crucial for assessing environmental risk associated with soil phosphorus (P) in high P soils. The objective of our study was to assess the effects of three soil moisture regimes (field capacity, water saturation, and waterlogging), two Fe3+ nitrate level (Fe3+ nitrate addition and no Fe3+ nitrate addition), and the duration of incubation (0, 3, 7, 14, 21, 28, 35, 49, 63, 90, and 120 days) on the (i) reduction of ferric (Fe3+) to ferrous (Fe2+) iron, (ii) solubility of soil P, and (iii) soil microbial biomass and greenhouse gas emissions. Surface soils (0-20 cm) were collected from a maize silage field located in the Fraser Valley (British Columbia, Canada). Decreased redox potential (Eh) of 155 mV in waterlogged soils coincided with the reduction of Fe3+ to Fe2+ of about 1190 mg kg-1 and an increase in soil pH of 0.8 unit compared to field capacity regime at 120 days after pre-incubation (P < 0.001). The increase of pH is due to the microbially-mediated reduction of metal cations which consumes H+ cations. Water-extractable P (Pw) concentrations increased with increasing soil moisture regimes from 1.47 to 2.27, and 2.58 mg kg-1 under field capacity, water saturation, and waterlogged regime respectively. Mehlich-3 extractable P concentrations significantly decreased from 196 to 184 and 172 mg kg-1 under water saturation, field capacity, and waterlogged regime respectively. Concomitant to Pw concentrations, microbial biomass carbon and nitrogen as well as DOC, CO2 and N2O emissions increased with increasing soil moisture regimes. The Fe3+ nitrate addition had an inhibitory effect on Fe reduction, Pw concentration at the first 35 days, and DOC but a stimulating effect on N2O emission. A high N2O emission at the first 63 days, CO2 emission after 35 days, and a non-remarkable concentration of Fe2+ at the first 63 days with Fe3+ nitrate addition under waterlogged soil suggests that NO3 - is more preferable than Fe3+ as an electron acceptor. Our results showed that soils maintained under extended anoxic conditions could increase the soluble and available P and subsequent risk of P transport to surface and drainage waters, whereas Fe3+ nitrate addition could minimize or delay this effect.
ABSTRACT
For centuries, some Indigenous Peoples of the Americas have planted corn, beans and squash or pumpkins together in mounds, in an intercropping complex known as the Three Sisters. Agriculturally, nutritionally and culturally, these three crops are complementary. This literature review aims to compile historical foods prepared from the products of the Three Sisters planting system used in Indigenous communities in the region encompassing southern Quebec and Ontario in Canada, and northeastern USA. The review does not discuss cultural aspects of the Three Sisters cropping system or describe foods specific to any one Indigenous group, but rather, gives an overview of the historical foods stemming from this intercropping system, many foods of which are common or similar from one group to another. Some of the methods of food preparation used have continued over generations, some of the historical foods prepared are the foundation for foods we eat today, and some of both the methods and foods are finding revival.
ABSTRACT
Nutrient leaching losses from horticultural production threaten the quality of groundwater and freshwater systems worldwide. The objectives of this study were to (a) assess the effects of annual applications of ammonium sulfate fertilizer through fertigation (FERT) and broadcast (BROAD) on nutrient leaching losses and (b) determine the links among chemical property changes in leachates and soil with berry yields after 9 and 11 years of blueberry production. The long-term blueberry site was established in 2008 using seven combinations of treatments including an unfertilized control (CONT) and three N fertilizer rates (100%, 150%, 200% of recommended rates) using BROAD and FERT methods. Nutrients concentrations (NO3--N, NH4+-N and SO42--S) and chemical properties (pH and electrical conductivity (EC)) of leachate, sawdust and soil and berries were assessed. All FERT methods resulted in concentrations of NO3--N in the leachates > 100 mg L-1 with a maximum of 200 mg L-1 for FERT-200 during the growing season due to the easy transport of dissolved nutrients with the irrigation water. All BROAD methods resulted into concentrations of NO3--N in the leachates >10 mg L-1 with a maximum of 35 mg L-1 for BROAD-200 between April and July, as well as between November and April, indicating two periods of NO3--N leaching losses. The pattern observed with BROAD indicates that irrigation water in the summer and heavy rainfall in the winter contribute to NO3--N leaching losses. Concentrations of NH4+-N in the leachates >1 mg L-1 were measured under FERT with a peak at 64.78 mg L-1 for FERT-200, during the period April to August, due to NH4+'s ability to quickly move through the sawdust layer with irrigation water. Principal component analysis linked berry yield decrease with ammonium sulfate applications above recommended rates (FERT and BROAD) and with changes in soil pH and EC. Our results demonstrated that excess fertilizer applications above recommended rates using FERT and BROAD can threaten the sustainability of blueberry production by enhancing nutrient leaching losses and reducing berry yield.
ABSTRACT
Outdoor hog-rearing operations are of interest for both producers and consumers due to high product quality, animal welfare status, and low input and potential environmental risks. However, hog manure is rich in phosphorus (P), an environmentally sensitive nutrient, and distribution of different P fractions down the soil profile in these production systems is not well understood. The objective of this study was to determine the spatial variability of soil P in different soil depth intervals following 1-year outdoor farrowing sows in a 0.5-ha paddock in cold-temperate climate of Eastern Canada. Soil samples were collected with 0-15, 15-30, and > 30 cm depth intervals (up to 60 cm or the depth that sampling was possible) in grazing/rooting, feeding, wallow, and farrowing hut areas. Soil samples were analyzed for Olsen P (Pol), organic P (PO), and total P (PT). Areas with more frequent presence of hogs showed 45-80% greater Pol concentrations, and movement of soluble PO down the soil profile was higher in these areas compared with the grazing/rooting area. The PO formed 80% of PT throughout the paddock, and the spatial distribution of PO was similar to PT in all soil depth intervals but different from Pol. Results also showed that PO concentrations in the paddock decreased at > 30 cm depth except for the feeding area. Findings of this study reveal that farrowing sow cycle in an outdoor hog-rearing farm setting can result in hot spots of P, which enhance the risk of environmental pollution.
