ALBERT

Beschreibung: Estimation of fertilizer N requirements of crops remains a challenge. Numerous field studies have been carried out to calibrate soil tests against yield response to applied fertilizer N. Synthesis and identification of common crop fertilizer N response across large data sets (years, sites) will allow maximum use of this past work and a framework for comparison of future work. The objective of this paper is to define macro-relationships between the economically optimum fertilizer N rate (EONR) and the yield increase at the EONR defined as the delta yield, ΔYec , for large data sets of 2nd- and 3rd-order estimates of fertilizer N response functions with both 0th and 1st-order rate relationships between fertilizer nitrogen use efficiency and applied fertilizer N. The derived macro-relationships are curvilinear, depend on the price ratio R = the ratio of the (price per kilogram of fertilizer N)/(price per kilogram grain), and are similar to measurements from data sets of corn fertilizer N response functions spanning decades (+20 yr) and representing areas in both the United States and Canada. The macro-relationships appear to be robust and therefore useful for quantifying (post-harvest analysis) soil fertility, crop fertilizer N requirement, and comparison/classification of N response functions.Key words: Response function, prediction, efficiency, economic N rate, corn

Beschreibung: Supplementing irrigation water with effluents could reduce the need for potable water for irrigation and promote nutrient recycling, but may require additional amendments to deal with Na. In a growth chamber experiment, winter wheat was seeded into a control soil and to soil amended with either gypsum or wood ash applied at an equivalent rate of 15 dry t ha-1. Wheat was irrigated at a rate of 6 mm d-1 with distilled water (DW), kraft pulp mill effluent (KPME) and waste-activated sludge (WAS), and three KPME/WAS combinations. This included two KPME/WAS combinations diluted with DW to 25 and 50% (KPME/WAS:DW) to evaluate the effect on the nutrient uptake and biomass and the impact on soluble ions in the soil. Effluent applications increased wheat biomass up to 70%, and increases of 97 and 140% were observed in soils amended with gypsum and ash, respectively. Effluent applications increased soluble Na, Ca, and SO4, but only on the gypsum-amended soils, except those irrigated with WAS, had lower sodium adsorption ratio (SAR) than control soils by 0.7 to 3 units. Effluent combinations at the lower dilutions in combination with gypsum could be used to provide supplemental water with moderate increases in electrical conductivity (ECe) and SAR that would still be within tolerable limits of many crops.Key words: Effluent irrigation, electrical conductivity, gypsum, sodium adsorption ratio, wood ash

Beschreibung: Most soil C sequestration research has focused on organic C stabilization, while carbonate precipitation has received little attention. Mineral colloids can accelerate abiotic humification reactions of biomolecules such as amino acids, sugars, and polyphenols, derived from the breakdown of biological residues and metabolites. During these reactions CO2 is produced as a result of the oxidation of biomolecules. However, the biomolecule-induced formation of carbonate during abiotic humification remained to be uncovered. Here we demonstrate using X-ray diffraction, Fourier transform infrared spectroscopy and C K-edge and Mn L-edge near edge X-ray absorption fine structure spectroscopy that the Maillard reaction (glucose and glycine) and the integrated polyphenol-Maillard reaction pathway (catechol, glucose and glycine), in the presence of birnessite (δ-MnO2) produce MnCO3 (rhodochrosite). Increasing the molar ratio of catechol to glucose and glycine dramatically hampered carbonate formation, which is attributed to the enhanced formation of humic polymers, which increased proton generation and perturbed rhodochrosite crystallization through Mn(II)-humic complexation in the reaction systems. Thus, rhodochrosite formation was a competing reaction with humic substance formation. Our findings are of fundamental significance in understanding the vital role of the nature and relative abundance of biomolecules in abiotic carbonate formation, which merits close attention in understanding and regulating C sequestration in natural environments.Key words: Abiotic humification, polyphenol-Maillard reaction, rhodochrosite, birnessite, C K-edge and Mn L-edge NEXAFS

Beschreibung: Tillage influences the retention and storage of organic matter (OM) in soil. We used a sequential density and particle-size fractionation to evaluate the total quantity and distribution of organic carbon (C) and nitrogen (N) in the profile of soils under mouldboard ploughing and no-till. Cores (0-60 cm) from four long-term tillage studies (in Prince Edward Island, Quebec, and two sites in Ontario) on soils of different textures, from sandy loam to clay were collected and divided into six depth increments. Four soil OM fractions were isolated on the basis of size and density from each sample. At two sites the standing stocks of C and N were larger in tilled than in no-till soil profiles at depths slightly greater than plough depth; tillage effects were also evident at a third site, where the mass of C in a layer close to the depth of ploughing was greater in tilled soils. Ploughing also had a substantial and consistent positive effect in all four soils on the quantity of C (and in some cases N) protected within aggregates, particularly at or near the bottom of the plough layer, and sometimes in surface soil layers. We attribute differences observed in whole soil C and N due to tillage mostly to differences in mineral-associated OM, particularly in soils with heavier textures, but the other size and density fractions could, together, account for as much as 25% of the difference. Because the C capacity level was not reached in heavy-textured soils, these soils show greater potential for further accumulation of C in the soil profile than coarse-textured soils, especially near the bottom of the plough layer.Key words: Light fraction, soil organic matter, soil tillage, physically-protected organic matter, no-till, soil texture

Beschreibung: New legislation to reduce the amount of fertilizer leached into the environment by horticultural growers and the need to implement water-saving irrigation systems require an understanding of salt build-up and of nutrient cycles in order to develop efficient water-use strategies for growers. Solute transport in growing media is central to this process, but has received little attention thus far. The objectives of this study were to determine how solutes behave in sub-irrigated growing media and to assess a solute transport model for these media. A steady state evaporation (upward water flow) experiment was carried out with three different growing media in packed columns in the laboratory. Bromide, potassium and copper concentrations were determined using in-column pore water solution samplers and by sectioning the columns at the end of the experiment to obtain concentration profiles. The Hydrus-1D model was fitted to the solution sampler data assuming non-linear Freundlich adsorption, and then used to obtain favorable predictions of the measured concentration profiles. Independent adsorption isotherm results from batch experiments were found to be inadequate when used to predict solute movement and the results indicate that the preferred approach is an in-column evaluation of the transport parameters.Key words: Solute transport, sub-irrigation, peat, growing media

Beschreibung: A modular approach is presented to assess terrain-specific soil trafficability in terms of soil resistance to penetration and machine-specific rut depths. These modules address: (1) soil resistance to cone penetration (cone index, or CI) as affected by soil moisture, texture and pore space (Module 1), (2) machine-induced rut depths (single-pass and multi-cycles) as affected by wheel loads, tire specifications and CI (accounting for depth of compactable soil, Module 2), (3) temporal variations in hydrothermal conditions, CI, and potential rut depths due to daily soil moisture and temperature variations (Module 3), and (4) spatial variations in CI and rut depth across terrain due to corresponding changes in soil moisture, depth of compactable soil, bulk density, texture, frost depth, organic matter and coarse fragments (Module 4). The approach is applied to off-road wood-forwarding operations. Modules 1 and 2 were calibrated to apply to a wide range of soil conditions. Modules 3 and 4 were initialized for a wood-forwarding case study at CFB Gagetown, New Brunswick, Canada. Model results should be most applicable for flat to near-flat terrain, with insignificant wheel obstructions, and no organic matter accumulations on top of the mineral soil. Key words: Forest harvesting, soil penetration resistance, cone index, soil rut depth, soil disturbance, soil trafficability, soil compaction, terrain modelling

Beschreibung: A study was conducted to examine the effect of tillage on soil conditions and crop growth at three long-term (〉 10 yr) no-till sites, one in each of the Brown, Black, and Gray soil zones of Saskatchewan. The four tillage treatments consisted of one cycle of tillage at three levels of intensity: spring cultivation only, fall + spring cultivation, and fall + spring + disc cultivation, all applied to no-till and also a no-till control. Total and particulate soil organic carbon, soil pH, and soil aggregation were not affected by the tillage operations. Tillage decreased the bulk density in the 5- to 10-cm soil depth, but did not affect soil water content (0-10 cm) or spring soil temperature (0-5 cm). Tillage decreased stratification of available phosphorus to some extent, but there appeared to be no associated effect on crop P uptake. Tillage did not effect crop production in any of the 3 yr following its imposition, except at one site where, in the first year, apparent tillage-induced nutrient immobilization resulted in lower yields. Overall, the imposition of one cycle of tillage on long-term no-till soils appears to have little effect on soil properties or crop growth.Key words: No-till, nutrient stratification, soil organic carbon, tillage

Beschreibung: Water loss from soil minerals has been known to cause errors in the determination of soil organic matter when the loss on ignition (LOI) method is used. Unfortunately, no known published studies reliably quantify the range of structural water in the soil. To do this, 15 common reference minerals were analyzed by LOI to obtain their individual water loss. In addition, 14 upland, loamy soil samples and 3 wetland/hydric soil samples with varied mineral contents were analyzed to collect their X-ray powder diffraction spectra. Based upon X-ray spectra peak intensities, the modal abundance of minerals in each soil sample was determined using the RockJock computer program. The resultant modal weight percentages of all identified minerals in each soil sample were then multiplied by the LOI value for each mineral to obtain the mineral structural water loss (SWL) of that soil sample. For the 17 soil samples analyzed, the range of mineral water loss is 0.56 to 2.45%. Depending on the LOI values of the soil samples, the SWL:LOI ratios range from 0.04 to around 1.00. The SWL:LOI ratios are particularly low for top wetland soil when the LOI value is higher. The ratios are lower for surface soil samples than for subsurface soil samples because of the high LOI values in surface soil samples. Understanding soil mineral water loss and its relation to the LOI patterns from various environments is important for the accurate evaluation of soil organic matter when the LOI method is used. Key words: Mineral, structural water, loss on ignition

Beschreibung: Soil acidity is a major problem in agriculture because it limits plant growth and reduces crop productivity. The neutralizing potential of industrial by-products and their impact on soil properties were evaluated in two acidic soils characterized by contrasting textures, and submitted to intensive agriculture practices. Soil pH, microbial (dehydrogenase and alkaline phosphatase) activity, and Mehlich-3 extractable P, K, Ca and Mg were monitored in the year of soil incorporation of eight liming products and in the following 2 yr. In the sandy loam, liming products did not result in significant increases in soil pH in the 0- to 7.5-cm soil layer. Lime mud (LM) significantly increased soil pH by 0.4 units in the 7.5- to 20-cm layer compared with cement kiln dust (CKD). In the silty clay, calcium-phosphate-magnesium (CalPoMag) significantly raised pH by 0.65 units over both natural calcitic lime (NCa) and the magnesium dissolution product (MgD) in the first soil layer, and by 0.5 units over carbide lime (CL) treatment in the second soil layer. Activities of dehydrogenase and alkaline phosphatase were increased to various degrees by all liming materials, especially on the silty clay; LM and CalPoMag were the most beneficial materials. The exception was MgD, which did not result in any impact on microbial activity relative to the control. Both enzymatic activities were related to the increase in soil pH, particularly the alkaline phosphatase. Ion leaching was more pronounced in the sandy loam than in the silty clay soil, where large differences in the Ca and Mg ion levels were still detected in the 20- to 40-cm layer of the sandy loam. In this study, LM and CalPoMag are interesting liming products, particularly in the silty clay soil. Key words: Enzymatic activity, soil pH, lime, soil cations

Beschreibung: Compositional nutrient diagnosis (CND) provides a plant nutrient imbalance index (CND - r2) with assumed χ2 distribution. The Mahalanobis distance D2, which detects outliers in compositional data sets, has a χ2 distribution. The objective of this paper was to compare D2 and CND – r2 nutrient imbalance indexes in corn (Zea mays L.). We measured grain yield as well as N, P, K, Ca, Mg, Cu, Fe, Mn, and Zn concentrations in the ear leaf at silk stage for 210 calibration sites in the St. Lawrence Lowlands [2300–2700 corn thermal units (CTU)] as well as 30 phosphorus (2300–2700 CTU; 10 sites) and 10 nitrogen (1900–2100 CTU; one site) replicated fertilizer treatments for validation. We derived CND norms as mean, standard deviation, and the inverse covariance matrix of centred log ratios (clr) for high yielding specimens (≥9.0 Mg grain ha–1 at 150 g H2O kg–1 moisture content) in the 2300–2700 CTU zone. Using χ2 = 17 (P 〈 0.05) with nine degrees of freedom (i.e., nine nutrients) as a rejection criterion for outliers and a yield threshold of 8.6 Mg ha–1 after Cate-Nelson partitioning between low- and high-yielders in the P validation data set, D2 misclassified two specimens compared with nine for CND –r2. The D2 classification was not significantly different from a χ2 classification (P 〉 0.05), but the CND – r2 classification differed significantly from χ2 or D2 (P 〈 0.001). A threshold value for nutrient imbalance could thus be derived probabilistically for conducting D2 diagnosis, while the CND – r2 nutrient imbalance threshold must be calibrated using fertilizer trials. In the proposed CND –D2 procedure, D2 is first computed to classify the specimen as possible outlier. Thereafter, nutrient indices are ranked in their order of limitation. The D2 norms appeared less effective in the 1900–2100 CTU zone. Key words: Nutrient balance, simplex closure, variance-covariance matrix, χ2 distribution, grain corn, nitrogen and phosphorus fertilization