Soil organic matter content and nutrient turnover in thin Black Oxbow soils after intensive conservation management

Non-Peer ReviewedCultivation and frequent fallowing has a significant impact on soil organic matter (SOM) concentration and soil bulk density. Conservation tillage systems, such as direct seeding, minimize mixing and disturbance of the surface soil which, in turn, is thought to improve SOM characteristics. This study was initiated to determine the extent to which four highly diverse management systems conserve SOM and influence potential nutrient supply. Conservation managements investigated in this study included a brome grass seed-down and a direct seeded cereal-oilseed rotation. A third site was selected from an area managed under conventional fallow-wheat (with intermittent fertilizer) from 1930 to present. Uncultivated native prairie was also analyzed and used as a control. Concentrations of organic C, N and S were highest in the native sod, followed by brome grass, direct seeded and conventional fallow-wheat. Soil bulk density indicated a significant increase in the mass of soil in the 0 to 5 cm rooting layer with increased disturbance and soil mixing. The inverse trend between % SOM and bulk density resulted in management having no significant effect on the mass of organic nutrients in the top 5 cm of the rooting volume (CV 9.6%). More important to crop growth however, is the potential supply of mineral nutrients from SOM, which was significantly influenced by conservation management. Managements which improve residue input and reduce soil mixing, although not changing the actual mass of nutrients per rooting layer, enhance the turnover of organically held N and S in the 0 to 5 cm root zone

Characterizing soil phosphorus supply on aggrading and degrading management regimes

Non-Peer ReviewedPractical concerns regarding P fertility usually focus on crop maturity and quality. However, on highly degraded soils P supply can be so low as to limit grain yield. A study of soils treated with conservation and conventional tillage methods indicated that mineralizable fractions of organic N and S were enhanced under conservation managements. Increased soil organic matter quality on these managements may also increase organic P supply. However, assessing the importance of organic P using soil incubations is of little value because mineralized P is quickly fixed as insoluble forms. In this study, we investigate the supply of P on aggraded and degraded soils, using a sequential chemical fractionation which has been operationally linked to plant uptake and net P supply. We also quantify the size of these P fractions on severely degraded and manure amended soils in an attempt to link visual P deficiency and sufficiency to soil P levels. Total and organic P differ little among tillage regimes. Native grassland contains the least mass of P in the 10 em surface layer, which indicates the importance of fertilizer additions and mixing of mineral soil. Available P fractions are 1.5 to 2.5 times higher in the aggraded conservation managements, reflecting the input of fertilizer P. Trends in available Pi for cultivated soils confirm previous soil quality rankings based on N and S supply. The chemical fractionation of available inorganic P (Pi) clearly delineates the sufficiency of P supply to durum wheat plants. Severely degraded soils showing visual P deficiencies, have 88 % less available Pi than the aggraded manure amended soil, while total and organic P differed by less than 25 %. Therefore, sequential chemical fractionation is a more sensitive indicator of P supplying power than is total or organic P

Dynamics of microbial biomass carbon and nitrogen and extractable nitrate in long-term rotation studies at Indian Head

Non-Peer ReviewedMineralization studies in the laboratory indicate that the net turnover of nitrogen is greatly affected by crop rotation. Recently, the field applicability of such incubation - intermittent leaching experiments has been questioned. Therefore, field sampling was undertaken during the summer of 1988 to determine the influence of rotation history on microbial biomass C and N, and levels of extractable NO3-N. Four long term rotation plots (Ag. Canada, Indian Head) were sampled in the fallow phase. These rotations consisted of: (1) Fallow-Wheat-Wheat, (2) Fallow-Wheat- Wheat (fertilized, straw retained), (3) Fallow-Wheat-Wheat (fertilized, straw removed), and (4) Fallow-Wheat-Wheat-Hay-Hay-Hay. Biomass C and N, as measured by a chloroform-direct extraction technique, was found to be significantly higher in the soils from the hay rotation. The proportion of organic C present as biomass was, on average, 29 % higher than in the three year rotations without hay. Similarly, nitrate levels were found to be significantly affected by rotation history and correlate strongly with the size of the microbial biomass. The prediction of microbial biomass based on carbon added as crop residue was poor since the intrinsic assumption that all carbon is equally available for decomposition does not hold for all residues. However, the levels of biomass C and N were closely related to the N content of the residues returned. This is to be expected since the N-rich "metabolic" fraction is readily decomposed and incorporated into the microbial biomass. These relationships are clearly illustrated using a conceptual model of N turnover

Salinity and salt contamination assessment using anion-exchange resin membranes

Non-Peer ReviewedExchange resins have the ability to sorb ions directly from the soil solution and, thereby show promise as a method to assess plant available nutrients. In salt affected soils, knowing the relative levels of various anions is useful in predicting the type of salts present and the potential for toxicity of specific anions, most importantly boron (B). The objective of this study was to apply the anion exchange membrane (AEM) burial technique to saline soils to rapidly assess anion composition and compare this to standard saturated paste extractions. Soils with a wide range in natural salinity levels were initially investigated. AEM extractable borate, chloride and sulfate were generally well related to the soluble levels found in saturated paste extracts (R2=0.79, 0.81 and 0.75, respectively). Toxic limit for boron in the saturated paste extract corresponded to 0-12 ug/cm2 in the AEM test. AEM testing performed as well as the saturated paste method in distinguished between soils contaminated by native salinity and saltwater brine Spills. AEM testing is simple and rapid and show promise as an in-field method for spill site diagnosis

Optimized forecaster farming: a new tool to put accuracy into precision farming

Non-Peer ReviewedFarmers looking at Precision Farming as a tool to better manage fields have found no real way to apply this technology to fertilization and crop production. The misconception between precision and optimization has lead many farmers to feel that the technology was oversold and not able to deliver more yield for less fertilizer dollars. Farmers required a tool to optimize the dollars spent on fertilizer to achieve the highest Net Return per acre. The PRS™ Forecaster is a constrained resource computer model that can forecast the yield potential and fertilizer response site by site through a field. The model was allowed to distribute $2160.00 of fertilizer N, P, and K across 54 acres in a way that optimized the whole field net return. This was compared to a control site where the same$40.00/acre was spent but on a best “average” blend of fertilizer. Field validation of this optimization proved that more net return ($19.50/acre) could be derived with reallocation of fertilizer dollars using the PRS™ Nutrient Forecaster

CENTURY model simulation of soil C and N on a thin Black Chernozem

Non-Peer ReviewedCENTURY is a process oriented soil organic matter (SOM) model, based on the conceptual division of SOM into active, slow, and passive phases. Carbon (C) and nitrogen (N) flow, from plant residue through the SOM compartments, is driven by monthly precipitation and temperature and moderated by the nutrient content of the residue. CENTURY simulations of cultivated soils in the American Great Plains have agreed well with the changes in C and N observed over the last 100 years. However, use of this model to predict SOM in Saskatchewan soils, is limited by incomplete validation under our conditions. The thin Black Chernozemic soils of the Indian Head Experimental farm provide a unique opportunity to validate the CENTURY model, since both cropping history and soil C and N have been recorded for over 100 years. CENTURY predicted C and N levels (mass per unit area basis) within 4 to 21 % of those observed, after 26 years under fallow-wheat, fallow-wheat-wheat, continuous wheat and fallow-wheat-wheat-hay-hay-hay. Where soil erosion was not considered as a mechanism of SOM loss, CENTURY over-predicted C and N by 30 to 45 % of the observed. CENTURY prediction of mean annual C production as grain was 25 to 41% lower than the observed levels. Such yield functions, which consider the loss of available nutrients in the SOM as well as less residue returned to the system may be useful in estimating the long term direct costs of soil erosion on grain production

The effect of repeated liquid swine manure applications on soil nutrient supply rates and growth of different hybrid poplar clones

Non-Peer ReviewedIntensive hog operations generate large amounts of manure that must be dealt with in an environmentally responsible and economically practical manner. Repeated applications of liquid swine manure within nearby hybrid poplar plantations recently has been proposed as an effective alternative manure management practice, given that these fast-growing tree species have high soil moisture and nutrient demands and, therefore, represent a tremendous sink for the applied effluent. The objectives of this two-year study were to: i) evaluate the effect of repeated broadcast applications of liquid swine manure on soil nutrient supply rates and growth of five hybrid poplar clones (CanAm, Hill, Katepwa, Walker, and WT-66V) and, ii) assess the relationship between growing season soil nutrient supply rates, measured using in situ burials of ion-exchange membrane (Plant Root Simulator™-probes), and growth of different hybrid poplar clones. There was a limited effect of applied hog effluent on soil nutrient supply rates after the first year and hybrid poplar growth after two years, which is surprising considering the application rate was three times larger than the agronomic rate typically applied. The limited measureable difference following manure addition may be attributable to a number of factors, including: substantial volatilization, microbial immobilization, increased leaching and denitrification losses, timing of manure application being out of sync with temporal nature of nutrient uptake by the trees, and a delayed growth response as absorbed nutrients are retranslocated within the trees. Determining the effects of repeated applications of hog effluent on soil nutrient supply rates and subsequent tree growth should help to support effective management strategies, in terms of developing practical effluent management practices required to mitigate any adverse environmental effects, but also increasing plantation productivity and the concomitant non-wood product benefit of increasing biodiversity within the agricultural landscape

Potential impact of group 2 (ALS inhibitor) herbicide residue on winter wheat survival – early reconnaissance

Non-Peer ReviewedNext to the coinciding harvest of spring crops, the biggest challenge winter wheat seeding faces is finding early matured and harvested crop land for seeding at the optimum window from late August to early September. Pulse stubble provides an opportunity to get winter wheat seeded in a timely basis. Growing winter wheat on pulse stubble is commonly discouraged due to the very limited residue and potential for snow trap. As overwinter success is connected to snow cover and subsequent insulation against cold temperatures. We propose another challenge that may be limiting success on pulse stubble. The repeated use ALS inhibiting (Group 2) herbicides and soil residual that can inhibit root growth, nutrient uptake and subsequent fall seedling establishment. A reconnaissance study was conducted on two locations, each with pulse stubble but with differing Group 2 herbicide residue. Soil temperature monitoring showed that of the three winter wheat cultivars examined, all should have easily survived the winter of 2010-11. Significant impact on stand survival and yield was observed on the soil having Group 2 residues. A cultivar interaction was also noted. Further investigation would facilitate identifying potential crop nutrition management techniques to overcome agronomic challenges of successfully growing winter wheat on pulse stubble. Investigation of winter wheat cultivar tolerance to ALS inhibiting herbicide residues would also be of value

The effect of weed control method on soil nutrient availability and growth of different hybrid poplar clones

Non-Peer ReviewedDuring the early establishment phase outplanted hybrid poplar seedlings are the most vulnerable to lethargic growth or mortality because of interspecific competition with non-crop plant species for available soil moisture and nutrients. Consequently, there is a need to develop practical weed control practices that are not only successful at controlling non-crop plant species, but also cost-effective for producers looking to minimize their input costs. The objectives of this two-year study were to: i) evaluate the effects of different combinations of in-row (plastic mulch, herbicide, and control) and between-row (tillage, herbicide, and control) weed control practices on soil nutrients bioavailability and the early growth of four hybrid poplar clones (Walker, Assiniboine, WP-69, and Hill) and, ii) assess the relationship between growing season soil nutrient supply rates, measured using in situ burials of ion-exchange membrane (Plant Root Simulator™-probes), and growth of different hybrid poplar clones. Determining the effects of different weed control practices on growth-limiting edaphic properties and subsequent seedling growth should help to support effective management strategies, in terms of selecting an efficacious and cost-effective weed control strategy that promotes the establishment and growth of hybrid poplar seedlings, while minimizing the input costs incurred by the producer

Are barley yields on eroded calcareous soils restricted by low zinc supply?

Non-Peer ReviewedCalcareous knolls are often relatively unproductive locations in a field landscape. This may be attributed to lack of moisture as well as limited nutrient supplies. A growth chamber study was initiated to investigate the role of micronutrient deficiencies in yield limitations observed on calcareous knolls. Three rates of zinc (Zn) fertilizer were applied to calcareous soils collected from both an Asquith and Amulet association. In addition, macronutrients were applied in sufficient quantities as to not limit plant yields. Barley was grown in the treatments, harvested, and the treatments were compared. Results indicated a highly significant barley dry matter yield response to Zn fertilizer