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

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

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

Developing simplified synergistic relationships to model topsoil erosion and crop yield

Non-Peer ReviewedTopsoil is highly enriched with organic matter, which provides a valuable source of plant nutrients as well as a favorable rooting environment. Over time, erosion processes selectively remove the organic matter-rich fine fraction which causes a measurable reduction in soil productivity. Assessments of past erosion are of little value in predicting future losses in productivity since the synergistic lowering of soil organic matter through lower residue inputs is not considered. Dynamic computer models, which simulate the plant/soil system, can project the long run future costs of soil erosion on crop yield. A simplified erosion-crop yield model was developed by first defining the most important soil productivity variables, then quantifying the effect of erosion on each variable. The model predicted a declining trend in grain yields similar to that observed on soil scalping experiments

Simulated Productivity Lost by Erosion (SimPLE): model development, validation, and use

Non-Peer ReviewedProductivity lost due to soil erosion can be estimated by existing computer simulation models such as EPIC, NTRM and CENTURY. However, these models require extensive input data and, to date, have had limited success in simulating Western Canadian conditions. The objective of this study was to develop a simple spring wheat model which captured the essential relationships between topsoil erosion and productivity loss in Chemozemic soils. Key relationships in our model describe: (i) how plants create yield from water, N, and P; (ii) how the soil provides these nutrients, and (iii) how erosion impacts on the supply of each nutrient. These relationships were logically connected using the Stella® II modeling environment. Agreement was highly significant (r = 0.55***) between predicted and observed grain yields over 75 site years at Indian Head, Saskatchewan. Also, grain yields from scalped Chemozemic soils in Alberta were closely simulated (r = 0.86****) by SimPLE. Fifty representative soil profiles from the Brown, Dark Brown and Black soil zones were eroded in SimPLE to numerically describe the production lost under wet, normal, and dry scenarios, with and without optimum fertilizer. Yield loss, as a percentage of non-eroded yield, increased with increasing soil erosion following a trend very similar to that reported in field studies. SimPLE is flexible and can be used for analysis of "what if' management scenarios or calculating soil loss tolerance (T) values

Lessons from a soil fertility laboratory

Non-Peer ReviewedA growth chamber experiment was established to demonstrate several basic principles of soil fertility to undergraduate students. Barley and field pea were grown in pots to demonstrate the effects of erosion and crop rotation on the yield potential and nitrogen response for two soils from the Brown soil zone. The results demonstrated differences in the ability of different crops to access nutrients, the effect of landscape position on nutrient availability and fertilizer response, and the ability of soil analytical tools like PRS to reveal differences in soil nutrient supplying power

Factors affecting nutrient supply rate measurements with PRS™-probes

Non-Peer ReviewedThis poster includes background information about how PRS™-probes are used to measure soil nutrient supply rates and how factors of the soil environment influence nutrient supply rate measurements. The discussion contains research examples of the effects of soil moisture, soil temperature, and competing sinks as well as the effect of the duration of PRS™-probe burial. These effects are important to consider when interpreting supply rate data

Attentive Learning of Sequential Handwriting Movements: A Neural Network Model

Defense Advanced research Projects Agency and the Office of Naval Research (N00014-95-1-0409, N00014-92-J-1309); National Science Foundation (IRI-97-20333); National Institutes of Health (I-R29-DC02952-01)

LDIP cooperates with SEIPIN and LDAP to facilitate lipid droplet biogenesis in Arabidopsis

Abstract Cytoplasmic lipid droplets (LDs) are evolutionarily conserved organelles that store neutral lipids and play critical roles in plant growth, development, and stress responses. However, the molecular mechanisms underlying their biogenesis at the endoplasmic reticulum (ER) remain obscure. Here we show that a recently identified protein termed LD-associated protein [LDAP]-interacting protein (LDIP) works together with both endoplasmic reticulum-localized SEIPIN and the LD-coat protein LDAP to facilitate LD formation in Arabidopsis thaliana. Heterologous expression in insect cells demonstrated that LDAP is required for the targeting of LDIP to the LD surface, and both proteins are required for the production of normal numbers and sizes of LDs in plant cells. LDIP also interacts with SEIPIN via a conserved hydrophobic helix in SEIPIN and LDIP functions together with SEIPIN to modulate LD numbers and sizes in plants. Further, the co-expression of both proteins is required to restore normal LD production in SEIPIN-deficient yeast cells. These data, combined with the analogous function of LDIP to a mammalian protein called LD Assembly Factor 1, are discussed in the context of a new model for LD biogenesis in plant cells with evolutionary connections to LD biogenesis in other eukaryotes