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Articles by Noura Ziadi
Total Records ( 6 ) for Noura Ziadi
  Noura Ziadi , Gilles Belanger , Athyna N. Cambouris , Nicolas Tremblay , Michel C. Nolin and Annie Claessens
  Efficient management of P in crop production requires the development of tools to quantify the P status of plants. Our objectives were to establish the relationship between P and N concentrations of spring milling wheat (Triticum aestivum L.) during the growing season and, in particular, to determine the critical P concentration required to diagnose P deficiency. Shoot biomass and P and N concentrations were determined weekly and grain yield was measured at harvest in an experiment with four to six N rates conducted over 2 yr (2004 and 2005) at three sites with adequate soil P for growth each year. Both shoot P and N concentrations decreased with time as shoot biomass increased during the growing season. They also increased with N fertilization, suggesting that they are closely related. The relationship between shoot P and N concentrations under nonlimiting N conditions is described by a linear function (P = 0.94 + 0.107N, R2 = 0.59, P < 0.001; n = 76) in which concentrations are expressed in g kg–1 dry matter (DM). Under limiting N conditions (relative grain yield <0.80), the relationship was different (P = 1.70 + 0.092N (R2 = 0.48; P < 0.001; n = 19) with greater P concentrations for a given N concentration. These relationships approximate the critical P concentration under both nonlimiting and severely limiting N conditions. This critical P concentration can then be used to quantify the degree of P deficiency during the current growing season.
  Noura Ziadi , Marianne Brassard , Gilles Belanger , Athyna N. Cambouris , Nicolas Tremblay , Michel C. Nolin , Annie Claessens and Leon-Etienne Parent
  Plant-based diagnostic methods of N nutrition require the critical N concentration (Nc) to be defined, that is the minimum N concentration necessary to achieve maximum growth. A critical N curve (Nc = 34.0W–0.37 with W being shoot biomass in Mg DM ha–1), based on whole plant N concentration, was determined for corn (Zea mays L.) in France. Our objectives were to validate this critical N curve in eastern Canada and to assess its plausibility to estimate the level of N nutrition in corn. Shoot biomass and N concentration were determined weekly during the growing season at three sites for 2 yr (2004 and 2005); four to seven N treatments were used at each site. Data points were divided into two groups representing either nonlimiting or limiting N conditions according to significant differences in shoot biomass at each sampling date. All data points included in the limiting N group were under the critical N curve and most data points of the nonlimiting N group were on or above the critical N curve, hence confirming the validity of the critical N curve determined in France. The nitrogen nutrition index (NNI), calculated as the measured N concentration divided by the predicted Nc, ranged from 0.30 to 1.35. A significant relationship between relative grain yield (RY) and NNI (RY = –0.11 + 1.17 NNI if NNI < 0.93 and RY = 0.98 if NNI > 0.93; R2 = 0.89) was determined. The critical N curve from France is valid in eastern Canada and the NNI calculated from that curve is a reliable indicator of the level of N stress during the growing season of corn.
  Gilles Belanger and Noura Ziadi
  Plant-based methods of determining P and N deficiencies require critical concentration values. We studied the response of timothy (Phleum pratense L.) to P and N fertilization over 7 yr with the objective of using relationships between P and N concentrations and dry matter (DM) yield to determine critical P and N concentrations. Timothy, seeded in 1998, was harvested during spring growth from 1999 to 2005 in an experiment with four sampling dates (stem elongation, early heading, late heading, and early flowering), four P applications (0, 15, 30, and 45 kg P ha–1), and four N applications (0, 60, 120, and 180 kg N ha–1). Maximum DM yield and, therefore, nonlimiting P and N conditions, were obtained with 120 kg N ha–1 without applied P. Under these nonlimiting conditions, relationships between P and N concentrations and DM yield changed with production years. Critical N concentration (Nc) in older swards (>4 yr; Nc = 37.0 x SB–0.35; R2 = 0.79), expressed as a function of shoot biomass (SB), was less than previous reports on younger swards (Nc = 48.0 x SB–0.32). Critical P concentration (Pc) was also less in older swards (Pc = 3.27 x SB–0.20; R2 = 0.68) than in younger ones (Pc = 5.23 x SB–0.40; R2 = 0.63). Critical P concentration can also be expressed as a function of N concentration (Pc = 1.07 + 0.063N; R2 = 0.71), a relationship independent of sward age and shoot biomass but affected by N deficiency; the slope is the same but intercept values vary from 1.31 to 1.41 when N limits shoot growth. Critical P and N concentrations can then be used to quantify the degree of P and N deficiency in young and old timothy swards.
  Noura Ziadi , Marianne Brassard , Gilles Belanger , Annie Claessens , Nicolas Tremblay , Athyna N. Cambouris , Michel C. Nolin and Leon-Etienne Parent
  Plant-based diagnostic techniques are used to determine the level of crop N nutrition but there is limited comparative research on the different methods. Our objectives were to establish the relationship between chlorophyll meter (CM) readings and N nutrition index (NNI) during the corn (Zea mays L.) growing season, and to compare both methods as diagnostic tools for predicting grain yield response to N fertilization. The study was established at eight site-years using four to seven N fertilization rates. The CM readings from the youngest collared leaf were taken on five to eight sampling dates in 2004, 2005, and 2006 along with NNI determinations. Generally, CM readings and NNI increased with increasing N rates. Chlorophyll meter readings and relative CM (RCM) readings were related to NNI, but the intercepts and/or slope of the response curves varied with site-year. Because they are site-specific, these relationships may not be reliable indicators of corn N status. The relationship between CM readings and relative grain yield (RY) at stage of development ≈V12 was also site-specific. Relative CM readings (RY = –0.64 + 1.65 RCM if RCM ≤ 0.98 and RY = 0.97 if RCM > 0.98; R2 = 0.60) and NNI (RY = –0.34 + 1.47 NNI if NNI ≤ 0.88 and RY = 0.96 if NNI > 0.88; R2 = 0.79) at stage of development ≈V12 were related to RY. These two relationships were stable across site-years and could be used to detect and quantify N deficiencies of corn.
  Cynthia Grant , Noura Ziadi , Bernard Gagnon , Don Flaten and Jeff Schoenau
   Régis Simard and his colleagues developed a research program focussing on the agronomic and environmental impacts of nutrients in agricultural systems. The success of this program resulted from an integrated approach, linking assessment of nutrient availability to an understanding of nutrient dynamics in the soil, and applying this understanding to development of improved management practices for a variety of nutrient sources. Research into nutrient availability conducted by Régis and his co-workers led to improvements in quantification of nutrient supply, using traditional soil analysis with batch chemical extraction as well as ionic exchange membranes (IEMs) and electro-ultrafiltration (EUF). Ion exchange membranes are now used as a tool in routine soil fertility assessments and in agronomic and environmental research to study nutrient ion release rates. Additionally, intensive analytical techniques, such as sequential extraction and X-ray absorption near-edge structure (XANES) were developed and used to characterize the forms and relative availability of soil nutrients for plant uptake or environmental effects. Characterization of nutrient pools improved understanding of nutrient dynamics in the soil, allowing a more accurate assessment of the agronomic value and environmental risk of nutrients applied to agricultural systems. Building on this knowledge, Régis and his colleagues developed improved methods of utilizing manures, composts, paper mill sludge (PMS) and liming by-products, effectively diverting nutrients from the waste stream into a resource for crop production. This paper describes the contributions of Régis and his colleagues to the improvement of agronomically and environmentally sustainable nutrient management practices, based on an integrated research approach that provided a clear understanding nutrient availability and soil nutrient dynamics.
  Mehdi Sharifi , Bernie J. Zebarth , David L. Burton , Cynthia A. Grant , Shabtai Bittman , Craig F. Drury , Brian G. McConkey and Noura Ziadi
  Tillage practices may affect the active fraction of soil organic N. As part of a national project to examine soil management and environmental controls on the active fraction of organic N, this study examined the effects of no-till (NT) and conventional tillage (CT) systems on the quantity of potentially mineralizable soil N (N0) and mineralizable N pools, and the potential to detect changes in these pools using N availability indices. Preplant soil samples from the top 15 cm were collected from four long-term tillage experiments at Swift Current, SK; Woodslee, ON; L'Acadie, QC; and Agassiz, BC. Potentially mineralizable N was determined by aerobic incubation at 25°C and periodic leaching for 24 wk. The N0 was greater under NT than under CT, but only at Swift Current. The labile and intermediate mineralizable N pools were significantly higher under NT than under CT at three of the four sites. The stable mineralizable N pool and the mineralization rate coefficient (k) were greater under NT than under CT at only one of the four sites. Adoption of NT influenced the quality of the active organic N fraction at three sites, as indicated by an increased proportion of mineralizable N in the more labile N pools. Among tested indices of N availability, KCl-extractable NH4–N, NaOH-extractable N, Illinois Soil N Test, phosphate-borate buffer extractable N, and particulate organic C were most sensitive to tillage-induced changes in the active organic N fraction. Tillage-induced changes in the size and quality of the active organic N fraction may influence soil N supply and should be considered in optimizing fertilizer N management.
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