Noura Ziadi

Critical Nitrogen Curve and Nitrogen Nutrition Index for Potato in Eastern Canada

Plant diagnostic methods of N deficiency should be based on the definition of a critical N concentration, that is the minimal N concentration required to achieve maximum growth. The critical N concentration (Nc) of potato was determined from six on-farm field trials in which two cultivars (Russet Burbank and Shepody) were grown under three or four N rates with and without irrigation. Dry matter yield and N concentration of shoots and tubers were determined approximately weekly during the growing season. The Nc was determined by selecting data points for which the highest total biomass comprised of shoots and tubers was obtained, and by expressing N concentration (N) as a function of total biomass (W). The N nutrition index (NNI), calculated as the ratio between measured N concentration and predicted Nc during the growing season, was then related to the relative yield measured at harvest. Under non-limiting water conditions, the allometric relationship between Nc and total biomass for Russet Burbank (Nc = 4.57W-0.42) was different from that of Shepody (Nc = 5.04W-0.42), indicating that Shepody had a greater N concentration than Russet Burbank. The N concentration of Shepody was also greater than that of Russet Burbank under limiting water conditions. These results suggest that there is intra-specific variability in potato for the relationship between N concentration and biomass. The NNI ranged from 0.50 to 1.4. The relationship between relative yield and NNI expressed by a quadratic function accounted for a greater proportion of the variability with irrigation (71% for Russet Burbank and 82% for Shepody) than without irrigation (65% for Russet Burbank and 32% for Shepody). Our results suggest that the NNI could be a reliable indicator of the level of N stress during the growing season, particularly under non-deficient water conditions.ResumenLos métodos de fitodiagnóstico de deficiencia de N deben basarse en la definición de una concentración crítica de N, es decir, la concentración mínima requerida para alcanzar el crecimiento máximo. La concentración critica de N (Nc) en la papa fue determinada en seis campos experimentales de agricultores, en los cuales crecieron dos cultivares (Russet Burbank y Shepody) bajo tres o cuatro niveles de N con y sin irrigación. Los rendimientos en materia seca y la concentración de N en las yemas y tubérculos se determinaron aproximadamente cada semana durante la temporada de crecimiento. La Nc se determinó seleccionando los datos por los cuales se obtuvo la biomasa total más alta, que incluía yemas y tubérculos, y expresando la concentración de N (N) como una función de la biomasa total (W). El índice de nutrición de N (NNI, en inglés) calculado como la relación entre la concentración medida de N y hl Nc pronosticada durante la temporada de crecimiento, se relacionó entonces con el rendimiento relativo medido y cosechado. Bajo condiciones de abundancia de agua, la relación alométrica entre Nc y la biomasa total para Russet Burbank (Nc = 4.57W-0.42) fue diferente que para Shepody (Nc = 5.04W-0.42), indicativo de que Shepody tiene una mayor concentración de N que Russet Burbank. La concentración de N de Shepody fue también mayor que la de Russet Burbank bajo condiciones limitadas de agua. Estos resultados sugieren que hay una variabilldad intraespecíflca en la papa en la relación entre la concentración de N y la biomasa. El índice de nutrición de N (NNI) osciló entre 0.50 a 1.4. La relación entre el rendimiento relativo y el NNI, se expresó por una función cuadrática contabilizada por una mayor proporción de la variabilidad con irrigación (71% para Russet Burbank y 82% para Shepody) que sin irrigación (65% para Russet Burbank y 32% para Shepody). Nuestros resultados sugieren que el NNI podría ser un indicador confiable del nivel de estrés de N durante la temporada de crecimiento, particularmente bajo condiciones no deficientes de agua.

Nitrogen Dynamics and Indices to Predict Soil Nitrogen Supply in Humid Temperate Soils

Abstract Knowledge of the nitrogen (N) available to crops during the growing season is essential for improving fertilizer-use efficiency and minimizing the adverse impacts of N losses on the environment. In humid temperate regions, soil N supply is dominated by in-season N mineralization because plant-available N (NH 4 –N and NO 3 –N) is transformed to nonlabile forms or lost from the soil–plant system during fall and winter. The microbially mediated reactions that generate the soil N supply in agroecosystems are affected by system-specific conditions, including soil properties, agricultural management (crop rotation, tillage system, organic amendments), and most importantly, climate. Potentially mineralizable N ( N 0 ) determined from long-term soil incubation is regarded as the standard measure of soil N mineralization potential and may provide a good approximation of the soil N supply. However, this method is time consuming and not practical for routine use. Several chemical methods to estimate the N mineralization potential of soils are discussed in this chapter. The major limitation of chemical methods is that they cannot simulate the microbial-mediated release of plant-available N under field conditions. Consequently, any single chemical method may not be a good predictor of soil N supply. Thus, we suggest a holistic approach to estimate soil N supply in humid temperate regions, which involves (1) the use of a combination of N indices together with weather data and (2) identification and quantification of a specific fraction (s) of organic N that is the dominant contributor (s) to N supply in a particular system.

Yield response of two potato culivars to supplemental irrigation and N fertilization in New Brunswick

Nitrogen and water are important factors influencing potato production, and crop response to these two factors may vary with cultivars. The yield response of two potato cultivars (Russet Burbank and Shepody) to six rates of N fertilization (0-250 kg N ha-1) with and without supplemental irrigation was studied at four onfarm sites in each of three years, 1995 to 1997, in the upper St-John River Valley of New Brunswick, Canada. On average, irrigation increased total yield from 31.9t ha-1 without irrigation to 38.41 ha-1 with irrigation and marketable yield from 25.61 ha-1 without irrigation to 30.71 ha-1 with irrigation. Potato yields were increased by irrigation at nine out of the 12 sites, and the irrigation response was similar for both cultivars. Nitrogen fertilization significantly increased both total and marketable yields at all sites except one. The yield response to N fertilization was greater with irrigation. The N fertilization rate (Nmax) required to reach maximum total and marketable yield, however, was similar with and without irrigation. A large variation in Nmax was observed among sites. With irrigation Nmax varied between 158 and 233 kgN ha-1 for total yield, and between 151 and 250 kg N ha-1 for marketable yield. There was no interaction between N fertilization and potato cultivar for both total and marketable yields. The two cultivars had similar total yields (35 t ha-1). Shepody, however, had a greater marketable yield (28.9 t ha-1) than Russet Burbank (27.4 t ha-1). Our results indicate that the response to two of the most significant factors of potato production, irrigation and N fertilization, varies greatly with sites and climatic conditions, and that field specific recommendations are required for the optimum management of N and irrigation.ResumenEl nitrógeno y el agua son factores importantes que influyen en la producción de la papa, y la reacción de la cosecha antes estos dos factores puede variar con diferentes cultivares. La reacción de rendimiento de dos cultivares de papa (Russet Burbank y Shepody) antes seis medidas de fertilizante N (0-250 kg N Ha-1) con y sin irrigación suplementaria se estudió en dos lotes en granja durante cada uno de los tres años, 1995–1997, en la parte superior del Valle del Río St-John en New Brunswick, Canadá. En un p romedio, la irrigación aumentó el rendimiento total de 31.91 ha-1 sin irrigación a 38.4 t ha-1 con irrigación y al rendimiento comerciable de 25.61 ha- 1 sin irrigación a 30.71 t ha-1 con irrigación. Los rendimientos de la papa aumentaron a causa de la irrigación en 9 de los 12 lotes, y el resultado de la irrigación fue similar para los dos cultivares. La fertilización con nitrógeno aumentó notablemente tanto los rendimientos totales y comerciables en todos los lotes menos uno. El rendimiento ante la fertilización N fue mayor con irrigación. La tasa de fertilización N (Nmax) que es necesaria para alcanzar el rendimiento total y comerciable, sin embargo, fue similar con y sin irrigación. Se observó una gran variación en Nmax en los lotes. Con irrigación, Nmax varió entre 158 y 233 kg N ha-1 en el rendimiento total, y entre 151 y 250 kg N ha-1 en el rendimiento comerciable. No había ninguna interacción entre la fertilización N y el cultivar de la papa para los rendimientos tanto totales como comerciables. Los dos cultivares tuvieron rendimientos totales similares 35 t ha-1). Shepody, sin embargo, tuvo un rendimiento comerciable mayor (28.9 t ha-1) que Russet Burbank (27.4t ha-1). Nuestros resultados indican que la respuesta a dos de los factores más significativos en la producción de la papa, la irrigación y la fertilización N, varía mucho entre lotes y condiciones climáticas, y que unas recomendaciones de campo específicas son necesarias para el manejo óptimo de N y de la irrigation.

Nitrogen fertilization and irrigation affects tuber characteristics of two potato cultivars

Nitrogen fertilization, irrigation, and cultivars affect tuber characteristics such as tuber size, specific gravity, and N concentration. Few studies, however, have investigated the interaction of irrigation and N fertilization on the tuber characteristics of potato cultivars, particularly in Atlantic Canada. The objective of this on-farm study, conducted at four sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and six rates of N fertilization (0-250 kg N ha-1) on the number of tubers per plant, the average fresh tuber weight, tuber N concentration, nitrate (NO3-N) concentration, and specific gravity of the cultivars Shepody and Russet Burbank. Nitrogen fertilization increased the average fresh tuber weight, tuber N and N03-N concentrations, and decreased specific gravity. Effects of increasing N fertilization on tuber characteristics were often more pronounced for Shepody than for Russet Burbank, and for irrigated than for non-irrigated conditions. Shepody had greater average fresh tuber weight and tuber N concentration, lower specific gravity, and fewer tubers per plant than Russet Burbank. Supplemental irrigation increased the average fresh tuber weight and the number of tubers per plant, but it had a limited effect on specific gravity and tuber N and NO3-N concentrations. Tuber NO3-N con centration and specific gravity were strongly related to tuber N concentration, which in turn depended primarily on N fertilization. Incidents of lowest specific gravity and highest NO3-N concentration occurred with a relative yield close to or equal to 1.0. We conclude that the risks of low specific gravity and high tuber NO3-N concentration are greater when fertilization exceeds the N requirements to reach maximum tuber yield.

Opportunities for, and limitations of, near infrared reflectance spectroscopy applications in soil analysis: A review

Near infrared reflectance spectroscopy (NIRS) is a cost- and time-effective and environmentally friendly technique that could be an alternative to conventional soil analysis methods. In this review, we focussed on factors that hamper the potential application of NIRS in soil analysis. The reported studies differed in many aspects, including sample preparation, reference methods, spectrum acquisition and pre-treatments, and regression methods. The most significant opportunities provided by NIRS in soil analysis include its potential use in situ, the determination of various biological, chemical, and physical properties using a single spectrum per sample, and an estimated reduction of analytical cost of at least 50%. Contradictory results among studies on NIRS utilisation in soil analysis are partly related to variations in sample preparation and reference methods. The following calibration statistics appear to be most appropriate for comparing NIRS performance across soil attributes: (i) coefficient of det...

Predicting nitrogen fertilizer requirements of potatoes in Atlantic Canada with soil nitrate determinations

Nitrogen greatly affects potato ( Solanum tuberosum L.) yield, but excess N can result in environmental degradation. In this study soil nitrate (NO3-N) content was determined pre-plant to predict fertilizer N requirements of potatoes in Atlantic Canada and in mid-season to adjust N fertilization during the growing season. Soil NO3-N contents were measured to a 0.30-m depth in spring prior to planting at four on-farm sites in each of 3 yr (1995 to 1997) in the upper St. John River Valley of New Brunswick, Canada. Mid-season soil NO3-N contents at a 0–0.30 m depth were also determined (32–47 days after planting) at two sites in three N treatments in 1995 (0, 50, and 250 kg N ha-1) and in four N treatments in 1996 and 1997 (0, 50, 100, and 250 kg N ha-1). The yield response of potatoes to six rates of N fertilization (0–250 kg N ha-1) with and without supplemental irrigation was used to determine the economically optimum N application (Nop). The pre-plant spring soil NO3-N test alone could not adequately pre...

Tuber growth and biomass partitioning of two potato cultivars grown under different n fertilization rates with and without irrigation

Nitrogen and water deficiencies are known to affect potato yield, but much less is known of their effect on tuber growth and biomass partitioning. The objective of this on-farm study conducted at two sites in each of three years, 1995 to 1997, was to determine the effects of supplemental irrigation and N fertilization rates on tuber growth and biomass partitioning of the cultivars Shepody and Russet Burbank. The N fertilization rates were 0,100, and 250 kg N ha-1in 1995, and 0, 50,100, and 250 kg N ha−1 in 1996 and 1997. The highest bulking rate observed in our study (7.3 g fresh tubers m-2 °C-1) can be considered near the potential bulking rate in New Brunswick. The water deficit in the absence of supplemental irrigation reduced this potential bulking rate by as much as 40%, but this reduction was much less at five of six sites and negligible at two of six sites. Nitrogen deficiency reduced the bulking rate at two of six sites. This negative effect of N deficiency on bulking rate was greater with irrigation than without irrigation at two of six sites; the tuber bulking rate with irrigation was reduced by as much as 50% with no N applied at one site. Shepody had a greater bulking rate than Russet Burbank. The tuber bulking of Russet Burbank, however, started earlier and lasted longer than that of Shepody. Water and N deficiencies increased biomass partitioning to tubers and large roots. Shepody partitioned a greater proportion of its biomass to large roots and had a greater root biomass than Russet Burbank. Our results demonstrate the ability of potatoes to modify biomass partitioning when grown under water and/or N stresses. As a result of this compensation, the reduction in tuber yield due to limited N and water stresses is minimized.

Long-term impact of tillage practices and phosphorus fertilization on soil phosphorus forms as determined by p nuclear magnetic resonance spectroscopy.

Conservation tillage practices have become increasingly common in recent years to reduce soil erosion, improve water conservation, and increase soil organic matter. Research suggests that conservation tillage can stratify soil test phosphorus (P), but little is known about the effects on soil organic P. This study was conducted to assess the long-term effects of tillage practices (no-till [NT] and mouldboard plowing) and P fertilization (0 and 35 kg P ha) on the distribution of P species in the soil profile. Soil samples from a long-term corn-soybean rotation experiment in Québec, Canada, were collected from three depths (0-5, 5-10, and 10-20 cm). These samples were analyzed for total P (TP), total C (TC), total N (TN), pH, and Mehlich-3 P (PM3); P forms were characterized with solution phosphorus-31 nuclear magnetic resonance spectroscopy (P-NMR). Results showed a stratification of TP, TC, TN, pH, PM3, and Mehlich-3-extractable aluminum and magnesium under NT management. The PM3 and orthophosphate concentrations were greater at the soil surface (0-5 cm) of the NT-P (soil treatment with 35 kg P ha) treatment. Organic P forms (orthophosphate monoesters, especially -IP, and nucleotides) had accumulated in the deep layer of NT treatment possibly due to preferential movement. We found evidence that the NT system and P fertilization changed the distribution of P forms along the soil profile, potentially increasing soluble inorganic P loss in surface runoff and organic P in drainage and decreasing bioavailability of inorganic and organic P in deeper soil layers.

Soil phosphorus availability in no-till versus conventional tillage following freezing and thawing cycles

Projected global warming may result in colder soil temperatures and a greater number of soil freezing and thawing cycles (FTC) during the winter in cool temperate and high-latitude regions. We evaluated the effects of seasons and repeated FTC on soil P availability in the topsoil of no-till (NT) and conventional tillage (CT) systems. In order to determine P availability during fall 2007 and spring 2008, soil samples (0-15 cm) were collected in both seasons from a long-term corn-soybean rotation experiment in plots that received 0, 17.5 and 35 kg P ha-1 and 160 kg N ha-1 every 2 yr since 1992. In addition, soil cores (0-5 cm) were collected in fall 2007 in plots that received 35 kg P ha-1 and 160 kg N ha-1 every 2 yr and were enriched or not with 2 g of soybean residues. Under controlled conditions, the cores were subjected to various FTC treatments, with each cycle consisting of 5 d of freezing and 5 d of thawing. The water-extractable P (Pw) and Mehlich 3 extractable P (PM3) contents were higher in soil ...

Cadmium accumulation in wheat grain as affected by mineral N fertilizer and soil characteristics

Li, X., Ziadi, N., Bélanger, G., Cai, Z. and Xu, H. 2011. Cadmium accumulation in wheat grain as affected by mineral N fertilizer and soil characteristics. Can. J. Soil Sci. 91: 521-531. Cadmium (Cd) is a heavy metal distributed in soil by natural processes and anthropogenic activities. It can accumulate in crops, such as spring milling wheat (Triticum aestivum L.), and its accumulation depends on crop species, soil factors, and agricultural practices like fertilizer inputs. Our objective was to study the effect of mineral N fertilizer and soil characteristics on wheat grain Cd concentration. A field study was conducted over 12 site-years (2004-2006) in Québec, with four N application rates (0, 40, 120, and 200 kg N ha-1). Wheat grain samples (n=192) were analysed for their Cd and N concentrations. Soil samples (n=48) taken before N fertilizer application were characterised for their chemical and physical properties, including Mehlich-3 extractable Cd concentration. Wheat grain Cd concentration increased significantly with increasing N application rates at 11 of the 12 site-years. Averaged across the 12 site-years, Cd concentration ranged from 53 µg kg-1 dry matter (DM) without N applied up to 87 µg kg-1 DM when 200 kg N ha-1 was applied. Wheat grain Cd concentration also varied significantly with site-years (34-99 µg kg-1 DM), but never exceeded the proposed tolerance for wheat grain of 235 µg kg-1 DM. Wheat grain Cd concentration was significantly related to Mehlich-3 extractable Cd in soil (R2=0.44, P=0.021) and nitrogen nutrition index (R2=0.69, P=0.001). We conclude that soil Cd concentration and the crop N nutrition status affect Cd accumulation in spring wheat grain produced in eastern Canada.