Ramona M. Mohr

Effect of nitrogen fertilizer rate on nitrous oxide emission from irrigated potato on a clay loam soil in Manitoba, Canada

Gao, X., Tenuta, M., Nelson, A., Sparling, B., Tomasiewicz, D., Mohr, R. M. and Bizimungu, B. 2013. Effect of nitrogen fertilizer rate on nitrous oxide emission from irrigated potato on a clay loam soil in Manitoba, Canada. Can. J. Soil Sci. 93: 1-11. This study examined the effect of N fertilizer application rate on N2O emissions for irrigated potato production on a clay loam soil near Carberry, Manitoba, over two growing seasons. Treatments were an unfertilized control, and urea-N fertilizer application rates of 80, 160 and 240 kg N ha-1, which were applied as split applications. The marketable yield increased at 80 kg N ha-1 relative to the unfertilized control, but did not respond to higher rates of fertilizer. Peak emission of N2O followed fertilizer application and rain or irrigation events. Emission rates following fertilizer application and water addition events were greater from hill than from furrow position in 2009, but not in 2010. In the latter, ponding of water in furrows likely resulted in the greater emissions than from the hill positions. Cumulative N2O emissions and yield based N2O intensity increased linearly with N application rate. The growing season emission factor (EFgs) for percent of added N emitted as N2O was 0.73% and did not increase with N application rate. The adjusted whole-year emission factor (EFwy) assuming 30% of annual emissions are emitted during winter and thaw was 1.04%, being lower than the Canadian IPCC Tier II protocol value of 1.72% for irrigated cropland in Canada. The lower measured EFwy may be because the protocol assumes that under irrigation water input (rain plus irrigation) equals potential evapotranspiration (PET) from May to October, implying no restriction of N2O emissions by water limitation. For the current study, however, the ratio of water input to PET averaged 70%, suggesting water may have restricted N2O emission, therefore resulting in a lower EFwy than predicted by the Tier II protocol. The results of the current study also suggest that a reduction in N2O emissions can be achieved by avoiding fertilizer N applications beyond optimal for marketable yield, limiting irrigation soon after application of N fertilizer, and managing irrigation to prevent ponding of water in furrows.

The influence of nitrogen, phosphorus and potash fertilizer application on oat yield and quality

Western Canada has become one of the key production areas for oat (Avena sativa L.) in North America. Limited information is available regarding fertilizer management strategies to optimize yield and quality in this environment. An experiment was conducted at two locations in southern Manitoba in 2000, 2001 and 2002 to assess the impact of factorial combinations of N (0, 40, 80, 120 kg N ha-1 as urea), P (0, 13, 26 kg P ha-1 as monoammonium phosphate), and KCl (0, 33 kg K ha-1) on the growth, yield and quality of AC Assiniboia oat. Low to moderate N rates significantly increased yield, with optimum relative yield achieved with a plant-available N supply of approximately 100 kg N ha-1. Increasing N rate also increased lodging and reduced test weight, kernel weight and kernel plumpness, suggesting that optimal N management must balance yield improvement against reductions in grain quality. Phosphorus application increased yield in 2 of 6 site-years, but had no overall effect on quality. Application of KCl r...

Crop response to current and previous season applications of phosphorus as affected by crop sequence and tillage

Field studies were conducted over a 4-yr period at two locations in western Manitoba, Canada, to evaluate the effect of phosphorus (P) fertilizer management on crop growth as affected by tillage system through a 2-yr cropping sequence. In the first phase of the cropping sequence, canola (Brassica napus L.), a non-mycorrhizal crop, and spring wheat (Triticum aestivum L.), a mycorrhizal crop, were grown under conventional (CT) and reduced (RT) systems, with 0, 11 and 22 kg P ha-1 applied as monoammonium phosphate (MAP). In the second phase of the sequence, flax (Linum usitatissimum L.) was seeded following the spring wheat or canola, with application of 0 or 11 kg P ha-1 as MAP. Phosphorus application increased the early-season biomass, P concentration, and P accumulation of canola and wheat and the seed yield of canola. Tillage system had no consistent effects on growth, P concentration or uptake, or seed yields of canola or wheat, nor were P by tillage system interactions observed. Early-season biomass pr...

Nitrogen dynamics under greenhouse conditions as influenced by method of alfalfa termination. 1. Volatile N losses

Use of herbicide to terminate alfalfa (Medicago sativa L.), while reducing soil erosion, could conceivably enhance volatile N losses from alfalfa residues. A controlled environment study was conducted to determine the effect of termination method on the quantity of NH3 volatilized from residues of alfalfa. A factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (incorporated, surface applied) was applied to alfalfa. Treatments were incubated in a flow-through chamber in the greenhouse for 95 d during which NH3 and CO2 evolution was measured periodically. After 95 d, 8% of surface applied legume N was lost as NH3 in tillage treatments compared to 12% in herbicide treatments. These losses amounted to 3% and 4% of total legume N in tillage and herbicide treatments, respectively. Incorporation of alfalfa residue essentially eliminated volatile N losses. Termination method had comparatively less effect on NH3 evolution than residue placement although herbi...

Nitrogen dynamics under growth chamber conditions as influenced by method of alfalfa termination 2. Plant-available N release

Herbicide application has been proposed as an alternative to tillage for termination of established alfalfa (Medicago sativa L.) stands but it may alter the pattern and amount of N released from alfalfa residues. A controlled environment study was conducted to investigate the effect of termination technique on the availability of N to four barley (Hordeum vulgare L.) crops. Four treatments consisting of a factorial combination of two termination methods (chemical, mechanical) and two methods of residue placement (surface, incorporated) were established. Nitrogen uptake by the four consecutive crops of barley was measured during a 125-d period after termination. Termination method, particularly residue placement, strongly affected N release from alfalfa residues. Nitrogen accumulation by the initial barley crop accounted for >60% of cumulative N uptake in incorporated treatments compared with 39% and 24% for herbicide and tillage treatments in which alfalfa residue was surface applied. Herbicide applicatio...

Effect of Rotation on Crop Yield and Quality in an Irrigated Potato System

The productivity of potato (Solanum tuberosum L.) systems may be strongly influenced by rotation. A field study consisting of six rotations (potato with canola (PC), wheat (PW), canola-wheat (PCW), oat-wheat (POW), wheat-canola-wheat (PWCW), and canola underseeded to alfalfa-alfalfa-alfalfa (PCAA)) arranged as an RCBD was established on a clay loam in Manitoba, Canada in 1998 and monitored for twelve years to determine effects on potato yield and quality. Higher yields for canola-containing rotations were evident in three years (P < 0.10), but not beyond 2005. From 2007 onward, 2-year rotations produced a markedly lower yield than other rotations. Yields of 3- and 4-year rotations were similar, although PCW and PCAA were most frequently among the higher-yielding rotations. Overall, PC had a lower specific gravity than other rotations. Results suggest 3- and 4-year rotations, particularly PCW and PCAA, helped maintain productivity. Two-year rotations of PC and PW were not sustainable due to declining yields.ResumenLa productividad de los sistemas de papa (Solanum tuberosum L.) pueden estar fuertemente influenciados por la rotación. Se estableció un estudio de campo consistente en seis rotaciones; papa con canola (PC), con trigo (PW), con canola-trigo (PCW), con avena trigo (POW), con trigo, canola, trigo (PWCW), y con canola mezclada con alfalfa-alfalfa-alfalfa (PCAA), arreglado en un diseño experimental de bloques completos al azar, en un suelo franco-arcilloso en Manitoba, Canadá, en 1998, y monitoreado por doce años, para determinar los efectos en rendimiento y calidad de la papa. Se hicieron evidentes más altos rendimientos en las rotaciones que incluían a la canola en tres años (P < 0.10), pero no más allá de 2005. A partir de 2007, las rotaciones de dos años produjeron un rendimiento más bajo bien marcado que en otras rotaciones. Los rendimientos de rotaciones de 3 y 4 años fueron similares, aunque PCW y PCAA estuvieron entre las más frecuentes de las rotaciones de mayores rendimientos. En general, PC tuvieron gravedad específica más baja que otras rotaciones. Los resultados sugieren que rotaciones de 3 a 4 años, particularmente PCW y PCAA, ayudaron a mantener la productividad. Rotaciones de dos años de PC y PW no fueron sostenibles debido a la disminución en rendimientos.

Cultivar Developments, Fertilizer Inputs, Environmental Conditions, and Yield Determination for Potatoes in Manitoba

While potato production on the Canadian Prairies has expanded significantly since the early 1990s and accounted for roughly one third of Canada’s production over the period 1990–2006, few studies have looked at Plant Breeder’s rights and cultivar releases in Canada, and the determinants of potato yield in Manitoba. This paper examines potato breeding developments in terms of cultivar releases, the extent that new cultivar releases are protected by Plant Breeders’ Rights (PBR), and the contribution of cultivar improvements, environmental conditions and fertilizer inputs to potato yield in Manitoba. The results from our study indicate that professional person-years devoted to potato breeding has declined since 1990 and that PBR granted to European and U.S. breeders have exceeded those granted to Canadian domestic breeding institutions. Manitoba processing potato yields have been affected more so by a combination of fertilizer inputs and regional effects than by improved cultivars. In the current study, the limited effect of protected cultivars on yield may be due to the small number of protected cultivars being assessed, and the relatively short time period considered. Lack of adoption of new cultivars in Manitoba may reflect slow adoption of new cultivars by the processing industry as it ensures that quality and processing specifications are met.ResumenMientras que la producción de papa en las praderas Canadienses se ha expandido significativamente desde inicios de 1990 y contabilizados someramente para un tercio de la producción de Canadá en el periodo 1990–2006, pocos estudios han analizado el derecho de los Genetistas en Plantas y lanzamiento de cultivares en Canadá, y los determinantes del rendimiento de papa en Manitoba. Este artículo estudia los desarrollos genéticos en papa en términos de lanzamiento de cultivares, la magnitud en que el lanzamiento de nuevas variedades es protegido por los Derechos de los Genetistas en Plantas (PBR), y la contribución en mejoras de cultivares, condiciones ambientales y aportes de los fertilizantes en el rendimiento de papa en Manitoba. Los resultados de nuestro estudio indican que persona profesionales-años dedicados al mejoramiento de papa ha declinado desde 1990 y que el PBR otorgado a los genetistas europeos y de Estados Unidos han excedido a aquellos otorgados a las instituciones genéticas domésticas canadienses. Los rendimientos de procesamiento de papa en Manitoba han sido más afectados, tanto por la combinación del aporte de los fertilizantes y efectos regionales que por cultivares mejorados. En el presente estudio, el efecto limitado de los cultivares protegidos en rendimiento podrían deberse al pequeño número de cultivares protegidos que son evaluados, y al relativamente corto periodo de tiempo considerado. La falta de adopción de nuevos cultivares en Manitoba podrían reflejar una adopción lenta de nuevos cultivares de parte de la industria de procesamiento mientras se aseguren conseguir las especificaciones de calidad y procesamiento.

Effect of Phosphorus Fertilizer Rate on Irrigated Russet Burbank Potato

Phosphorus (P) fertilizer is routinely applied to potato (Solanum tuberosum L.) in Manitoba, Canada; however, little information is available regarding P responses in this region. Field studies were conducted from 2003 through 2006 to determine the impact of P rate [0, 15, 29, 43 kg P ha−1 as broadcast incorporated monoammonium phosphate (MAP)] on Russet Burbank potato. Increasing P rate resulted in a linear increase in marketable yield in 2005, a quadratic increase in 2006, and no effect in 2003 and 2004. Phosphorus application had no effect on the yield of tubers <85 g, tuber number, or quality, but petiole P concentration and postharvest soil-test P levels increased with increasing P rate. Results of this and other studies show that P fertilization may improve potato yields, although increases are not completely predictable. Additional research is required to refine soil-test guidelines and petiole P sufficiency levels for this region.

Effect of rate and timing of potassium chloride application on the yield and quality of potato (Solanum tuberosum L. 'Russet Burbank')

Mohr, R. M. and Tomasiewicz, D. J. 2012. Effect of rate and timing of potassium chloride application on the yield and quality of potato ( Solanum tuberosum L. ‘Russet Burbank’). Can. J. Plant Sci. 92: 783-794. Potassium is frequently applied to irrigated potato in Manitoba. Field experiments were conducted at two sites in each of 2006, 2007 and 2008 to assess effects of rate and timing of potassium chloride (KCl) application on the yield, quality, and nutrient status of irrigated potato (Solanum tuberosum ‘Russet Burbank’) in southern Manitoba. Preplant application of KCl increased total and marketable yield at one site, and tended (0.05<P = 0.10) to increase total and marketable yield at three additional sites. At three of the four K-responsive sites, soil test K levels were <200 mg NH4OAc-extractable K kg-1, the level below which K fertilizer is recommended based on existing guidelines. Effects of timing of KCl application on total and marketable yield were limited although, averaged across sites, KCl applied at hilling reduced the yield of small tubers (<85 g) and increased the proportion of larger tubers (170 to 340 g) compared with preplant application. Averaged across sites, KCl applied preplant or at hilling reduced specific gravity compared with the 0 KCl treatments. Improvements in fry colour with KCl application were evident at only one site. Petiole and tuber K and Cl- concentration, K and Cl- removal in harvested tubers, and post-harvest soil test K concentration increased with KCl application. However, petiole K concentration measured 82 to 85 d after planting predicted only 24% of the variability in relative marketable yield for sites containing between 164 and 632 mg NH4OAc-extractable K kg-1 to 15 cm. Results demonstrate the potential for yield increases and specific gravity declines with KCl application under Manitoba conditions, but suggest that further research will be required to better predict the potential for yield responses using soil and petiole testing.

Effect of nitrogen fertilizer rate, herbicide rate, and soil disturbance at seeding on the productivity of a wheat-pea rotation

Rotational productivity is a function of the rotational crops and their interactions, as well as the management employed. Understanding the functioning of the overall production system, as well as its component parts, may contribute to improved management. Effects of nitrogen fertilizer rate (25, 50, 75, 100 kg N ha-1 as urea) and herbicide rate (66 or 100% of recommended) applied to wheat, and of the level of soil disturbance at seeding, on the productivity and N status of a 2-yr rotation of spring wheat (Triticum aestivum L.) and field pea (Pisum sativum L.) were assessed over two rotation cycles at two locations in southwestern Manitoba. Management factors typically acted independently to influence the cropping system. In both wheat and pea, high soil disturbance at seeding reduced or tended to reduce plant density in most site-years, resulting in reduced yields in about half of site-years. In 2 site-years where weed pressure was high, wheat yields for high disturbance treatments were less than 60% of ...