Canola Yield Research Articles

Adaptation of oilseed crops across Saskatchewan

Differences in response to nitrogen (N) fertilizer will affect the production economics of field crops. Currently, there is limited information comparing the agronomic and economic performance of juncea canola (Brassica juncea L.) and sunflower (Helianthus annuus L.) to napus canola (Brassica napus L.) and flax (Linum ustitatissimum L.) in Saskatchewan under no-till practices. A study of these species was carried out at five Saskatchewan locations over 3 yr and included eight nitrogen rates. All four species had a curvilinear increase in grain yield as N rate increased with the largest yield response observed in napus canola to as much as 200 kg N ha-1. The majority of the increase in flax grain yield occurred as the N rate increased from 10 to 90 kg ha-1, while most of the increase in grain yield of juncea canola and sunflower occurred as N increased from 10 to 70 kg ha-1. Biplot analysis indicated that grain yield variation was reduced at and above 50 kg N ha-1 in flax, napus canola and juncea canola, but not in sunflower. Analysis indicated that a wide range of N rates would provide a similar adjusted gross return within each crop with the exact N range being determined by crop price and nitrogen cost. The N rate affected the kernel weight of sunflower but not the kernel weight of other crops. The protein concentration of all the species increased as N rate increased. Seed oil concentration tended to decrease as the N rate increased, but this was not consistent. In conclusion, higher yielding cultivars of sunflower and juncea canola are needed before they will replace a large acreage of flax or napus canola; however, in the drier regions of the Saskatchewan there is potential to expand sunflower production.Key words: Brassica juncea, Helianthus annuus, Brassica napus, Linum usitatissimum, nitrogen, economic analysis

Interrelationships between seed yield and 20 related traits of 49 canola (Brassica napus L.) genotypes in non-stressed and water-stressed environments

Development of new canola (Brassica napus L.) cultivars requires efficient tools to monitor trait association in a breeding program. The efficiency of a breeding program depends mainly on the direction of the correlation between yield and its components and the relative importance of each component involved in contributing to seed yield. This research uses sequential path analysis to determine the interrelationships among seed yield and 20 related traits. Forty nine canola genotypes were grown in two environments (non-stressed and water-stressed conditions) to determine the important components of seed yield. Observations were recorded on 20 other canola traits. Correlation coefficient analysis revealed seed yield was positively correlated with all the traits except stem diameter and days to flowering in the non-stressed environment. Seed yield was significantly positively correlated with all measured traits except first pod height, first lateral branch height, number of lateral branches pod-1, number of pods plant-1 and stem diameter in the water-stressed environment. Sequential path analysis identified the 1000-seed weight (TSW) and main stem length as important first order traits that influenced seed yield in the non-stressed environment. Plant height and the TSW were important first order traits that influenced seed yield in the water-stressed environment. All direct effects were significant, as indicated by bootstrap analysis. The results suggest that TSW could be used as a selection criterion in selecting for increased seed yield in canola in both non-stressed and water-stressed conditions.

Effects of changes in climatic variability on agricultural production

Daily outputs of the CSIRO Conformal Cubic Atmospheric Model (C-CAM) for the periods of 1961-1990 and 2065-2094 were used in the present study to derive changes in mean climate and in climatic variability, which were used by the stochastic weather generator LARS-WG to generate climatic change scenarios for 3 sites in southeast Australia. Climatic scenarios were coupled with the Agricultural Production System sIMulator (APSIM)-Wheat/Canola models to identify the influence of changes in climatic variability on wheat and canola production at 3 sites (Condobolin, Nhill and Wagga Wagga). Changes in climatic variability had negative effects on average wheat and canola yields at Wagga Wagga and Condobolin, and, in most cases, on the coefficients of variation (CV) of wheat yield, while the CV of canola yield experienced both positive (50% of the cases) and negative (50% of the cases) effects. Changes in climatic variability had positive (50% of the cases) or no (50% of the cases) effect on the average harvest index (HI) of wheat, whereas they had negative (33% of cases) or no (67% of cases) effect on the average HI of canola. Negative effects of changed climatic variability on the CV of HI for both crops were found. Our results demonstrate that the effects of changes in climatic variability on crop production vary across locations and impact indicators. Changes in climatic variability there- fore need to be taken into account in agricultural impact assessment.

Residue burning and tillage effects on diseases and yield of barley ( Hordeum vulgare) and canola ( Brassica napus)

Crop residue is often managed by tillage or burning in western Canada. This study was conducted to test the hypothesis that burning crop residues reduces the severity of barley ( Hordeum vulgare L.) and canola ( Brassica napus L.) diseases, and increases seed or grain yield or quality. Experiments were conducted at 2 sites, a Gray Luvisol (Typic Cryoboralf) and a Dark Gray Luvisol (Mollic Cryboralf) over 5 years in northeast Saskatchewan, Canada, with treatments of: zero (ZT) and conventional (CT) tillage, and burning (B) or no burning (NB) of previous crop residue. At each site, an experiment for barley and another for canola was established in a 2-year barley–canola rotation. Severity of leaf spotting diseases of barley, mainly net blotch [ Pyrenophora teres Drechsler], and incidence of sclerotinia stem rot [ Sclerotinia sclerotiorum (Lib.) de Bary] of canola were sometimes greater in the B treatment than the NB. Leaf spot severity of barley was usually slightly reduced under CT compared with ZT, but regardless of severity, barley yields were either similar, or more often higher under ZT than CT (337–766 kg ha −1 or 11–57%). There were occasionally effects of B on barley yield, but results were inconsistent and sometimes depended on tillage system. Canola yield tended to be greater under ZT than CT (141–233 kg ha −1 or 9–44%), but the effect of B was inconsistent. Tillage system had the greatest impact on crop yields with higher yield more often under ZT than CT, most likely as a result of improved soil moisture under the ZT system. We conclude that use of fire to manage diseases of barley and canola is ineffective.

Nitrogen Fertilizer and Urease Inhibitor Effects on Canola Emergence and Yield in a One‐Pass Seeding and Fertilizing System

Field studies were conducted over 3 yr at two locations on the eastern Canadian prairies to evaluate the impact of urea and urea ammonium nitrate (UAN) placed near the seed‐row in a one‐pass seeding and fertilizing operation on seedling damage, biomass yield at flowering, and final seed yield of canola (Brassica napus L.). Seedling damage occurred in canola with increasing rates of urea or UAN fertilizer applied as a side‐band targeted to place the fertilizer placed 2.5 cm to the side and 2.5 cm below the seed row at the time of seeding. Decrease in stand density with UAN was similar to that resulting from urea application. The urease inhibitor (UI) N‐(n‐butyl) thiophosphoric triamide (NBPT) decreased seedling damage in canola from both urea and UAN fertilizer. Dry matter yield at flowering was only rarely affected by seedling damage, but NBPT increased canola seed yield at high rates of N application in three of six site‐years and decreased seed yield at one site‐year. Chlorophyll concentration in the seed increased as stand density decreased, indicating a negative effect of seedling damage on both maturity and seed quality. Caution should be used to ensure that seed and fertilizer separation is adequate and safe rates of N application are not exceeded when fertilizer is banded near the seed‐row. Use of NBPT can reduce the risk of seedling damage and increase the amount of urea or UAN that can safely be side‐banded in a one‐pass seeding and fertilizing operation.

Fertilizer response for hybrid and open-pollinated canola and economic optimal nutrient levels

Hybrid (HY) canola (Brassica napus L.) produces a higher seed yield than open-pollinated (OP) canola. While it is expected higher-yielding HY canola may require higher total available nutrients, especially nitrogen (N), the evidence is not conclusive. This study used canola yield data from several site-years and fertility experiments to determine whether HY and OP canola types require different rates of total available N (TAN) and total available phosphorus (TAP). The yield response of the two canola genotypes to TAP was the same, but for TAN the yield response was greater for HY canola. The quadratic yield response results were confirmed using three plateau equations. Optimal TAN for HY canola was higher than for OP canola. Soil test laboratories and producers growing HY canola need to modify N fertility for HY canola, compared with OP canola for which most of the current N fertilizer recommendations were developed. Key words: Economics, fertilizer, yield response, canola, hybrid, open-pollinated

Effects of Salinity on Yield and Component Characters in Canola (Brassica napus L.) Cultivars

Cultivars ‘Okapi’, ‘SLM046’, ‘Elite’, ‘Fornax’ and ‘Licord’ Brassica napus were tested for yield and component characters under different levels of salinity. The variations due to salinity levels, cultivars and cultivarxsalinity (interaction) were significant for different characters. The variable degrees of increase and decrease of regression coefficient estimate mates (curve estimation) showed the performance as influenced by different salinity levels. The performance of Brassica napus variety in plant height and days to first flowering was the best for ‘SLM046’, ‘Okapi’ ‘SLM046’ and ‘Okapi’ cultivars. ‘SLM046’ showed the best performance in days to maturity, followed by ‘Licord’ and ‘Elite’. ‘Okapi’ performed better than others regarding the increased number of seeds per plant and seed yield per plant, followed by ‘Fornax’. Considering all characters, the most tolerance ability was found in ‘SLM046’ and ‘Okapi’, against different levels of salinity.

Effects of Manure and Fertilizer Applications on Canola Oil Content and Fatty Acid Composition

Increasing fertilizer costs have resulted in more growers evaluating the use of alternative nutrient sources such as manure. Coincidentally, the questions about fertilizer effects on oil yield and oil fatty acid composition have been a concern. A 2‐yr study was conducted to investigate nutrient source (fertilizer urea plus S and manure) and N level (0, 84, and 168 kg N ha−1) effects on canola seed yield, total oil content, and oil composition at East Lansing and Chatham, MI. Results indicated nutrient applications were not necessary to increase canola yield (865–1991 kg ha−1) in fertile fields. However, N fertilizer appeared to reduce total oil content (444−536 mL kg−1), and at similar N levels, total oil content in canola with fertilizer was sometimes lower than that with manure application. Compared with the no nutrient control treatment, fertilizer application sometimes decreased linolenic acid (LN) content, and increased palmitic acid (P) and arachidic acid (A) at Chatham, while it appeared to decrease oleic acid (O) and increase P, linoleic (L) and A at East Lansing. Fertilizer applications often increased canola total saturated fatty acid content (6.80–8.32%) and decreased ratio of O/(L+LN) (2.04–2.52). Manure application had milder effects on oil composition than fertilizer application. Compared with less N (84 kg N ha−1) applications, greater N level (168 kg N ha−1) tended to lower oil quality by increasing total saturated fatty acid content and decreasing the O/(L+LN) ratio.

Emergence, height, grain yield and oil content of camelina and canola grown in saline media

Crops of CS15 camelina and InVigor 9590 canola, grown under field conditions in Canada’s Salinity Tolerance Testing Facility, were evaluated for plant emergence, height, shoot biomass, grain yield, oil content and composition. The crops were seeded directly into sand tanks flushed four times daily with hydroponics consisting of nutrients and salts ranging in salinity from negligible to severe. Sulphate-based solutions averaging 1.4 (nutrients only), 3.0, 6.0, 10.0, 14.7, 19.9, and 27.0 dS m-1 in electrical conductivity (ECsol) resulted in respective cumulative emergence of 99.0 to 42.1% for the camelina and 99.3 to 79.6% for the canola and showed statistical differences only at the two highest salinity treatments. Plant height differences between the camelina and the canola increased as salinity increased: from 16% at 1.4 dS m-1 to 60% at 19.9 dS m-1. Grain yields under salinity relative to the salt-free yield decreased more for the camelina than for the canola at all ECsol-levels. The salinity tolerance index based on the ECsol -value at 50% of the maximum grain yield indicated that the camelina registered less than half (7.4) of that for the canola (18.0). The percentage oil content of the canola oilseed averaged 40% until salinity exceeded 20 dS m-1, while that of the camelina averaged 35% until 10 dS m-1, before declining. Key words: Camelina sativa, false flax, salinity tolerance, salt resistance, Brassica napus, canola

Effects of Salinity and NO3:NH4 Ratio on Yield and Quality in Canola (Brassica napus L.)

The effect of salinity and NO3: NH4 ratio (0:100, 75: 25, 50:50, and 25:75) in the nutrient solution on growth, yield quality and N metabolism in hydroponically grow canola (Brassica napus L.) was evaluation. Both fresh and dry weights of leaves were significantly lower when a high concentration of either NO3 (100%) or NH4 (75%) was the sole N source in the nutrient solution. In nonsaline condition, increasing of both NH4 and NO3 ratio in the nutrient solution reduced photosynthetic (pn) rate, however in salinity condition the reduction of pn became more pronounced at a higher ratio of NH4 in the nutrient solution. The yield in terms of fresh and dry weight of seed per plant was significantly increased at the 75:25 (NO3: NH4) treatments. Total fat in nonsaline condition was increased with increasing NH4 ratio in the nutrient solution, however in saline condition it was reduced, at high NH4 ratio in the nutrient solution. The increase of tissue N concentration was nearly proportional to the NH4 concentration in the nutrient solution.The activity of nitrate reductase (NR) was increased by increasing NH4 form 0 to 50% and then reduced at a higher ratio of NH4 in the solution. Salinity increased NH4 concentration so that the saline condition had nearly twice high NH4 concentration in the leaves. The increase of NH4 concentration induced by salinity could be parially the reduction of NH4 assimilate because of the shortage of carbohydrate.

Energy use efficiency is characterized by an epigenetic component that can be directed through artificial selection to increase yield

Quantitative traits, such as size and weight in animals and seed yield in plants, are distributed normally, even within a population of genetically identical individuals. For example, in plants, various factors, such as local soil quality, microclimate, and sowing depth, affect growth differences among individual plants of isogenic populations. Besides these physical factors, also epigenetic components contribute to differences in growth and yield. The network that regulates crop yield is still not well understood. Although this network is expected to have epigenetic elements, it is completely unclear whether it would be possible to shape the epigenome to increase crop yield. Here we show that energy use efficiency is an important factor in determining seed yield in canola (Brassica napus) and that it can be selected artificially through an epigenetic feature. From an isogenic canola population of which the individual plants and their self-fertilized progenies were recursively selected for respiration intensity, populations with distinct physiological and agronomical characteristics could be generated. These populations were found to be genetically identical, but epigenetically different. Furthermore, both the DNA methylation patterns as well as the agronomical and physiological characteristics of the selected lines were heritable. Hybrids derived from parent lines selected for high energy use efficiencies had a 5% yield increase on top of heterosis. Our results demonstrate that artificial selection allows the increase of the yield potential by selecting populations with particular epigenomic states.

Comparison of Certified and Farm‐Saved Seed on Yield and Quality Characteristics of Canola

Relatively high seed prices and low canola (Brassica napus L.) grain prices created a controversy over using farm‐saved seed from hybrids. Agronomic implications of saving seed from a canola crop were investigated by planting certified seed and saved‐seed of an open‐pollinated and a hybrid canola cultivar at eight site‐years in Saskatchewan and Alberta, Canada. In one series of experiments cultivars and seed rates were compared, while in another experiment seed treatments and use of sized seed were investigated. Results tend to agree with similar studies with other crops where agronomic performance was unaffected when farm‐saved seed from open‐pollinated crops was used, but declined when this practice was used with hybrid cultivars. Using farm‐saved seed from hybrid canola (HY‐FSS) compared with hybrid certified seed (HYC) reduced plant population density by 16 to 18% at the time of crop maturity and yield by an average of 12%, delayed maturity by 2 d, reduced seed oil content by 5 g kg−1, and resulted in a small increase in incidence of green seed. Yield and quality loss associated with using HY‐FSS could not be recovered by using increased seeding rates or by sizing and planting only large seed. The inability to use the most effective combined insecticide plus fungicide seed protectant treatments with farm‐saved seed resulted in a 20% yield loss compared with treated certified hybrid seed. Our study demonstrates the production risks of growing HY‐FSS on plant density, yield, maturity, and seed oil content.

Estimating canola (Brassica napus L.) yield potential using an active optical sensor

Active optical sensors have potential as tools to increase N fertilizer use efficiency in crop production; however, empirical data are required to utilize the sensors for this purpose. Data were compiled from N fertilizer trials at five Canadian locations (2004-2007) to determine the feasibility of using optical sensors during the growing season to estimate the seed yield potential of canola (Brassica napus). The normalized difference vegetation index (NDVI) of each plot in each trial was measured using a hand-held optical sensor several times each season. The NDVI between the six-leaf stage and the beginning of flowering was divided by one of several different heat unit summations to normalize the measurements, and data were combined across locations. Linear and exponential regression analyses were completed for canola seed yield as a function of both the original and normalized NDVI measurements. When data from all locations were combined, NDVI was significantly correlated with canola seed yield (R2 = 0.35; P < 0.001) and normalizing NDVI did not improve the correlation. Categorizing the locations by soil zone (Brown-Dark Brown and thin-Black-Black) and completing separate regression analyses for each group increased the correlation coefficients for NDVI and seed yield (R2 = 0.36-0.43). Furthermore, dividing NDVI by the heat unit summations generally improved the correlation when the data were categorized by soil zone. The largest correlation coefficient occurred when NDVI was divided by growing degree days with a base temperature of 5°C (R2 = 0.53-0.67). Our results show that optical sensors can be used to estimate canola yield potential early enough in the growing season to have potential as an N management tool.Key words: Normalized difference vegetation index, agriculture, precision, nitrogen use efficiency

Diverse no-till irrigated crop rotations instead of burning and plowing continuous wheat

Field burning of residue is a traditional management tool for irrigated wheat ( Triticum aestivum L.) production in the Inland Pacific Northwest of the United States (PNW) that can result in reduced air quality. A 6-year no-till field experiment to evaluate two complete cycles of a 3-year irrigated crop rotation of winter wheat–spring barley ( Hordeum vulgare L.)–winter canola ( Brassica napus L.) was sown (i) directly into standing residue of the previous crop, (ii) after mechanical removal of residue and, (iii) after burning of residue. The traditional practice of continuous annual winter wheat sown after burning residue and inverting the topsoil with a moldboard plow was included as a check treatment. Over-winter precipitation storage efficiency (PSE) was markedly improved when residue was not burned or burned and plowed after grain harvest. Grain yield of winter wheat trended higher in all no-till residue management treatments compared to the check treatment. Average grain yields of spring barley and canola were not significantly different among the no-till residue management treatments. Winter canola failed in 5 of 6 years due to a combination of a newly identified Rhizoctonia damping-off disease caused by Rhizoctonia solani AG-2-1 and cold temperatures that necessitated replanting to spring canola. Six-year average net returns over total costs were statistically equal over all four systems. All systems lost from $358 to $396 ha −1. Soil organic carbon (SOC) increased linearly each year with no-till at the 0–5 cm depth and accumulated at a slower rate at the 5–10 cm depth. Take-all of wheat caused by Gaeumannomyces graminis var. tritici was most severe in continuous annual winter wheat. The incidence and severity of Rhizoctonia on roots of wheat and inoculum of R. solani AG-8, was highest in the no-till treatments, but there was no grain yield loss due to this disease in any treatment. Residue management method had no consistent effect on Rhizoctonia root rot on barley. The annual winter grass downy brome ( Bromus tectorum L.) was problematic for winter wheat in the standing and mechanically removed residue treatments, but was controlled in the no-till residue burned and the burn and plow check. Another winter annual grass weed, rattail fescue ( Vulpia myuros L.), infested all no-till treatments. This was the first comprehensive and multidisciplinary no-till irrigated crop rotation study conducted in the Pacific Northwest.

First Report of Charcoal Rot on Canola Caused by Macrophomina phaseolina in Western Australia.

In the spring of 2006, canola (Brassica napus L.) plants suffering from wilt were observed in an experimental plot at Merredin, Western Australia. Symptoms on the affected plants were tan-brown, longitudinal streaks along the main stem and on some lateral branches. Lesions on the stem were predominantly unilateral but sometimes covered the entire stem. Some of the lateral branches were completely wilted, and if present, pods were either shriveled or contained small seed. At the base of the stem, the lesions were grayish brown streaks that caused longitudinal splitting of the stem base. Small spherical (55 to 75 μm in diameter) and elongated (75 to 120 μm long) microsclerotia were seen in the pith and vascular region. Roots appeared to be symptomless, but upon removing the epidermis, grayish streaks were also seen on the roots and small sclerotia were observed in the pith and the vascular region of roots. One hundred and four small pieces (1 to 2 cm) of stem and root from 10 symptomatic plants were surface sterilized with 1.25% NaOCl, rinsed twice in sterile distilled water, and plated on potato dextrose agar (PDA) supplemented with 10 ppm of aureomycin. These were incubated under a blacklight at 22°C. Macrophomina phaseolina (Tassi) Goid. was isolated from 80% of the pieces as identified by colony morphology and the size of microsclerotia that ranged between 50 and 190 μm (3). Eight-three isolates were obtained. None of the isolates produced pycnidia on PDA. However, pycnidia (100 to 190 μm) with pycnidiospores (17.5 to 30 × 7.5 to 10 μm) were produced on the affected stems collected from the field. Pathogenicity tests with one of the isolates were conducted on seven 2-week-old canola plants (cv. Stubby). Three uninoculated plants served as the control. Roots of 2-week-old plants were dipped in an aqueous conidial suspension (1 × 104 conidia/ml) of M. phaseolina for an hour while roots of control plants were dipped in sterile water. Inoculated and control plants were repotted in separate pots and transferred to a glasshouse. A week after inoculation, M. phaseolina produced chlorosis of the leaves, and subsequently, complete wilting and death of the inoculated plants. M. phaseolina was successfully reisolated from roots and stems of symptomatic plants. No symptoms developed on the control plants. Pathogenicity was also tested by soaking seeds of cv. Stubby with an aqueous conidial suspension of M. phaseolina for one-half hour and incubating on agar media after drying. Germinating seeds were colonized by the growing mycelium and seedlings were completely killed within a week. Abundant microsclerotia were produced on the dead seedlings. M. phaseolina has been previously reported on canola in the United States (1) and Argentina (2) and more recently has been reported on canola in eastern Australia (4). To our knowledge, this is the first record of occurrence of M. phaseolina on canola in Western Australia and its impact on canola yield needs to be determined.

Fertilizer N response and canola yield in the semiarid Canadian prairies

Canola is a viable crop when grown under fallow in the semiarid prairie, but is also grown in longer rotations, most often no-till seeded into standing stubble. Selecting the proper N fertilizer rate is a very challenging production decision, but most of the available nitrogen response for canola has been derived for the more subhumid parts of the Canadian prairies. We developed simple quadratic equations to describe the yield relationship for stubble-seeded open-pollinated and hybrid canola in the semiarid Canadian prairie. These relationships indicate that hybrid canola produced higher grain yields at all fertilizer rates and had optimum N fertilizer rates about 50% higher than those for open-pollinated canola. Key words: Canola, fertilizer N, grain yield, water use, semiarid prairie

Field screening of canola ( Brassica napus) cultivars against wild mustard ( Sinapis arvensis) using competition indices and some empirical yield loss models in Golestan Province, Iran

In order to evaluate the competitive ability (CA) of canola cultivars against wild mustard, two experiments were conducted at the Gorgan Institute in Iran during the 2005–2007 cropping seasons. The experimental factors were canola cultivars (1st year: Zarfam, Option500, Hayola330, Hayola401, Talayh, RGS003 and Sarigol; 2nd year: Zarfam, Hayola330, RGS003 and Option500) and weed density (1st year: control and 30 plants m −2; 2nd year: control, 4, 8 and 16 plants m −2). The result of the first year of experiment indicated that the grain yield and competitive indices differed significantly between the cultivars. Cultivar Zarfam showed a high ability to withstand competition (AWC = 47%), high competitive indices (CI = 1.79 and CI 2 = 10 1.83) and low grain yield in the weed-free plots (1729 kg ha −1). The cultivar Option500, a less competitive cultivar had the lowest ability to withstand competition (AWC = 4%) and the lowest competitive indices (CI = 0.09 and CI 2 = 0.11) amongst the cultivars. However, the cultivar Option500 showed more grain yield in the weed-free plots (2333 kg ha −1) than cultivar Zarfam. In the second year of the experiment, the result of the yield loss models showed that the lowest and highest yield loss belonged to cultivars Zarfam and Option500 (50 and 95% respectively). A comparison of different empirical models revealed that the empirical yield loss model based on weed relative leaf area was more reliable for predicting canola yield loss according to a high coefficient of determination ( R 2 = 0.99). The relative damage coefficient ( q) of the weed relative leaf area model showed that wild mustard was more competitive than canola ( q > 1).

Modeling Vegetative Stage Response of Canola (Brassica napus L.) to Combined Salinity and Boron tresses

Boron (B) is essential to growth at low concentrations and limits growth and yield when in excess. Little is known regarding plant response to excess B and salinity occurring simultaneously. In this study, two models of Leibig-Sprengel (LS) and Mitscherlich-Baule (MB), originally proposed to explain plant response to nutrients only, were modified to evaluate canola yield response to combined levels of B and salinity stresses. The water salinity treatments were consisted of non-saline water, 3, 6, 9 and 12 dS m -1 . The B treatments were 0, 10, 20 and 30 mg kg -1 added to soil as H3BO3. It was revealed that modified LS model can satisfactorily predict canola dry matter yield. The calculated statistics: Maximum Error, Root Mean Square Error, Modeling Efficiency, Coefficient of Determination and Coefficient of Residual Mass, indicated that the estimated relative dry matter yield for soil B concentrations and salinity levels by modified LS model compared to modified MB model was closer to the measured relative yield. Therefore, the use of modified LS model for estimating canola relative yield in salinity and B stresses is recommended. The threshold value of salinity increased with higher B concentration and maximum dry matter yields decreased with increasing B concentration. Excess B was found to decrease dry matter yield of canola. This effect was inhibited when plants were exposed to simultaneous B and salinity stresses. Both irrigation water salinity and B concentration influenced water use efficiency (WUE) of plant, however, only B concenteration influenced canola yield in in the same manner.

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 production and seed yields of flax were relatively unaffected by P fertilization whether applied in the same season as flax or in the previous season, although early-season P concentration and P accumulation were increased when P fertilizer was applied to the flax. Of the factors evaluated in this study, preceding crop had the greatest influence on flax growth with flax establishment, early-season biomass, and P accumulation, and seed yield all being significantly greater when flax was seeded after wheat than after canola. Key words: Crop rotation, fertilization, monoammonium phosphate, flax, wheat, canola

Phosphorus accumulation by field-grown canola crops and the potential for deep phosphorus placement in a Mediterranean-type climate

When the bulk of phosphorus (P) is located near the soil surface, spring drying of topsoil in Mediterranean-type climates can reduce P availability to crops and cause potential yield loss. In crop species that require a P supply during spring, deep-placement of P fertiliser has proved an effective method of improving P availability and grain yields; however, the spring P demand of field-grown canola (Brassica napus L.) and therefore potential response to deep P placement is not known. This study investigated the effect of deep- (0.17–0.18 m), conventional- (shallow, 0.07–0.08 m), split- (50% deep, 50% shallow), and nil-P fertiliser treatments on P accumulation and seed yields of canola in two field trials. In addition, a glasshouse experiment with different depths of P fertiliser placement and topsoil drying at different growth stages was conducted. In the glasshouse study, deep P placement resulted in greater P uptake by plants, but did not increase seed yields regardless of the time of topsoil drying. At the relatively high-soil-P field site (canola grown on residual P application from the previous year) in a dry season, there was no biomass response to any residual P fertiliser treatments, and P accumulation had ceased by mid flowering. At the low-P field site, P accumulation continued throughout flowering and silique-filling, and seed yields increased significantly (P ≤ 0.05) in the order of split- > deep- > shallow- > nil-P treatments. Improved seed yields in the split- and deep-P treatments appeared to be the direct result of enhanced P availability; in particular, P uptake during vegetative growth (winter) was higher in the treatments with deep P placement. A greater understanding of P accumulation by field-grown canola in relation to soil P properties is needed for better defining optimum P fertiliser placement recommendations.