Canola Yield Research Articles

Vernalisation in Australian spring canola explains variable flowering responses

Abstract Previous studies have shown significant canola yield increases when flowering occurs at the optimal time. The geographic and within-season range of Australian canola production is expanding; crops are being sown earlier and in areas that experience warmer winters. However, observations of unpredictable flowering in these circumstances have raised uncertainty about our current understanding of the cultivar traits that determine development and the ability to predict phenology in these environments. To address these concerns, a detailed phenological study of Australian canola cultivars was undertaken at three locations which differ in vernal temperature and photoperiod (Canberra ACT Australia, Latitude −35.201°, longitude 149.082°; Ottawa Ontario, Canada, Latitude 45.23° Longitude −75.72°; Gatton Qld, Australia, Latitude −27.55° Longitude 152.31°) combined with an artificial light system to extend photoperiod (daylength) to 16 h. Most Australian commercial cultivars displayed significant vernal responses and only a few had significant photoperiod responses. In addition, the method used to calculate vernal time (using average daily temperature calculated from maximum and minimum temperature or using a sub-daily temperature estimate) influenced conclusions about how vernal exposure reduced the time to flowering. The improved understanding of the mechanisms that control flowering in canola can inform breeders making appropriate selections for target environments and assist growers to match canola cultivars to environment and sowing date. Capturing this new knowledge in phenological parameters will also improve outputs of simulation models used to investigate improved management in novel canola production systems.

Effect of Vermicompost and Municipal Solid Waste Compost on Growth and Yield of Canola under Drought Stress Conditions

ABSTRACT In order to study the effect of municipal solid waste (MSW) compost and vermicompost on morpho-physiological properties and yield of canola under drought stress conditions, an experiment was conducted as factorial arrangement based on randomized complete block design with four replications. Treatments consisted of three levels of water regimes, including: 75% of the field capacity for well-watered and 55% and 35% for moderate and severe stress, respectively, and biofertilizer in five levels, including: nonapplication of biofertilizer (control), application of MSW compost, and vermicompost at 2% and 4% levels. Results showed that interaction of irrigation and biofertilizer had significantly affected on all traits except leaf area ratio and nitrogen percent. The moderate and severe stress significantly reduced all traits compared to normal irrigation. Application of 4% vermicompost was resulted in increased growth, biomass and yield of canola under normal irrigation, moderate and severe drought stress compared to other biofertilizer treatments.

Canola yield and its association with phenological, architectural and physiological traits across the rainfall zones in south-western Australia

• Multiple-environment trials were used to understand yield and associated traits. • Genotype × environment interaction reveals two environment and four genotype clusters. • Flowering time, biomass and harvest index were the main factors determining yield. • Both specific and broad adaption were identified. Understanding genotype and environment interaction (G × E) and the association between yield and phenological, architectural and physiological traits plays a crucial role in successful canola breeding and agronomic management. We investigated yield performance of 20 open-pollinated and hybrid canola across multiple environments over five years and its association with these traits. Heterogenic genetic variance and genetic correlation among the environments demonstrated significant G × E interactions in yield, biomass, but not in harvest index (HI). Flowering time, biomass at maturity and HI are the three most important traits underlying the G × E interaction. Principal component analysis (PCA) based on the yield across the environments identified two mega-environments (the low/medium rainfall zone (LMRZ) and the high rainfall zone (HRZ)) and four genotype clusters (early-flowering, late-flowering, average performing, and broadly adapted varieties). Early flowering genotypes were better adapted to the LMRZ mega-environment and late-flowering ones to the HRZ mega-environment. Despite the G × E interaction, a group of hybrid varieties were identified as broadly adapted, producing either the highest or similar yield to specifically adapted varieties. The genotype by trait PCA revealed that yield was positively associated with biomass and HI but negatively with flowering time in the LMRZ mega-environment. In contrast, yield was positively associated with increased biomass, late-flowering but negatively with HI in the HRZ mega-environment. In both mega-environments, HI was negatively correlated with delay in flowering and increased plant height and biomass. Reducing plant height in late flowering hybrid varieties offers a solution to the trade-off between biomass and HI. It can have the potential to increase yield by increasing HI while maintaining biomass in the HRZ mega-environment.

Improvement in canola yield and growth indices and water-use efficiency with subsurface drainage in a humid climate

Improving the productivity of limited land and water resources is necessary to meet the increasing demand for food and feed. A 2-year (2016–18) field study was conducted in a humid climate in the north of Iran to examine the effect of different drainage systems on green water-use efficiency (GWUE), economic water productivity (EWP) and yield and growth indices of winter canola. The treatments consisted of surface drainage (Control) and three conventional subsurface drainage systems. Leaf area index (LAI) and total dry weight were measured randomly during different growth stages. The traits were then used to determine crop growth rate and relative growth rate. Subsurface drainage significantly improved yield and growth indices as well as GWUE and EWP compared with Control, with grater effectiveness under wet season. Yield, GWUE and EWP increase in subsurface drainage systems compared to surface drainage ranged from 460–890 and 825–1090 kg ha−1, 0.13–0.25 and 0.22–0.29 kg m−3 and 0.04–0.08 and 0.07–0.09 US $ m−3 in 2016–2017 and 2017–2018 growing seasons, respectively. Mean LAI in the subsurface drained area was 23–24% and 5–10% more than that in Control in the first and second growing seasons, respectively. The results indicated that an appropriate subsurface drainage system as well as a management strategy is necessary to prevent potential adverse effects of waterlogging in wet seasons and to increase land and water productivity in the study area.

Fertilizer systems deployment and zeolite application on nutrients status and nitrogen use efficiency

Nitrate leaching (NL) has become an issue in intensive agricultural systems with destructive results on the environment. The efficacy of zeolite incorporation with different organic and inorganic fertilizers was investigated in order to improve crop yield, nutrient uptake, and nitrogen use efficiency (NUE) in canola and wheat during 2014–2018. A field experiment was conducted using a randomized complete block design, with the split-plot layout. Two crop rotations of “canola-soybean-wheat” and “canola-wheat” were applied in the main-plots and nine fertilizing management systems (F1: urea, F2: urea + zeolite, F3: composted manure, F4: composted manure + zeolite, F5: urea + composted manure, F6: urea + composted manure + zeolite, F7: urea + azocompost, F8: urea + azocompost + zeolite and F9: Control) provided the sub-plots. The highest yields in canola and wheat were observed with the application of F6 and F8 treatments. The highest nitrogen (N) uptake was found in the second year through F6 and F8 application (115.1 and 120.4; 115.1 and 114.4 kg ha−1), while the lowest was found in the F9 (30.3 and 28.0 kg ha−1) in canola and wheat, respectively. The highest and the lowest rates of NL were obtained in the F1 and F9 treatments, respectively. Zeolite incorporation into integrated fertilizer management systems fulfilled the experimental goals in preserving more nutrients in the rhizosphere.

Different Post-Sowing Nitrogen Management Approaches Required to Improve Nitrogen and Water Use Efficiency of Canola and Mustard.

Strategic use of nitrogen (N) may improve N use efficiency, but there is limited information on the influence of N supply at crucial growth stages on N accumulation, water use, and water use efficiency of canola and mustard. In this study, we hypothesize that genetic variation among canola and mustard can alter the response of timing and rate of post-sowing N application at targeted phenological growth stages by improving N and water use and their efficiencies. Field experiments were conducted in South Australia during two growing seasons with contrasting water availabilities. Two mustard and four canola cultivars, including two triazine tolerant (TT) and two non-TT cultivars were evaluated under different post-sowing N application strategies comprising three N rates and different timings of application. Mustard used more water than canola in the season with higher rainfall, but canola and mustard used similar amounts of water in the drier season. Nitrogen increased the water use efficiency (WUE) of canola and mustard cultivars. Nitrogen rate and timing did not influence the total water use of canola and mustard but influenced the partitioning of pre- and post-flowering water use. Even though, highest N uptake was observed in the treatment with continuous supply of N with 200 kg N ha−1 in five splits it did not influence the N efficiencies parameters which indicate that yield of canola and mustard are limited by N rate in these environments. In treatment with limited N supply, targeting N at the rosette stage improve N use efficiency of canola and mustard. However, the limited N uptake potential of mustard makes timing of N application the most important consideration whereas correct N rate should be main consideration for canola.

Effects of crop straw biochars on aluminum species in soil solution as related with the growth and yield of canola (Brassica napus L.) in an acidic Ultisol under field condition.

The toxicity of aluminum (Al) to plants in acidic soils depends on the Al species in soil solution. The effects of crop straw biochars on Al species in the soil solution, and canola growth and yield were investigated in this study. In a long-term field experiment, there were four treatments, which were a control, rice straw biochar (RSB), canola straw biochar (CSB), and peanut straw biochar (PSB). The soil solution was collected in situ, the Al species were identified, and the relationships between the concentration of phytotoxic Al and canola growth and yield were evaluated. The results showed that applying the three biochars resulted in significant decreases in the concentrations of total Al, monomeric Al, and monomeric inorganic Al (P < 0.05). The Al3+, Al-OH, and Al-SO4 proportions of the total Al also decreased. The abilities of the different biochars to reduce dissolved Al followed the order PSB > CSB > RSB, which was consistent with the alkalinity of these biochars. Application of the biochars significantly decreased the concentration of phytotoxic Al (Al3+ + Al-OH), which improved canola growth and increased the canola seed and straw yields. Plant height, leaf number per plant, area per leaf, chlorophyll content, and canola yield were negatively correlated with the Al3+ + Al-OH concentrations. Therefore, the results showed that crop straw biochars can be used to ameliorate soil acidity and alleviate Al toxicity in acidic soils, and that peanut straw biochar is the best amendment for acidic soils.

Integration of poultry litter and mineral nitrogen on growth and yield of winter canola

AbstractCanola (Brassica napins L.) has the potential to be used as a winter crop in the southeastern United States, but little is known about its nitrogen management when grown in this region. Increasing fertilizer costs have increased interest in using poultry litter (PL) as an alternative nutrient source for crops in this region. However, evaluation of the use of PL on canola growth and yield is lacking. Thus, a field study was conducted at Shorter, AL (loamy sand soil) and Prattville, AL (fine sandy loam soil) using a randomized complete block design with four replications. Fertility treatments consisted of an unfertilized control (P0U0), commercial fertilizer N (urea, 180 kg N ha−1, P0U180), PL at 68 kg N ha‐1 with 112 kg N ha−1 urea (P68U112), PL at 112 kg N ha−1 with 68 kg N ha−1 urea (P112U68), and PL at 180 kg N ha−1 (P180U0). Overall, the combination of PL and urea application significantly increased canola growth (plant height and aboveground biomass) and elevated grain yield compared with PL application alone or with the control. The P68U112 treatment resulted in an equivalent aboveground biomass, grain yield, and N uptake compared with the recommended urea treatment. This study suggests that a combination of PL and commercial fertilizer N could provide sustainable canola yield production in the southeastern United States.

Effect of nitrogen scheduling on nitrogen uptake pattern and seed protein yield, oil yield and oil quality of canola oilseed rape (Brassica napus) sown on different dates

A field experiment was conducted at the Punjab Agricultural University Ludhiana during rabi 2016-17 to study the effect of nitrogen (N) application dose and time on N uptake pattern, protein and oil yield and oil quality ofcanola oilseed rape (Brassica napus) under different sowing dates. The treatments comprised three sowing dates (15 October, 30 October and 15 November) in the main plots and seven combinations of dose (100 and 125 kg/ha) and time of application of N (two or three splits) in sub plots. Loamy sand soil of experimental field was low in organic carbon and available N in the upper 15 cm soil profile. The test variety GSC 7 was sown at spacing of 45 cm x 10-12 cm. Delay in sowing significantly reduced the N content and uptake by canola oilseed rape at all growth stages in different plant parts as well as in seed and stover at maturity except N content in stem at 80 DAS. The highest oil yield (941 kg/ha) obtained with 125 kg/ha of N applied as 50 kg at sowing + 50 kg at initiation of stem elongation + 25 kg at initiation of flowering was at par with application of 125 and 100 kg/ha of N in two equal splits at sowing and initiation ofstemelongation. The highest protein yield (738 kg/ha) obtained with 125 kg/ha of N applied in three splits (50 + 50 + 25) was significantly higher than all other treatments. The highest oil yield produced by 15 October sown crop with application of 125 kg/ha of N in three splits (1056 kg/ha) was 7.3% and 40.4%% higher than application of 100 kg/ha of N in two equal splits and 6.7% and 35.9% higher than 125 kg/ha of N in three splits in 30 October and 15 November sown crop, respectively. Fatty acid composition of oil was not influenced by sowing dates and N scheduling.

Grazing and Cutting under Different Nitrogen Rates, Application Methods and Planting Density Strongly Influence Qualitative Traits and Yield of Canola Crop

Canola crop has the potential for both seeds and grazing. Optimal planting density, time of nitrogen (N) fertilizer application and rates are the major aspects for successful qualitative traits and canola yield formation. In this content, optimization of planting density, N levels and its time of application in dual purpose canola are needed. This study was carried out in RCB design with split pot arrangement having three repeats during winter 2012–2013 and 2013–2014. The study evaluated N levels (120 and 80 kg N ha−1), cutting treatment, N application timings and planting density (20 and 40 plants m−2) effects on qualitative traits and yield of canola. No-cut treatment had 7.02%, 2.46%, and 4.26% higher, glucosinolates, oil, and protein content with 31.3% and 30.5% higher biological and grain yield respectively, compared with grazed canola. Compared with no-cut canola, grazed canola resulted in 7.74% of higher erucic acid. Further, application of N at 120 kg N ha−1 had 8.81%, 5.52%, and 6.06% higher glucosinolates, percent protein, and seed yield, respectively than 80 kg N ha−1. In-addition, the application of N into two splits was most beneficial than the rest application timings. Cutting had 15% reduction in grain yield of canola and fetched additional income of 143.6 USD compared with no-cut. Grazing resulted in a 23% reduction in grain yield while had additional income of 117.7 USD from fodder yield. Conclusively, the application of N in two splits at 120 kg N ha−1 combined with 20 plants m−2 is a promising strategy to achieve good qualitative attributes and canola yield under dual purpose system.

Improving crop yield forecasts with satellite-based soil moisture estimates: An example for township level canola yield forecasts over the Canadian Prairies

Satellite-derived vegetation indices are widely utilized in yield forecasting models; however, they can be heavily impacted by atmospheric conditions due to their reliance on visible and near-infrared portions of the electromagnetic spectrum. Given the importance of soil moisture (SM) for crop development, the objective of this study was to investigate the use of passive microwave-derived estimates of surface SM obtained by the SM Ocean Salinity Mission (SMOS) satellite for forecasting canola yields across the Canadian Prairies within Agriculture and Agri-Food Canada’s (AAFC) Canadian Crop Yield Forecaster (CCYF) model. Weekly SMOS SM observations were combined with climate variables and normalized difference vegetation index (NDVI) data derived from the Advanced Very High Resolution Radiometer (AVHRR) platform and used as an input for forecasting canola yields at the township-scale across the Canadian Prairies from 2010 to 2016. Top predictors were identified, and regression models were built using a robust least angle regression (RLARS) and leave-one-out cross-validation (LOOCV) scheme. SM was found to provide a better descriptor of canola stress than the more widely utilized NDVI, being selected as a predictor in 74.2 % of developed ecodistrict models over the 7-year period, compared to just 41.2 % for NDVI. The difference between model R2 values (i.e. R2diff) when SMOS SM predictors were included and excluded from the forecast, respectively, revealed varying degrees of model improvements; however, the majority of ecodistricts under study (53.3 %) showed improved model fit (i.e. R2diff > 0) with observed canola yields when SMOS SM indices were included as potential predictors within the CCYF. Overall, greater improvements in the CCYF performance were observed in Manitoba and Saskatchewan where meteorological stations are more sparsely distributed. However, performance for both sets of model inputs was relatively low with R2 values ranging from 0 to 0.74 (mean = 0.13) and from 0 to 0.52 (mean = 0.12) across the study area both when SM was included and excluded from the model, respectively. These findings suggest that while SMOS SM observations may provide a more effective indicator of canola yields, the CCYF’s performance at the township-scale, where interannual yield variability is often quite high, is limited by the short temporal satellite record.

The effects of different methods of zinc application on canola seed yield and oil content

Zinc (Zn) as a microelement plays a salient role in the vital processes of plants such as metabolism and nutrition. This experimental study was conducted in the research field of Agriculture Faculty, Zanjan University using two genotypes of canola as main factor (Okapi and Tassilo) and zinc fertilizer application method in 7 levels including control, foliar spraying (2, 3.5, and 5 g/L) at the beginning of flowering and soil application (25, 50, and 75 kg/ha) were considered as sub-plot factor. The results showed that the application of zinc significantly increased the chlorophyll content as compared to control treatment. The highest chlorophyll content was observed in foliar spraying of 3.5 and 5 g/L zinc in Okapi cultivar. While, the highest value of RWC content resulted only with spraying 5 g/L of zinc. The result showed that zinc foliar of 5 g/L obtained the highest oil and seed yields and seed yield components. In addition, the highest qualitative seed traits (oil and protein content and zinc content in seed and plant) resulted with spraying 5 g/L of zinc. Also, Okapi cultivar had more quantitative and qualitative yields than Tassilo cultivar. The foliar spray of 5 g/L Zn can be recommended to increase the quantity and quality seed yield of canola.

Improving yield, oil content and water productivity of dryland canola by supplementary irrigation and selenium spraying

Determining the timing of supplementary irrigation in water limited conditions is one approach to reducing drought damage, increasing water productivity, and improving the yield of dryland canola. Selenium spraying may be an appropriate strategy for increasing crop tolerance to drought stress. The aim of this research was to evaluate supplementary irrigation and selenium spraying on the yield and water productivity of two canola cultivars under subtropical dryland conditions. The experiment was a split factorial in a randomized complete block design with three replications conducted during 2016–2018 at Gachsaran Agricultural Research Station, Iran. The main factors consisted of irrigation regimes (no irrigation (I1), supplementary irrigation at flowering stage (I2), grain filling (I3) and flowering + grain filling (I4)), and a sub-factor comprising Hyola 401 (water stress tolerant) and Delgan (less tolerant to water stress) cultivars and selenium spaying from the source of sodium selenate (Na2SeO4) (zero (S0), 1.5 (S1) and 3 (S2) mg L−1). Results showed that the application of supplementary irrigation increased the yield, yield components, oil percentage, harvest index and water productivity. Selenium spraying increased the weight of 1000 seeds and grain yield. Grain yield was increased from 802 kg ha−1 in S0 and I1 treatment up to 2274 kg ha−1 in S2 and I4. The Delgan and Hyola harvest index rose from 19.94 % and 22.1 % in I1 to 29.13 % and 26.99 % in I4, respectively. The highest oil percentage (37.6 %) was observed in the I4 regime, the highest water productivity (0.67 kg m-3) was obtained from I4 and S2 treatments, and the lowest water productivity (0.34 kg m-3) was seen in I1 and S0 treatments. Generally, the results showed that high yielding canola production can be achieved through supplementary irrigation in two stages (flowering and grain filling stages) and by applying 1.5 mg L−1 selenium foliar application in subtropical dryland conditions.

Alleviation of Salinity-Induced Oxidative Stress, Improvement in Growth, Physiology and Mineral Nutrition of Canola (Brassica napus L.) through Calcium-Fortified Composted Animal Manure

Salinity stress is one of the serious restrictive issues for optimum crop production in arid to semi-arid areas. Application of organic amendments have shown positive effects on crop growth and yield under such scenario. The present study was conducted to estimate the potential of calcium-fortified composted animal manure (Ca-FCM) to enhance growth and yield of canola under saline soil conditions. Salt affected soils with various electrical conductivity (EC) levels (original 1.5, 5, and 10 dS m−1) were developed via spiking the soil with sodium chloride (NaCl) salt. The results reveal that soil salinity reduced the growth, physiological, yield, and nutritional parameters of canola. However, application of 3% calcium-fortified composted manure significantly enhanced the growth and yield parameters at all EC levels as compared to control. Plant physiological parameters such as photosynthetic rate, relative chlorophyll contents (SPAD value), and relative water content were also increased with the application of 3% Ca-FCM at all EC levels in comparison to control. Application of 3% Ca-FCM also mediated the antioxidant enzymes activities at all EC levels in comparison to control. Moreover, application of 3% Ca-FCM caused maximum increase in nitrogen, phosphorus, and potassium concentrations in shoot at all EC levels. Conversely, application of 3% Ca-FCM showed maximum decrease in Na+/K+ ratio in leaf up to 83.33%, 77.78%, and 71.43% at EC levels 1.5, 5, and 10 dS m−1, respectively, as compared to control. It was concluded that application of calcium-fortified composted animal manure (Ca-FCM) could be an efficient method for improving growth, yield, physiological, and nutritional parameters of canola through mediation of antioxidant defense machinery under saline soil conditions.

Influence of soil temperature and moisture on micronutrient supply, plant uptake, and biomass yield of wheat, pea, and canola

Crop yield response to micronutrient fertilization is difficult to predict, particularly under unfavorable environmental conditions as these may alter both crop nutrient demand and the soil micronutrient supply to plant roots. The research objective was to evaluate the effect of various soil temperature and moisture conditions on crop growth response to added micronutrient copper (Cu), zinc (Zn), and boron (B) along with soil micronutrient supply and distribution among fractions. Brown and Dark Brown farm soils collected from southern Saskatchewan were used to grown wheat, pea and canola within controlled environment chambers. The biomass yields of all crops decreased under cold soil temperature and moisture stress (drought and saturated) conditions. Greater plant uptake of Cu, Zn, and B was associated with optimum (i.e., field capacity) soil moisture and warm temperature (23°C) growing conditions, compared to drought (i.e., 50% field capacity), saturated, and cold (5°C) temperature conditions. Environmental stress had the greatest impact on pea growth, reducing crop yield and micronutrient utilization efficiency more than 95%. Soil supplies of Cu and Zn were most negatively impacted by drought stress due to reduced mobility of these diffusion limited nutrients. The extractable micronutrients levels and chemical speciation fractions of Cu, Zn, and B indicating that bioavailability and micronutrient transformation were not affected during our short-term (i.e., six-weeks) study. However, it is suggested that assessments of micronutrient forms also be conducted on soil samples under actual moisture and temperature conditions as they exist in the experiment, as well as on dried, processed samples.

Sulphur doses and application times on yield and oil quality of canola grown in calcareous soil

Pakistan has been constantly deficient in its oil seed production and it is very difficult to meet the edible oil requirement of its ever-increasing population. A field experiment was conducted at the Agronomy Research Farm, The University of Agriculture Peshawar, Northern Pakistan during winter (2013–14). Five sulphur levels (15, 30, 45, 60 and 75 kg·ha-1) and times of application (at seedling, bolting and flowering stages) were used for the canola variety Abasin-95. The experiment was laid out in a randomized complete block design replicated four times on a 5 m × 3.2 m plot size. The results showed that the sulphur-applied plots gave the highest seed yield, biological yield, glucosinolate, erucic acid, oil content, protein content, oleic acid and linoleic acid compared to the control plots. Sulphur applied at the rate of 60 kg·ha-1 and applied at the bolting stage increased seed yield, biological yield, oil content, and protein content.

Soil-test critical values for wheat (Triticum aestivum) and canola (Brassica napus) in the high-rainfall cropping zone of southern Australia

Nutrient deficiencies are considered a reason for commercial yields of wheat (Triticum aestivum L.) and canola (Brassica napus L.) in the high-rainfall zone (HRZ) of southern Australia being well below predicted potential yields. With the aim of developing soil-test interpretation guidelines suitable for HRZ conditions, nutrient-response experiments, 15 with wheat and 12 with canola, were conducted between 2015 and 2018. These experiments quantified responses to nitrogen (N), phosphorus (P), potassium (K), sulfur (S), copper (Cu) and zinc (Zn) in pre-sowing soil tests. The highest yielding treatment of the wheat experiments averaged 7.1 t/ha (range 2.6–10.8 t/ha), and of the canola experiments 4.2 t/ha (range 0.7–6.2 t/ha). The most frequent responses were to N and P, followed by S and K. There were no significant positive responses to Cu or Zn. Across the experiments, the 95% critical value for Colwell P in wheat was 52 mg/kg, with a 95% confidence range of 39–68 mg/kg. For canola, the critical value was 59 mg/kg, with a range of 38–139 mg/kg. These values are higher than from lower rainfall regions of Australia. Critical values for K and S were also higher than from drier regions of Australia. The Sprengel–Lieberg Law of the Minimum overestimated yield where there were multiple nutrient limitations, whereas an equivalent Law of the Product underestimated yield under these conditions. These higher critical values based on evidence from the HRZ are expected to assist in closing the yield gap for wheat and canola in the region.

QTL mapping reveals genomic regions for yield based on an incremental tolerance index to drought stress and related agronomic traits in canola

Drought stress, especially at the reproductive stage, is a major limiting factor that compromises the productivity and profitability of canola in many regions of the world. Improved genetics for drought tolerance would enable the identification and development of resilient cultivars, resulting in increased canola production. The main objective of the present study was to dissect the genetic basis of seed yield of canola under water-limited conditions. A doubled haploid population derived from a cross between two Australian parental lines, RP04 and Ag-Outback, was evaluated to identify the genetic variation in fractional normalised deviation vegetative index (NDVI), aboveground shoot biomass accumulation, flowering time and plasticity in seed yield under irrigated and rainfed field conditions in two consecutive years. An irrigation treatment was applied at the 50% flowering stage and an incremental drought tolerance index (DTI) was estimated for seed yield. By utilising a genetic linkage map based on 18851 genome-wide DArTseq markers, we identified 25 genomic regions significantly associated with different traits (logarithm of odds (LOD) ≥ 3), accounting for 5.5–22.3% of the genotypic variance. Three significant genomic regions on chromosomes A06, A10 and C04 were associated with DTI for seed yield. Some of the quantitative trait loci (QTL) were localised in the close proximity of candidate genes involved in traits contributing to drought escape and drought avoidance mechanisms, including FLOWERING LOCUS T (FT) and FLOWERING LOCUS C (FLC). Trait-marker associations identified herein can be validated across diverse environments, and the sequence-based markers may be used in a marker assisted selection breeding strategy to enhance drought tolerance in canola breeding germplasm.

High nitrogen rates do not increase canola yield and may affect soil bacterial functioning

AbstractNitrogen fertilization has a fundamental role in agricultural productivity. However, injudicious N applications to crops are common. It is important to ensure the minimum N required for satisfactory crop growth is applied but that excess amounts are avoided due to potential impacts on agroecosystem functioning. Nitrogen at 0, 60, and 150 kg ha–1 was applied as limestone ammonium nitrate to plots arranged in a randomized complete block design, on three farms to determine the impact of rate and temporal distribution of fertilizer on canola (Brassica napus L.) production in South Africa, and the effect of N fertilizer application on the composition and diversity of soil bacterial communities. The amount and distribution of N had only minor effects on canola growth (P &lt; .05) and no effects on yield or harvest index. Splitting fertilizer into two or three applications throughout the season resulted in more mineral N available in the soil later in the season. Increasing the N rate from 60 to 150 kg ha–1 had a significant impact on bacterial community composition. The lower rate favored bacteria that are more able to break down N‐containing C sources. No effects of fertilizer amount or distribution were observed on either N fixation potential (number of nifH gene copies) or bacterial community diversity. Overall, a low rate of N fertilizer split into multiple applications is recommended for canola production, as higher rates do not increase yield and may have a detrimental impact on soil C and N cycling.

Yield, dry matter and N characteristics in canola as affected by fertilizer N rate and split-application ratio under high soil fertility condition

The effects on seed yield, dry matter and nitrogen (N) characteristics under two fertilizer N rates of 240 and 270 kg ha−1 and three N split-application ratios (SAR) of basal: bolting fertilizer 7:3, 6:4 and 5:5 were investigated. Under 240 kg N ha−1 condition, seed yield was positively correlated with the number of effective pods (r = 0.90**), which was the main determinant of seed yield. Under 270 kg N ha−1 condition, seed yield was closely related to 1000-seed weight (r = 0.97**) and the number of seeds per pod (r = 0.90**), with the former appeared to be the most important determinant. The yields and numbers of effective pods in the N SAR 6:4 with N rate of 240 kg ha−1 were the highest among three SARs, while the yields of N SAR 5:5 under 270 kg N ha−1 were the lowest, attributable to the high lodging angle, low 1000-seed weight and low number of seeds per pod. Under 240 kg N ha−1 condition, the biomass, root dry weight, ratio of root to shoot, harvest index (HI), total N accumulation, N harvest index (NHI)and N utilization efficiency for grain yield (NUEg)in the N SAR 6:4 were the greatest among different SARs. The study revealed that, to achieve stable and high yields of winter canola, N recommendation at a rate of 240 kg ha−1 and N SAR 6:4 was suggested in this high soil fertility region.