Plant characteristics suited to higher canola yields in the High Rainfall Zone of southern Australia

Transcription

1 Plant characteristics suited to higher canola yields in the High Rainfall Zone of southern Australia Penny Riffkin 1, Trent Potter 2, Angela Clough 3 1 DPI, Hamilton PB105, Hamilton, Vic 3300, Australia, penny.riffkin@dpi.vic.gov.au 2 SARDI, Naracoorte SA 5271, Australia, potter.trent@saugov.sa.gov.au 3 DPI, Ballarat, 402 Mair St, Ballarat Vic 3350, Australia, angela.clough@dpi.vic.gov.au ABSTRACT Field experiments were conducted at Hamilton in south west Victoria in 2005 and 2006 to identify plant characteristics associated with canola yield in the High Rainfall Zone (HRZ) of southern Australia. Seven cultivars with different reported maturities and growth habits were sown at either 2 sowing times or under different N application regimes. Dates of key phenological development were recorded and biomass of various plant parts determined at bud, anthesis and harvest. Growth, development and climate data were assessed in relation to yield and yield components. Both years had considerably lower rainfall than the long-term average especially during grain fill. Data showed a significant (P<0.001) positive relationship between pods/m 2 and grain yield and between biomass at anthesis and grain yield. Despite the shorter growing seasons, the longer season winter type, Caracas did not suffer yield penalties relative to the earlier maturing cultivars. The unexpected robustness of this different plant type indicates that there may be potential to significantly increase yields through the introduction of different germplasm to the HRZ. It is recommended that germplasm with a wider range of developmental patterns is assessed to identify the appropriate phenology and canopy structure to optimise pre-anthesis biomass and pods/m 2 so that yields, yield stability and quality can be increased in the HRZ. Key words: winter - spring phenology yield components INTRODUCTION Canola production in the HRZ has increased from 16,400 t in 1985 to more than 660,000 t in 2005 (Neil Clarke and Associates, pers. comm.) and accounts for more than 40% of the national production. This increase has come from a 36 fold increase in area sown with yields per hectare remaining relatively static over the 20 year period (average 1.47 t/ha). Based on modelling and knowledge of resource conversion, it is estimated that average canola yields in the HRZ should be closer to 3-4 t/ha. Experiments were conducted to identify plant characteristics better able to utilise resources in the HRZ to achieve yield potential. MATERIALS AND METHODS Experiments were conducted at DPI, Hamilton Victoria (37 o 49 S, 142 o 04 E) in 2005 and Cultivars were selected to provide a wide range of growth and developmental patterns and hence create different demands for resources (radiation, water, temperature, nitrogen). Cultivars tested were commercial spring types including conventional, hybrid and triazine tolerant (TT) types ( AV Sapphire, Hyola 61 and 75, ATR Grace, Rivette and AV Garnet) and a winter type (Caracas) introduced from France through the DPI Victoria Canola Breeding Program (Table 1). Different resource availability was provided through 2 times of sowing (April and May in 2006) and nitrogen fertiliser rates and timing (Hamilton 2005). Dates of bud appearance, flowering (50%) and maturity (40-60% colour change in seeds) were recorded. At these key developmental stages, biomass (leaf, stem and pods) and green leaf area were measured. Climate data from the experiments at Hamilton was recorded using the DPI Hamilton weather station. Long-term climate data analysis was performed using Silo Patch Point Datasets and risks calculated in collaboration with GRDC Visiting Fellow Professor Roger Sylvester-Bradley (ADAS, UK). Experimental designs were factorial designs with four or five replicates. Data was analysed through regression and ANOVA using GenStat 9.1 (GenStat Committee 2003).

2 RESULTS Rainfall in both years of the experiments was below the long-term average (LTA). Growing season rainfall (GSR) for 2005 was 70% of the LTA (390 mm compared to 545 mm for the LTA). The season of 2006 was the second driest on record with the GSR only 50% of the LTA. Reasonable rains in the first half of the season (356 mm Jan-Aug) did not appear to have a major impact on early biomass production. However low rainfall (44 mm or 37% of the LTA) and low minimum temperatures during grain fill reduced grain yields. Apart from differences between N fertiliser treatments and the nil control (Hamilton 2005), there was no significant effect of N fertiliser rate or timing on grain yield. At Hamilton in 2006 grain yields from the April sowing were significantly (P<0.001) higher than for the May sown crops (1.74 and 1.25 t/ha respectively) but there was no time of sowing (TOS) x cultivar interaction. This paper will therefore only focus on cultivar, crop development, yield and quality in relation to resource availability and climatic risks. Yield, yield components and quality Regression analysis showed a significant (P<0.001) positive relationship between pods/m 2 and yield and between anthesis biomass and yield in both 2005 and The mean number of pods/m 2 for cultivars ranged from 1270 for Rivette (2006) to 4480 for Hyola 61 (2005). Higher yields in 2005 were due to a combination of more pods/m 2 and/or more seeds per pod. Where pod numbers were low, some yield compensation occurred through an increase in seeds/pod and/or seed weight (eg Rivette and Caracas 2006) (Table 1). Pre-anthesis biomass ranged from 2880 kg/ha (Rivette) to 6500 kg/ha (Caracas 2005). Preanthesis biomass was higher for the winter type (mean of both years 6130 kg/ha) than the spring types (mean for all spring types 3550 kg/ha) and overall higher in 2005 than in Plant height ranged from 170 cm for Caracas (2005) to 130 cm for Rivette. Seed oil ranged from 40% for Hyola 61 and ATR Grace (2005) to 44% (Rivette 2006) (Table 1). Table 1. Yield, yield components, quality, plant height and anthesis dates and biomass of one winter and six spring canola types sown at Hamilton in 2005 and 2006 Yield (t/ha) Pods/m 2 Seeds/ pod Seed Weight (mg) Anthesis Biomass (kg/ha) Seed Oil (6%) c Days 50% flowering to Plant Height (cm) a Hamilton 2005 Caracas AV Sapphire ATR Grace Hyola Significance <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 <0.001 LSD b Hamilton 2006 April May Caracas Hyola Rivette AV Garnet Significance <0.001 <0.001 <0.001 <0.001 < LSD a Experiments show mean values for N treatments, b experiment shows mean values for time sowing treatments, c Sowing dates 27/4/2006, and 29/5/2005 & Crop phenology Different developmental patterns were achieved through different times of sowing but not between cultivars within the same sowing time (except Caracas). Flowering times of spring types often coincided with periods of higher frost risk and low radiation (Figure 1). Frost risk (<0 o C) at flowering ranged from 20% for late sown Caracas to 61% for early sown Rivette,

3 Hyola 75 and AV Garnet. Radiation levels at anthesis ranged from 9.1 MJ/m 2 (early sown Rivette, Hyola 75 and AV Garnet) to 16.5 MJ/m 2 (late sown Caracas). The risk of drought at windrowing increased rapidly in late November and ranged from 19% for early sown spring types to 63% for late sown Caracas (Figure 1). 100% Frost <2 C (%) Frost 0 C (%) 30 Probability frost/drought 80% 60% 40% 20% Early sown spring Late sown spring Early sown winter Late sown winter Drought (%) Radiation Radiation (MJ/m 2 /day) 0% Julian Day 0 Figure 1. Anthesis Julian days for early and late sown spring canola cultivars (broken vertical lines) and early and late sown winter type canola (solid vertical lines) with climate risks (frost and drought) and radiation based on long-term (50 years) climate data. Crops were sown at Hamilton in 2005 and Data is mean of spring sown cultivars (Rivette, Hyola 61 and 75, AV Sapphire, ATR Grace, and AV Garnet) and mean of winter type (Caracas) at early (April 27) and late (May 29) sowing times. DISCUSSION Crop growth and development need to be matched to environmental conditions to maximise yields, yield stability and grain quality. It is necessary for periods of crop demand to coincide with resource availability in order to create a structure capable of supporting the required number of seeds/m 2. The canopy must also maximise light interception for the production of assimilates to generate and sustain seed numbers and weight to maximise grain yield and quality. Optimum crop development and the timing of phase onset and duration in relation to environmental conditions are necessary to avoid climatic risks especially around flowering (e.g. frost and drought) and maximise assimilate production (Mendham et al 1981, Thurling 1991, Lunn et al 2001). It is difficult to determine the appropriate phenology for this environment based on the results from these experiments due to the lack of variation in developmental patterns in the commercial cultivars and the atypical seasonal conditions. However results from these experiments and the assessment of long-term climate data indicate that flowering dates of commercial cultivars often coincide with high frost risk and low radiation. The fact that the late maturing cultivar Caracas did not suffer yield penalties in relation to the earlier maturing cultivars despite the extremely dry conditions, suggests that flowering could be delayed in this environment without encountering severe moisture stress in more typical seasons. Robertson et al (2002) developed a simulation model which indicated that later flowering genotypes showed greater responses to vernalisation and photoperiod than early-flowering genotypes. Such models could provide a useful tool in assisting to identify germplasm with the optimum phenology for this environment with respect to risk avoidance.

4 Results showed a positive relationship between pod/m 2 and yield. However the range in numbers of pods/m 2 was insufficient to determine an optimum density for this environment. With the exception of Hyola 61, the number of pods/m 2 for all cultivars were below 4000/m 2, a level considered to be yield limiting in other HRZ regions (optimum /m 2, Lunn et al 2001). It is therefore likely that pod density will need to be increased to improve yields in this environment. Mendham et al (1981) showed a crop size of approximately 5 t/ha was required at full flowering to maximise grain yield with later sown crops. With the exception of Caracas, crop biomass at anthesis was below 5 t/ha and may need to be increased to maximise grain yield. A lengthening of the pre-anthesis phases through the early sowing of later maturing crop types is likely to increase anthesis biomass and possibly grain yield. However, in the UK, no yield advantage was reported from crops with excessively large canopies (>5 t/ha and LAI >1.75 at anthesis) due to shading of the lower pods and less assimilate available per pod for seed filling (Lunn et al 2001). The optimum biomass and canopy structure (e.g. pod length, leaf size, apetalous flowers, canopy depth) for maximum grain yield and quality for this environment requires further investigation. Despite maturity dates between the spring cultivars being very similar, differences in anthesis biomass, grain yield, pods/m 2 and seeds/pod did occur. This suggests that either differences in maturity may not have been expressed due to the abnormal seasonal conditions or there are other factors besides phenology that could be manipulated to improve yields. The unexpected robustness from the unadapted winter type Caracas suggests that there is potential to alter the current plant type to better fit the HRZ environment. The testing of germplasm with a wider range of developmental patterns in relation to yield and yield components is required to identify optimal phenology, canopy structure and resource use efficiency in the HRZ. ACKNOWLEDGEMENTS The authors thank GRDC, DPI and SARDI for providing financial support for the project. Wayne Burton and Dr Rob Norton are acknowledged for their input into experimental design and providing germplasm. Professor Roger Sylvester-Bradley is acknowledged for input into defining resource availability in the HRZ. REFERENCES GenStat Committee (2003) GenStat Release 7.1. (VSN International Ltd: Oxford) Lunn, G.D., J.H. Spink, D.T. Stokes, A. Wade, R.W. Clarke and R.K. Scott, 2001: Canopy management in winter oilseed rape. HGCA Project Report No. OS49. Mendham N. J., P.A. Shipway and R.K. Scott, 1981: The effects of delayed sowing and weather on growth, development and yield of winter oilseed rape (Brassica napus). Journal of Agricultural Science (Cambridge) 96, Thurling, N., 1991: Application of the ideotype concept in breeding for higher yield in oilseed brassicas. Field Crops Research 26, Robertson, M.J., A.R. Watkinson, J.A. Kirkegaard, J.F. Holland, T.D. Potter, W. Burton, G.H. Walton, D.J. Moot, N. Wratten, I. Farre, and S. Asseng, 2002: Environmental and genotypic control of time to flowering in canola and Indian mustard. Australian Journal of Agricultural Research 53,

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