Oilseed rape is not exempt from nutritional stresses during establishment and with a delicate and easily limited root structure, the consequences can be more important. Maximising growth at this early stage is critical. Ensuring optimal P supply leads to increased yield, oil content and higher stored phosphorus, enhancing seed quality.
Reviewing the nutrient uptake curves for oilseed rape, there are two peaks – one during establishment and then another as the crop moves into reproductive growth in the spring.
World Fertiliser Manual
Honing in on the establishment phase in more detail, a large amount of phosphorus is required relative to the size of the plant and slightly exceeding the requirement for N and K, although all the macro elements are elevated.
So what are we trying to obtain with OSR establishment? Root length is often fixed by Christmas, so early development is critical as it is a lazy rooting crop. Good biomass development is therefore important to access more nutrition from the soil.
Ideally the OSR crop should be at the 6-8 leaf stage pre-Christmas, with the aim of GAI 3.5 by flowering.
The OSR crop takes up to 3 Kg/ha/day in the spring so we need a good foundation set to be able to deliver this, as well as being able to stimulate it as key timings e.g. TWOXO (at onset of stem extension) and also if limitations are imposed by the weather we can make nutritional applications to overcome them e.g. WHOLLY K.
The challenge with oilseed rape is to get it up and away as fast as possible, with the most likely environmental factor being moisture and soil conditions rather than temperature.
Once imbibition starts the conversion of phytic acid (primary P storage) to release active phosphorus by the enzyme phytase is very quick and shows why a bioavailable form has to be ready to support to continued growth as soon as the seed runs out after approximately 7-8 days.
Assessing phosphorus limitations with respect to oilseed rape gives a guide to deciding upon treatment:
- Limited by low organic matter
- Limited by low soil oxygen levels
- Limited by water logging and compaction, which can severely impact on root growth of oilseed rape.
- Fixation – predominantly to Calcium, Iron or Aluminium
- Dependent upon soil biology to supply P to the crop
- High or Low pH affect availability
With respect to root dynamics, oilseed rape is not as prevalent in the topsoil as other crops. Roots occupy around 0.5 % of the top soil whereas certain grassweeds can occupy 2-2.5%, highlighting why they are so competitive.
Roots, in general, can only access P from within 1mm of the root hair, unlike N which can be obtained from 3-5 mm away. So it is critical to get biomass as soon as possible. P can only move approx. 25mm per year through the soil profile in contrast to N, which is highly mobile and can move the same distance in a week.
Temperature is unlikely to be a driver for P availability in OSR. On average in August there is approximately 50% of soil P available for uptake by plants. The optimum soil pH is between 5 and 6.5, either side of that range fixation to either calcium, aluminium etc reduces availability from 60% to 20%.
There are many factors that can limit the availability of P to the crop during the establishment phase. This gets more complicated as it is a biologically-mediated nutrient, so protecting soil biology is critical. High levels of macro fertilisers have a negative impact on soil biology, particularly nitrogen and phosphate. Fertiliser applications can overcome the negative impact by making P more available for a time, but it will take time for the biology to recover and play a role in providing nutrition later on. Phosphite, on the other hand, does not impact negatively on soil biology.
The Unium biostimulant seed treatments – Tigga, Voltek and Boost have proven to set new standards by improving:
- Root length,
- Root biomass,
- Shoot biomass and
Photosynthetic Capacity – chlorophyll concentration, as shown at Nottingham University Trials in both OP and Hybrid varieties.
UBS002 and UBS002a are Unium Biostimulant Seed Treatments
These seed treatments have now been joined and are perfectly complimented by TIROS, the first global commercialisation of the endophytes discovered by Prof S Doty of the University of Washington.
The endophyte strains in TIROS have been specially selected over the past two decades for their specific nutritional efficiencies and confers the ability to plants to fix atmospheric nitrogen and to solubilise and sequester phosphorus (along with other nutrients).
These endophytes live within the plant for the life of the crop and, as such, are much less susceptible to environmental stress compared with the biology that inhabits the rhizosphere. This helps to mitigate any environmental stresses that limit these two nutrients, increasing their bioavailability throughout the season.
TIROS is co-applied with our biostimulant package (Tigga Bio, Boost Bio, Voltek Bio) and supports the colonisation of the endophytes to maximise their effect.
So not only do you get the normal benefits you would expect from a Unium biostimulants seed treatment:
- Improved germination
- Enhanced established
- Promotes strong early growth
- Uniform stand
Increased root length and biomass along with activity (exudation)
- Increased ability to withstand abiotic stress
- Improved overwintering survival
The addition of TIROS adds even more nutritional enrichment. This extends beyond nitrogen and phosphorus because a balance is maintained when used in combination with a biostimulant. This means you don’t get leggy growth like you’d expect from more available N. The nutritional stoichiometry is maintained – keeping everything in balance for optimal growth.
The data below shows the comparison of the biostimulant seed treatments alongside TIROS. As it is applied with a Unium biostimulant, you would expect seed performance to be at the same, but clearly it is quicker to germinate and produces more roots in the first 6 days to support establishment.
UBS002 and UBS002a are Unium Biostimulant Seed Treatments.
TIROS is an endophyte consortia applied in combination with a Unium biostimulant support package.
How does that translate into the field……
Unfortunately, all our trials over the last two years haven’t made yield due to CSFB and or Pollen Beetle, but the work at Nottingham University has translated to the farm/field experiences in terms of nutrient efficiency.
In North Lincolnshire the enhancement is very clear:
How did this translate for the final assessment in Spring:
This is the same for the trial site in Suffolk.
How did this translate post winter:
With oilseed rape establishment becoming ever more important, rapid emergence, root development and minimal restrictions to growth are crucial. TIROS offers the best opportunity to get the crop off to a flying start.
*All Trademarks are duly acknowledged.