Canola Phosphorus Placement Trial

The aim of this trial is to assess the impact of starter fertiliser placement on canola establishment and final yield, in a knife point press wheel and disc sowing system.

Southern & Central NSW Nutrien Ag Solutions Partnering with Farmlink

Background

Successful canola establishment plays a significant role in final canola production. In a central west survey conducted in 2017 (McMaster et al), canola establishment ranged from 17-86%, with the average establishment being 48%. Growers are moving towards hybrid canola seed for the increase in yield potential and early vigour, however, there is a significant risk and cost associated with reduced canola establishment. There are a number of factors that impact on canola establishment, including nutrient availability and uptake, starter fertiliser placement and concentration, stubble cover, sowing depth and speed, and conditions over the sowing/germination period.

Phosphorus is an important nutrient for canola growth and development, with the greatest demand for phosphorus in the early development stages. Limited P availability during this phase can impact root development and maturity, affecting yield and oil production. 

Current sowing practice is to apply starter phosphorus fertiliser, which is generally MAP, to canola in a knife point press wheel system (KPPW), or, more recently in a disc sowing system. These systems concentrate the fertiliser near the seed increasing the risk of damage to the developing seedling. Due to canola’s small seed size, it is particularly sensitive to fertiliser damage.

Dry sowing and cool germination condition, which often occur in southern NSW, can increase the time the developing seedling is in contact with the starter fertiliser, increasing the risk of damage. Trials carried out by Street & O’Brien (2020) indicate that P fertiliser placed away from the seed, reduced the impact on canola plant establishment, including IBS and top-dressed applications, as well as, below the seed to a lesser extent.

The aim of this trial was to assess whether there is a similar impact on canola plant establishment and yield from starter phosphorus fertiliser applied at sowing in Southern NSW in KPPW and disc systems.

Trial Overview and Results

Sowing Date:         30th April 2021

Variety:                    SF Dynatron Hybrid canola

Sowing rate:           2.1kg/ha – 33 plant per m2   (target 80% germ , 75% establishment)

Crop History:         Barley 2020 – long term crop paddock.

Cowell P:                 85 mg/kg

Soil pH:                     6.7 CaCl2

Soil type:                 Silty loam

Rainfall:                    2021 Jan-Dec - 763mm (GSR – 322mm)

Location:                 TAIC

The trial was sown directly into barley stubble from 2020. With no April rainfall and a drying sowing bed, the crop was sown on April 30th in front of early May rain on the 4th. The crop germinated in mid-May, with the 60 days following sowing receiving 133mm of rain. Rainfall through the season from May onwards was above average, with a total annual rainfall of 763mm; 240 mm above the annual average, as shown in the rainfall chart below (Figure 1). Nitrogen was applied throughout the season so the crop was not limited by nitrogen, targeting >2.5 t/ha crop.

The trial treatments were sown with a tyned knife point/press wheel (kppw) system and also a disc system. The trial is a replicated plot design. The kppw and disc sowing rigs both placed the seed and fertiliser down the tube together. Fertiliser treatments were either sown with the seed or applied on the surface, or a combination of both to identify impacts on establishment.

Fertiliser treatments include the Mono Ammonium Phosphate (MAP) and also Single Super Phosphate, as well as Basis XC®fertiliser biocatalyst and Structure® liquid fertiliser.

Basis XC® (Loveland) is a fertiliser biocatalyst that is applied to the fertiliser granule to accelerate fertiliser breakdown. It has shown improvements in fertiliser utilisation by making nutrients more available for uptake, benefiting early vigour and plant development.

Structure® (Loveland) is a highly efficient liquid phosphorus product containing 9.1% Nitrogen, 11.9% Phosphorus and 0.26% Zinc and 7.8% Reacted Carbon technology. The phosphorus in Structure® is highly resistant to soil tie up and is more mobile and available to the plants for uptake.

The plant establishment across all treatments was equal to or greater than the target plant population of 33 pl/m2 (75%), as shown in graph 1. This is largely due to the favourable start to the season and on-going rainfall. There was a considerable improvement in plant establishment of the Low MAP (50kg) at sowing compared to the MAP (100kg) at sowing particularly in the KPPW system indicating the higher fertiliser rate with the canola seed at sowing may have impacted on germination and growth. 

Although the number of plants per m2 in the disc system were in general greater than in the KPPW sowing system, this was not reflected in yield (Graph 2 &3). The disc sown plants were smaller and less vigorous early compared to the canola in the KPPW sown plots, which is often seen in paddock situations with disc sowing systems. 

The yield results for the KPPW show little significant difference between many of the treatments, which is more than likely a consequence of the above average seasonal moisture and high soil P levels at the site, which encouraged more plant and root growth. Overall, the KPPW system was higher yielding than the disc system due to increased soil disturbance around the seed and more vigorous growth early.

The highest yielding results in the KPPW system were the treatments with low MAP or surface MAP at sowing, although, these treatments were not significantly different to the untreated and other treatments in the trial.  

Graph 3: Disc System Plant Establishment and Yield 

In the disc system, the highest yielding treatments were also those with low MAP or surface MAP at sowing, however, these were not significantly different to the untreated. MAP (100kg) at sowing with the seed in the disc system, was the lowest yielding treatment across the whole trial. Although plant establishment was greater than 75%, this did not follow into yield. This likely to be due to the slow root growth in the disc system and the impact of the high fertiliser rate with the seed slowing growth.

There was no significant difference between the Basis XC fertiliser treatments compared to the Low MAP (50kg) at sowing by itself in the KPPW and disc system, however, it would be beneficial to explore this further in a lower soil P environment and more ‘average’ conditions. The high application of Structure performed well in both KPPW and disc systems 

Conclusion

The mild conditions and higher than average rainfall in 2021 resulted in above average yields, with very little significant difference in yield and plant establishment between treatments across the trial.  The good soil moisture conditions aided in plant germination and growth, resulting in high establishment counts. In this trial, higher plant establishment did not automatically correspond to higher yield comparing the KPPW and disc system. The trial has highlighted that as long as there are optimum plants/m2, the growth and vigour of the plants post germination is a key factor in yield.

There was a trend across the treatments highlights the potential improvement in yield from lower starter fertiliser applications with the sowing seed and surface applied fertiliser. 

In a lower rainfall year and reduced soil P environment, variances in establishment and yield would be expected to be greater, particularly with drying soil and cooler conditions. Further trial work to identify these differences in varying environmental and soil conditions would be worthwhile to advance our understanding of the impact of starter fertiliser placement on establishment and utilization in canola in Southern NSW.

References:

McMaster. C, Stevenson. A, Menz. I, Canola Establishment across central NSW, GRDC, 2019.

Maurie Street and Ben O’Brien, Optimising canola establishment and performance by phosphorus fertiliser placement,

 (Grain Orana Alliance), 2020.

GRDC Grownotes, Canola Section 5, Nutrition and Fertiliser, Northern, 2018.

Jim Laycock, Agronomic Insights, Managing Fertiliser application with the seed, Incitec Pivot Fertilisers, May2020.