Take home messages
- In two years, no yield benefit was found from zinc fertiliser or pulse seed coat when used on a pulse crop going into a situation with reasonable starting nitrogen levels.
- Growers are advised to make sure they test products under their own systems by utilising test strips for side-by-side comparison to avoid unnecessary costs.
- As highlighted in 2016, make sure you get the big things right in your farming system, then the small things come into play.
Background
In recent years there has been a resurgence in lentil production in the Mallee due to their relatively high value, the rotation benefits, an improvement in management practices, new varieties and more favourable growing conditions. This has also led to an increase in product offerings which claim a range of benefits including improved growth, nodulation, harvestability and ultimately yield. In some cases, the evidence to support these claims is limited.
In 2016, BCG researched some options that were available, including seed coatings and zinc foliar fertilisers. It was found that all products added an input cost with no difference in yield detected (Angel, K. 2016). Although there appeared to be a small trend that doing something was better than nothing.
For this reason, it was decided to look at this work for a second season with a focus on seed coatings and zinc fertiliser and application timing to determine if product or timing is the key, or whether something more complex is occurring. The effectiveness of these products was challenged by placing the trial on a site with high boron levels. Research conducted by Gunes, A. et. al. (1999) in tomatoes demonstrated that the detrimental effects on the development of tomato plants was partially alleviated through applications of zinc. Could this also happen with lentils, or are these practices just a cost to the system?
Aim
To determine if seed dressings or zinc applications can improve lentil growth and yields.
Paddock details
| Location: | Curyo |
| Crop year rainfall: | 297mm |
| GSR (Apr-Oct): | 215mm |
| Soil type: | Sandy clay loam |
| Paddock history: | 2016 cultivated fallow |
Trial details
| Crop type: | PBA Jumbo 2 lentil |
| Treatments: | Refer to table 1 |
| Target plant density: | 120 plants/m² |
| Seeding equipment: | Knife points, press wheels, 30cm row spacing |
| Sowing date: | 12 May 2017 |
| Replicates: | Four |
| Harvest date: | 9 November 2017 |
| Trial average yield: | 1.75 t/ha |
Trial inputs
| Fertiliser: | Refer to Table 1. | |
| Herbicide: | May 12 | Glyphosate @ 2L/ha + Trifluralin @ 1.5L/ha + Terbyne® @ 0.8kg/ha |
| June 22 | Brodal Options® @ 250mL/ha | |
| July 7 | Clethodim @ 300mL/ha + Haloxyfop @ 75mL/ha + Uptake @ 0.5% + Liase @ 2% | |
| November 2 | Glyphosate 2.5L/ha + Sharpen 34g/ha + Hasten @ 1% | |
| Insecticide: | August 30 | Alphacypermethrin @ 400mL/ha |
| October 16 | Alphacypermethrin @ 300 mL/ha + Trojan® @ 50 mL/ha | |
| Fungicide: | August 2 | Carbendazim @ 1100 mL/ha + Chlorothalonil @ 1200 mL/ha |
| September 22 | Carbendazim @ 1100mL/ha + Chlorothalonil @ 1200mL/ha | |
| Inoculant: | Group EF peat | |
Method
A replicated field trial was established at Curyo using a complete randomised block design (Table 1).
Assessments included establishment scores, visual observation of nodulation 12 weeks after establishment, fortnightly normalised difference vegetation index (NDVI) and biomass and harvest index at maturity. Grain collected was assessed for grain size by thousand grain weight. Plot harvest was undertaken to determine grain yield of the treatments.
Table 1. Treatments for lentil seed coat and zinc fertiliser trial.
Results and interpretation
Establishment and crop development
Assessment of establishment found a consistent number of plants (P=0.751) across all treatments near to the target of 120 plants/m2. Likewise, fortnightly NDVI assessments, using a drone, revealed no treatment differences. It was apparent that the treatments did not affect biomass production and post canopy closure greenness.
Nodulation assessments 12 weeks post sowing did not show any treatment affects. All assessed plants had comparable nodule colonies and nodule colour. Total nodulation was below desired levels of 50-100 nodules/plant (Ryder M., et. al. 2017). This may be a reflection on the high nitrogen (N) status of the site (138kg N/ha), limiting the need for nodulation in the plant. This is a common occurrence in pulses that can tend to get ‘lazy’ if adequate nitrogen is available, reducing nodulation effectiveness and total nitrogen fixed by the crop (Saskatchewan Pulse Growers).
Maturity and grain yield
Harvest results were consistent with earlier assessments revealing the same trends. The trials achieved an average yield of 1.75t/ha and no yield differences were observed between treatments (Figure 1.).
Harvest index (P=0.288) and 1000 grain weight (P=0.501) assessments produced no difference between treatments. Consistent with the results from 2016, no impact on yield and biomass were observed at this site. This result should not be a deterant from applying zinc fertiliser to pulses. It is a well-known fact that no-till systems and the increasing use of more highly refined fertilisers that have less contaminants present (ie. zinc in superphosphate), has seen a need to increase zinc fertiliser use. This result simply highlights that this site had adequate nutrition to negate any effect of additional zinc on lentil yield.
The use of pulse seed coat also provided no yield benefit for the second year in a row. Like 2016, residual soil N was high preventing any benefit from being realised. The impacts of these types of seed dressings in a lower fertility soil may warrant further investigation. However, in 2016 and 2017, both above average seasons their use could not be justified.
It should be noted that some of the treatments in this trial do not facilitate healthy rhizobia populations. Some products in close proximity with rhizobia can kill them, reducing their efficacy in fixing nitrogen. Zinc is one of these products and it is therefore not advised to apply zinc in high concentration close to the seed for this reason (Ryder M., et al.). The reason this treatment was included in the trial was to compare placement and timing of zinc on production. Given there was no benefit in this trial of the treatments, growers are advised to follow best practice guidelines of using a strategy where zinc is not directly applied to the seed and thus in direct contact with rhizobia. This will ensure there is no negative impact on successful nodulation and ultimately N benefits to the subsequent crop.
Commercial practice
Trials of this nature look to prove or dispel marketing myths and see if products can really live up to the performance expected from them, because at the end of the day, every dollar counts, regardless of how insignificant it may seem in the scheme of things.
From results in 2016 at Warmur, pulse seed coating or zinc foliar sprays offered no significant yield benefit. Given this result, the cost of the products and application could only be considered a burden. The same result was found in 2017 at Curyo. It should be noted that both trials were conducted on fallows with significant N. This work highlights the benefit is likely to be limited in fertile soil. However, in different circumstances or in soil types where background levels of the components found in these products may be lacking, the seed coating or zinc application may have had a different effect. Growers are advised to assess the requirements of their own paddock, either through soil testing prior to sowing or tissue testing in crop to ensure adequate zinc is available.
Nevertheless, if considering the use of such products for the first time, ensure there is some untreated crop in the paddock to determine and assess whether it works in the farming system or not.
On-farm profitability
Pulse seed coating or zinc fertilisers have not generated any benefit in two years of trials. However, in situations where nitrogen or zinc levels are low, a benefit may be realised and as such it is recommended to do so where a deficiency is detected or expressed.
Growers need to understand these limitations in their own system or paddock and make informed decisions to ensure that profitability is maintained, and that unnecessary costs are avoided. Small costs can add up when calculated over a whole program.
Zinc is an essential nutrient to crops grown in the Wimmera and Mallee. Growers should ensure that adequate zinc is applied at some parts of the rotation to ensure that there is sufficient nutrition to meet crop demand. Tissue testing, soil testing, seed testing or test strips in the paddock are all options to assess how deficient your crops might be. This can then be used two ways, to ensure returns are not limited due to yield reductions from deficiencies, and secondly to not apply products unnecessarily which incurs avoidable costs.
References
Saskatchewan Pulse Growers, Innoculation and Fertility, 2017Â
Acknowledgements
This trial was funded by BCG members through their membership.
