Inoculant trials in chickpeas and other pulses

Rohan Brill^¹, Myles Parker^² & Matthew Denton³

Take home message

Nitrogen fixation of pulses is a critical factor in farm profitability for most producers in the region. In the past, inoculation has usually been done by applying root nodule bacteria in peat slurry to the seed and sowing on the same day. Recent developments include granular inoculant formulations and the injection of slurry into the furrow with the seed.

 

Trials were conducted on chickpeas and albus lupins in 2008 to compare new and traditional inoculants. There was no significant difference for nodulation of the lupins, due to background rhizobia. There were significant differences in nodulation for the chickpea trial; peat granules provided effective nodulation, peat and freeze dried slurry on seed produced reliable nodulation, while bentonite and attapulgite clay granules provided variable nodulation. Nodulation was poor without inoculant application.

 

Further local trials were set up in 2009, with the aim of testing new and traditional products further. In addition, we tested the effects of seed-applied fungicides in affecting nodulation and whether the length of time between inoculation and sowing affected nodulation.

Trials were conducted at Coonamble and Walgett in 2009, with treatments including:

·         Traditional peat slurry applied to seed

·         Dry peat applied with seed at sowing

·         Attapulgite clay granules applied with seed at sowing

·         Peat granules applied with seed at sowing

·         Peat slurry injected into furrow with seed

 

There was no significant difference between any of the products for nodulation of roots or for yield. These paddocks had not been planted to faba beans in the past, but rhizobia were believed to be present due to naturalised vetches and flooding, which can transport root nodule bacteria.

 

Pot tests showed good nodulation from road sides near the trials, but showed poor nodulation from lake-bed soil west of Walgett. For this reason it is still recommended to apply an inoculant to faba beans, as it is impossible to determine if rhizobia are present across a whole paddock or region.

The lupin trial was conducted at Curban with similar treatments except that liquid injection was not applied. There was again no significant difference between the products for nodulation of roots or yield, due to high background of rhizobia in soil.

The Walgett chickpea trial included treatments similar to the faba bean trial. There was no significant difference in the level of nodulation achieved by any product. This was in a paddock that was sown to chickpeas in 2005.

 

A more comprehensive trial was conducted at Trangie, which included the following products (at label rates):

 

In addition, the seed was either treated or untreated with fungicide (thiram + thiabendazole). The effect of timing and method of inoculation was determined for the peat slurry treatments, with the inoculant applied 6 hours prior to sowing (6h) or 48 hours prior to sowing (48h), as well as a treatment with peat slurry and fungicide mixed together and applied to the seed as a slurry (mix).

 

     

 

Figure 1: Effect of product, fungicide on seed and timing of peat slurry treatment on nodulation of chickpeas at Trangie, 2009

 

Figures 1 shows that the highest level of nodulation was achieved where peat slurry and freeze dried rhizobia were applied to seed that was not treated with fungicide. Both the peat slurry and freeze dried rhizobia treatments had significantly greater nodulation than any granular product when seed was not treated with fungicide.

 

Where fungicide was applied to seed, the peat slurry treatments and the freeze dried rhizobia slurry had a significant reduction in nodulation compared to fungicide untreated. The nodulation scores for the peat slurry treatment applied according to label recommendations, (PS 6h) was not significantly less than the nodulation scores achieved from using any of the granular products. The freeze dried rhizobia treatment had significantly less nodulation than all other inoculant treatments where seed was treated with fungicide, with resulting nodulation being similar to the untreated.

 

The peat slurry treatments applied to fungicide treated seed 48 hours prior to sowing and the peat slurry mixed with fungicide (and applied to seed as one) had similar nodulation as the slurry treatments applied 6 hours prior to sowing.

 

The overall performance of the granular products was variable. The nodulation from bentonite clay granules was not significantly affected by fungicide, while nodulation from the attapulgite clay granules was reduced and nodulation from the peat granules was increased. Where seed was treated with fungicide, nodulation from the peat granules and bentonite granules was similar to what was achieved with the peat slurry (6h) treatment.

 

There was no significant difference for yield in this trial due to the dry finish to the season. Wheat will be sown across the plots in 2010 to determine if there are any rotational benefits from the treatments.

There has been a significant amount of research conducted in the area of granular inoculant product performance in southern NSW, Victoria and South Australia (Denton et al. 2009). This research found that peat slurry inoculants provided effective nodulation of all legumes. Peat granules and attapulgite clay granules were as effective as peat slurry treatments at median levels of background rhizobia, while bentonite granules often did not increase nodule numbers much above the un-inoculated treatments. These results were consistent across a range of pulses, including chickpeas, faba beans, lupins, lentils and field peas.

 

Denton et al. (2009) found that there was a yield advantage where peat slurry treatments were used, with that advantage decreasing as background rhizobia levels increased. Of the granules, peat granules had similar yields to peat slurries, bentonite granules produced yields similar to uninoculated treatments, and the attapulgite granules were in between the two other granules. 

 

Corbin et al. (1977) state that there is a distinct advantage in using solid inoculant applied in the row with the seed instead of conventional inoculation when fungicide treated seed is sown. The Trangie 2009 trial showed no advantage in using any of the granular inoculants compared to the peat slurry treatment applied as per label recommendations. The trial did show that all granular products provided a significantly greater level of nodulation than the freeze dried rhizobia treatment when seed was treated with fungicide.

 

The peat granules had a significant increase in nodulation when seed was treated with fungicide. This is feasible and similar results have been reported previously. Kyei-Boahen (2002), report that the application of the fungicide metalaxyl-m may improve overall plant health, by reducing the detrimental effect of Pythium spp. This in turn may increase the supply of carbohydrate to rhizobia in the roots, which results in an increased level of nodulation.

 

The variable results associated with granules across sites and years may be partly explained by the variability in rhizobia numbers in the product. The rhizobia numbers in the peat granules and bentonite clay granules have been shown to vary by as much as a factor of 10⁴, the attapulgite granules by up to 10³, while the peat slurry treatments remained relatively consistent (Denton et al. 2009).

Results from the local trials combined with trials from SE Australia show that attapulgite granules and peat granules may have a fit in northern farming systems where background rhizobia levels are known to be at least moderate. There are few reported cases of granular products providing greater nodulation than peat slurry treatments.

 

The 2009 trial at Trangie has shown that fungicides may significantly affect nodulation, especially of the peat slurry and freeze dried rhizobia treatments. The trial showed that granular inoculants have a significant advantage over the freeze dried rhizobia where a fungicide is applied to seed. The best fit for freeze dried rhizobia appears to be where seed is not treated with fungicide, and potentially in a system where it can be injected into the furrow with the seed.

 

The peat slurry treatment has been the traditional method of inoculation for pulses in this region. From the research work that has been completed to date, it would be recommended to continue with this product unless significant efficiency gains can be made using granular products.

 

There are a number of areas that require further work including the role of liquid injection of inoculants, compatibility of inoculant products with pesticides and fertilisers, and the rotational and economic effects associated with product performance. 

Corbin EJ, Brockwell J, Gault RR (1977) Nodulation studies on chickpea (Cicer arietinum). Australian Journal of Experimental Agriculture and Animal Husbandry 17, 126–134

 

Denton, M.D., et al., A multi-site field evaluation of granular inoculants for legume nodulation, Soil Biology and Biochemistry (2009), doi:10.1016/j.soilbio.2009.09.009

 

Kyei-Boahen S, Slinkard AE, Walley FL, (2002). Evaluation of rhizobial inoculation methods for chickpea, Agronomy Journal 94, 851-859.

Rohan Brill

Industry and Investment NSW

62 Aberford St Coonamble 2829

Phone- (02) 68221000

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