June 2018

By Philippe Delval, ACTA, France and Ludovic Bonin, Arvalis, France

Experimental trial of weed management on wheat, Vallangoujard, France 95

Open day: June 12th, 2018

Number of participants: 110 people

The trials of Vallangoujard are located in the Northwest of Paris, in the department of Val-d’Oise. They are led in a farm where conservation agriculture is practised:  in order to protect the organic matter, the structure and the microbiological activity of ground, the farmer hasn’t been ploughing his plots for 20 years. Today, he has to face a Ryegrass infestation (more than 500 plants per square meter) which significantly decreases his wheat yields.

Several solutions have been tested which combine chemical treatments with different mechanical processing: ploughing (to a depth of 30 cm) + false seed-bed, pseudo-ploughing (to a depth of 10-15 cm) + false seed-bed, 2 false seed-beds, direct sowing with and without vegetative cover.

Ploughing was the most efficient solution against Ryegrass (the removal rate achieved 99 %) because deep ground, not ploughed for 20 years, was free of weed seed. The pseudo-ploughing seems to be a rather satisfactory solution (the removal rate achieved 86 %) but it is likely to postpone the problem for one or two years by burying weeds in shallow depth. Direct sowing gave very disappointing results (the weed removal rate was about 45 % with or without vegetative cover). At the end of the winter, the corresponding plots seemed particularly clean but heavy rain in spring caused emergence of Ryegrass.

Experimental trial of weed management on wheat, Prunay-le-temple, France 78

Open day: June 5th, 2018

Number of participants: 100 people

The trials of Prunay-le-Temple are located in the West of Paris, in the department of Yvelines. They are led, as previously, in an agricultural plot which has not been ploughed for 20 years. Therefore, it is infested by another type of grass: black grass .

As previously, different kinds of tillage were tested: ploughing, pseudo ploughing, direct sowing. For every modality, three dates of sowing were tested (October 11th, October 25th and November 7th) in order to estimate its impact on the final black grass’ infestation. The mechanical processing was always completed by the same chemical treatments.

We can notice that a late sowing (3 weeks after the first one), without ploughing, enables a weed control’s rate of 97%. Concerning tillage, ploughing is the best solution to remove black grass when the plot has not been ploughed for a very long time. Direct sowing (with or without vegetative cover) also produced quiet good results. The worst results were achieved with pseudo ploughing modalities.

 

IWMPRAISE preliminary synthesis on IHDS trials (sowing date X herbicides) of WP3Trials on delayed drilling

1. Main objectives of these trials:

• Study of three drilling dates crossed with herbicides’ programs- in order to validate the most effective strategies, limiting the herbicide use.
• On ryegrass (1 trial) and blackgrass (8 trials)
• Evaluate the impact on the margin of these strategies in delayed drilling, in addition to herbicide reduction.

1 trial was abandoned (L’épine – 51) due to a lack of blackgrass density.

 

Trial in St Ambroix (18) on blackgrass :

 

Trial in St Pourcain sur besbre (03) on blackgrass:

 

Trial in St Saturnin du bois (17) on blackgrass :

 

Reverse effect on blackgrass ! Probably due to the dry conditions in autumn (delayed emergence of blackgrass)

Trial in Quesmy (60) on blackgrass :

 

Results equivalent to the previous trial : dry conditions in autumn lead to a delay in emergence of blackgrass.

Trial in Mespuits (91) on rye grass:

 

Preliminary conclusions :

We observed a significant impact of the delayed drilling on blackgrass emergence:

• Delayed drilling of 20 days in October => reduces the densities by 18 and 74% in blackgrass and 60% in rye grass
• Delayed drilling from 20 to 30 days (late October to early/mid November): decrease of 80% in one trial and nil in the other in the blackgrass’ trial and 76% in the RG
• Delayed drilling from 40 days: 85 to 90% reduction in ryegrass and blackgrass.

Possible yield losses will be analyzed later and in relation to the herbicide costs generated between early and delayed drilling (to follow).

2. Early drilling and impact on blackgrass:

3 trials have been set up to study the effect of a very early drilling date on the blackgrass populations and the crop. The objective is to maximize the development of the crop, in order to limit the emergence of blackgrass.

• Date 1: beginning of September
• Date 2: end of September
• Date 3: mid October
  • Trial in Crenay (52)
    
  • Trial in Marandeuil (21)
    
  • Trial in Saint Hilaire (55)
    

Blackgrass was not present but wild oat and scentless chamomille were present.

The “sowing date” effect, in favour of the latest sowing date on these three trials is demonstrated and does not allow to highlight a “cover” effect of the crop. Not to mention the risks taken on other bio-aggressors (aphids in particular) with protection to be repeated.

The competition from the crop which covers faster does not allow to gain in satisfaction compared to the shift of the sowing date. If populations resistant to HRAC A and B herbicides groups are present, these early seedlings are not sustainable. The herbicide investment required is also close to 100 or even 150€ to be satisfactory or close to a satisfactory level.

Yields to follow.