Sprayers and Water Volumes

Knapsack Spraying

Roundup ProBio and Roundup ProVantage may be applied in water volumes between 40 and 250 litres per hectare. Different nozzles are designed to deliver different water volumes.

Standard knapsack sprayers are supplied with a set of deflector nozzles of varying swath width but each with an output of 200 litres per hectare. This is the standard rate we use in the table below.

However, Roundup works very well at low water volumes, enabling improved operator efficiency with less downtime for filling and less clean water to carry on site. The dilution rates will need to be adjusted pro-rata for nozzles of different outputs.

Calibration of the knapsack should always be carried out by individual users according to the procedures covered in the syllabus of the PA6 Certificate of competence in hand held spraying and the Code of Practice for using plant protection products, 2006.

Droplet size should be in the range of Medium to Coarse, (BCPC). These can be easily seen but are neither large enough to roll off the target leaves nor fine enough to drift onto non-target areas to cause damage. Use a sprayer hood to avoid damage to non-target plants in close proximity.

Once sprayed the leaves should have an even coverage of drops without running off.

Using standard nozzles giving 200 litres per hectare at 1 bar pressure, a 20 litre knapsack covers 1000 square metres, when walking at 1 metre per second.

Rate Table

Roundup ProBio (360 g/l glyphosate)Roundup ProVantage (480 g/l glyphosate)Weeds Controlled
Rate in Litres per hectareEquivalent dilution mls of product per litre of water in the sprayer*(dilution ratio)Rate in Litres per hectareEquivalent dilution mls of product per litre of water in the sprayer*(dilution ratio)
1.5 7.5
1.13 5.5
Seedling annual grasses and annual broad-leaved weeds
2 10
1.5 7.5
Weed suppression Overall in conifers
3 15 (1:66) 2.25 11.5 (1:87) Woody weeds around trees
4 20 (1:50) 3 15 (1:66) Perennial grasses
5 25 (1:40) 3.75 19 (1:53) Standard Rate Perennial broad-leaved weeds. Emerged aquatic weeds
6 30 (1:33) 4.5 23 (1:44) Floating aquatic weeds. Heather
10 50 (1:20) 7.5 37 (1:27) Rhododendron, Ivy, Horsetail and difficult waxy leaved plants

Further Advice

Monsanto produces further guidance on knapsack nozzle selection and calibration.

CDA application

Roundup amenity products can be used through Controlled Droplet Applicators, (CDA). These produce a uniform sized droplet between 200-300 microns which has low drift characteristics and is applied at 10-40l/ha in carrier oil or water. In addition Roundup ProBiactive 450 can be used neat through specialist ULV (Ultra Low Volume) equipment with drift reduction systems. For more detail on CDA equipment see http://www.spraycda.com.

Useful reference: Hand-held & amenity sprayers handbook - A complete guide to safe effective spraying. (BCPC Publications, Bear Farm, Binfield, Bracknell, BERKS, RG42 5QE Tel: 0118934 2727)