The Crop Sprayer

This year has been a tricky mix of disease and weeds. The high pressure has meant that the use of pesticides has been unavoidable to maintain potentially high yields into harvest.

Protected operator adding high concentration
chemical to the water in tank.

The machine that is used to apply these expensive products is called a crop sprayer (pictured). It is a very detailed piece of machinery that accurately applies the right amount of chemical to the target part of the plant towards which the operator is aiming. Ours is a self propelled sprayer so has its own engine to move it, but you can get different ones that are pulled or mounted on the back of tractors depending on your needs, crops grown and your budget!

The design in theory is very simple. Firstly, a large water tank in the middle that the chemical is added to via an induction bowl at the back. This tank has a pump that circulates the fluid to make a consistent solution. The sprayer has a set of folding booms: ours are 24m wide but some new models have booms of 36m or more. Along the booms, run pipes from the tank that have outlets regularly spaced along them. These outlets have specialist controls and nozzles which do a particular job in releasing the fluid, under the control of the operator on the seat.

The 24m booms open out horizontally for safety so power
lines are not touched by them.

The operator can open the outlets as he drives along, we have 7 sections on our boom so we can shut or open 3.5m at a time. This reduces any over-lapping or under-dosing of the crop. The operator has a computer on board which measures pressure, forward speed, tank level, area covered etc. The computer adjusts the water flow out of the nozzles to make sure that the application of the chemical and water mix is constant over the whole area. We normally apply between 100 and 200 litres of water, mixed with chemical, to each hectare of the individual crops. The chemicals used in the cans are of very high concentration, therefore the operator needs to be trained and protected when handling them out of the special secure store on the farm. Once they are added to the 3000L of water in the tank they become diluted to the desired concentration as determined by the chemical company to do the best job of controlling the weed, pest or disease.

Each chemical that makes it to general sale on farms has had millions of pounds and years of detailed research done on it to make sure it is safe to be used on crops, around humans and has no adverse effect on the environment.  The chemicals under most people’s kitchen sinks are of higher concentrations and more dangerous to the environment than anything we store on the farm - and we have to be trained to use ours!

The sprayer must be maintained to high standards and is the only piece of farm machinery that needs to be tested each year by law. It has an MOT for road worthiness and application of chemicals each year; if it fails, it cannot be used on the farm until it is re-inspected following repairs.

The sprayer applies the chemical solution by producing a line of water droplets out of the nozzles that hit the plant or soil, the nozzles are designed to produce different size droplets of solution so that the farmer gets best use of the chemical. The problem is, that the small droplets can get blown by wind. This is call spray drift and is a problem to the industry. As farms become bigger and labour becomes less on farms, operators are increasingly asked to spray larger areas and they physically cannot cover the areas needed, so they start to compromise on what weather conditions in which they can spray, to make sure they cover all the crops. This means that incidents of drift have become a real problem, so the chemical manufactures have invested in new technology to help reduce drift. The nozzles used to be fairly simple and as the solution was forced through it, it would produce a flat fan of droplets going straight down into the crop. These were ok but the droplet sizes were small and irregular, so the smaller ones drifted off. Now, on our sprayer, we have special nozzles called air induction or bubble jets. These nozzles, at point of release, fill each droplet with air to create a larger heavier droplet. This reduces drift by being heavier but, on impact with the crop, the bubble pops and the chemical solution sprays out to cover the target area of the plant. So one large droplet becomes lots of smaller ones on impact in the safety of the crop canopy and not on anyone’s prize winning roses in a neighbouring garden!

Our Sprayer has three different Nozzles that can be chosen
depending on the target droplet required.

With every application of a chemical, a full traceability record is kept on the farm. Each field has a full record of what has been applied and when. This is done by a work sheet being produced by the farmer and his crop doctor advisor who guides him on how to keep the crops clean of unwanted weeds, pests and disease. The work sheet is then given to the operator who picks the best weather conditions to go and apply the right chemical to the right field. On completion of the job, the operator fills in the date, time, soil conditions; weather conditions; temperature and area covered for the job and then signs it, so that if any problems occur we can trace back a problem to an operation. On the farm we also have a weather station that takes and records all weather conditions on the farm, this helps the operator to predict the current and short term weather as well as backing up the climate conditions of each day, to help with any traceability of problems that could have been caused chemical drift.  Drift is something we and all farmers take very seriously, as it can not only cause damage to sensitive habitats but it is also our pound coins drifting off out of the field which is the target area for which it was bought.  In the last 12 months, we have bought over £100,000 pounds worth of chemicals that have all been applied by the crop sprayer.  It’s an expensive bill and that is why we want to apply it in the optimum conditions by a well maintained, highly advanced machine and secondly we need to keep it in the field where it benefits us and our business. 

The crop sprayer is an important and well used machine on our farm and all farms but chemical control of pests, weeds and disease is not sustainable and that is why it needs to be viewed as the last resort. Cultural controls like different cultivations to kill weeds, crop rotations and choice of which varieties of crop to grow, all play their part in reducing that expensive bill. This year has been a difficult one but who knows what climate change has in store for us next year and beyond!  One thing is for sure, crop sprayers play a massive part in making sure we all are fed each day.        BWB