Developments in application technology for soil fumigation

19.09.2017

Figure 1 Mix Tiller Dry in action in open field situation

Figure 2 Mix Tiller Liquid fumigating pre-planting in greenhouse

Figure 3 The Deeper Ino in action

Figure 4 Tarping in a single pass behind the Deeper Ino

Figure 5 Deeper Ino Twin in trials

Soil fumigants can be used to control plant pests pre-sowing or pre-planting.  They aim to reduce very significantly the populations of nematodes (microscopic worms), soil-borne fungi and weeds whose development can cause major yield reduction or even the destruction of the crop.  The application of these substances aims to provide a uniform treatment on a volume of soil in which these pests damage the crop.  Very careful attention must be paid to the details of how the fumigation is done in order to guarantee excellent control of the targeted organisms and complete safety for workers and other persons close to the treated area, whilst also limiting the impact the product could have on our environment.

As part of Certis Europe’s commitment to the ongoing development of its management solutions for the quality of soil health very thorough and advanced ‘product stewardship’ has been developed for use with its range of fumigants.  One of the main components of this programme is to develop, in partnership with manufacturers sharing the same values, application equipment perfectly adapted to the characteristics of this category of products.

To this end Certis has been working with Forigo Roteritalia over the last 10 years or more, during which time several machines have been developed that follow Certis stewardship guidelines and support the sustainable use of the fumigant range.

Fumigants are sold in various formulations including solids (granules, as in the case of Basamid) or liquids (concentrates, emulsifiable in water or a liquid for use without dilution).  In addition to the physical presentation of the fumigants, any machinery developed must take account of the location of the crop (open field or protected), as well as the need for plastic film.

The first machines developed were in the Mix-Tiller family of technologies: Mix-Tiller Liquid and Mix-Tiller Dry.  The Mix-Tiller dry is specialised for the application of Basamid (dazomet) in micro-granule form.  The Mix-Tiller’s high precision dosing is managed by computer and delivered at a rate proportional to the forward speed of the Figure 2 Mix Tiller Liquid fumigating pre-planting in greenhouse machine.  The dose can be adjusted during operation and the product is evenly distributed ahead of the equipment used for ground tilling and stone burying.  These features improved the quality of application and safety of the product by comparison to other machines available on the market at the time.

Subsequently the Deeper-Ino was designed.

In this machine the product is transferred from its packaging to the tank of the machine (or the reverse), an automatic suction system, using a pump and valves, providing for complete safety of operation.  Linked to a tank of pure water, it also allows rinsing of the device, avoiding direct contact with the product.  The distribution system is perfectly enclosed from the tank to the injectors and fully computer-controlled with a driving-speed-related dosing system and electronic warning system in case of malfunction.  The injectors are equipped with ‘anti-drip’ systems positioned right next to the nozzles to minimise the volume of product leaking by gravity when the application equipment is lifted.  All these improvements have been made to comply with the safe use of a new fumigant: dimethyl disulfide (dmds).

To guarantee the best efficacy of the treatment it is important to work the soil to be treated to create a fine texture with no clods so that the product is evenly spread in the soil.  To this end, tools offering the preparation of a fine tilth are used (rotavator or stone- burier) to remove any obstacles that could hinder a homogeneous diffusion of the gas from the point of injection.  Application through large, perfectly angled coulters helps to ensure the homogeneity of the treatment.

The efficacy of the fumigation is also highly dependent on the depth of the injection of active ingredient in the soil, close to the target pests or pathogens.  The ability to regulate the depth of the coulters is essential to allow adjustments to be made for the specific target.  As an example, weeds need surface fumigation (the top 10 to 15 cm) whilst most soil fungi or nematodes need a deeper application (25 up to 45 cm).

When fumigation is started, the coulters are inserted into the soil before being supplied with product to prevent any surface application.  Immediately after injection, a sealing roller, rotating faster than the forward speed of the tractor, ensures surface compaction of the soil to create a smooth crust as a physical barrier against the evaporation of the active ingredient.

Finally, the last stage of the operation, to prevent any escape of the gas from the treated soil, involves the application of a gas impermeable plastic film in one pass immediately behind the fumigation equipment.

The combination of these developments allows a very significant reduction in the chemical odours associated with fumigation, which is a fundamental consideration at a time when there is increasing overlap of residential and horticultural production areas.  Its compact design makes the Deeper-Ino suitable for working in specialised cultivations in small greenhouses, terrace cultivations and open field.

More recent developments allow for simultaneous shank applications of two different liquid fumigants at two distinct injection depths with the Deeper Ino Twin.

The two fumigants are managed completely independently (with their own tanks, shanks, distribution and dosage systems) to prevent any unauthorised mixing from a regulatory perspective.  This machine will make it possible, in one pass including tarping, to target simultaneously weeds located in the upper layers of the soil and nematodes and pathogens positioned lower in the soil.  The use of precision farming systems allows continuous control of the situation, with appropriate adjustments, and warn the operator of any anomaly that requires intervention from him.  Thus, his attention can be fully focused on driving the machine. 

The machine has been designed in strict compliance with Certis Europe’s stewardship guidelines and will allow high quality application indoors and out with stringent protection for workers, bystanders and residents.  The Deeper Ino Twin equipment was first presented at the Nematology Congress in Bari, Italy in October 2016.  The coming season will see checks on the performance of the equipment under different climatic conditions in several countries.  The co-application of dmds and metham made possible with this machine will allow the refinement of growers’ programmes of soil health management and fine tuning of dose rates for valuable and sustainable protection against pests.

Certis and Forigo Roteritalia plan to continue their programme of development in this critical area of soil fumigation application equipment to ensure that stringent stewardship requirements are met and growers benefit fully from the efficiencies afforded by the latest products and technology.

 All pictures sourced from Forigo library