Benefiting Soil Fumigant Application

In 2009, the J.R. Simplot Company initiated a several-year study of Metam CLR fumigant in combination with soil wetting agents. The purpose of the study was to determine if adding a wetting agent during soil fumigation benefitted the soil fumigant application.

The study was conducted by Dr. Saad Hafez, Idaho state nematologist at the University of Idaho Research and Experiment Center in Parma, Idaho. Initially, experiments were conducted in both center pivot chemigation and ground-applied Metam CLR. The Metam CLR, manufactured by Taminco, was used with and without the addition of a specialized soil surfactant. The soil surfactant used in this study was Ad-Sorb RST, manufactured for Plant Health Technologies, a division of Simplot Grower Solutions. Simplot Grower Solutions is a full-service provider of crop nutrition, crop protection, seed and other services in the Western U.S.

EPA regulations have become more stringent concerning center pivot applications of fumigants. Many growers and applicators of soil fumigants are finding regulations for ground rig-applied active ingredients easier to abide by as compared to center pivot chemigation applications. In this research study, Simplot Grower Solutions has focused on ground application in response to grower demand and the fact that center pivot applications of fumigants will become increasingly scrutinized.

It is important to understand how Metam CLR works in the soil as a fumigant to see how using AdSorb RST can help increase performance. Metam CLR is highly water soluble, at 722,000 ppm. Metam CLR also has very low vapor pressure, 24mm/Hg @25 C. This means that metam sodium, the active ingredient in Metam CLR, is very stable with adequate moisture. In addition, it distributes well in a type of capillary action in moist soil.

On the contrary, if the soil is dry, distribution is poor, plus the MITC (which Metam CLR converts to when it comes in contact with moisture in the soil) can escape in dry conditions. The problem is that typical field conditions have uneven moisture and/or compacted layers in the soil profile. This is working against an ideal or uniform performance of Metam CLR. Metam CLR is a contact pesticide; therefore, uniform distribution in the soil profile is important to ensure the best performance. Growers need to get value from every dollar of this very costly treatment, AdSorb RST is the solution to this problem.

Understanding how AdSorb RST functions helps to see how it maximizes performance of Metam CLR. AdSorb RST is formulated with multiple active ingredients that make it an ideal tank mix partner with Metam CLR. AdSorb RST contains a flash wetter derived from coconut oil and corn starch, both renewable resources, which helps eliminate surface tension of moisture. In addition, it contains a block co-polymer surfactant that aids in soil moisture retention, as well as reverse block co-polymer surfactant that re-wets for a period of four to six weeks. These components aid in moisture management, which as was earlier discussed, are critical for metam sodium to function properly and uniformly. AdSorb RST helps bring soil moisture and Metam CLR together and fill in the gaps between rig shanks, helping distribution of active ingredient.

The experiments have been conducted in a randomized complete block design with five treatments and one untreated control, each with five replications in a silt loam field. The average initial population density of Columbia root-knot nematode was 352 per 500 cc soil. The Metam CLR treatments were applied by a commercial applicator fumigation bar to a depth of 12-14 inches. Adsorb RST was mixed with Metam CLR at the rate of 2 qt/A. An additional treatment of Mocap was also made for comparison purposes.

It is important to note that nematodes are listed as suppression only on all formulations of Metam CLR soil fumigants. The addition of AdSorb RST does not change the label in any way and should be used accordingly. The performance of nematode control was simply used as an indicator of performance characteristics with and without AdSorb RST in these treatments. It does not imply control.

In Figure 1, performance characteristics are diagrammed from 2009. Untreated check had 49.6 percent infection Columbia root-knot nematode (CRKN), 40 gal Metam CLR had 17.1 percent, whereas the same rate of Metam CLR plus AdSorb RST reduced this to 1.5 percent.

In Figure 2, performance characteristics are diagrammed from 2011. Yield improvements were statistically significant, by an impressive 87 cwt per acre increase with AdSorb RST as compared to metam alone.

In conclusion, growers are investing a substantial amount of their crop budget with soil fumigation; they need to capture as much ROI as possible. AdSorb RST, as shown in repeated trials with the University of Idaho, when included in Metam CLR fumigation makes this happen. The combination has shown both yield and quality improvements as compared to untreated and Metam CLR alone.