Non-Foliar Yield Enhancements
Last week we tackled foliar yield enhancements so thisweek we’re changing gears just slightly and tackling non-foliar yield products.Various non-foliar yield enhancement products are available to North Carolinasoybean producers. Profit margins are currently narrow for soybeans and muchthought should go into the potential yield advantages and associated costs fromthe use of these products. Over the last five years, the NCSPA has utilized checkofffunding to evaluate the efficacy of these products with NCSU Extension. Havingan unbiased and trusted source evaluate the efficacy of such products isessential to making decisions about what products, if any, should be added to afarm operation.
This test was conducted across 15 environments from 2014– 2018. While products have varied from year-to-year, this trial has generallyincluded seed treatments, in-furrow applications, broadcast applications.Products tested included insecticides, fungicides, nematicides, inoculants,biologicals, and fertilizer. The number of environments a product was evaluatein is included in the graph and only products that were tested multiple yearsare reported here. Confidence in the results increase the more times andenvironments a product has been tested.
Fungicide seedtreatments
When combining over environments, the use of a fungicidalseed treatment did not significantly impact soybean yield but most of thesetrials were planted in June or July. It is possible that fungicidal seedtreatments would have more of an impact at earlier soybean planting dates, whenconditions are generally cooler and wetter, which can intensify seedlingdiseases. Fungicidal seed treatments may be more important in years where thereis low seed quality and limited seed quantities of some varieties as it wouldbe more important to prevent the chance of having to replant.
Insecticidal/Biologicalseed treatments
The Poncho/Votivo seed treatment was evaluated over eightenvironments and had no impact on soybean yield. We clearly did notcomprehensively evaluate insecticidal or nematicidal seed treatments in thistrial but other work carried out by Dr. Dominic Reisig have consistently shownno yield advantage to using an insecticidal seed treatment on soybeans in NorthCarolina. In addition to lack of yield response, the use of an insecticidalseed treatment in soybeans can intensify resistance development to these seedtreatments used in other crops, like cotton, where they are needed.
In separate NC State studies, nematicide seed treatmentsshow inconsistent results for reducing damage from nematodes. Withinconsistency in yield response from nematicidal seed treatments, their useappears to be best placed in systems with moderate nematode populations, andare likely not economical in low or high nematode population environments.
Inoculant seedtreatments
Soybeans can fix their own nitrogen through a symbioticrelationship with bacteria (Bradyrhizobia japonicum) that can convertatmospheric nitrogen (N2) into a plant useable form. For this reason, soybeansare often not fertilized with any additional N fertilizer, and farmersgenerally depend on N-fixation and residual soil N to fulfill soybean N demand.There has been recent interest in the value of inoculating soybeans withappropriate bacteria to promote N-fixation. In this trial we evaluated two seedapplied inoculants. The two inoculants evaluated in this study, Optimize LCO XCand TagTeam LCO XC, provided a slight yield advantage from the nontreatedcontrol (+1.1 bu/A). Other University conducted trials also have observedmodest yield increases from the use of the Optimize inoculant. Previous work byDr. Jim Dunphy would indicate that in-furrow inoculants are generally moreeffective than seed applied inoculants. It is generally believed thatinoculating soybeans is more valuable on a field that has not produced soybeansfor 4-5 years, than one which has had soybeans consistently in the rotation.
Biological seedtreatments
BioForge is a biological plant growth promoter thatclaims to promote early root growth by reducing stress. This product wasevaluated as a seed application over five years in this study and did notsignificantly impact soybean yield. Other University research has found thatBioForge applied both as a seed treatment and a foliar treatment was moreeffective at impacting soybean yield than use as a seed treatment alone.
In-furrowfungicides
The use of Quadris, Proline, and Headline did not impactsoybean yield across environments, however Priaxor did increase soybean yield(+1.6 bu/A). It should again be noted that the trials were generally planted inJune and July and a larger impact on soybean yield may have been observed from in-furrowfungicide use at earlier soybean planting dates when environmental conditionsmight be more conducive for disease development. In-furrow fungicides are bestused in environments with high disease risk (cool, wet soils), as fungicideresistance develops rapidly in soilborne fungi populations. Continued use ofthe same fungicide chemistry could result in fungicide-resistance, which wouldmake future disease management more challenging.
In-furrow microbialstimulants
Agzyme and Environoc 401 are both microbial stimulantproducts that are advertised to enhance microbial activity. Both hadapproximately a 1.5 bu/A increase on soybean yield when evaluated in thistrial.
Fertilizerapplications
There is some question about the necessity of addingadditional N fertilizer to soybeans as we push yields higher. At some point,the evaluation of both ESN and ammonium sulfate applications in soybeans was ofinterest to growers in North Carolina. In this trial, the use of ESN atplanting or pre-bloom or the use of ammonium sulfate did not impact yield.There are many field experiments that have been conducted in North Carolinathat show that inorganic N fertilizer applications to effectively nodulatedsoybeans are rarely profitable. A recent nationwide study found in mostenvironments there was a minimal effect of N fertilizer application on soybeanyield and that this practice would rarely return profits.
Over the years the non-foliar yield enhancement productsevaluated in this program have provided modest soybean yield increases, if any.The evaluation of these products across 15 environments is context specific tolate-May through early July planting and these results may be different ifearlier planting dates were evaluated. Many of these products are relativelyinexpensive, however, so growers must decide if the modest increases in soybeanyield observed with some of these products coupled with the risk of resistancedevelopment would justify investment.