Speciality fertilizers in agriculture: An overviewDr. Hugo OppermanHead chemist MBFiFERTASA Congress 19 APRIL 2018

Biggest problem the world is facing today is food security

Reasons for the crisis?

Decreasing agricultural land and increasing world population

ErosionDesertificationPoor soil management Poor water qualityPollution

FAO study reports 2 billion hectares lost since 1950’s

By 2050 there will be 9 billion mouths to feed (FAO, 2010)

South African contextOnly 12 % of the surface area of South Africa has

the potential for efficient crop production. Most

of the crop production areas are marginal, with

only 3 % being classified as high potential

cultivatable land.

SA population expected to grow 2 % annually

and reach 82 million by 2035.

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SA Maize production

Crop production (1000 Ton) Area planted (1000 Ha) Consumption (1000 Ton)

Traditional

Increasingly

Nutrition Soil biology Structural

Holistic approach

Plant physiology

Nutrition

Definition: ‘Fertilizer’ can be defined as any substance, natural or chemical, that is added to the soil or directly to plants to improve fertility or enhance plant growth and health.

Better soil and plant fertility practices = Smarter speciality fertilizer

Speciality fertilizers provide tools in your toolbox to improve/manipulate various plant growth factors

Can be overwhelming and feel more like a black box

Specialty fertilizers are applied to soil, seed and plants to improve the crop’s physiological processes – its growth, blooming and maturity period.

Speciality fertilizer is a fast growing market, with an estimated growth rate of 8.5 % per annum globally. The market is estimated to reach 24 billion USD by 2022.

Speciality fertilizers to improve productivity

Speciality fertilizers 3 main classes

Nutrients Biostimulants Biologicals

Nutrient speciality fertilizers

Nutrient speciality fertilizers

• High purity macro- and secondary nutrient salts• Micronutrients• Modified fertilizers - Inhibitors and slow/controlled

release fertilizers

Nutrient speciality subclasses

Very versatile can either be applied via seed treatment, pre-plant, with planting fertilizer or as foliar fertilizer

Speciality micronutrientsMicronutrients are often overlooked and can limit crop production significantly

88 % of soils in Sub-Saharan Africa is deficient in zinc

73 % of soils in South Africa is deficient in boron

Various application methods

Foliarly applied

Seed treatments

With planting fertilizer

Applied to soil: Pre-plant

Foliarly applied

Special considerations

Most micronutrients with the exception of boron and molybdenum are in a cationic form – divalent transition metals M2+

Highly reactive to anions such as phosphates and sensitive to changes in pH

Must be in water soluble (ionic) form for plant uptake

Can also react with other compounds such as herbicides in tank mixture

Problems can be overcome by process of chelation

Many types of chelation molecules have been developed

Synthetic chelates – EDTA, DTPA, EDDHA etc.

Organic chelates – Organic acids such as amino acids, fulvic acid, citrates, carbohydrates

Binds to metal (M) ion and protects it from reacting

The foliar uptake of nutrients is one important part, but the aspect which is

even more critical is the ability of the nutrients to be translocated to other plants

cells and organs once taken up.

Chelates bulky molecules - decreaseabsorption and translocation of the nutrient

Excellent chelating agents - high absorption and translocation characteristics

Should be comparable with inorganic salt nutrients

Micronutrient seed treatmentsSupply young seedling with micronutrients for its early growth period - roots are still developing.

Micronutrients are immobile in most soils -early season deficiencies.

This has been shown to result in stronger seedlings which can translate into higher yields.

A polymer in often added - adhesion onto the seedColorant for identification of treated seeds.

Micronutrient application with fertilizer

Most bulk blenders in South Africa add micronutrients to a blend in the form of micronutrientGranules.

Blended micronutrients Coated micronutrients

Leads to uneven spatial distribution Even spatial distribution

Micronutrients immobile soil

Blended vs coated zinc trials

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Bothaville Delmas Lichtenburg BethlehemLEAF

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Zinc leaf analysis of maize at 4 different trial locations (2016/2017 season). Treatments differed only in zinc type. No zinc, granular zinc sulphate and coated zinc. The same zinc equivalent was used for the zinc sulphate and coated zinc treatments per hectare.

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Bothaville Delmas Lichtenburg BethlehemMAI

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Average maize yields of the four trial locations for thedifferent zinc treatments (2016/2017 season). Fivestatistical plots were planted for each treatment at eachlocation.

Modified fertilizers - Inhibitors and controlled release fertilizers

Main goal of modified fertilizers are to enhance the nutrient use efficiency of the fertilizer

Nitrogen cycleUrea

Ammonium

Urease

Nitrites (NO2-)

Nitrates (NO3-)

Nitrosomonas

Nitrobacter

Ammonia(volatile gas)

Leaching

Inhibitors - chemical actionUrease inhibitors inhibit urea to ammoniumNitrification inhibitors inhibit ammonium to nitrites and nitrates. Inhibition lasts between 14 and 28 days.

Controlled/slow release fertilizer - physical barrier Usually polymer coating. Release nutrients under very specific conditions – temperature,humidity, soil water level etc. Provides a sustained nutrient release.

Biostimulants

BiostimulantsDefinition: Biostimulants are defined as any substance or microorganism applied to seeds, plants or the soil with the aim to enhance nutrition efficiency, abiotic stress tolerance and/or crop quality traits, regardless of its nutrients content.

Global market value of almost 2 billion USD in 2018.

Biostimulant classes

Seaweed extracts

Synthetic plant hormones

Organic compounds

Inorganic compounds

Seaweed extracts

Contains complex carbohydrates, plant hormones (cytokinins and auxins), macro- and micronutrients, betaines and sterols.

Can be applied on soils, in hydroponic solutions as seed or foliar treatments.

Growth stimulating effect High amounts of antioxidants which is effective in plant stress relief.

The effect of seaweed treatment (left) and untreated (right) on root development.

Synthetic plant hormonesThe use of synthetic plant hormones (also produced naturally in the plant) has also been shown to be very effective in stimulating plant growth and crop quality traits. There are 5 major classes of plant hormones and each of them are involved in controlling specific metabolic processes.

Auxins – IAA, NAA, IBACytokine – Kinetin, Zeatin, 6-BAPGibberellins – GA3, GA7Abscisic acid - ABAEthylene – Ethylene releasing compounds

Hormones levels fluctuate withphenological stages.

Each hormone type causesspecific metabolic response.

Hormones work in synergy withplant specific plant nutrients atthe specific growth stages.

Adapted from Stoller USA.

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Soya trials BethalX-press Fuctional at sprayed V6

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Soya trials DelmasX-Press MoB sprayed V4 and R1

Control X-press MoB

The effect of two different hormone products containing complimentary nutrients on the average soya crop yield over 3 trial years. The control treatments only contained nutrients without the hormone compounds. Five replicates were done per treatment.

Organic compoundsHumic acid

Fulvic acid

Amino acid

Organic compoundsVast amount of organic compound have been identified and are being used for theirbiostimulant properties. Only the most commonly used examples will be discussed in thispresentation.

Humic and fulvic acid compounds – Improve soil structure, improve nutrient uptake,protects against stress conditions

Amino acids – improves nutrient uptake, increase stress tolerance, increases plantenergy

Salicylates – increases plant stress tolerance

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Riversdal trials Aminex at 2L/Ha - 2016/2017

Untreated control Aminex

The effect of an amino acid spray treatment on the yieldresponse of wheat and canola in the Riversdal area.Application of the product was 2L/Ha. Wheat was sprayedat flag leaf stage, whilst canola was sprayed at the end offlowering.

Inorganic compounds

Phosphites – Increased root developmentIncreased disease resistanceImproves fruit yield and quality

Silicon - Increases stomatal regulation – increased salt and drought toleranceRegulates antioxidant system – increased stress toleranceProtects the plant against heavy metal stress

Biological fertilizer/stimulants

Biological fertilizers/stimulants can be of bacterial or fungal origins.

Most products available in the market are either applied directly to the soil or as seed treatments.

They improve plant growth by improving nutrient availability and uptake (biofertilization), producing compounds that stimulate growth and disease resistance (biostimulants), control of pathogenic organisms and pests as well as improving soil structure.

Beneficial bacteria

The most widely used biological organism in agriculture is nitrogen fixing rhizobium bacteriaThese bacteria are widely applied as seed treatment or in furrow to help nodulation in legume crops. Eg. Bradyrhizobium japonicum

Another example of beneficial bacteria is members of the genus Bacillus. They are termed plant growth-promoting rhizobacteria (PGPR) and are capable of effectively colonizing plant roots

Bacillus advantages

• Produces natural cytokinins and auxins –promotes plant growth

• Produces enzymes such as phytases to solubilizeplant nutrients, especially bound phosphates

• Supresses plant pathogens• Produces enzymes which elicits and improves

plant defencesBacillus subtilis (green) biofilms on an Arabidopsis root surface. Credit: University of Delaware/Thimmaraju Rudrappa

Beneficial fungi

The most common beneficial fungi used in agriculture is Trichoderma.

Forms a physical bond with the root system of its host plant and establish itself in the rhizosphere.

• Production of plant hormones or hormone like substances• Supresses the growth of pathogenic fungi such as rhizoctonia solani• Solubilisation of essential plant nutrients such as iron • Elicits induced systemic resistance against pathogens through the

production of enzymes such as cellulose and xylanase

Trichoderma advantages

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Control Tri-cure WP 100g/100 kg seed

Tri-cure WP 200g/100 kg seed

Tri-cure WP 400g/100 kg seed

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Tri-Cure WP applied as a seed treatment on maize across 2 regions in 2015/16

Average maize yield over two trial locations of with untreatedand treated maize seeds. Tri-cure WP is a Trichoderma harzianumfungal specie. Twelve statistical plots per region.

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