Micronutrients Zinc, Manganese and Boron

By Dale Cowan

Micronutrients are essential nutrients. An essential nutrient is defined as one that is required for a plant to complete its normal lifecycle. The application rate of these micronutrients is often less than 3 lbs. per acre. The rates seem small relative to primary and secondary nutrients of nitrogen phosphorus, potassium, magnesium and sulphur, but they are no less important. It does not matter how much you have of any one nutrient it is the nutrient in the least amount of supply that can be yield limiting.

Micronutrients play key roles in crop development by enhancing metabolic processes that can and do optimize the use of the primary and secondary nutrients and increase nutrient use efficiency.

The Role of Zinc (Zn)

The two main broad acre crops that are highly responsive to zinc are corn and edible beans in particular white beans. Zinc activates many enzymes in the plant responsible making proteins and carbohydrates that promote root growth early in the season. Increase leaf surface area with auxin hormone production which can lead to better drought tolerance. It is necessary for chlorophyl formation responsible for photosynthesis and sugar production and ultimately yields with more dry matter production. It also plays a role in reproduction with support of flowering and pollen production.

The Role of Manganese (Mn)

The main broad acre crops are wheat and soybeans. Manganese has a unique behavior in our soils which drives how we manage the application of Mn. It is by far the micronutrient of the most importance and therefore warrants our attention. It is involved in photosynthesis it is involved in the photo system II, that splits the water molecule which ensures adequate oxygen to drive energy production in plants. Indeed, a Mn deficient plant can have its photosynthetic activity cut in half. It is further involved in nitrogen metabolism, lignin production and anti-oxidant defense mechanism to fight disease invasion. It one of the main components of chlorophyll pigment formation. Hence one of the diagnostic features in the pale-yellow striping in wheat and chlorotic leaves and green veins in soybeans.

Mn availability in the soil is governed by soil pH, soil test level, soil organic matter (SOM) , soil moisture and oxidation reduction reactions. High soil pH >7.0 limits availability, both low SOM<2% and high SOM >5%. I think the biggest factor for our soils is the relative amounts of soil moisture. Under dry soil conditions there is an elevated amount of oxygen that oxidizes plant available Mn to unavailable forms. When it rains the oxygen is displaced and Mn is reduced to a more plant available form. This is why we see far more deficiencies under dry conditions with wheat and soybeans especially. Another tell tale sign of Mn soil reactions is sometimes we see a greener crop in the tire tracks. This is because the soil is more compacted there reducing the oxygen content and increasing Mn availability. The best way to apply Mn is foliar and it may take more than 2 applications to fix a deficiency in season. We have had some success by including Mn in dry starter bands with MAP that create an acidic zone keeping Mn available longer early in the season.

Manganese (Mn) deficient soybean

Role of Boron (B)

Boron has had a much higher usage rate in vegetable crop production due to it s influence on fruit quality. We just now realizing a more important role in the yield potential in our broad acres crops- mostly corn even though corn only has a moderate demand for boron. We have seen a steady response to applied boron in sidedress UAN. Boron is required all season long. Placing some in the starter and some at sidedress time assures a season long supply. Excess B can be toxic to crop growth our rates are 0.5 lbs. of actual B in UAN at sidedress timing.

Boron is important in cell wall integrity to maintain cell structure in conjunction with calcium. Boron has important role in reproduction with pollen viability. It assists in sugar movement by assuring that cells stay connected to facilitate the flow to the phloem and on to the grain.

Our agronomy program considers all the essential nutrients that may be required. Utilizing current soil tests, crop needs and growing conditions we can tailor a program to optimize nutrient use efficiency under a 4 R Stewardship approach. By considering the best management practices that support Source, Rate, Time and Placement of essential nutrients. Reach out to your Crop Specialists to learn more.

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Add Zinc to your Spring Plans

by Andre Coutinho 

As Spring approaches, we intensify efforts on planning fertilizer and how to maximize profit and achieve higher yields. Once we take care of our N-P-K needs, we should focus on micronutrient strategy and how they can impact the crop throughout the season. One micro that should receive more attention is Zinc.

Zinc is a micronutrient that is a structural component of many enzymes, driving different metabolic reactions. Zinc is essential for plant growth, internode elongation, and photosynthesis. When a plant is deficient in Zinc, it reduces the formation of carbohydrates, protein and chlorophyll, impacting optimum growth and maximum yield. A plant with all the required Zinc will also be more tolerant to stress and diseases.

The impact of Zinc on plants varies, with some crops being more responsive than others. For example, corn has a high response to Zn, soybean a moderate response, and wheat a small response.

The main symptoms of Zn deficiency in corn are:

-Striped tissue in the lower leaves

-Stunted growth

-Distorted leaves

-Yellowing of the leaf tips

Factors that can increase the occurrence of Zinc deficiency include:

-soil test level – current soil tests should be used to start evaluating zinc levels in your fields

- High PH levels

-Low organic matter

-High phosphorus level in the soil

Different strategies and products to correct Zinc deficiency are available today, from dry (Zinc Sulphate) to liquid formulations (foliar sprays). A rate of 2 to 3.0 lb/ac of Zinc will usually be enough to prevent it from happening.

One interesting product is Zinc Procote from Yara. It as a coating to the fertilizer granule we apply at the blender , it will allow the even dispersion of the micronutrients with your starter fertilizer. Another product that can be used later in the crop is Agro-Zn, from Agro-100, a foliar formulation that can be applied as a tank partner with your herbicide. In this case, the application rate should be based on a tissue test.

At AGRIS you can count on your crop specialist to help you plan to use appropriate Zinc formulation to improve your crop yields and maximize profit in such a challenging season.

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Early Season Diseases in Corn and Soybean Production 

by Cory Cowan

In both corn and soybean production, early-season diseases can pose significant challenges to crop establishment and yield potential. Here are some common early-season diseases to be aware of in both crops:

Corn Production:

Seedling Blights: Various fungi can cause seedling blights in corn, including species of Pythium, Fusarium, and Rhizoctonia. These pathogens can infect seeds and seedlings, leading to damping-off and poor stand establishment.

Figure 1. Stunted seedlings have a rotted mesocotyl due to Pythium (Photo credit: J Thomsen)

Stewart's Wilt: Caused by the bacterium Erwinia stewartii, Stewart's wilt primarily affects young corn plants. Symptoms include yellow streaks on leaves, wilting, and stunted growth. This disease is often transmitted by corn flea beetles.

Figure 2. Severely infected plants develop cavities in the pith area near the soil line. (Photo: RL Nielsen, Purdue University). Figure 3. Corn flea beetle plays an integral part in the Stewart’s wilt disease cycle (Photo Credit: Frank Pearis, Colorado State University, Bugwood.org)

Fallow Syndrome: Corn plants that appear stunted and purple in colour can be a sign of phosphorus deficiency symptoms especially between emergence to 5 leaf stage. Often occurs after sugar beets,as sugar beets do not support mycorrhizal populations.

Mycorrhiza is a symbiotic fungi that is important for corn to gather phosphorus not only early but throughout the entire season. They are rootlike hyphae strands that can be 100 times longer than roots.

Figure 4. Significant phosphorus deficiency symptoms expressed in young corn plants that were grown following sugarbeets. This phenomenon is referred to as the fallow syndrome. Photo Credit: J. Ransom, NDSU

Soybean Production:

Seedling Diseases: Similar to corn, soybeans are susceptible to seedling diseases caused by Pythium, Fusarium, and Rhizoctonia species. These pathogens can rot seeds and young seedlings, leading to poor emergence and stand establishment.

Image created by Ashley Joyce

Phytophthora Root Rot: Phytophthora sojae is a soilborne oomycete that causes root rot in soybeans, particularly in wet and poorly drained soils. Symptoms include stunted plants, yellowing, and necrotic lesions on roots.

Pythium Root Rot: Pythium species can infect soybean seedlings, causing damping-off and root rot. Symptoms include water-soaked lesions on stems and roots, leading to plant wilting and death.

Photo Credit: Jenny Carleo Area Specialized Agent, Agriculture - Grain Crops Iredell County Center

Soybean Cyst Nematode (SCN): Although not a disease in the traditional sense, SCN is a parasitic nematode that infects soybean roots early in the season. SCN infestations can stunt plant growth, reduce nodulation, and decrease yield potential.

Figure 1. Small white to yellow lemon-shaped SCN cysts on root. Figure 2. Note the small size (1 mm) of SCN cysts compared to much larger Rhizobium nodules. Photo Credit Albert Tenuta OMAFRA

Management Strategies:

Seed Treatment: Using fungicide-treated seeds can help protect against early-season seedling diseases in both corn and soybeans.

Crop Rotation: Rotate crops to break disease cycles and reduce pathogen pressure in the soil.

Resistant Varieties: Planting disease-resistant corn and soybean varieties can provide effective control against specific pathogens.

Seedbed Preparation: Ensure proper seedbed preparation to promote uniform emergence and minimize stress on seedlings.

Timely Planting: Planting corn and soybeans at the optimal time can help avoid conditions favorable for early-season diseases.

Integrated Pest Management (IPM): Implement IPM strategies, including cultural practices and chemical control measures, to manage disease risks effectively.

Early detection and proactive management are essential for mitigating the impact of early-season diseases on corn and soybean production. Regular scouting and monitoring can help identify disease outbreaks early, allowing for timely intervention to protect crop yield potential. Here at AGRIS our team is ready to help you identify these early season signs & symptoms within your row crop production and provide the resources you need to correct them.