Article taken from the Agronomist & Arable Farmer
The Agronomist’s view
Manganese is one of the most important trace elements, involved in several metabolic processes but most crucially in photosynthesis itself. It’s essential for normal plant nutrition and development, yet it’s one of the most common deficiencies seen in crops.
Agrovista’s Luke Hardy, based in Staffordshire, guarantees that it’s the one trace element most regularly applied to his customers’ crops. The light land predominant in this part of the country creates perfect conditions for deficiency.
“In worst cases, we can lose a crop through insufficient manganese,” he explains. “More often we see a loss of vigour and crop thinning, as tillers fail. Yield loss follows.”
Last year’s mild autumn kept crops growing longer, placing extra burden on metabolic processes, he notes. “Some fields saw big patches of crop suffer nutrient stress. With manganese, the obvious symptom is inter-veinal yellowing and discolouration of the youngest leaves – a direct result of the element’s role in photosynthesis.”
While light land is particularly vulnerable, soil pH is also a good indicator of problems. “The higher the pH, the less likely that manganese is available – irrespective of indicated soil levels,” he points out.
“Here, land coming out of vegetable production tends to have artificially high pH, so coming back into combinable crops it’s almost a dead cert they’ll need manganese applications.
“For the rest of the country, any land where barley or oilseed rape is in the rotation should also raise a red flag on manganese deficiency,” he advises.
Soil testing’s a great way to investigate trace element levels, but broad-spectrum tests are needed to account for the likely effect of pH levels. “Just don’t rely on soil tests alone,” stresses Mr Hardy. “As important is getting the seedbed right.
“Growing cereals demands well-prepared, well-consolidated seedbeds, because pre-em herbicides – especially those containing flufenacet – won’t perform to their best.
“But puffy seedbeds also have a detrimental effect on crop rooting. In turn, that can lead to lower-than-optimal levels of nutrient uptake.”
Tissue testing remains the best option. “Analysing the leaf tells you what’s in the plant, as opposed to what you think might be in the plant. It reveals any ‘hidden hunger’ in the plant – sub-optimal levels of nutrients which, although not yet causing symptoms, nevertheless affect the plant’s metabolic efficiency.”
Fortunately, manganese deficiency is also one of the easiest to remedy, say Mr Hardy, “provided you do it the right way – appropriate applications of the right products, at the right time.”
“Many growers may be familiar with older manganese sulphate products – and probably therefore familiar with their inconvenience, high dose rates and often questionable results.
“But products have moved on and modern foliar products should now be in every grower’s nutrient armoury.”
Mr Hardy relies on the Safagrow product Manganese Aloy. “Much depends on the crop and analysis of needs, but its strong tank-mix compatibilities – both herbicides and fungicides – allow us to use it every time a pass is made. That might be up to five or six applications in the most needy cases, whereas borderline cases might take one in autumn and one in spring, or one in spring alone.”
In spring, it’s nitrogen application that prompts borderline fields to start to break down, notes Mr Hardy. Nitrogen causes a growth spurt, but manganese suddenly becomes a limiting factor.
“Crops can go from green to yellow in days, because the nitrogen wasn’t followed up with manganese. It’s a really good example of where Aloy helps, because its rapid uptake and persistency on the leaf means the crop is back on its feet pretty quickly.
The Chemist’s view
Micronutrients, or trace elements, are a specialised area of plant nutrition. Formulating products that deliver the right dose at the right time can be tricky, particularly when the sector has not benefited from the same advances as, say, crop protection formulation over the last couple of decades.
Taking manganese as an example, but equally applicable to other trace elements, there are three main points to understand,” says Martin Edwards, Safagrow’s formulation and development chemist.
“You’ve got three methods of applying manganese: soil, foliar and seed. Uptake into the plant is dependent on solubility of the manganese is an element, it does not degrade.
“On that basis, one might think that the more soluble the salt, the quicker and more available to the plant it would be therefore absorbing more. In reality, this is less likely.”
Considering soil applications first, Mr Edwards uses the example of the herbicides simazine (pre-emergence) and atrazine (post-emergence). “Simazine has a solubility of 6.3mg/kg and atrazine 33mg/kg/ Simazine sits on the soil surface, killing weeds by contact as they emerge. Atrazine is root and leaf absorbed, and leaches about six inches outside the spray target. So the solubility doesn’t have to be too high for leaching to occur.”
A manganese salt with solubility in excess of 200mg/kg will be inefficient in soil, as most of the product won’t reach the roots – especially during high rainfall periods such as autumn.
“Also present during autumn is phosphate. At 1mg/kg, manganese phosphate is very insoluble – which means manganese effectively becomes inactive in the soil. Thus seed dressing becomes the best way to apply manganese in the soil, but there it has to compete with other pesticides in the dressing.”
Thus foliar application becomes the best method. “But applying soluble salts of manganese is inefficient – while absorption into the plant will be washed off the leaf at the next rainfall,” points out Mr Edwards.
“A low soluble salt that remains in contact with the leaf presents the best compromise. Rainfast elements in the formulation help it remain on the leaf for long periods, so it’s persistent.
“The only drawback with that is that often the plant needs a rapid injection of manganese. That’s why Aloy also has a small amount of high solubility manganese in the mainly low solubility suspension concentrate. It’s held in place on the leaf by the rainfast formulation, but available more quickly to the plant. And by using elemental manganese, there’s no degradation of the active over time. That means fewer sprays are needed.”
The plant nutritionist’s view
Photosynthesis is just one of the processes in which manganese is involved, writes Dr Apostolos Papadopoulos, of Crop Intellect. Low levels are also essential for normal nutrition and development.
The most soil available form of manganese is Mn²+, but the presence of microorganisms or other elements can either make manganese more available or reduce its availability. For instance, manganese oxidising bacteria can turn Mn²+ into an oxide form that is not available to plants. And despite its importance, the amount of manganese required in relatively low – yet the capacity for manganese uptake greatly exceeds this requirement. Excess manganese is stored in organelles such as the vacuole, and plant tissue analysis will reveal if the level is at deficient or toxic state.
At low pH<5 manganese becomes available and at pH>8 it oxidises, making it less available and it binds to soil particles. Acid soils can make excessive manganese amounts toxic for the plant; however, liming will reduce its availability. High levels of manganese can cause severe toxicity, with symptoms including chlorosis and necrotic leaf spots – often very similar to iron deficiency. Low levels of other elements such as calcium, magnesium and potassium can intensify manganese toxicity.
Historic knowledge of the soil is the best indicator for application timings. Soils that will cause manganese deficiency at establishment should receive applications at planting. When the deficiency at planting. When the deficiency becomes visible, the plants productivity has already been suppressed: in severe cases, correction will not provide a full recovery. Observation to correction usually takes between three and five weeks, which will usually be reflected in the yield reduction.
The minute requirements of manganese make frequent foliar applications the most appropriate, as well as reducing the complexity of the element when soil-applied, risking its transformation to unavailable forms.
The Agronomist’s view
Manganese is one of the most important trace elements, involved in several metabolic processes but most crucially in photosynthesis itself. It’s essential for normal plant nutrition and development, yet it’s one of the most common deficiencies seen in crops.
Agrovista’s Luke Hardy, based in Staffordshire, guarantees that it’s the one trace element most regularly applied to his customers’ crops. The light land predominant in this part of the country creates perfect conditions for deficiency.
“In worst cases, we can lose a crop through insufficient manganese,” he explains. “More often we see a loss of vigour and crop thinning, as tillers fail. Yield loss follows.”
Last year’s mild autumn kept crops growing longer, placing extra burden on metabolic processes, he notes. “Some fields saw big patches of crop suffer nutrient stress. With manganese, the obvious symptom is inter-veinal yellowing and discolouration of the youngest leaves – a direct result of the element’s role in photosynthesis.”
While light land is particularly vulnerable, soil pH is also a good indicator of problems. “The higher the pH, the less likely that manganese is available – irrespective of indicated soil levels,” he points out.
“Here, land coming out of vegetable production tends to have artificially high pH, so coming back into combinable crops it’s almost a dead cert they’ll need manganese applications.
“For the rest of the country, any land where barley or oilseed rape is in the rotation should also raise a red flag on manganese deficiency,” he advises.
Soil testing’s a great way to investigate trace element levels, but broad-spectrum tests are needed to account for the likely effect of pH levels. “Just don’t rely on soil tests alone,” stresses Mr Hardy. “As important is getting the seedbed right.
“Growing cereals demands well-prepared, well-consolidated seedbeds, because pre-em herbicides – especially those containing flufenacet – won’t perform to their best.
“But puffy seedbeds also have a detrimental effect on crop rooting. In turn, that can lead to lower-than-optimal levels of nutrient uptake.”
Tissue testing remains the best option. “Analysing the leaf tells you what’s in the plant, as opposed to what you think might be in the plant. It reveals any ‘hidden hunger’ in the plant – sub-optimal levels of nutrients which, although not yet causing symptoms, nevertheless affect the plant’s metabolic efficiency.”
Fortunately, manganese deficiency is also one of the easiest to remedy, say Mr Hardy, “provided you do it the right way – appropriate applications of the right products, at the right time.”
“Many growers may be familiar with older manganese sulphate products – and probably therefore familiar with their inconvenience, high dose rates and often questionable results.
“But products have moved on and modern foliar products should now be in every grower’s nutrient armoury.”
Mr Hardy relies on the Safagrow product Manganese Aloy. “Much depends on the crop and analysis of needs, but its strong tank-mix compatibilities – both herbicides and fungicides – allow us to use it every time a pass is made. That might be up to five or six applications in the most needy cases, whereas borderline cases might take one in autumn and one in spring, or one in spring alone.”
In spring, it’s nitrogen application that prompts borderline fields to start to break down, notes Mr Hardy. Nitrogen causes a growth spurt, but manganese suddenly becomes a limiting factor.
“Crops can go from green to yellow in days, because the nitrogen wasn’t followed up with manganese. It’s a really good example of where Aloy helps, because its rapid uptake and persistency on the leaf means the crop is back on its feet pretty quickly.
The Chemist’s view
Micronutrients, or trace elements, are a specialised area of plant nutrition. Formulating products that deliver the right dose at the right time can be tricky, particularly when the sector has not benefited from the same advances as, say, crop protection formulation over the last couple of decades.
Taking manganese as an example, but equally applicable to other trace elements, there are three main points to understand,” says Martin Edwards, Safagrow’s formulation and development chemist.
“You’ve got three methods of applying manganese: soil, foliar and seed. Uptake into the plant is dependent on solubility of the manganese is an element, it does not degrade.
“On that basis, one might think that the more soluble the salt, the quicker and more available to the plant it would be therefore absorbing more. In reality, this is less likely.”
Considering soil applications first, Mr Edwards uses the example of the herbicides simazine (pre-emergence) and atrazine (post-emergence). “Simazine has a solubility of 6.3mg/kg and atrazine 33mg/kg/ Simazine sits on the soil surface, killing weeds by contact as they emerge. Atrazine is root and leaf absorbed, and leaches about six inches outside the spray target. So the solubility doesn’t have to be too high for leaching to occur.”
A manganese salt with solubility in excess of 200mg/kg will be inefficient in soil, as most of the product won’t reach the roots – especially during high rainfall periods such as autumn.
“Also present during autumn is phosphate. At 1mg/kg, manganese phosphate is very insoluble – which means manganese effectively becomes inactive in the soil. Thus seed dressing becomes the best way to apply manganese in the soil, but there it has to compete with other pesticides in the dressing.”
Thus foliar application becomes the best method. “But applying soluble salts of manganese is inefficient – while absorption into the plant will be washed off the leaf at the next rainfall,” points out Mr Edwards.
“A low soluble salt that remains in contact with the leaf presents the best compromise. Rainfast elements in the formulation help it remain on the leaf for long periods, so it’s persistent.
“The only drawback with that is that often the plant needs a rapid injection of manganese. That’s why Aloy also has a small amount of high solubility manganese in the mainly low solubility suspension concentrate. It’s held in place on the leaf by the rainfast formulation, but available more quickly to the plant. And by using elemental manganese, there’s no degradation of the active over time. That means fewer sprays are needed.”
The plant nutritionist’s view
Photosynthesis is just one of the processes in which manganese is involved, writes Dr Apostolos Papadopoulos, of Crop Intellect. Low levels are also essential for normal nutrition and development.
The most soil available form of manganese is Mn²+, but the presence of microorganisms or other elements can either make manganese more available or reduce its availability. For instance, manganese oxidising bacteria can turn Mn²+ into an oxide form that is not available to plants. And despite its importance, the amount of manganese required in relatively low – yet the capacity for manganese uptake greatly exceeds this requirement. Excess manganese is stored in organelles such as the vacuole, and plant tissue analysis will reveal if the level is at deficient or toxic state.
At low pH<5 manganese becomes available and at pH>8 it oxidises, making it less available and it binds to soil particles. Acid soils can make excessive manganese amounts toxic for the plant; however, liming will reduce its availability. High levels of manganese can cause severe toxicity, with symptoms including chlorosis and necrotic leaf spots – often very similar to iron deficiency. Low levels of other elements such as calcium, magnesium and potassium can intensify manganese toxicity.
Historic knowledge of the soil is the best indicator for application timings. Soils that will cause manganese deficiency at establishment should receive applications at planting. When the deficiency at planting. When the deficiency becomes visible, the plants productivity has already been suppressed: in severe cases, correction will not provide a full recovery. Observation to correction usually takes between three and five weeks, which will usually be reflected in the yield reduction.
The minute requirements of manganese make frequent foliar applications the most appropriate, as well as reducing the complexity of the element when soil-applied, risking its transformation to unavailable forms.