In last week’s article, we looked at the nutrition of potatoes to build yield potential through the number of tubers produced. This week we complete the growth cycle by attempting to ensure that the tubers produced are filled to the required level for the specific target market.
This nutrition advice continues from a presentation by Vincent Claux from Tradecorp. Having fertilised to build yield potential in the early stages of growth, the approach recommended here is concerned with delivering high saleable yield.
The main nutrients for the bulking stage will be potassium (K) and magnesium (Mg). How the crop is fertilised is especially important where rented land, or any land, is not particularly high in K to begin with. K is a significant driver of tuber size and yield in potatoes and, as stated last week, Mg is important to help drive photosynthesis and dry matter production.
Vincent indicated that application of Mg can add up to 15% additional yield through its impact on chlorophyll production for photosynthesis which then makes more sugars for the bulking process. But it is important to have balanced nutrition because both major and minor nutrients affect the yield and quality of the tubers produced, as indicated in Table 1.
The bulking phase
Potash is extremely important during the bulking phase of the crop. It impacts on all aspects of tuber quality, including bruising resistance, skin quality, stress reduction, cooking quality and shelf life. It is also hugely important to help put size into tubers and hence crop yield. So, not surprisingly, crops tend to be responsive to additional K during this stage.
In the latter half of the year, growth can only be influenced by foliar application of nutrient. Tradecorp sell Final K for this use but they also highly recommend the application of Mg late in the season for the purposes indicated previously.
Potash boost
Final K is moderately well known in this country following the responses attained in winter wheat in the trials conducted by Drummonds. Each year this product generated significant additional grain yield in wheat on a site that had low soil fertility.
Final K is seen as a potentially important input where soil K level is likely to be limiting for the bulking-up process. This can either be because of insufficient K in the soil or inadequate availability to plant roots. Potash plays a role in controlling the opening and closing of the breathing stomata on the leaf surface and so influences water loss through the leaf.
Potash is very important for the generation of tuber size and thus marketable yield. However, Vincent warned that it is not to be seen as the total solution. There is still a necessity to optimise the availability of Mg to the leaves and canopy.
Importance of Mg
Vincent indicated that the majority of Mg deficiency is induced in the plant by environmental factors, the most important being light levels for photosynthesis. Magnesium is important for the production of chlorophyll in plant leaves and the efficiency of photosynthesis. Mg is the core atom in the chlorophyll molecule where it is essential to its efficient functioning. And the application of Mg via foliar application is seen as highly efficient, with 1kg of foliar being the equivalent of 75kg via the soil.
Chlorophyll is the green pigment in leaves which collects light and converts it to plant energy via photosynthesis. And photosynthesis involves the conversion of carbon dioxide and water into sugars and oxygen using light energy to fuel plant growth.
Trials show that foliar Mg treatment is consistently adding 16-17% yield benefit in potatoes. This is regardless of soil fertility or soil K levels. In general, the further north one is the greater the benefit from Mg application as light intensity tends to be lower. The addition of Mg helps to produce greener foliage in the crop which remains greener for longer.
Magnitech is the Mg product that Tradecorp sells for this purpose. Irish trials confirmed the response from three applications of this product during the bulking phase of the crop. Vincent said that Mg deficiency tends to be more problematic in August and September so light levels in those months may give an indication of the likely benefit from Mg application.
However, Vincent said that one may not always benefit from the double application of K and Mg. A lot depends on nutrient availability from the soil, light intensity and also the level of tubers produced that need to be filled to a specific level. Where maximum tuber size is an issue for a market, there is no substitute for test digs to guide treatment and desiccation when appropriate.
Where big tuber numbers are present, the benefit from additional late-season foliar K is likely to be greater. And this is likely to be greater again on land that is low in K, such as conacre or following extensive grassland.
Alternate to finish
Vincent believes that it is important to alternate the K and Mg applications towards the end of bulking up. This is important because K and Mg compete in the plant and applying them separately can help. But it’s important to be aware that K and Mg need to be in balance in the plant to help tuber dry matter. Having excess K towards the end of the growth season will tend to encourage the plant to take in more water and this can depress tuber dry matter levels.
Boron is another element that is important in the latter phase of growth. Boron helps to move sugars around the plant but it is not held on sandy soils and so may need to be applied. It is important that it is available during the intensive growing bulking-up phase of growth. Vincent described boron as the anti-freeze element and he suggested that it might be used earlier in colder regions.
Asked about blackening of the tubers either side of cooking, Vincent suggested that this is mainly related to an N:K imbalance in the plant. So, in the main, this is an excess N issue which relates to the accumulation of sugars in the tuber which cause the discolouration.
Nutrition of potatoes to help bulk up the tubers mainly involves K and Mg but other nutrients are still important.K is critical to help bulk up the tubers but excess late in the season can be negative for dry matter.Mg effectiveness will be greater when light levels are more limiting but it can add 15% to tuber yield.Foliar K and Mg should be applied separately to help reduce antagonism.
In last week’s article, we looked at the nutrition of potatoes to build yield potential through the number of tubers produced. This week we complete the growth cycle by attempting to ensure that the tubers produced are filled to the required level for the specific target market.
This nutrition advice continues from a presentation by Vincent Claux from Tradecorp. Having fertilised to build yield potential in the early stages of growth, the approach recommended here is concerned with delivering high saleable yield.
The main nutrients for the bulking stage will be potassium (K) and magnesium (Mg). How the crop is fertilised is especially important where rented land, or any land, is not particularly high in K to begin with. K is a significant driver of tuber size and yield in potatoes and, as stated last week, Mg is important to help drive photosynthesis and dry matter production.
Vincent indicated that application of Mg can add up to 15% additional yield through its impact on chlorophyll production for photosynthesis which then makes more sugars for the bulking process. But it is important to have balanced nutrition because both major and minor nutrients affect the yield and quality of the tubers produced, as indicated in Table 1.
The bulking phase
Potash is extremely important during the bulking phase of the crop. It impacts on all aspects of tuber quality, including bruising resistance, skin quality, stress reduction, cooking quality and shelf life. It is also hugely important to help put size into tubers and hence crop yield. So, not surprisingly, crops tend to be responsive to additional K during this stage.
In the latter half of the year, growth can only be influenced by foliar application of nutrient. Tradecorp sell Final K for this use but they also highly recommend the application of Mg late in the season for the purposes indicated previously.
Potash boost
Final K is moderately well known in this country following the responses attained in winter wheat in the trials conducted by Drummonds. Each year this product generated significant additional grain yield in wheat on a site that had low soil fertility.
Final K is seen as a potentially important input where soil K level is likely to be limiting for the bulking-up process. This can either be because of insufficient K in the soil or inadequate availability to plant roots. Potash plays a role in controlling the opening and closing of the breathing stomata on the leaf surface and so influences water loss through the leaf.
Potash is very important for the generation of tuber size and thus marketable yield. However, Vincent warned that it is not to be seen as the total solution. There is still a necessity to optimise the availability of Mg to the leaves and canopy.
Importance of Mg
Vincent indicated that the majority of Mg deficiency is induced in the plant by environmental factors, the most important being light levels for photosynthesis. Magnesium is important for the production of chlorophyll in plant leaves and the efficiency of photosynthesis. Mg is the core atom in the chlorophyll molecule where it is essential to its efficient functioning. And the application of Mg via foliar application is seen as highly efficient, with 1kg of foliar being the equivalent of 75kg via the soil.
Chlorophyll is the green pigment in leaves which collects light and converts it to plant energy via photosynthesis. And photosynthesis involves the conversion of carbon dioxide and water into sugars and oxygen using light energy to fuel plant growth.
Trials show that foliar Mg treatment is consistently adding 16-17% yield benefit in potatoes. This is regardless of soil fertility or soil K levels. In general, the further north one is the greater the benefit from Mg application as light intensity tends to be lower. The addition of Mg helps to produce greener foliage in the crop which remains greener for longer.
Magnitech is the Mg product that Tradecorp sells for this purpose. Irish trials confirmed the response from three applications of this product during the bulking phase of the crop. Vincent said that Mg deficiency tends to be more problematic in August and September so light levels in those months may give an indication of the likely benefit from Mg application.
However, Vincent said that one may not always benefit from the double application of K and Mg. A lot depends on nutrient availability from the soil, light intensity and also the level of tubers produced that need to be filled to a specific level. Where maximum tuber size is an issue for a market, there is no substitute for test digs to guide treatment and desiccation when appropriate.
Where big tuber numbers are present, the benefit from additional late-season foliar K is likely to be greater. And this is likely to be greater again on land that is low in K, such as conacre or following extensive grassland.
Alternate to finish
Vincent believes that it is important to alternate the K and Mg applications towards the end of bulking up. This is important because K and Mg compete in the plant and applying them separately can help. But it’s important to be aware that K and Mg need to be in balance in the plant to help tuber dry matter. Having excess K towards the end of the growth season will tend to encourage the plant to take in more water and this can depress tuber dry matter levels.
Boron is another element that is important in the latter phase of growth. Boron helps to move sugars around the plant but it is not held on sandy soils and so may need to be applied. It is important that it is available during the intensive growing bulking-up phase of growth. Vincent described boron as the anti-freeze element and he suggested that it might be used earlier in colder regions.
Asked about blackening of the tubers either side of cooking, Vincent suggested that this is mainly related to an N:K imbalance in the plant. So, in the main, this is an excess N issue which relates to the accumulation of sugars in the tuber which cause the discolouration.
Nutrition of potatoes to help bulk up the tubers mainly involves K and Mg but other nutrients are still important.K is critical to help bulk up the tubers but excess late in the season can be negative for dry matter.Mg effectiveness will be greater when light levels are more limiting but it can add 15% to tuber yield.Foliar K and Mg should be applied separately to help reduce antagonism. 
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