Sulphate of potash increases tuber numbers
Tuberisation is inhibited when stolons are immersed in liquid
High N levels may delay tuberisation, tuber growth rate may also be reduced by high N levels although growth rate of vegetative shoots is enhanced
N increases tuber size
Phosphate application stimulates the initiation of tubers, but a percentage of these may be aborted resulting in little effect on tuber number at harvest. At higher P levels more tubers are initiated but a lower percentage reach maturity
P application enhances ground cover expansion, radiation interception and, as a result, crop growth rate during the early stages of growth. Consequently during the main period of tuber initiation the larger leaf area of crops receiving P represented a considerable advantage in terms of capacity to produce assimilates at that time. Due to the effects on tuber number there tends to be a decrease in tuber size, resulting in fewer tubers in the baker fraction
High N and high K tend to reduce dry matters N above 150k/ha reduces DM by 1-2%, similar pattern occurs with K above 170k/ha
Insufficient calcium in the tuber zone can cause tuber abortion
High Ca increases starch and reduces sugar
High P can increase starch % applied as foliar P
Boron deficient potatoes rapidly turn brown when cut.
Tubers lacking boron also sprout less readily
Plants with adequate B levels have better resistance to viral, fungal and insect attack..
Boron helps the plant modify its transpiration to match water availability, increasing when water is plentiful and decreasing when it is dry.
High potassium availability can intensify an existing boron deficiency
A good boron status is reported to enhance calcium metabolism, both uptake and translocation
Potato tubers deficient in K are softer and therefore more susceptible to bruising.
N:K fertiliser ratios for potatoes should ideally be 1:1
Zinc uptake is reduced in cooler conditions. Zinc is involved in the production of auxin in the plant. If auxin levels are high during early growth the leaf area will be greater. Tuber initiation is influenced by the leaf/shoot ratio- the greater the leaf area the greater the tuber set
At pH of 7 and abovecopper, manganese, zinc and phosphate all begin to lock up in the soil
Many pests are a greater problem when nitrogen levels in plants are high or there is impaired protein synthesis
Deficiency of sulphur or of other nutrients reduces the effectiveness of nitrogen metabolism
In cotton the effects of nematodes are significantly greater when soil potassium supply is low than when it is good
Manganese deficiency has been shown to have similar effects on barley plants
Copper is involved in the lignification and strengthening of cell walls
Zinc is involved in auxin production, a hormone which has effects on root production and growth.
Sulphur application acidifies soil thereby making more of these nutrients available to the plant
Nematicides tend to have a shorter half-life as the pH rises- by acidifying soil they should remain effective for longer
By strengthening cell walls good crop nutrition will enhance the plants ability to resist both pests and diseases.
A healthy plant is also better able to overcome the damaging effects of pests such as nematodes
Application of 50-80kg SulFer 95 depending on soil pH should significantly reduce pH €“ in some cases reduction from 7.5 to 6.5 has been acheived