• 
  Micronutrients
  • Nitrogen (N)
  • Phosphorous (P)
  • Potassium (K)
  • Magnesium (Mg)
  • Calcium (Ca)
  • Sulphur (S)
  • Boron (B)
  • Copper (Cu)
  • Cobalt (Co)
  • Iron (Fe)
  • Manganese (Mn)
  • Zinc (Zn)
  • Chloride (Cl)
• 
  Advice by Sector
  • Cereal Crops
  • Oil Seed Rape
  • Potatoes
  • Sugar Beet
  • Pulses, Peas, Beans & Soya
  • Vegetables, Melons & Salad Crops
  • Top and Soft Fruit
  • Grassland / Pasture
  • Amenity & Sports Turf
  • Home & Garden
• 
  Identifying & Rectifying Deficiencies
  • The Effect Of Soil pH On Nutrient Availability
  • Soil Type, Condition And Likely Deficiencies
  • Crop Susceptibility
  • Typical Deficiency Symptoms by Nutrient

OPTIMUM SPRAY TIMINGS

® Optimum time for application             ¦ Application Useful

TOP TIPS

ŸStart with manganese tank mixed with early blight treatments and switch to magnesium as the canopy matures.

ŸCorrect low soil magnesium indices with Kieserite or Calcined Magnesite

Nitrogen

Levels start high at the beginning of the season, due to the ready availability of soluble N around the root zone. If high levels continue through the growing season yield will be lost to excessive leaf growth, and plant senescence will be delayed. High levels of basal N are unsuitable for long top varieties such as Cara and those destined for crisping or chipping. As the tops grow, N levels can fall rapidly. Only apply liquid N if a deficiency is observed early and never apply more than 10 kg N per ha at a time. More commonly the level of basal N is reduced with low levels of liquid N applied with the blight program, feeding the crop throughout the growing period.

Phosphate

Potatoes are very responsive to foliar phosphate regardless of soil indices. This is due primarily to the availability and mobility of the nutrient, it is not mobile therefore root hairs must be in contact with the available soluble P.

The demand pre and post tuber initiation is high, with both foliar and tuber development taking place. Basal P is not available in high enough quantities to supply the crops immediate demand and must be supplemented with foliar P to maximise yield. Responses are very consistent, with firm evidence to suggest that applications made shortly after tuber initiation will increase tuber size at harvest and applications before initiation lead to more tubers at harvest.

Potassium

Maincrops and second earlies are very responsive to basal K. Being soluble and very mobile it is readily accessed and taken in by the roots. Applications of foliar K have proved worthless in most situations unless a deficiency needs correcting. Deficiencies are uncommon unless basal K was applied too early and has leached or application rate was below recommendation.

Excessive K will induce luxury uptake and will decrease the availability of Manganese, Magnesium and Calcium. Excessive K will also adversely affect dry matter, decreasing storage quality and increasing damage at harvest. Do not apply foliar K unless a deficiency becomes apparent through petiole analysis.

Sulphur

Sulphur is taken into the plant in the form of sulphate, either through the roots or foliage. A 40t/ha crop will require approximately 20 kg S per ha. It is important to balance the ratio between S and N as in a deficiency situation the uptake of N maybe limited, conversely excessive N will induce a deficiency in S. It is similar in its properties to N, i.e. mobile and easily leached.

Careful product selection can help during the season i.e. use of Manganese or Magnesium Sulphate or if deficiency is apparent the use of Elemental Sulphur will help .

Recent work suggests that applications of sulphur prills (e.g. Tiger mini Prills) at 50 kg/ha on top of the ridges at planting can produce up to a one-point localised reduction in soil pH. This can lead to reductions in common scab by as much as 50%.

Calcium

Deficiencies are rarely a problem but may show in low pH soils or where high rates of basal K have been applied. Deficiencies are exacerbated in dry/hot conditions. Correction in the growing crop is difficult; if applied as a foliar spray it is immobile in the plant; if applied as lime it will induce scab. Careful pH management is required in the years before the crop is planted, as is careful management of K inputs.

Internal rust spot in potatoes is caused initially by temperature and moisture stress, which leads to an induced calcium deficiency in the plant. Symptoms show as characteristic brown rings inside the tuber, which might easily be confused with Spraing (virus testing can help distinguish the two). Some varieties, e.g. Maris Piper and Russet Burbank, seem more prone to the condition.

Trials in Lincolnshire have shown that early Calcium applications can reduce the occurrence of the condition, as well as giving improvements in long-term storage. Foliar applications of calcium can not travel downwards in the plant to increase tuber calcium levels.

Any action that reduces crop stress (such as irrigation at the right time) is likely to help limit internal rust spot.

Manganese and Magnesium

The importance of these elements must never be underestimated. Both are important for chlorophyll production, therefore they become a necessary part in photosynthesis. Deficiency, regardless of soil type, pH etc. becomes apparent (not always visibly) during the period from emergence to early bulking. During this period the crop is under going enormous growth rates with foliage and tubers developing and the roots struggle to absorb enough of these nutrients to maintain growth.

Applications must be made prophylactically pre and post tuber initiation.

Boron

A deficiency can reduce the storability of the crop. Boron is necessary for the development of roots and shoots. Although the potato crop can be sensitive to a deficiency, excessive Boron can be extremely toxic to the crop. Unless a deficiency becomes apparent, an application of Boron is generally inadvisable. Where deficiencies are a problem Boron should be applied early.

Zinc

Zinc is important for root development, cell membrane integrity and general plant health. As with Boron it must be applied early at or before tuber initiation to aid root development. High levels of soil P exacerbate problems.

To be effective, Zinc must be placed as close as possible to the tubers, as it is very immobile in the soil.

The application of elemental Zinc to the soil is restricted to 15 kg Zn/ha/year by statutory force.

Often, Zinc deficiency does not occur alone, and other elements such as Copper and Manganese may also be deficient. The soil status of all nutrients should be carefully monitored to ensure that the correct balance is available.

Petiole Analysis

Leaf petiole analysis can be used as an occasional crop management tool for assessing the actual nutrient status of the plant at the time of sampling. This is a more accurate tool than standard tissue analysis, the major drawback is that by the time the sample has been taken and tested and the results communicated, the crop may have undergone a fundamental change to growing conditions due to weather or irrigation, and decisions made at that point, then acted upon 2 to 3 days later may be wildly at odds with the true situation at the time the actual treatment is applied.

The information provided by this analysis service can then be used as a guide for applying trace elements to fully satisfy the crops requirement during growth.

ŸRecommend appropriate trace elements on the back of this data.

ŸOffer a petiole analysis service to test the crop and benefit from the opportunity to return and discuss any problems.

This testing service should not detract from applying foliar phosphate to the growing crop.

Leaf Petiole Analysis: Sample Technique

• ·Take samples from at least 20 locations in the field

• ·Take at least 1 branch from each of 3 - 4 plants at each location - i.e. a total of 60-80 branches

• ·Seal the sample in a plastic bag and send to the laboratory for testing as quickly as possible.

• ·NB: If more than 3 days elapse between sampling and remedial treatment then this system becomes unreliable.