The Teagasc ‘Spring Barley Guide’ confirms that the ideal soil-pH value for these crops comes in at approximately 6.5.
This will ensure optimum availability of both major and minor nutrients. To achieve this, growers should apply lime as recommended on a recent soil test report.
Ground limestone should be worked into the seedbed before sowing in springtime. It is advised not to exceed 7.5t/ha in a single application.
Where quantities in excess of this are recommended, growers should apply half in the first year and the remainder two years later.
Where soils are low in magnesium, it’s a case of applying magnesium (MG) lime (dolomitic limestone). Granular lime is fast acting but must be applied annually.
Phosphorus (P) is critical in the first six weeks of establishment (for both root and tiller development).
Potassium (K) plays a vital role in building more robust plants and maintaining water balance. Plant K uptake is highest during the reproductive phase.
Soil test for P and K
The rates of P and K required will depend on the soil test P and K reading.
Soils at P and K index 1 and 2 have a high nutrient demand. This is required to build soil fertility to index 3 plus meet annual crop P and K requirements for yield.
Soils at index 3 for P and K have optimum levels to maximise grain yield annually. The advice at index 3 is to replace P and K removed at harvest time (grain and straw) to maintain soil fertility.
Soils at index 4 have a high nutrient supply and offer the opportunity to save on fertilisers. Growers should omit P for two to three years, after which a soil test should be taken to assess soil P levels.
For K, applications should be omitted for a single year, reverting back to index 3 advice until the next soil test is completed.
Growers should always ensure that soil pH is in optimum range for soil P and K availability.
On soils with very low levels of P, research shows that placing the nutrient next to the seed is the most efficient way to achieve target yields.
Growers should, therefore, consider combine drilling the appropriate compound fertiliser with the seed where possible.
Adequate P is particularly important at this time for rapid root and tiller development.
Other minerals for crops
Sulphur (S) is another fundamentally important crop nutrient. Cereal crops grown on light- to medium-type soils are most responsive to S. They should apply 15kg/ha of S with the first nitrogen split.
Trace elements such as copper (Cu), manganese (Mn) and zinc (Zn) are important for cereal production.
Soil levels will depend on the soil type and factors such as high soil pH or recent liming. Growers should apply trace elements where soil levels are low based on the ‘S4 tillage soil test’.
Copper deficiency is found most often on light textured, acidic or alkaline soils where deficiency can occur at index 3. On heavy soils only apply if index 1.
Copper sulphate applied to soil can be an effective option to improve Cu levels. Alternatively, growers can apply foliar Cu formulations where a deficiency is present. Copper can be added to fertilisers and applied at sowing time.
Manganese deficiency is one of the most widespread trace element deficiencies in cereals. There are a number of risk factors including deficient soils and low availability due to poor soil conditions, low soil temperature/moisture and loose seedbeds.
The soil test is a poor indicator of Mn deficiency. Treat crops based on previous field experience, ensure seedbeds are well consolidated and check crops regularly early in the season for symptoms of Mn deficiency, Teagasc has advised.
Options to control deficiency include Mn treated seed, Mn added to fertilisers or foliar Mn applications.
Zinc deficiency is most common on light textured soils. High soil pH values (>7.0) in conjunction with high soil P levels, reduce Zn availability.
A soil test result of less than 1mg/L is a very reliable indicator of possible deficiency. Zinc deficient soils can be treated with zinc sulphate. Alternatively growers can apply foliar Zn in the early stages of crop development.