As stated in the previous issue, this series is a brief overview and assumes that a would-be producer understands the basics of growing wheat.
When compiling a fertilisation programme for a barley crop, consider the following factors:
- Barley needs a soil pH of 5,5 (KCI medium);
- If a soil analysis indicates that you should apply lime, aim for pH 5,5 to pH 6,0;
- A slightly higher pH is better – anything below 5,5 is likely to lead to a lower yield.
An unnecessary increase in pH could lead to a zinc and manganese deficiency, to which barley is very sensitive.
Barley needs more phosphorus (P) than wheat does. Base your quantities on a soil analysis; aim for a citric acid soluble phosphorus level of 30mg/kg, or a Bray 1 soluble phosphorus level of 20mg/ kg in the soil.
To achieve this, apply 4kg/ ha P for each 1mg/kg if the analysis indicates a level below 30mg/ kg (citric acid), or 6kg/ha P for each 1mg/ kg if it shows a P level below 20mg/kg (Bray 1). If it is higher than the above levels, apply P at a rate of 12kg/ha to 15kg/ ha to maintain soil fertility.
A potassium (K) deficiency is possible in a light-textured soil under irrigation. Table 1 shows how to correct the situation. A split application of K (at planting and at eight weeks after planting) can decrease the risk of lodging.
Apply nitrogen (N) at different growth stages, the first just before or during planting. Trials show that a N topdressing increases yield, especially with overhead irrigation. With improved production practices and optimal irrigation scheduling, a total N application of 140kg/ha – depending on soil texture and the rotation system – is sufficient for optimal yield and quality.
Cocktail has a genetically higher yield potential and lower kernel nitrogen content than other cultivars. As a result, it requires 20kg to 30kg N/ha more to achieve the same kernel N levels than other cultivars do. On very sandy soil, where N leaching is a problem, apply an extra 20kg/ha.
Split N applications are more important under overhead irrigation (especially centre pivots) and on sandy soil than in the case of flood irrigation and heavy clay soil.
Two-thirds of the total N application at planting and the balance six weeks after emergence seems to give the best results.
Source: Kotzé, GJ: ‘Guidelines for the production of malting barley under irrigation’, SAB Maltings, Kimberley.
For more information, phone the SA Barley Breeding Institute on 028 212 2943. Visit sabbi.org.