To maximise the return from of expensive fertiliser (N, P, K & S) it is essential to assess the risk of a crop trace element deficiency. Trace elements are required in small amounts but never the less essential to maximise crop yield and quality. Identify the risk of a trace element deficiency using soil analysis (Teagasc, S4 test), experience of previous crops, field history, and knowledge of soil properties such as pH, soil type and organic content.
Copper has a major function in grain / ear fertility and deficiency symptoms can go unnoticed and result in a yield reduction. Cereal crops will take of in the region of 80grams/ha of copper. Copper deficiency symptoms can go unnoticed; symptoms associated with a server deficiency are leaf twisting and white leaf tipping and tend to appear in the youngest leaf. Copper deficiency may be due to low soil availability or low total soil copper and is problematic on light, acidic soils, low soil organic matter, granite parent materials and dry soil conditions. Cereal crops grown on soils with < 3 mg/l will require a foliar copper application.
Manganese is the most widespread trace element deficiency in Ireland and is due to a number of factors from deficient soils to low availability aggravated by poor soil conditions, low soil temp / moisture etc. Manganese availability is largely influenced by soil pH and soils recently limed can result in a manganese deficiency. Poor seedbed conditions and poorly consolidated seedbeds will result in poor root / soil contact resulting in a manganese deficiency. Research work has show yield responses up to 20% from the application of manganese to barley and 7% yield increase in wheat on deficient sites. Foliar manganese applications are required to treat crops on deficient soils. Where crop leaf area is small there will be a small transfer of foliar manganese into the plant therefore repeated applications are required for efficient plant uptake. Crops will take off in the region of 500 – 1,000 grams/ha of manganese. Soils with < 90mg/l ER manganese and high soil pH will possibly be manganese deficient and require treatment.
Zinc has a major role to play in fertility, seed formation, plant growth and defence against diseases. A cereal crop will remove in the region of 200 grams/ha annually. Zinc deficiency is a major problem is many parts of the cereal growing areas in Ireland . Zinc deficiency is problematic on continuous tillage soils and soils with elevated levels of soil phosphorus. Plant symptoms are very distinctive, in cereals zinc deficiency generally shows up in the early stages of growth, when the plant is only a few inches high, appearing first as yellow streaks in the young leaves with a white to yellowish tip. White spots often appear in the leaves or along the edges and a portion of the marginal area my die. Frequently the entire plant is stunted, due to shortening of the internodes. Cereal crops grown on soils with < 2 mg/l will require a foliar zinc application.
Treating Trace element Deficiencies
There is a wide range of trace element products available see Teagasc Crop Report appendix 7 for details. Generally all available products applied as per product recommendation (check product compatibility with other agri – chemicals) will meet crop seasonal requirements. More importantly is early identification and treatment of a trace element deficiency. This is essential to reduce any reduction in grain yield therefore a little and often approach is often best .