Peter King, Consultant
August 2005

Using tissue analysis to assist farmers with nutrient decisions

Crop plants search different horizons for nutrients as the season develops. Initially the surface soil is damp and the roots are confined to top layers. Later the roots access deeper, usually more alkaline horizons with very different levels of the essential nutrients.

Uptake of nutrients also varies with the crop genotype and at various growth stages.
Early testing of leaf tissue and later of the grain provides complementary data relating to these different situations.

Zinc
Crops with adequate zinc early may show deficiency later in the season as top soils dry and roots explore the deeper soil horizons.

Early testing also reveals the impacts of herbicides. The groups B's (Ally, Logran Glean etc) have a major effect on zinc nutrition.

Crops in alkaline soils may be deficient from early growth stages and show visible symptoms and large growth responses to applied zinc.

Copper
Particularly on Eyre Peninsula and in the South East copper deficiency is still common. It is the most debilitating of deficiencies robbing large amounts of yield.

Testing at tillering may detect this deficiency, but more commonly grain tests show the problem areas of the farm. Remedial action is then made to the areas in subsequent crops and testing can be is continued to follow the effects of copper dressings.

Phosphorus
Both leaf tissue and grain testing reveal different scenes. Deficiency can be detected early and both deficiency and luxury consumption can be detected by analysing the grain.

Some farmers have been able to reduce phosphorus application to reduce wasteful exportation of P from the farm.

Sulphur
Sulphur deficiency occurs widely in Australia and is increasing. Recently the use of extra nitrogen on crops has led to increased sulphur requirements.

Both tissue and grain testing has helped farmers develop responses to deficiency and to make applications of this nutrient.

New crops like canola have high requirements for this nutrient.

Toxicity
Tissue and grain tests allow traces on the effects of salt, boron and other potentially harmful substances in the soil.

Systematic testing
Some farmers have developed a data bank of nutrition for their farms and have been able to trace the effects of adding the nutrients over time and to regulate the application of them.

Regional strategies
Coordinated examination of data across a region can point to areas of concern with nutrition and enable experts to pinpoint problems and to develop local strategies and emphases.

Nutrient audits
Australian farms export all their products and it is imperative to follow the movement of nutrients on and off the farm. Unfortunately many nutrients s are mined by crops and never replaced and their unseen cost never considered.

Human health issues
Grain nutrient content can be manipulated to approach the needs of humans. Zinc, iron, iodine and selenium are crucial elements needing attention in the world population buying our products. Farmers can set their sights on lifting their products to international (WHO) standards through growing more efficient varieties and by supplementary fertilisation. With time the world will pay more for top quality products.