Thursday, 15 June 2017

Nutrient Status

Nutrient Status

A healthy soil will provide sufficient nutrients for both plants and soil organisms. It is not just dependent on having nutrients existing in the soil as chemical compounds, it also depends on access to those nutrients. Nutrients can be locked-away from plants and soil organisms because of various soil conditions. The conditions that can influence availability and accessibility of soil nutrients include: soil moisture content; soil porosity; soil conductivity; pH; temperature; and competitive demand between organisms.

Biological activity (including plant growth and development) is dependant on nutrients being readily available in the soil solution. There are 15 elements that are essential nutrients for plants. 

Common deficiencies in Victorian soils

Most soils have limiting supplies of nitrogen and phosphorus for agricultural production. Further, soils in high rainfall areas often have limiting supplies of potassium and sulphur. In some situations these deficiencies have been addressed through the application of fertiliser, in other situations these deficiencies have been intensified by farming practices where nutrients in agricultural products (eg. grain) are removed from the soil and are not replaced. Other common deficiencies include copper, zinc, boron and molybdenum. 

Other factors limiting nutrient access by plants

There can be a complex of factors in one or more parts of the soil profile that restrict access by the plant roots to nutrients. Victorian soils often limit crop access to nutrients because of limited amounts of large soil pores, restricted drainage, poor friability, undesirable quantities of salts, and toxic quantities of elements such as aluminium and boron. 

Managing nutrient supply for agricultural production

From the above it is clear that agricultural production requires careful attention to the maintenance of a reliable nutrient supply. Plant harvest rates, organic matter decline,erosion, weed competition, salinity, compaction, acidification, and fire will decrease nutrient availability. 

What can I do to improve the nutrient availability (fertility) of my soil?

1. Test your soil to check nutrient status
2. Determine and improve possible constraints to nutrient access, such as
  • pH
  • Aeration
  • Drainage
  • Compaction
  • Salinity
  • Toxicities
3. Ensure adequate organic matter in your soil
4. Use fertiliser to supply nutrients to plants as appropriate

Improving soil nutrient supply requires sampling and analysis of the soil, interpretation of analysis results, formulating a recommendation, and execution of the recommendation. The tests must reliably predict soil and plant response to an ameliorant or ameliorating practise. Some tests do this better than others, some have been proven not to do this and some are unproven.

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