Early season fertility: Beware of ‘hidden hunger’

Plants need 17 essential elements for growth and reproduction. The main criterion used in designating an element as essential is that it must be required for a plant to complete its life cycle. Elements were accepted into the ‘essentiality’ clique at different times based on when somebody proved they had met the aforementioned criterion. For example, nitrogen was accepted as an essential element in 1804. The newest addition to the family is nickel, determined to be essential in 1987. Crop yield and quality are reduced when plants don’t take up these nutrients in sufficient amounts.

There are 3 ways of diagnosing nutrient deficiencies – soil testing, plant tissue analysis, and visual observation of the plant.  Soil testing and plant tissue analysis are quantitative tests that compare nutrient concentrations in soil or plant to the sufficiency range for a particular crop. Visual observation, on the other hand, is a qualitative assessment of indicators such as specific leaf symptoms or stunted growth. Plants can show visual signs when there is a nutrient deficiency. But sometimes they don’t. ‘Hidden hunger’ is a term used to describe a situation in which a crop needs more of a given nutrient but shows no obvious deficiency symptoms. Hidden hunger can only be picked up by tissue or soil testing. If and when visual symptoms do appear, crop yield and quality will already have been reduced and corrective actions may not be effective. If detected early, hidden hunger can be corrected by foliar application of the insufficient nutrient. Foliar feeding normally elicits a quick response from the plant and is particularly advantageous where soil conditions keep nutrients in inaccessible forms.

As seeds become seedlings, it is important to keep the possibility of hidden hunger in mind. One nutrient that is vital at this stage of crop growth is phosphorus (P). Seedlings rely heavily on the P taken up in the first few weeks of growth for crop establishment and yield. Early season limitations in P availability can go undiagnosed but will result in consequences from which the plant will not recover, even when P supply is increased to adequate levels later in the season.

Most soils in the Prairies are low in plant-available P because their high pH and calcareous nature favour the tie-up of P in insoluble compounds. Under this condition, P use will be most efficient when soil contact with fertilizer is minimized by placing the P in a band in or near the seed-row. This allows roots to access and utilize the nutrient soon after emergence. In addition, biologicals containing microbes such as Penicillium bilaii will increase the phytoavailability of P in this kind of soils. Your SynergyAG rep can provide you with a low salt index phosphorus source, as well as natural products that solubilize P from soils.

-Ikenna Mbakwe, PhD, PAg
Head of Research
SynergyAG

 

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