Monitoring Nutrient Status
Field Observations
Field observations for symptoms of nutrient deficiencies provide important clues as to whether plants are suffering nutrient stress. Symptoms usually include chlorosis, stunted growth of shoots, necrosis of leaf margins, irregular fruit set, and small berries. The position or age of symptomatic leaves on a given plant provides information about which nutrient might be causing the deficiency symptoms. Generally, deficiencies of the mobile elements such as nitrogen, potassium, and magnesium appear on older or mid-shoot leaves (Table 11.1). Deficiency symptoms of some of the less mobile trace elements, notably iron and zinc, first appear on the youngest leaves of the shoot. Finally, the particular pattern of symptoms on individual leaves can also yield information. For example, interveinal chlorosis is symptomatic of zinc deficiency. However, it is possible to be misled by foliar disorders because some are not nutritional in origin but the result of herbicide toxicity or insect infestation.
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