Before you assume the plant has a nutrient deficiency, make sure theproblem is not due to other causes. Examine the plant leaves, and along the stem and in the soil.
Even under the bestconditions, not all leaves form perfectly or remain perfectly green. Small leaves that grew on the young seedlingnormally die within a month or two. Under artificial lights, bottom leaves may be shielded from the light,or be too far away from the light to carry on chlorosynthesis. These leaves will gradually turn pale oryellow, and may form brown areas as they die. However, healthy large leaves should remain green at least three to fourfeet below the plant tops, even on those plants under small light systems. Under low light, the lower-growing shoots aswell as the large leaves on the main stem are affected. Some symptoms of nutrient deficiencies beginfirst at the bottom of the plant, but these symptoms generally affect the lowerleaves on the main stem first, and the progress to the leaves on the branches.
Although somedeficiency symptoms start on the lower, older leaves, others start at thegrowing shoots or at the top of the plants. This difference depends on whether or not the nutrient is mobile and canmove from the older leaves to the active growing shoot. Deficiency symptoms of mobile nutrients startat the bottom of the plant. Conversely,deficiency symptoms of immobile nutrients first appear on the younger leaves orgrowing shoots at the top of the plant. N, P, K, Mg, B, and Mb are mobile in the plant. Mn and Zn are less mobile, and Ca, S, Fe, andCu are generally immobile.
A dry atmosphere or wetsoil may cause the blade tips to turn brown. Brown leaf tips also may indicate a nutrient deficiency, but in thiscase, more tissue will turn brown than just the end tips.
Chlorosis and necrosisare two terms which describe symptoms of disease in plants. Chlorosis means lacking green(chlorophyll). Chlorotic leaves are palegreen to yellow or white. Chloroticleaves often show some recovery after the necessary nutrient is supplied. Necrosis means that the tissue is dead. Dead tissue can be gold, rust, brown, orgrey. It is dry and crumbles whensqueezed. Necrotic tissue cannotrecover.
Symptoms of deficiencies of either N, P, or K have the following in common: all involvesome yellowing and necrosis of the lower leaves, and all are accompanied byred/purple colour in stems and petioles. The simplest way to remedy these deficiencies is to fertilise with acomplete fertiliser containing nearly equal proportions of three nutrients.