Abstract:
Coffee plants (Coffea arabica L.) were grown in nutrient solutions for the purpose of studying deficiency symptoms of the following elements : nitrogen, phosphorus, potassium, magnesium, calcium, sulphur and iron. The methods employed in the growing of coffee plants in the nutrient solutions are described. After preliminary tests with several nutrient solutions Hoagland's formula was selected as most suitable for the present tests. However, the quantity of phosphate employed in the basic nutrient solution was reduced to one third of that given in Hoagland's formula. This reduction in phosphate was made because of the previous results obtained by Jacob which seemed to indicate that the coffee plant requires only very small amounts of phosphorus. In the present tests phosphorus deficiency symptoms were obtained and these results suggest that Jacob's failure to obtain phosphorus deficiency symptoms may be ascribed to use of Shive's solution, which has a very high phosphate content. While growing in this complete nutrient solution his plants may have stored enough phosphorus to supply their needs later when they were transferred to the solution lacking this element. In the course of the present investigation it was found that in the nutrient solutions containing KH2PO4 and having a pH higher than 5.5, the coffee plant absorbs insufficient iron. This difficulty of iron absorption by the coffee plants grown in nutrient solution was overcome by a technique previously described that is, when iron deficiency symptoms appeared on plants being tested for other deficiencies the nutrient solution was changed and the new solution used contained no phosphate. The plants were allowed to grow in this solution for two to four days and then the phosphate was added. In this way the plants absorbed sufficient iron for their requirements. The present paper describes and the color plates illustrate the symptoms on coffee plants that were associated, in the present studies, with nutrient solutions deficient in the various elements listed.
