MAINTAINING FERTILITY 
Plant growth and appearance are good guides to fertilizer requirements. Monthly soil testing likewise 
is a valuable aid. A combination of the two is the best thing available in controlling the fertilizing 
program. 
Soil tests (Spurway) should show about 15 to 25 p.p.m. nitrate nitrogen; 5 to 10 p.p.m. phosphorus; 
20 to 40 p.p.m. potassium, and around 200 p.p.m. calcium. To increase the nitrate level, fertilize with 
sulfate of ammonia at the rate of 1 pound per 100 square feet. Frequently the original incorporation of 
superphosphate in the soil before benching is adequate to maintain phosphorus levels for the season. 
If not, superphosphate can be applied in a supplementary way at the rate of 3 to 5 pounds per 100 
square feet. To raise the potassium level, muriate of potash can be applied at the rate of 1 pound 
per 100 square feet. To raise the calcium level, gypsum (calcium sulfate) can be applied at the rate 
of 2 to 3 pounds per 100 square feet. 
As a practical expedient growers may find it desirable to use complete fertilizers instead of the single- 
element fertilizers mentioned in the foregoing. These can be obtained in different combinations and 
applied dry or as liquid feedings. Liquid feeding is increasing in use because of the laborsaving in 
application, plus more even distribution. 
Frequent light feedings are safer and preferable to heavier feedings spaced farther apart. 
Remember also that plant requirements are less during the slow-growing dark winter months than dur- 
ing the periods of rapid growth in spring and fall. In the summer months growth may be rapid, but 
the high soil temperatures cause speedy breakdown of organic matter in the soil, releasing considerable 
amounts of nitrogen in this process. Thus excess fertility, particularly nitrogen, can occur at that season. 
However, recent experiences have indicated that a program of liberal feeding, accompanied by liberal 
watering during the summer months is advisable from the standpoint of maintaining active growth and 
keeping the plants vegetative. In timing fertilizer applications, allow for two or three week’s lag between 
application and the beginning of response in the plants. 
It has been reported that Patrician carnations had less splits when nitrates were 100 to 140 p.p.m. This 
reduction of splits by high nitrates is interpreted as being due to a more uniform nitrate level, rather 
than high level itself. 
Excess fertility is not uncommon. When plants stand still, show no new root action and appear yellowish 
and stunted, excess soil fertility is a likely cause. Leaching is the corrective measure. We recommend 
(1) a normal watering so that water just drips through the bottom of the bench, followed three or four 
hours later by two or three extremely heavy waterings that bring the water streaming through the 
bench bottoms. 
SOLUBLE SALTS 
Soluble salts are chemical compounds consisting of an acid part or ion and a basic part or ion. For 
example, common table salt, sodium chloride, consists of one ion of chloride and one of sodium. Chloride 
is an acid forming ion and sodium a basic or alkali forming ion. The two combine in chemically equi- 
valent quantities to form a neutral salt. Other common acidic ions are sulfate, nitrate, bicarbonate, and 
phosphate. Other common basic ions are calcium, magnesium, potassium and ammonium. Any basic ion 
may combine with any acidic ion giving rise to a great variety of salts. 
All plant nutrients which are absorbed by plants from the soil or from culture solutions are absorbed 
in the form of salts or their constituent ions. All organic materials become “Mineralized” through decay 
processes and the nutrients in them are converted into salts before being absorbed by plants. Some 
salts contain plant nutrients and are beneficial in the small quantities required for plant growth, Others 
contain no nutrients. All salts are harmful beyond the small quantity required for plant growth. A little 
is bad, more is worse, up to the point where plants will be killed. Salts are found in most water and 
are applied as fertilizer. Improper watering may permit a concentration into the harmful range. 
Instruments called Wheatstone’s bridges are available which measure total soluble salts in terms of elec- 
trical conductivity or conductance. Many laboratories of the Agricultural Extension Service are equipped 
with Solubridge instruments for use in assisting with soluble salt problems. 
It has been found that when planting rooted cuttings, the Solubridge readings should not be higher than 
40 while established plants do not withstand readings of 100 without showing some harmful effects. To 
remedy excess soluble salts apply two to three gallons of water per square foot and leach out this high 
salt content. 
