The subirrigation system consisted of perforated plastic pipe 16 inches apart placed lengthwise of the plant bed under the soil surface. Pipes were connected to a sunken tank with water-level controlled by a float mechanism. A non-perforated transparent plastic cover was used to protect the plants from low temperatures. Five fertilizer treatments replicated four times were applied. Two of the treatments were different rates of a formulation containing all organic nitrogen, two treatments were different rates of a formulation containing all inorganic nitrogen and one treatment had N-P-K supplied by ammonium polyphosphate and potassium nitrate. Maximum plant density was obtained with ammonium polyphosphate and potassium nitrate. Poor germination occurred with the higher rates of fertilizer due to excessive soluble salts. A pipe depth of 6 inches produced the highest percent stand for this particular soil (Norfolk loamy fine sand). This depth is in agreement with capillary rise data taken from air-dry soil samples placed in glass columns with the Iower end in water.

(Full article published with kind permission from "Tobacco International")