The effect of soil conditions and treatment on yields of tubers and sugar from the American artichoke (Helianthus tuberosus)

Tuber yields of Improved White artichokes at New Brunswick, N.J., were greatly affected by soil texture, presumably through the soil moisture relations during the critical period of tuber formation between August 15 and October 15. Loams were distinctly superior to light sandy loams in dry seasons, whereas sandy loams were superior to heavier types in abnormally wet years. Yields of 8 to 10 tons of artichoke tubers per acre may be anticipated on strong sandy loam soils or loams in fine tilth in normal years, with a maximum of about 15 tons. The total hexose sugar (largely levulose) content obtained on acid hydrolysis of tubers ranged from 14.6% in a moist year to 19.3% in the driest season. A large part of the fluctuations in sugar content in a single year is due to variations in moisture percentage of the fresh tubers. The moisture content of tubers is higher when the soil moisture capacity is higher and vice versa. The extent of normal fluctuation in tuber moisture with changes in soil moisture at specific 10-cations was not determined. On a light sandy loam having a pH of 5.9 and relatively low organic matter content, lime and 6-8-4 fertilizer increased tuber yields 39.8% over lime alone and 46.6% over untreated plats; and 8-8-6 fertilizer alone increased yields 43.7% above untreated plats. These were the two most profitable fertilizers, assuming the tubers to have a value of $10.00 per ton. Increasing the amount of fertilizer from 500 pounds to 1,000 pounds per acre did not increase yields in the test period, indicating a much smaller requirement for plant nutrients than for white potatoes. Total yields of hexose sugars per acre were greatest with lime and 6-8-4 or 4-8-2 fertilizers, or with 8-8-6 fertilizer alone. Acre yields of hexose sugar ranging from 2,500 tO 3,300 pounds are indicated as average yields in normal seasons on suitable soils.