Plant growth with nutrient solutions: II. A comparison of pure sand and fresh soil as the aggregate for plant growth

Abstract

Statistical experiments have been carried out as pot cultures in the greenhouse, with sand and soil as the aggregates (nutrients being supplied to both aggregates in the form of nutrient solutions), on the growth of the two vegetables turnip and spring cabbage to the stage of maturity usual in actual practice. With full nutrients, the soil, possibly because of such factors as its nutrient reserves, its physical properties, and its capacity for retaining certain nutritional elements supplied, was superior to the sand as judged by yields of fresh and dry matter for tops and whole plants of both vegetables, and roots for the turnip, thus including the edible portion ofboth plants; the (true) root of the cabbage, however, yielded more in the sand under these conditions. Similar results were obtained even when the concentrations of the nutrients for the soil were only half those in the full nutrient solution applied to the sand, so that it may be stated that fresh soil is greatly superior to sand under equal conditions as an aggregate in the growth of vegetables with nutrient solutions.

Plant growth with nutrient solutions: III. A comparison of sand and soil as the aggregate for plant growth, using an optimum nutrient solution with the sand, and incomplete supplies of nutrients with ‘once-used‘ soil

“…The concentrations of the fertilizer elements in the nutrient solutions are given in Table 1. The proportions of minor elements present in solution A are given in the subscript of Table 1 of Woodman & Johnson (1946). Quantities of the two elements marked with an asterisk were added after the commencement of the experiment as detailed in the notes made during growth (see later).…”

“…Solution A, which was applied to the sand, was the same optimum solution as was used in a previous turnip experiment (Woodman & Johnson, 1946). The three 'once-used' soil treatments consisted of full nitrogen only as in solution A for sand, constituting treatment B, half nitrogen only (treatment C), and distilled water only (treatment D).…”

“…Plants were harvested on 15 June 1944. Just previous to harvesting, the usual measurements on the tops, greatest average diameter, and the average diameter at right angles to the greatest diameter, were made (Woodman & Johnson, 1946); similar measurements were made by calipers on the cleaned 'roots' just before these were weighed. The measurements in cm.…”

“…In Part II of this series it was pointed out that soil should possess certain advantages over the usual aggregates used in plant growth with nutrient solutions, one being that it could act as a reserve of certain fertilizing elements in virtue of the clays and humates it contained (Woodman & Johnson, 1946). This second set of experiments was designed to test out this view, the soil aggregates used being those left over from the first set of experiments detailed in Part II.…”

“…The reason for the inclusion of nitrogen in two of the three soil treatments for each crop was, of course, the fact that all nitrates are soluble, so that none could have been retained by the soil in 0-0681 NU NU NU 0-2% of ' 4 0 % formaldehyde', a n d t h e n washed free from the formaldehyde. The cultures with sand as aggregate received absolutely the same nutrients as before, the optimum one for each of t h e crops grown, turnip a n d spring cabbage; thus t h e sand treatments were exactly t h e same as A a n d E described in t h e previous communication (Woodman & Johnson, 1946). The soil cultures t h a t in t h e first set of experiments h a d received these optimum solutions, B a n d F , now received distilled water containing full optimum nitrogen only; those soils in treatment C and G, which had previously received the major elements a t half the optimum concentrations, now received distilled water plus half t h e optimum concentration of nitrogen only; while those soils in treatments D and H t h a t h a d formerly received t h e major nutrients a t half t h e optimum concentrations, b u t the nitrogen a t full, now received distilled water only.…”