Der Einfluß des NO3 : NH4 ‐Verhältnisses in der Nährlösung auf Ertrag und Gehalte an organischen und anorganischen Ionen von Tomatenpflanzen

Abstract

The influence of the relation between NO3 and NH4 in the nutrient solution on yield and organic and inorganic ion contents of tomato plants..Tomato plants were grown in aerated media of oppositly varying supply of (NH4)2SO4‐and NaNO3 with a constant N‐quantity of 15 meq/1 or a quantity of NH4‐, NO3 or (NO3 + NH4) increasing from 3 to 30 meq.N/1. Yield and ion content were determined.A maximum yield was achieved by a mixed N‐supply i.e. 4 to 5 parts NO3, 1 part NH4‐N and 7, 5 meq N/l. The “(C‐A) value” was calculated by the content of the cationions “C” (=K+ + Na+ + Ca++ + Mg++ + NH4+) and the inorganic anions “A” (= NO3− + Cl− + H2PO4− + SO4–). The “(C‐A)” value is equivalent to the content of the organic anions. Furthermore we determined the citrate, malate, oxalate, and pektinate content. These make up 60–80% of the (C‐A) value.The NO3‐ and K content increase considerably, the Ca‐, Mg‐, Na‐, Citrate, Malate and Oxalate content increase less pronounced, the Cl‐, H2PO4‐ and SO4‐ content decrease as the NO3 content increases from 0–80%.If the medium contains 80–100% NO3 ‐ N, the NO3 and K content remain almost constant, while the Ca‐, Mg‐, citrate, malate and oxalate content especially increase in this case.The K content decreases in the presence of a high (NH4)2SO4 supply. Parallel to this the value (C‐A) decreases greatly, so that it is less than the sum of the determined organic anions. In this case the content of organic anions obviously does not correlate with the (C‐A) value. The yield correlates with the carboxylate contents. (C‐A) values of 150–170 mval/100 gm. d. m. cause a lowering of the yield.The plants contain an almost equal amount of citrate, malate and oxalate. Depending on the N‐concentration of the medium, the malate content will be a bit more than the amount of citrate in case of maximum yield.If there is a lack or toxicity in the medium the citrate content will be higher than the malate content. The yield per dry weight correlates positivly with the quotients of citrate and malate.