Nitrogênio, cloro, cálcio, ferro, arsênio, mercúrio e chumbo em Steiner (2007)

There is a saying you will often find repeated in agricultural literature, in many variations. No doubt it arises from the experiences which they believe they have collected. It is to this effect: “Nitrogen, phosphoric acid, calcium, potash, chlorine, etc., even iron — all these are essential in the soil if plant-growth is to prosper there. Silicic acid, on the other hand, lead, arsenic, mercury” — and they even include soda in this category — “have for plant-life at most the value of stimulants or irritants. One may stimulate the plants with them, but that is all.” In this very statement, the men of to-day betray the fact that they are really groping about in the dark. It is a very good thing — as a result of tradition, no doubt — that they do not treat the plants as madly as they would do if they really followed this proposition. It is, as a matter of fast, impossible to do so. (Steiner 2007:44)

STEINER, Rudolf. 2007. The Agriculture Course. (Trans.: George Adams) Shrewsbury: Wilding & Son Ltd.