DOC trial: yields from arable crops treated with halved and commonly used applications of fertiliser, 1992 to 2005

In the DOC trial in Therwil (Canton of Basel, Switzerland), organic and conventional farming systems have been run for 30 years, differing mainly in fertilisation and plant protection. Three systems are being compared – bio-dynamic (D), bio-organic (O) and conventional (K) – as well as two supplementary variants: conventional with mineral fertiliser only (M) and no fertiliser (D0). Since the trial started in 1978, D, O and K plots have been divided into a commonly used fertiliser-application level (2) and a halved fertiliser-application level (1). The yields from potatoes, winter wheat and clover grass (1992 to 2005) and from silage maize and soya (1999 to 2005) were recorded in a seven-year crop rotation. The results showed that the organic systems D2 and O2 treated with commonly used applications of fertiliser achieved average yields of 82 % by comparison with conventional farming method (K2). In the organic systems D1 and O1 with halved fertiliser use, 74 % of the yields of K2 were measured on average, 90 % in the case of K1. An average yield of 50 % compared with K2 was still obtained in the bio-dynamic system D0 with no fertiliser use, corresponding roughly to the natural nutrient delivery potential of the loess soil in the DOC trial. In the average of all crops, the yields with the halved amount of fertiliser in D1 and O1 increased by 32 %, in K1 by 40 %. With the fertiliser applications in common use the increase in yield was still around 10 % in the three systems D2, O2, K2. The least differences in yield between the fertiliser-application levels were 4 to 7 % for winter wheat; the greatest were 17 to 20 % for potatoes.