Does Lupinus angustifolius L. need sulfur fertilization under central European conditions?

In order to answer the question of whether narrow‐leaf lupin (Lupinus angustifolius L.) needs sulfur (S) fertilization under central European conditions, field trials were carried out at several sites in Germany on long‐term (> 10 years) organically cultivated arable land from 2012 to 2014. The effect of S‐containing fertilizers kieserite, gypsum, epsom salt, and elemental sulfur on S accumulation, yield, yield structure, and nitrogen (N) accumulation in narrow leaf lupin as well as the recovery of fertilized S was investigated. Under the given conditions, the fertilization did not influence seed yields. The S accumulation in shoots ranged from 11.8 kg ha^?1 to 14.1 kg ha^?1. The bulk of the absorbed S was accumulated in the straw (average S harvest index: 0.40). The N : S ratio in the youngest open leaf at BBCH 60–65 was about 20 and the corresponding S concentration was 0.24% in the leaf dry mass. The apparent recovery efficiency of S (RE) of kieserite, gypsum, and epsom salt, whose S form is generally plant‐available, was low with 4.0%, –2.1%, and 6.6%, respectively. The S requirement of the lupin was obviously completely filled by plant‐available S from the soil as well as atmospheric S deposition in all tested environments. Application of kieserite, gypsum, and epsom salt resulted in a partially significant increase in S concentration of seeds and straw, and also partly significantly narrowed the N : S ratios in the plants but did not increase yield. Application of elemental S did not lead to an increase in plant S concentration in the year of application.