Sulphur demand, accumulation and fertilization of Pisum sativum L. in pure and mixed stands with Hordeum vulgare L. under field conditions

With the aim of gaining a better understanding of the Sulphur (S) supply of pea (Pisum sativum L.) in pure stands and in mixed stands with barley (Hordeum vulgare L.), field trials were conducted at several sites in central Europe. The fertilizers gypsum, kieserite, elemental S (40 kg S ha(-1)) and the foliar fertilizer epsom salt (8.4 kg S ha(-1)) have been tested on long-term (> 10 years) organically cultivated arable land in the years 2012 to 2014. The objectives of this study were to evaluate pea's capacity to acquire sulphur as a sole crop and as intercrop with barley. The present investigations suggest that S supply via the pedosphere and the atmosphere was obviously high enough for adequate S concentrations in the pea plants and therefore compensated the barleys competition for plant available S in the mixed stands. The study showed that pea and barley adjusted its S accumulation to its yield formation. Although the fertilization with gypsum and kieserite significantly increased S concentrations and narrowed the N:S ratios in pea, the yield did not rise significantly. An average N:S ratio in pea leaves at flowering of 15.6 and a corresponding S concentration of 0.29% in DM seemed to be adequate to cover the S requirement of pea. The sulphur harvest index (SHI) averaged 0.63 and has not been influenced by the cropping system (sole or mixed crop). The fertilizers gypsum, kieserite and epsom salt showed effects on S concentration in the pea plant, elemental S did not. The apparent recovery efficiency of S of gypsum, kieserite, epsom salt and elemental S was low with 5.7%, 4.5%, 8.2% and 0.1%. In summary, S fertilization does not currently appear to be necessary for pea seed yield level up to 4.1 Mg ha(-1) under the tested environmental conditions.