LAUSR

Abstract Relay strip intercropping systems have the advantage of increasing land yield, but there are few studies on how pre-crops affect the grain yield and phosphorus (P) use of subsequent crops in such systems. Field experiments were carried out for four consecutive years, covering two complete cycles of the crop sequence, to evaluate the effects of pre-crops on crop yield, P uptake, and topsoil P balance of maize and wheat. Three pre-crops were used, i.e. fallow, pea, and rutabaga planted with two P levels with (+P) and without (0P) P fertilizer applied to maize and/or the wheat season. Pea significantly improved grain yield in cycle 1 and grain yield, biomass and P uptake of subsequently grown maize in cycle 2, compared with fallow, and P fertilizer application had no effect on maize yield, P uptake and above-ground biomass in cycle 1, but significantly improved yield and P uptake in cycle 2. Regarding the subsequently grown wheat, on average, pea significantly increased the wheat average yield by 11.57 % and 4.27 % under the 0P and + P treatment, respectively; and rutabaga had 5.22 % and 6.40 % higher wheat average yield than under the same conditions of fallow. Pea prominently improved the above-ground biomass, P uptake; soil Olsen-P in the 0–20-cm soil profile, and the inorganic Pi fraction concentration after two consecutive cycles, with a significant positive correlation between Olsen-P and most Pi fractions. Rutabaga prominently improved above-ground biomass and P uptake. The above parameters performed better under pea than rutabaga. P fertilizer application during the maize season barely affected the growth or P uptake of subsequently grown wheat, P applied during the wheat season, however, significantly enhanced agronomic traits and P uptake, and this effect was more pronounced under pea. We therefore conclude that pea as pre-crop is instrumental for subsequent maize and wheat production, and provides more benefits for farmers.