Ridge-furrow with film-mulching and phosphorus fertilizer application enhances maize-soybean intercropping productivity by synergizing phosphorus acquisition strategies in rainfed acidic soil

: Maize-soybean intercropping is widely adopted by farmers in rainfed areas in southern China where crop productivity is constrained by low soil phosphorus (P) availability and seasonal drought. Adaptive crop management practices are essential for the improvement of seed yield and land-use efficiency. We firstly applied a ridge-furrow with film mulching (RFM) to a rainfed maize-soybean intercropping system in karst acidic soils, while its combination effects with three (0, 45 and 90 kg P ha -1 ) P-application rates on seed yield, P uptake, soil P fractions and root morphological and physiological traits were investigated for consecutive four years in southwest China. There were 12 treatments combinations: maize and soybean monocultures (M), maize-soybean intercropping with RFM and ridge-furrow (RF) under three P-application rates. The results showed averaged maize and soybean seed yields and land-equivalent ratio with RFM were 51%, 17%, and 29% higher than those under RF, which was explained by the significantly increases of biomass (averaged 53% for soybean and 37% for maize) and P uptake (averaged 57% for soybean and 54% for maize) with RFM. The root length, surface area and rhizosheath carboxylates amount with RFM were averaged 31%, 56%, and 36% higher than those with RF across all treatment combinations. The RFM significantly increase plant-available soil P concentration (averaged 44%) while reduced the inorganic-P concentration (averaged 9%) in rhizosheath soil. We conclude the combination of RFM and P application is a promising practice to achieve high yield and land-use efficiency by conquering the combinations of low soil P concentration and seasonal drought in rainfed intercropping systems, which was associated with enhanced P-scavenging and P-mining strategies that promoted P uptake and biomass accumulation. Our results provided insights into the soil P transformation by enhancing P-acquisition strategies induced by RFM to achieve high crop yield and land-use efficiency in intercropping systems in acidic soil.