Do Mixed‐Species Legume Fallows Provide Long‐Term Maize Yield Benefit Compared with Monoculture Legume Fallows?

The deliberate planting of fast‐growing N 2 –fixing legume monoculture species in rotation with cereal crops can be an important source of N for soil fertility replenishment. We hypothesized that mixed‐species fallows have a higher potential of giving long‐term residual benefits in terms of biomass, nutrients, and quality of residuals leading to long‐term nutrient supply to postfallow maize ( Zea mays L.) crops. To test these hypotheses, two experiments were established in farmers' fields on very fine Kandiudalfic Eutrudox soils with monoculture and mixed‐species fallows. Treatments included: sesbania [ Sesbania sesban (L.) Merr.], crotalaria ( Crotalaria grahamiana Wight and Arn.), pigeonpea [ Cajanus cajan (L.) Millsp.], siratro [ Macroptilium atropurpureum (DC.) Urb.], and calliandra ( Calliandra calothyrsus Meissn.) as monoculture‐species fallow and mixture fallows of sesbania + crotalaria, sesbania + pigeonpea, sesbania + siratro, or sesbania + calliandra compared with continuous maize cropping with or without N fertilizer, and natural weed fallow. Total aboveground biomass ranged from 4.1 to 20.5 Mg ha −1 for monoculture and 7.8 to 23.3 Mg ha −1 for mixed‐species fallows. Recyclable fallow biomass N ranged from 70 to 313 kg ha −1 and there was a positive interaction in some mixtures leading to increased N accumulation. Postfallow maize yields for fallows over five cropping seasons were 161–272% or 61–103% higher when compared with continuous maize without or with N fertilizer, respectively. Long‐term postfallow effects on maize yield were linearly related to the amount of recycled fallow N yield. Thus, choice of fallow species to mix should be primarily driven by a better risk management strategy and an increased basket of multiple products and services.