Abstract:
Th e deliberate planting of fast-growing N2–fi xing 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 longterm residual benefi ts 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’ fi elds on very fi ne Kandiudalfi c
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 fi ve cropping seasons
were 161–272% or 61–103% higher when compared with continuous maize without or with N fertilizer, respectively. Long-term
postfallow eff ects on maize yield were linearly related to the amount of recycled fallow N yield. Th us, 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.
