Effects of mulching, N-fertilization and intercropping with Desmodium uncinatum on Striga hermonthica infestation in maize

The parasitic weed Striga hermonthica is a major constraint to maize production in sub-Saharan Africa and causes serious food insecurity. We discovered serendipitously an effective control method for the weed that involves intercropping cereals with the fodder legume, silverleaf desmodium, Desmodium uncinatum (Jacq.) DC., through mechanisms that involve soil shading and nitrogen fixation. In the current study we investigated long-term effects of inorganic nitrogen (N), mulching and D. uncinatum, singly and in combinations, on S. hermonthica infestation, maize plant growth and grain yields. Treatments comprised sole maize with and without 120 kg N/ha; sole maize plots covered with maize straw (i.e. mulching), with and without N; and maize–D. uncinatum intercrop, with and without N. Intercropping maize with D. uncinatum gave the most significant suppression of S. hermonthica, with addition of N only minimally enhancing its effect. Similarly, mulching significantly suppressed S. hermonthica, although to a much less extent. Application of N both to sole maize and mulched plots reduced seasonal S. hermonthica infestations but the effect was largely insignificant. The effect of D. uncinatum was again notable as it dramatically increased maize plant height and grain yields, with the addition of N only minimally improving both effects. Application of N and mulch, singly and in combination, to the sole maize crop generally enhanced plant height and grain yields, although to a less extent, with the effect of N on grain yields being statistically insignificant during most of the cropping seasons. These results confirm the efficacy of D. uncinatum in S. hermonthica suppression leading to better growth and yields of maize. The effects of N application, mulching and a combination of both treatments in S. hermonthica control in maize were also observed, although these effects were much weaker. The results and their implications are discussed in the context of smallholder cropping systems in the region.

► We investigated effects of mulching, N and desmodium on striga infestation.
► Desmodium dramatically suppressed striga and significantly improved grain yields.
► Mulching suppressed striga but the effect was weaker.
► N had insignificant effect on striga but marginally improved maize grain yields.
► Minimal synergistic effect of N was only observable with mulching.