Striga hermonthica infestation causes significant losses of maize yield in the Nigerian savannas and several technologies have been developed and promoted to control Striga in maize. However, since no single technology has been found to be effective against Striga, integrated management is needed to achieve satisfactory and sustainable Striga control. Both on-station and on-farm trials were undertaken from 2013 to 2015 in Bauchi and Kano States of Nigeria to evaluate the performance of integrated Striga control technologies. In the on-station trials, a soybean–maize rotation did not suppress Striga in maize in either location. However, nitrogen application suppressed and reduced Striga infection, except in Bauchi in 2014. The soybean–maize rotation accompanied by N application reduced Striga damage in both locations. On farmers’ fields, rotating soybean with maize significantly reduced Striga infection. At the same time, the use of maize varieties with a combined tolerance to drought and resistance to Striga parasitism also increased maize grain yield on farmers’ fields, probably due to three factors: a reduction in Striga infection, reduced effects of a mid-season moisture deficit, and increased uptake of nutrients from the soil. We concluded that the use of Striga-resistant maize varieties in combination with the application of N fertilizer and rotation with soybean could increase the productivity of maize in Striga-infested fields in the Nigerian savannas.

Amendment of recalcitrant organic materials with high carbon/nitrogen (C/N)-ratio may improve and maintain soil labile C for a longer period, thus enhancing the productivity of soils with low fertility; however, immobilization of N may affect the plant growth negatively. To reduce the negative impacts, recalcitrant organic materials can be pre-incubated with N-rich sources or applied in combination with fertilizers. The current study evaluated sawdust biochar (BC) and pre-incubated cattle manure–sawdust mixture (CS) amendments with synthetic fertilizers in improving soil carbon pool, soil fertility and maize (Zea mays L.) yield on a tropical Alfisol. Four treatments: control, site-specific fertilizer (SSF), site-specific fertilizer with sawdust biochar (BC + SSF) or pre-incubated cattle manure-sawdust mixture (CS + SSF), were evaluated for two seasons with maize. The residual effect was evaluated in the third season. During the year of active C application, lability index, C management index and potentially mineralizable N were significantly greater in CS + SSF than BC + SSF treatment. However, the same indices measured in the third season with no further application of amendments were significantly greater in BC + SSF than in CS + SSF treatment, indicating an increase in more recalcitrant C pool with BC amendment. Application of organic amendments improved soil fertility parameters compared with the application of fertilizer alone. Maize yield was significantly increased by fertilizer, with or without organic amendments; with significantly greater yield in BC + SSF than other treatments. Results suggest that soil amendment with BC had greater potential to improve the soil carbon pool and maintain labile carbon for a longer period than a pre-incubated CS.

Weed control is one of the most important practices for a satisfying crop performance. In organic farming, weeds are mainly controlled by using mechanical methods, which may result in incomplete crop selectivity. Maize is one of the crops for which mechanical weed control is commonly applied. To assess weed control efficacy and the possible crop injuries caused by mechanical interventions (harrowing, hoeing and ridging), a field experiment was carried out in 2013–2014 on traditional flint Italian varieties of maize (Marano, Ottofile, Pignoletto, Nostrano and the hybrid Maranello) suited for organic food production. The study included the following treatments: weed control with a spring tine harrow + hoeing and ridging (STH), manual weed removal all season long (MWR), spring tine harrowing + manual weed removal (STH + MWR) and an untreated check (CHK). In the 2 years, the experiment was carried out in two similar fields in which 60 plots (6 × 10 m) were arranged in a RCBD with three replications. Weed control efficacy was assessed by determining weed density, weed species composition and weed cover after each mechanical intervention in the STH and CHK plots. Weed diversity indices were also calculated at the final assessment. The possible crop injuries caused by mechanical means were assessed by determining maize plant height, number of leaves, and plant density after each mechanical intervention. At maturity, maize yield and other yield-related traits (1000-seed weight, hectolitre weight, and grain moisture) were determined. The results showed that the mechanical treatments lowered the weed infestation, without changing weed species dominance and slightly lowering species richness; even though they were not able to completely control the weeds. In both years, the final weed density in STH plots was of about 50 plants m−2. Better weed control was obtained when weeds were at early growth stages and with a repeated number of harrowing. Mechanical weeding did not cause significant injury in terms of plant height nor density; however, for Marano and Maranello, a delay in the crop cycle was observed as shown by the lower number of leaves in STH compared with MWR. Yield ranged from 0.3 t ha−1 for Marano CHK to 10.4 t ha−1 for the hybrid Maranello in MWR + STH. Yield and yield-related traits were not affected by mechanical weeding.

Conservation agriculture (CA) systems are based upon minimal soil disturbance; crop residue retention and crop rotation and/or intercrop association are increasingly seen to recycle nutrients, increase yield and reduce production costs. This study examines the effects of CA practices on crop productivity, profitability and soil quality under the conditions encountered by smallholder farmers in two farming communities from 2005 to 2011 in Malawi, as part of the contribution to remedy a lack of supporting agronomic research for these relatively new systems. The drier agroenvironment of Lemu of Bazale Extension Planning Area (EPA) is characterized by sandy clay loam soils and lower rainfall. Here, CA showed positive benefits on maize yield after the first season of experimentation, with highest increases of 2.7 Mg ha−1 and 2.3 Mg ha−1 more yield in CA monocrop maize and CA maize–legume intercrop, respectively, than the conventional tillage in the driest season of 2009/10. In the high rainfall environment of Zidyana EPA (characterized by sandy loam soils), substantial maize yield benefits resulted in the fifth season of experimentation. Farmers spent at most 50 days ha−1 (US$140) producing maize under CA systems compared with 62 days ha−1(US$176) spent under conventional tillage practices. In Lemu, both CA systems resulted in gross margins three times higher than that of the conventional control plot, while in Zidyana, CA monocrop maize and CA maize–legume intercrop resulted in 33 and 23% higher gross margins, respectively, than conventional tillage. In Zidyana, the earthworm population was highest (48 earthworms m−2 in the first 30 cm) in CA monocrop maize, followed by a CA maize–legume intercropping (40 earthworms) and lowest (nine earthworms) in conventionally tilled treatment. In both study locations CA monocrop maize and CA maize–legume intercrop gave higher water infiltration than the conventional treatment. Improvements in crop productivity, overall economic gain and soil quality have made CA an attractive system for farmers in Malawi and other areas with similar conditions. However, for extensive adoption of CA by smallholder farmers, cultural beliefs that crop production is possible without the ubiquitous ridge and furrow system and residue burning for mice hunting have to be overcome.