Maize and sesbania production in relay cropping at three landscape positions in Malawi

The relay cropping of sesbania (Sesbania sesban) — a N2-fixing legume — with maize (Zea mays) has been proposed as a strategy to increase soil fertility and food production in densely populated areas in southern Africa. We determined the production of relay-cropped maize and sesbania at three landscape positions under researcher-designed and farmer-managed conditions in southern Malawi. Three landscape positions (dambo valley or bottomland, dambo margin with 12% slope) were examined in factorial combination with N sources for maize (no added N, relay-cropped sesbania, and calcium ammonium nitrate fertilizer). Relay cropping of sesbania with maize increased maize grain yield, as compared to unfertilized sole maize in two of three years. Split application of 96 kg N ha−1 as N fertilizer, however, was more effective than sesbania in increasing maize yields. Survival of sesbania seedlings and biomass production of sesbania were greater in the dambo valley and dambo margin than on steep slopes. Maize yields tended to be lower on steep slopes than in the dambo valley and dambo margin areas. Biomass production of sesbania and hence the potential benefits of intercropping sesbania with maize appear greater in the dambo valleys and dambo margins than on steep slope

Soil nitrate dynamics in relation to nitrogen source and landscape position in Malawi

Nitrogen is normally the nutrient most limiting production of maize (Zea mays) — the main staple food crop — in southern Africa. We conducted a field study to determine the effect of N sources on soil nitrate dynamics at three landscape positions in farmers' fields in southern Malawi. The landscape positions were dambo valley or bottomland, dambo margin, and steep slopes. The N sources were calcium ammonium nitrate fertilizer applied at 120 kg N ha−1, biomass from Sesbania sesban, and no added N. Sesbania biomass was produced in situ in the previous season from sesbania relay cropped with maize. Nitrate in the topsoil (0 to 15 cm depth) increased to 85 days after maize planting (mean = 48 kg N ha−1) and then decreased markedly. Application of N fertilizer and sesbania biomass increased soil nitrate, and nitrate-N in topsoil correlated positively with amount of incorporated sesbania biomass. The strongest correlation between sesbania biomass added before maize planting and topsoil nitrate was observed at 85 days after maize planting. This suggests that the sesbania biomass (mean N content = 2.3%) mineralized slowly. Inorganic N accumulated in the subsoil at the end of the maize cropping season when N fertilizer and sesbania were applied. This study demonstrated the challenges associated with moderate quality organic N sources produced in smallholder farmer's fields. Soil nitrate levels indicated that N was released by sesbania residues in the first year of incorporation, but relay cropping of sesbania with maize may need to be supplemented with appropriately timed application of N fertilize

Farmer and researcher partnerships in Malawi: developing soil fertility technologies for the near-term and far-term

In Malawi, intensive production of maize (Zea mays) is pursued on over 60% of smallholder land, yet application of nutrients is almost nil. To improve adoption of soil productivity-enhancing technologies, two participatory methods were pursued: (i) a novel 'mother-and-baby' trial design and (ii) participatory action research with communities in a southern Malawi watershed. The central 'mother trial' was managed by researchers (replicated within a site) and systematically linked to farmer-managed 'baby' trials to cross-check biological performance with farmer assessment. The watershed approach involved a partnership of researchers and farmers addressing soil management. Technologies tested in both approaches integrated legumes into existing maize-based systems, sometimes in combination with inorganic fertilizers. Across methods, legume intensification increased yields by approximately 40% (net benefit increase of approximately US$50 ha-1) and fertilizer increased yields by approximately 70% compared with continuous maize grain yields of about 1100 kg ha-1. Farmer assessment prioritized technologies that included secondary benefits, such as weed suppression, grain legume yields, and low-labour-demanding fertilizer. A survey indicated that participating researchers and extension staff had reservations about the amount of time required to interact with farmers, and no clear consensus emerged regarding the best approach. There has been wider adoption of the mother-and-baby trial method by scientists in neighbouring countries, indicating the value of systematically incorporating farmers' input

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Effect of stocking rate and grazing method on forage-on-offer, forage intake, and animal weight changes on cool-season pastures

Last updated: 6/26/201