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Undersowing green manures for soil fertility enhancement in the maize-based cropping systems of Malawi

By: Gilbert, R.A | Centro Internacional de Mejoramiento de Maiz y Trigo (CIMMYT), Mexico DF (Mexico).
Contributor(s): Waddington, S.R.|Murwira, H.K.|Kumwenda, J.D.T.|Hikwa, D.|Tagwira, F [eds.].
Material type: materialTypeLabelBookAnalytics: Show analyticsPublisher: Harare (Zimbabwe) Soil Fert Net|CIMMYT : 1998ISBN: 970-648-006-4.Subject(s): Biomass AGROVOC | Cropping systems | Green manures | Malawi | Sowing date | CIMMYT | Soil Fert Net | Zea mays AGROVOC | Soil fertility AGROVOC | Nitrogen fertilizers AGROVOCDDC classification: 631.45 Summary: Malawi's burgeoning human population has led to declining per capita food production and declining soil fertility in continuously cropped maize systems. The use of inorganic fertilisers has fallen as the N:grain price ratio has risen. The challenge for agronomists in Malawi is to design, evaluate and disseminate cropping systems that will increase soil fertility and maize yields in regions where maize is planted every season. While green manure systems can accumulate > 200 kg N ha-1 when sole cropped, the magnitude of biomass produced and N2 fixed by green manures when undersown to maize is not known.|An on-farm experimental program was established in the 1996/97 season at 11 sites in central and southern Malawi to determine if intercropped green manures can produce the minimum biomass (> 2000 kg ha-1) necessary to improve soil fertility without reducing maize yields. Three factors (species selection, time of undersowing, and seeding rate) were examined in a 3 x 2 x 2 factorial experiment in a randomized complete block design. There were two replicates at each site. The factors were:|A. Crop undersown B. Time of undersowing C. Seeding rate|1. Crotalaria juncea (CJ) 1. First weeding (T1) 1. Low (S1)|2. Mucuna pruriens (MP) 2. Second weeding (T2) 2. Medium (S2)|3. Lablab purpureus (LP)|or Tephrosia vogelii (TV)|Crotalaria and Mucuna were grown at every site, while Lablab and Tephrosia were alternated as the third green manure species at a site. Lablab was grown at lowland sites while Tephrosia was planted at highland sites.|Preliminary results after one season of growth indicate that Tephrosia, Crotalaria and Mucuna, when undersown early, can produce significant amounts of biomass (> 2000 kg ha-1) when intercropped with maize at low-fertility sites in Malawi. Tephrosia undersown at T1 yielded the most biomass, peaking at 6646 kg ha-1 at Bvumbwe. The Tephrosia biomass produced was strongly correlated to rainfall received at a site. Mucuna, with an aggressive climbing growth habit, was very competitive with maize when undersown at first weeding. The MP T1 S2 treatment reduced maize yields by 60% compared to sole maize controls. Lablab failed to yield more than 1000 kg ha-1 at any of the sites tested. Broadcasting small-seeded Crotalaria and Tephrosia led to low survival rates (< 40%) for these species. The increased seed costs of broadcasting must be weighed against the labour advantages of this planting method.|In the 1997/98 season, the experimental plots will be split and fertiliser added to half the plots to determine whether small amounts of organic plus inorganic amendments can significantly increase maize yields. Future research will compare promising undersown green manure treatments (e.g. TV T1 S1, TV T1 S2, or CJ T1 S2) to other leguminous interventions (e.g. maize/pigeonpea intercrops or soybean rotations) on the basis of N added to the soil system and economic net benefit. In this way Malawian farmers can choose the organic matter technology that best suits their needs.|Collection: CIMMYT Publications Collection
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Conference proceedings CIMMYT Knowledge Center: John Woolston Library

Lic. Jose Juan Caballero Flores

 

CIMMYT Publications Collection 631.45 WAD (Browse shelf) 1 Available I628739
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Malawi's burgeoning human population has led to declining per capita food production and declining soil fertility in continuously cropped maize systems. The use of inorganic fertilisers has fallen as the N:grain price ratio has risen. The challenge for agronomists in Malawi is to design, evaluate and disseminate cropping systems that will increase soil fertility and maize yields in regions where maize is planted every season. While green manure systems can accumulate > 200 kg N ha-1 when sole cropped, the magnitude of biomass produced and N2 fixed by green manures when undersown to maize is not known.|An on-farm experimental program was established in the 1996/97 season at 11 sites in central and southern Malawi to determine if intercropped green manures can produce the minimum biomass (> 2000 kg ha-1) necessary to improve soil fertility without reducing maize yields. Three factors (species selection, time of undersowing, and seeding rate) were examined in a 3 x 2 x 2 factorial experiment in a randomized complete block design. There were two replicates at each site. The factors were:|A. Crop undersown B. Time of undersowing C. Seeding rate|1. Crotalaria juncea (CJ) 1. First weeding (T1) 1. Low (S1)|2. Mucuna pruriens (MP) 2. Second weeding (T2) 2. Medium (S2)|3. Lablab purpureus (LP)|or Tephrosia vogelii (TV)|Crotalaria and Mucuna were grown at every site, while Lablab and Tephrosia were alternated as the third green manure species at a site. Lablab was grown at lowland sites while Tephrosia was planted at highland sites.|Preliminary results after one season of growth indicate that Tephrosia, Crotalaria and Mucuna, when undersown early, can produce significant amounts of biomass (> 2000 kg ha-1) when intercropped with maize at low-fertility sites in Malawi. Tephrosia undersown at T1 yielded the most biomass, peaking at 6646 kg ha-1 at Bvumbwe. The Tephrosia biomass produced was strongly correlated to rainfall received at a site. Mucuna, with an aggressive climbing growth habit, was very competitive with maize when undersown at first weeding. The MP T1 S2 treatment reduced maize yields by 60% compared to sole maize controls. Lablab failed to yield more than 1000 kg ha-1 at any of the sites tested. Broadcasting small-seeded Crotalaria and Tephrosia led to low survival rates (< 40%) for these species. The increased seed costs of broadcasting must be weighed against the labour advantages of this planting method.|In the 1997/98 season, the experimental plots will be split and fertiliser added to half the plots to determine whether small amounts of organic plus inorganic amendments can significantly increase maize yields. Future research will compare promising undersown green manure treatments (e.g. TV T1 S1, TV T1 S2, or CJ T1 S2) to other leguminous interventions (e.g. maize/pigeonpea intercrops or soybean rotations) on the basis of N added to the soil system and economic net benefit. In this way Malawian farmers can choose the organic matter technology that best suits their needs.|

English

9906|AGRIS 9902|R98-99ANALY

Jose Juan Caballero

CIMMYT Publications Collection

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