Green Manure / Cover Crop Legumes
Green Manure / Cover Crop Legumes
Green manure is defined as a crop that is grown and then intentionally plowed under to improve the underlying soil while green or just after flowering.
Cover crops are plants grown over the soil to protect the soil and as a soil ammendment
How to start
It is therefore possible to calculate how much nitrogen a well grown cover crop will add to the soil as follows:
Example - Crotolaria as given below:
Biomass yield 8 t DM ha-1. within 3-5 months
N content in leaves 3.6 - 4.7%
8 tonnes=8,000 kg. about 4 % of 8,000 kg =320 kg N per hectare if the whole crop is incorporated into the soil. This is a lot - most crops need less than 100 kg/ha of Nitrogen to grow well. So this type of green manure yield allows for partial harvest before incorporating the rest of the crop as green manure into the soil
Best-Bet Green Manurel Legumes and their Characteristics
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Mucuna Pruriens |
(c) Joseph G. Mureithi, KARI, Kenya
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Crolataria Ochroleuca |
(c) Joseph G. Mureithi, KARI, Kenya
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Mucuna Pruriens - Mucuna | |
Altitude range | 0-1800 m asl |
Time to maturity | 4-12 months |
Biomass yield | 7 t DM ha-1. within 6 months |
Seed production | Excellent |
N content in leaves | 2.5 - 5.4 % |
Effects on weeds | Suppresses broad leaved weeds and obnoxious ones like striga |
Toxic | Yes, L-dopa |
Food | Under study |
Fodder | Yes |
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Crotolaria Ochroleuca |
(c) Joseph G. Mureithi, KARI, Kenya
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Crolataria Ochroleuca - Sunhemp seeds |
(c) Joseph G. Mureithi, KARI, Kenya
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Crolataria Ochroleuca - Sunnhemp | |
Altitude range | 0-1900 m asl |
Time to maturity | 3-4 months |
Biomass yield | 8 t DM ha-1, within 3-5 months |
Seed production | Fair to good because of pest |
N content in leaves | 3.6 - 4.7% |
Effects on weeds | Fair |
Toxic | No |
Food | Yes as vegetable |
Fodder | Yes |
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Canavalia ensiformis |
(c) Joseph G. Mureithi, KARI, Kenya
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Canavalia ensiformis seeds |
(c) Joseph G. Mureithi, KARI, Kenya
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Canavalia Ensiformis
Altitude range | 0-1900 m asl |
Time to maturity | 6-12 months |
Biomass yield | 5 t DM ha-1 |
Seed production | Excellent |
N content in leaves | 2.3 - 4.7% |
Effects on weeds | Fair |
Toxic | Yes, Canavalin |
Food | No |
Fodder | No |
Lablab Purpureus |
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Lablab purpureus |
(c) Joseph G. Mureithi, KARI, Kenya
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Lablab purpureus seeds |
(c) Joseph G. Mureithi, KARI, Kenya
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Lablab Purpureus
Altitude | 0-1900 m asl |
Time to maturity | 3-12 months |
Biomass yield | 8 t DM ha-1 within 3-5 months |
Seed production | seasonal variation due to pest |
N content in leaves | 3.0 - 5.8% |
Effects on weeds | as mucuna |
Toxic | No |
Food | Yes, beans and leaves |
Fodder | Yes |
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Desmodium uncinatum |
(c) Joseph G. Mureithi, KARI, Kenya
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Desmodium uncinatum seeds |
(c) Joseph G. Mureithi, KARI, Kenya
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Desmodium Unicatum
Altitude range | 0-1900 m asl |
Time to maturity | 8-12 months |
Biomass yield | 8-10 t DM ha-1 |
Seed production | Fair (pests) |
N content in leaves | 2.5 - 5.0% |
Effects on weeds | Good |
Toxic | No |
Food | No |
Fodder | Yes |
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Neontonia wightii |
(c) Joseph G. Mureithi, KARI, Kenya
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Neontonia wightii seeds |
(c) Joseph G. Mureithi, KARI, Kenya
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Neontonia Wightii
Attitude range | 0-2000 m asl |
Time to maturity | 12 months |
Biomass yield | 8-10 t DM ha-1 |
Seed production | Fair |
N content in leaves | 3.3 - 4.0% |
Effects on weeds | Good |
Toxic | No |
Food | No |
Fodder | Yes |
Potential Benefits of Green Manure Cover Crop Legumes
Potential for soil improvement through integrated nutrient management
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Response of maize grain yield to inorganic NFYM, green manure legumes and their combination in Kakamega, Western Kenya |
(c) Joseph G. Mureithi, KARI, Kenya
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Potential for soil erosion control
Table: Cumulative soil loss (t ha-1) and percent crop cover two weeks after the on-set of the rains during the experimental period.
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Potential for soil moisture conservation
Potential for feeding livestock
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Post harvest legume cover |
(c) Joseph G. Mureithi, KARI, Kenya
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Cropping Systems/Niches
Intercropping green manure legumes with maize
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Vetch/Maize intercrop (left) and Mucuna/Maize intercrop (right) |
(c) Joseph G. Mureithi, KARI, Kenya
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Late intercropped legumes in maize
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Late planted mucuna into maize |
(c) Joseph G. Mureithi, KARI, Kenya
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Intercropped with vegetables
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Crolataria kales intercrop |
(c) Joseph G. Mureithi, KARI, Kenya
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Rotational short-term fallow with green manure legumes
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Crotolaria short term fallow before maize |
(c) Joseph G. Mureithi, KARI, Kenya
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Cover crop for conservation agriculture in dry areas
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Lablab cover crop |
(c) Joseph G. Mureithi, KARI, Kenya
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Furrow for direct palnting in lablab |
(c) Joseph G. Mureithi, KARI, Kenya
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Cover crops for plantation
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Neontonia in sisal |
(c) Joseph G. Mureithi, KARI, Kenya
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Mucuna in citrus |
(c) Joseph G. Mureithi, KARI, Kenya
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Mucuna in coffee |
(c) Joseph G. Mureithi, KARI, Kenya
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Garden pea in papaya |
(c) Joseph G. Mureithi, KARI, Kenya
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Cover crop as a nurse crop for establishing plantation crops
When establishing plantation crops (e.g., coffee, tea, coconut, citrus, sugarcane etc) cover crops can provide excellent ground cover for weed suppression and control of soil erosion. For example lablab was used as nurse crop in establishment of sugar cane in western Kenya (see photo)
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Lablab as nurse for sugar cane |
(c) Joseph G. Mureithi, KARI, Kenya
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Recommended Spacing and Seed Rate for Green Manure Legumes for pure Stand Establishment
Species name | Common name | Spacing (cm) * - inter-row spacing | Seed per hole | Seed rate (kg/ha) |
Arachis hypogaea | groundnut | 50 x 10 | 2 | |
Arachis pintoi | wild peanut | 50 x 10 | 2 | |
Cajunus cajan | pigeon pea | 50 x 40 | 2 | |
Calopogonium mucunoides | calopo | 30 | 30 | |
Canavalia ensiformis | jackbean | 50 x 50 | 2 | |
Crotalaria ochreleuca | tanzanian sunnhemp | 30 | 30 | |
Crotalaria juncea | sunnhemp | 30 | 45 | |
Desmodium intortum | greenleaf desmodium | 30 | 30 | |
Desmodium uncinatum | silverleaf desmodium | 30 | 30 | |
Dolichos biflorus | horsegram | broadcast | 45 | |
Dolichos lab lab cv Rongai | hyacinth bean | 60 x 30 | 2 | |
Fagopyrum esculentum | buckwheat | broadcast | 95 | |
Glycine max | soybean | 50 x 5 | 2 | |
Glycine wightii | perennial soybean | 30* | 30 | |
Lupinus albus | sweet white lupine | 30 x 15 | 2 | |
Macroptilium atropurpureum | siratro | 30 | 30 | |
Medicago sativa | lucerne, alfalfa | 30 | ||
Medicago truncatula | barrel medic | 28 | ||
Melilotus alba | white sweet clover | 30 | ||
Mucuna pruriens | velvet bean | 60 x 30 | 2 | |
Neotonia wightii | glycine | 30 | 30 | |
Pisum sativumcv Prussian | pea, garden pea, field | 150 | ||
Austrian winter, Trapper | pea | |||
Phaseolus lunatus | lima bean | 50 x 15 | 2 | 2 |
Phaseolus vulgaris | common bean | 50 x 15 | 2 | 2 |
Pueraria phaseoloides | tropical kudzu | 30 | ||
Stylosanthus gianensis cv Cook | stylo | 30 | 30 | |
Trifolium alexandrinum | berseem.clover | 30 | 30 | |
Trifolium subterraneum | subclover | 30 | 30 | |
Trifolium vesiculosum | arrowleaf clover | 30 | 30 | |
Vicia benghalensis | purple vetch | 30 | 67 | |
Vicia faba | faba bean | 30 x 15 | 2 | |
Vicia dasycarpa | lana woolly pod vetch | 30 | 67 | |
Vicia sativa | common vetch | 30 | 67 | |
Vicia villosa | hairy vetch | 30 | 67 | |
Vigna radiata | green gram | 50 x 5 | 2 | |
Vigna unguiculata | cowpea | 50 x 20 | 2 | |
Voandzeia subterranean | bambara groundnut | 50 x 10 | 2 |
Information Source Links
- Joseph G. Mureithi , Kenya Agricultural Research Institute