Grain Legumes and Green Manures for Soil Fertility in ... - cimmyt

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and K to maize as an equivalent amount of commercial NPK fertilizer, and in some caGes maize yields were higher with tithonia biomass than commercial inorganic fertilizer. Recent work in Malawi (Ganunga et al. 1998) and Zimbabwe (Jirl and Waddington, 1998) have similarly reported tithonia biomass to be an effective nutrient source for maize. Biomass transfer using leguminous species is a far much sustainable means of maintaining nutrient balances in maize:based systems as these trees are able to fix atmospheric N2. Tithonia is not a legume, and it does not biologically fix atmospheric N2. The transfer of tithonia biomass to fields, therefore, constitutes the cycling of nutrients within the farm and landscape rather than a net input of nutrients to the system. The continual transfer of nutrients from tithonia hedges to crop fields constitutes nutrient mining and might not be sustainable for long periods. Whereas the application of fertilizers to tithonia could ensure sustained production of tithonia, this is unlikely to be an option for resource-poor farmers. The integration of tithonia with N2-fixing legumes may merit investigation. Synchrony between nutrient release from tree litter and crop uptake can potentially be achieved in a biomass transfer system. The management factors that can be manipulated to achieve this are litter quality, rate of litter application, method and time of litter application (Mafongoya et al. 1998; 1999). However variability in climatic factors such rainfall and temperature makes the concept of synchrony ·an elusive goal to achieve in practical terms (Myers et al. 1994). Although prunings from MPTs increased maize yield, cutting transporting and managing prunings on crop fields require high labour inputs Oama et al. 1997; Jama et al. 1998; Mutuo et al. 2000). Where family labour is available at no additional cost, the technology can be profitable even where land is SC(lrce Oama et al. 1997; Mutuo et al. 2000). However, considering that farm labour is one of the most constraining inputs in smallholder agriculture, the associated cost makes this technology unattractive and may serve as a disincentive for its adoption by farmers. In monetary terms, the higher maize yield does not compensate for the high labour cost. In promoting this technology, farmers may require to be provided with additional resources to invest in labour and land. Most economic analyses have shown that it is unprofitable to invest in a biomass transfer system when labour and land are scarce. However, in areas where land is abundant and the prunings are applied to high value crops like vegetables, the technology·is profitable (ICRAF, 1997). Biomass transfer could find a niche for vegetable production in dambo areas of southern Africa. A dambo is a shallow, seasonally or permanently waterlogged depression at or near the head of a natural drainage network, or alternatively occurs independently of a drainage system (Chenje and Johnson, 1996; Breen et al. 1997). Dambos cover about 240 million hectares in sub-saharan Africa (Andriesse, 1986). They are some of the most productive natural ecosystems in the Southern African region. They provide water for domestic use, good soils for agricultural production, grazing grounds for livestock, fish and support a wide range of wildlife and birds (Raussen et al. 1995). Dambos are considered extremely vulnerable to poor agricultural practices, and hence dambo cultivation was illegal for instance in Zimbabwe. However, rising population pressure has caused the agricultural use of dambos to become increasingly important (Kundhlande et al. 1994). For example, vegetable gardens cover 15000-20000 ha (Bell et al. 1987) of the estimated 1.28 million ha of dambos in Zimbabwe. However, without applying fertilizers or cattle manure smallholder farmers cannot produce vegetables successfully in some vf the dambos (for example in eastern Zambia) that are degraded due to continuous cultivation for over 25 years (Raussen et al. 1995). The removal of subsidies and increase in interest rates in most of sub Saharan Africa has caused decline in inorganic fertilizer use, and this decline in the smallholder sector is even greater, suggesting that for many farmers the use of fertilizer is not a viable option any more. Cattle manure use could also become limited since not all farmers have animals to produce adequate quantities of manure. In addition, transport problems for the large quantities of manure needed and the spread of weeds due to the manure use may limit its utilization. Therefore, the use of biomass transfer in sustaining vegetable production in the dambos of southern Africa could be a viable option. An experiment conducted with 43 farmers by Kuntashula et al (2003) showed that Gliricidia biomass transfer technologies produced cabbage, onion and subsequent maize yields comparable with the full fertilizer application (Tables 7 and 8). The biomass transfer technologies also recorded higher cabbage, onion and maize net incomes than the control, and required lower cash inputs than the fully fertilized crop (Figures 8 and 9). Like in maize based systeMS, net incomes of the biomass treatments in vegetable production were substantially reduced by the labour costs for pruning and incorporation of the biomass. However, in vegetables the high price of products more than compensated these costs. The study concluded that the use of gliricidia biomass 150 Grain Legumes and Green Manures for Soil Fertility in Southern Africa
Table 7. Mean cabbage and onion yields (fresh weight) in dambos using inorganic fertilizers or organic inputs from manure, gliricidia and leucaena biomass in Chipata South district, 2001 Treatments Cabbage yield Onion yield (t ha·l ) n 31 (t hal) n - 12 Manure 10 t ha· l + half fertilizer 66.8 96.0 Fully fertilised 57.6 57.1 Gliricidia 12 thaI t 53.6 79.8 Gliricidia 8t hal 43.1 68.3 leucaena 12 t ha I 32.6 Control 17.0 28.1 S.e.d (p - 0.05) 5.41 11.48 .. leucaena 12t ha·' was not used in onion trials I Biomass treatments are reported on dry weight basis N - Number of farmers participating in the experiment transfer could be a viable alternative to inorganic fertilizer although farmers taking up the technology will however need adequate supply of labour. The effectiveness of biomass transfer of nutrient sources using organic inputs from MPT species depends on their chemical composition (Mafongoya and Nair, 1997). These systems can meet the N requirement of most crops in smallholder farming systems. However, they cannot meet the requirement of P. There is need to apply inorganic sources of P in addition to organic sources. When biomass is also valued as fodder there is need to assess the trade off of applying it directly to the soil or feeding it to livestock and then applying the resultant manure.. There is evidence to indicate that depending on the quality of the biomass there may be no adliiICabbage • Maize + Cabbage 16000,--------------------------- 14000 12000 10000 8000 6000 4000 2000 o Table 8. Maize grain yields (t ha· t at 13% moisture content) on residual plots in dambos after cabbage and onion production using inorganic fertilizers or organic inputs from manure, gliricidia and leucaena biomass'in Chipata South district, 2001 Treatments After cabbage After onion (n - 21) (n - 10) Manure lOt ha·1 + Y2 fertilizer 4.2 3,1 Fully fertilized 3.9 2.5 Gliricidia 12 t ha It 4.9 3.9 Gliricidia 8 thai 4.3 3.3 leucaena 12 t ha I 3.2 Control 2.9 1.7 S.e.d (p - 0.05) 0.48 0.49 .. leucaena 12t ha I was not used in onion trials I Biomass treatments are reported on dry weight basis N - Number of farmers participating in the experiment vantage in feeding it to livestock and then applying the manure as a source of N to crops (Mafongoya et al. 1999). However, in other Instances, it has been shown that it is more advantageous to first feed the biomass to livestock and then apply the resulting manure to crops Gama et al. 1997). In summary, the biomass transfer system hasgreatest potential when biomass is of high quality and rapidly releases nutrients, the opportunity cost of labour is low, the value of the crop is high and if the biomass does not have other valued uses other than as source of nutrients. Future Research Needs This synthesis has described the progress that has been made during the past 10 years in research efmlOnion • Onion + maize 6000 ;------------------~ 5000 4000 3000 2000 1000 • Above nel incomes are reported per hectare basis. Average actual area put to cabbage by a • Above net incomes are reported per hectare basis . Average actual area put to onion by a farmer Figure 8. Net income US$ hal)" from cabbage and subsequent Figure 9. Net income US$ hal)" from onion and subsequent maize maize on 31 vegetable gardens in Chipata South District in 2001 on 12 vegetable gardens in Chipata South District in 2001 Grain Legumes and Green Manures for Soil Fertility in Southern Africa 151
Page 2 and 3:
Grain Legumes and Green Manures for
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Acknowledgments • The Leopard Roc
Page 6 and 7:
Evall!ating mucuna green manure tec
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INTRODUCTION AND CONFERENCE OBJECTI
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Table 1. Paradigm shifts underlying
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100 90 80 - - 0 - - Uptake by ihe m
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- 6 ~ 9 8 7 0- 5 CḎ ns 4 0::: 3
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Table 3. Millet grain and total dry
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Dvorak KA 1996. Adoption potential
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LEGUMES FOR SOIL FERTILITY IN SOUTH
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to the system in such a way that th
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Muetzelfeldt, R.1. 1995. A framewor
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ing capacity. Legumes offer other b
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people/km2), land holdings are smal
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ments. It would help researchers to
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Own livestock Gununo farmers for th
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Questions and Answers ~ey Papers To
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Historical Perspective on Soyabean
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ganic amendment for resource-poor f
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MPhil. Thesis. University of Zimbab
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deal of research work has been bias
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1600 '7 ns 1400 ~ 1200 Cl ~ 1000 "C
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Arbuscular mycorrhizal fungi (AMF)
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Boswell EP, Koide RT, Shumway DL, A
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Materials and Methods The trial was
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0.9 0.8 ~ 0.7 Rec '-' 0.6 Vl ::9 0.
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Series no 5. Soil Science SOciety o
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Materials and Methods Persistence o
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content resulted in increased rhizo
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(Mugwiia and Murwira, 1997). Howeve
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Table 2. Average maize yield estima
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implied that most fanners prefer to
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] Questions and Answers Rhizobium,
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ADDING A NEW DIMENSION TO THE IMPRO
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Materials and Methods The study use
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a) Chikwaka b) Chinyika !21 C. absu
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Table 3. N, P and Kconcentrations (
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Abstract SCREENING OF SHORT DURATIO
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Table 2. Characteristics of short d
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RISK DIVERSIFICATION OPPORTUNITIES
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management technologies with differ
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Table 3. Expected annual returns (Z
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Table 6. Risk diversification indic
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een renewed interest in green manur
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unfertilised maize crop of over 200
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Questions and Answers Screening of
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GREEN MANURE AND FOOD LEGUMES RESEA
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7000 6000 ';' €.. 5000 .~MzSole :
Page 107 and 108: Table 5. Maize grain yield (kg ha")
Page 109: Phiri, A.D.K. 1999. Effects of Sesb
Page 112 and 113: amount of roots with sl:nnhemp. It
Page 114 and 115: It was proved that a mixed farming
Page 116 and 117: Table 3. Above·ground biomass (t/h
Page 118 and 119: and horticulture in Zimbabwe: Case
Page 121 and 122: GRAIN LEGUMES AND GREEN MANURES IN
Page 123 and 124: Results Table 1. Adaptation of gree
Page 125 and 126: Four rates of fertilizer N were app
Page 127 and 128: THE ROLE OF COWPEA (VIGNA UNGUICULA
Page 129 and 130: Table 1. Non-legume cropping patter
Page 131 and 132: Table 9. Common pests on cowpeas as
Page 133 and 134: few of the farmers interviewed acqu
Page 135: Murwira, H.K., M.J. Swift and P.G.H
Page 138 and 139: Materials and Methods On farm exper
Page 140 and 141: 18000 1600) 14000 a) Zambia 12000 m
Page 143 and 144: EFFECT OF DIFFERENT GREEN MANURE LE
Page 145 and 146: .. ~ Table 2. The effect of time o
Page 147: Chivinge, O.A., E. Kasembe, and I.K
Page 150 and 151: times with regionally specific adap
Page 152 and 153: ter content at 180 cm was still wel
Page 154 and 155: to amount of biomass, quality of bi
Page 156 and 157: with the natural fallow, which did
Page 160 and 161: forts to understand the mechanisms
Page 162 and 163: gen recovery rates in relation to p
Page 164 and 165: The first steps to improve soil fer
Page 167 and 168: Questions and Answers .Identificat
Page 169 and 170: MUCUNA - MAIZE ROTATIONS AND SHORT
Page 171: Table 3. Percent nitrogen (% N) con
Page 174 and 175: ~e decomposition of legume residues
Page 176 and 177: Table 3. Effect of forage legumes o
Page 178 and 179: available nutrients and vice versa,
Page 180 and 181: Conclusion and Recommendation Mucun
Page 182 and 183: Specific objectives were to: • Te
Page 184 and 185: '"~ v '" ~ ~ 1400000 1200000 100000
Page 187 and 188: EFFECT OF SURFACE APPLICATION AND I
Page 189: it 4 a···· · ... - :.!! e.....
Page 193 and 194: PERFORMANCE OF GREEN MANURES AND GR
Page 195: Mungwi soil, cowpea and soyabean pr
Page 198 and 199: Among BNF systems, symbiotic system
Page 200 and 201: 3500 .f"'3000 ca ,c2500 CI "" - 200
Page 202 and 203: above-ground biomass was not transl
Page 204 and 205: 3000 "0 ]i >. ,5 ~ C> 800 600 400 2
Page 206 and 207: Most interventions involving green
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~ ~~----.-~r-~-------------r~~ Aoo
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stover N, followed by after pigeon
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tems in Malawi and Zimbabwe. Procee
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1965). The tailings and AgLi were a
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The significant soybean yield could
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twice the yield is necessary. We ha
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Table 1. Maize and Grain Legumes Pr
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Recommendations and Conclusion In v
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performance of private sector compa
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the investment costs incurred. The
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Results and Planning Workshop. Soil
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A SOCIO-ECONOMIC ANALYSIS OF LEGUME
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Table 1. Gross margins from the dif
Page 235 and 236:
Abstract LINKING TECHNOLOGY DEVELOP
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3. If households are linked to prod
Page 239 and 240:
Table 9. Average Table 8. Pigeonpea
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ance of sorghum-pigeonpea intercrop
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Mligo, J.K., 1995. Pigeonpea breedi
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To Charles Nhemachena, et al. Q: 1)
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• Assessment of the potential ben
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few studies characterized the house
Page 252 and 253:
• Conduct more research to measur
Page 254:
Socio-Economics, Policy and Technol
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