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

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with the natural fallow, which did not lose its aggregate stability. The decrease in aggregate stability was more pronounced under sesbania and maize without fertilizer as compared ~ith cajanus and maize with fertilizer. Under a sesbania fallow system, the improvement in soil structure is more evident and this is reflected by results from our time to runoff studies. Time to runoff after fallow clearing was in the order of: natural fallow> S. sesban > fertilized maize. After one season of cropping, time to runoff decreased in all treatments except that the natural fallow maintained the longer time to runoff, reflecting good maintenance of aggregate stability. Through rainfall simulation studies we evaluated effects of improved fallows on runoff infiltration soil and nutrient losses under improved fallows. Tree fallows of sesbania, gliricidia mixed with archer dolichos increased infiltration rates significantly compared with continuously fertilized maize plots (Figure 7). Fallows compared to no tree plots also significantly reduced soil loss (Table 5). Improved fallows improve soil physical properties as evidenced by increase in infiltration rates, increased infiltration decay coefficients, reduced runoff and soil losses. However these benefits are short lived and they decline rapidly during the first year of cropping. This was supported by increase in soil loss in the second year (TableS) and decrease in in 40 35 i )0 ! 2S ~ 20 c .g 15 g ~ 10 S. sesban T. vogelii N. rallow fl:t1ilizal. maize G. sepium+ A. dolichos Treatmenls I-October 2000 [JOclober2001 I Figure 7. Infiltration rate under different fallows measured at Msekera (source; Nyamadzowo et a/2002) Table 5. Soil loss (g/m2) measured under various fallow species and maize at Kalunga Farmers Training Center in eastern Zambia Treatment October 2000 October 2001 Sesbania sesban 0.0 5.0 Tephrosia voge/ii 4.5 15.8 Natural fallow 0.0 19.5 Fully fertilized maize 63.8 ..0.5 ~iratro (Macroptilium atropurpureum) 0.0 0.7 ILSO 15.3 . Source: Nyamadzowo et al2002 filtration rates as well (Figure 7). However, mixing a coppicing species like gliricidia and a herbaceous legume like archer dolichos maintained high infiltration rates and reduced soil loss over two years of cropping. Sustainability of Improved Fallows Improved fallows with sesbania or tephrosia have been shown to give maize grain yields of 3 to 4 t/ha without any inorganic fertilizer addition. Palm (1995) showed that organic inputs of various tree legumes applied at 4 t/ha can supply enough nitrogen for maize grain yields of 4 t/ha. However, most of these organic inputs could not supply enough phosphorus and potassium to support such maize yields. The question ferr sustainability is: Can improved fallows potentially mine P and K over time while maintaining a positive N balance? To answer that question we conducted nutrient balances on improved fallow trials at Msekera Research Station. These plots were under fallow-crop rotations for 8 years. The objectives of these studies on nutrient balances addressed the following questions: • Can nutrient balances be used as land quality indicators? • Can they be used to assess soil fertility status, productivity and sustainability? • Can they be used as a policy instrument for the types of fertilizers to be imported or distributed to farmers? The nutrient balances considered nutrients added through leaves and litter fall, which were incorporated after fallows as inputs. The nutrients in maize grain harvested, maize stover removed and fuelwood taken away at end of the fallow were considered as nutrient exports. For all the land use systems, there was a positive N balance two years of cropping after the fallows (Table 6). Fertilized maize had the highest N balance due to the annual application of 112 kg N/ha for the past 10 years. However, unfertilized maize had lower balances due to low maize grain and stover yields over time. The tree-based fallows had a positive N balance due to BNF and deep capture of N from depth. These results are consistent with those of Palm (1995) that showed that organic inputs could supply enough N to support maize grain yields of 3 to 4 t/ha. However in the second year of cropping (1999) the N balance was very small. This is consistent with our earlier results, which showed a decline of maize 148 Grain legumes and Green Manures for Soil Fertility in Southern Africa
Table 6. Nutrient balance (kglha) under two year non·coppicing fallow species at Msekera, eastern Zambia Nitrogen Phosphorus· Potassium limd use systems 1998 1999 1998 1999 1998 1999 Cajanus cajan 27 5 21 8 13 ·9 Sesbania sesban 22 5 39 24 -42 ·32 Natural fallow 8 11 19 15 ·10 ·4 Fully fertilized maize 150 103 57 43 ·19 ·17 Unfertilized maize 31 11 29 20 19 ·1 yields in the second year of cropping after two-year fallows. The huge amount of N supplied by fallows could be lost through leaching beyond the rooting depth of maize. Our leaching studies have clearly shown substantial inorganic N at depth under maize after improved fallows. These results imply that if cropping goes beyond three years after fallows there will be a negative N balance. Thus the recommendation of two years of fallows followed by two years of cropping is well supported by N balances and maize grain yield trends. Most of the land use systems showed a positive P balance. This can be attributed to low offtake of P in maize grain yield and stover. In addition, this site had a high phosphorus status. The trees could also have increased P availability through secretion of organic acids and the increased mycorrhizal population in the soil. These issues are under investigation at our site. In general, we have observed positive P balances over eight years. However this result needs to be tested on farm where the soils are inherently 10winP. Most land use systems showed a negative balance for K. For tree based systems, sesbania showed a higher negative K balance compared to pigeonpea. This is attributed to the higher fuelwood yield of sesbania with subsequent higher export of K compared to pigeonpea. The higher negative K balance for fully fertilized maize is due to higher maize and stover yield which exports a lot of potassium. This implies that the K stocks in the soil are very high and that K mining has not reached a point where it negatively affects maize productivity. However in sites with low stocks of K in the soil, maize productivity may be adversely affected. Nutrient balances were conducted for coppicing fallows using gliricidia compared to non-coppicing fallows using sesbania for four cropping seasons after fallow clearance. Gliricidia fallows maintained a positive N balance. This was attributed to resprout growth, which was applied to maize as a source of nutrients and deep capture of N from depth by the well-established gliricidia rooting system. All land use systems showed a positive P balance. However from the third season of cropping onwards sesbania fallows, fertilized maize and gliricidia fallows had a large negative balance. This was attributed to removal of nutrients in ·stover maize or leaching of K from surface soils .. Overall, the tree based fallows maintained a positive Nand P balance. However on low· P status, a negative P balance would be expected. There was a negative K balance with most land use systems. It can be hypothesized that as we scale up improved fallows on depleted soils on farmer's fields, 1
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Grain Legumes and Green Manures for
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Acknowledgments • The Leopard Roc
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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
Page 105 and 106: 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 158 and 159: and K to maize as an equivalent amo
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
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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
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Abstract LINKING TECHNOLOGY DEVELOP
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3. If households are linked to prod
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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
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• Conduct more research to measur
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Socio-Economics, Policy and Technol
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