EFFECTS OF Calliandra calothyrsus and Alnus acuminata GREEN MANURES IN MAIZE PRODUCTION IN THE HIGHLAND VOLCANIC SOILS OF RWANDA Didace HABAMENSHI ISAE BUSOGO, RWANDA 2ND WORLD CONGRESS OF AGROFORESTRY Nairobi, August 22

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EFFECTS OF Calliandra calothyrsus and Alnus
acuminata GREEN MANURES IN MAIZE PRODUCTION IN
THE HIGHLAND VOLCANIC SOILS OF RWANDADidace
HABAMENSHIISAE BUSOGO, RWANDA2ND WORLD
CONGRESS OF AGROFORESTRYNairobi, August 22
28th, 2009
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INTRODUCTION
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INTRODUCTION

• volcanic soils found in the northwestern Rwanda
  are naturally fertile and good for cropping.
• 62.0 and 32.5 of national Irish potato and
  maize are respectively produced
• Low available phosphorus (P) because ofhigh
  allophanes
• continuous depletion as a result of continuous
  cropping without addition of adequate inorganic
  fertilizer and manure.
• Most farmers are aware of the severity of soil
  degradation and rely on organic manures
  (especially animal manure and compost from
  household waste) to improve soil fertility
  improvement.

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Introduction (Cntd)

• However, low supply of these manures and high
  cost of inorganic fertilizers limit their use by
  many farmers.
• Agroforestry technologies are seen as alternative
  to compensate for insufficient OM costly min.
  fertilizers

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Introduction (Cntd)

• However, there is a knowledge gap on the required
  amounts, methods, frequency and time of
  application relative to soil fertility and
  nutrient release from manures.
• The study evaluated the potential of Calliandra
  calothyrsus and Alnus acuminata green manures as
  sources of N and P for soil improvement and maize
  production

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MATERIALS METHODES
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Location of study area
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Materials

• Calliandra calothyrsus green manure (0, 5, 10
  t/ha DM)
• Alnus acuminata green manure (0, 5, 10 t/ha DM)
• Maize (Zea mays pool 8A variety)

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Alnus
Calliandra
Alnus intercropped with Irish Potato in Musanze
Calliandra and other AF trees on degraded land
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Methods

• Design Factorial Experiment in RCBD with 6
  treatments (including 2 controls), 3 replicates
• Split application of manures with equal amounts
  at maize planting and 4 wks later
• Data collection
• Soil sampling before after the trial and
  analysis for N, P, OM pH
• Measurement of maize yield

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Methods (Cntd)

• Statistical analysis using GENSTAT package

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RESULTS DISCUSSION
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Soil characteristics of the study area before the
experiment
Site pH (H2O) pH KCl N () P(mg/kg) OM ()
ISAR Farm 5.36 4.73 0.55 4.7 6.53
ISAE farm 5.73 5.08 0.45 40.3 5.35
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• Before cultivation, studied soils were
• moderately acidic, moderate in N and high in OM
  content before cultivation.
• low in available P content
• ISAR site had low available P (4.7 mg kg-1) Vs
  moderate P concentrations at ISAE farm

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Effects of green manures on soil properties
Site Treatment Parameters
N () P (mg/kg) pH water OM ()
ISAE Farm Control 0.38 60.0 5.42 5.4
DAP Urea 0.43 80.0 5.74 5.7
Calliandra (5t/ha) 0.46 54.7 5.78 5.6
Calliandra (10t/ha) 0.46 52.0 5.97 5.4
Alnus (5 t/ ha) 0.45 48.6 5.87 5.4
Alnus (10 t/ ha) 0.50 53.7 5.99 5.7
ISAR Control 0.52 4.8 5.52 6.1
Farm DAP Urea 0.59 78.8 5.49 6.4
Calliandra (5 t/ ha) 0.56 5.4 5.32 6.0
Calliandra (10 t/ ha) 0.64 6.0 5.44 6.2
Alnus (5 t/ ha) 0.53 4.7 5.49 6.1
Alnus (10 t/ ha) 0.56 4.8 5.43 6.2
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• At the end of the experiment
• No effect of green manures on soil N, P, OM and
  pH status at both study sites.
• This may be attributed to
• (i) Low decomposition of the applied
  materials
• (ii) high content in allophane of the
  study area.
• The application of mineral fertilizers (DAP and
  urea) increased the level of soil available P at
  both sites significantly. Hence, high response of
  volcanic soils to P fertilizers.

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Effects of green manures on maize yields
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• Maize grain yields were higher at ISAE site.
• The applied green manures did not improve maize
  grain yields unlike the mineral fertilizers (DAP
  and urea).
• This was mainly attributed to the low P content
  and lack of synchrony between nutrient release
  and maize nutrient needs.
• These results suggest that the application of C.
  calothyrsus and A. acuminata green manures some
  weeks before planting may benefit the season
  growing crop.

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CONCLUSION RECOMMENDATION
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• Increasing depletion of volcanic soils of Rwanda
  due to overcultivation.
• Low effects of C. calothyrsus and A. acuminata
  green manures on soil N, available P, OM contents
  and pH
• Similarly, no effect of the applied manures on
  maize yields.
• Based on the results, the direct application of
  applied manures is likely to benefit the
  subsequent crop rather than the first one.
  Therefore, advisable to incorporate studied green
  manures some weeks before sowing or compost them
  before application

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MurakozeThank youAsante SanaMerci