EFFECTS OF Calliandra calothyrsus and EFFECTS OF Calliandra calothyrsus and Alnus acuminata GREEN MANURES IN Alnus acuminata GREEN MANURES IN

MAIZE PRODUCTION IN THE HIGHLAND MAIZE PRODUCTION IN THE HIGHLAND VOLCANIC SOILS OF RWANDAVOLCANIC SOILS OF RWANDA

Didace HABAMENSHIDidace HABAMENSHIISAE BUSOGO, RWANDAISAE BUSOGO, RWANDA

22NDND WORLD CONGRESS OF WORLD CONGRESS OF AGROFORESTRYAGROFORESTRY

Nairobi, August 22 – 28Nairobi, August 22 – 28thth, , 20092009

EFFECTS OF Calliandra calothyrsus and EFFECTS OF Calliandra calothyrsus and Alnus acuminata GREEN MANURES IN Alnus acuminata GREEN MANURES IN

MAIZE PRODUCTION IN THE HIGHLAND MAIZE PRODUCTION IN THE HIGHLAND VOLCANIC SOILS OF RWANDAVOLCANIC SOILS OF RWANDA

Didace HABAMENSHIDidace HABAMENSHIISAE BUSOGO, RWANDAISAE BUSOGO, RWANDA

22NDND WORLD CONGRESS OF WORLD CONGRESS OF AGROFORESTRYAGROFORESTRY

Nairobi, August 22 – 28Nairobi, August 22 – 28thth, , 20092009

INTRODUCTION

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.

Introduction (Cnt’d)

•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

Introduction (Cnt’d)

• 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

MATERIALS & METHODES

Location of study area

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)

Alnus intercropped with Irish Potato in Musanze

Calliandra and other AF trees on degraded land

CalliandraAlnus

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 & pHMeasurement of maize yield

Methods (Cnt’d)

Statistical analysis using GENSTAT package

RESULTS & DISCUSSION

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

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

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

At the end of the experiment:At the end of the experiment:

No effect of green manures on soil N, P, No effect of green manures on soil N, P, OM and pH status at both study sites. OM and pH status at both study sites.

This may be attributed to This may be attributed to (i) Low decomposition of the applied (i) Low decomposition of the applied

materialsmaterials

(ii) high content in allophane of the (ii) high content in allophane of the study area. study area.

The application of mineral fertilizers The application of mineral fertilizers (DAP and urea) increased the level of soil (DAP and urea) increased the level of soil available P at both sites significantly. available P at both sites significantly. Hence, high response of volcanic soils to Hence, high response of volcanic soils to P fertilizers.P fertilizers.

Effects of green manures on maize yields

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

Control DAP+urea

Calliandra(5 t/ha)

Calliandra(10 t/ha)

Alnus(5t/ha)

Alnus(10t/ha)

Treatment

Mai

ze y

ield

(t/

ha)

ISAE

ISAR

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.

CONCLUSION & RECOMMENDATION

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

MurakozeThank you

Asante SanaMerci