manipulating cropping systems to improve soil fertility

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The need to move from fallow-based to legume-based systems.Legume-based cropping system that combines suboptimum inorganic fertilizer rate can enhance nutrient-use efficiency and increase productivity

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Page 1: Manipulating cropping systems to improve soil fertility

Manipulating cropping systems to improve soil fertility

S. BoahenIITA – Mozambique

Nampula

Page 2: Manipulating cropping systems to improve soil fertility

Agricultural production in SSA characterized by low productivity

Per capita food production in SSA declined by 1.0% annually

between 1980 and 1993 (World Bank, 1996)

Major factor: decline in soil fertility and increasing nutrient

depletions through nutrients removal from harvests, run-off

erosion, leaching etc

Long duration fallows traditionally use to restore soil fertility

are not feasible

-increasing population and resulting demand for agric land

Background

Page 3: Manipulating cropping systems to improve soil fertility

Results: Continuous cropping with little or no external input

Inorganic fertilizers are expensive and majority of farmers can’t afford

Moreover, the inorganic fertilizers are not easily available

Page 4: Manipulating cropping systems to improve soil fertility

Develop strategies that focus on organic sources of nutrients to build up and maintain soil fertility

- Cropping systems

- A shift from fallow-based to legume-based

- Capitalize on the ability of legumes to fix free atmospheric N

- Options includes: crop rotations, green manures,

intercropping, improved fallow, alley cropping, agroforestry

- Yield advantages due to cropping system are well

documented

Challenge

Page 5: Manipulating cropping systems to improve soil fertility

Increased soil organic matter

Enhanced Cation Exchange Capacity of the soil

Increased soil aggregation – indicator of soil structure

Increased soil microbial activity

Improved nutrient availability Improved soil quality Observed Yield advantages

How do these practices influence soil properties?

Page 6: Manipulating cropping systems to improve soil fertility

Treatment Marama Ngwa Yimirshik

a

Tilla Maina Harii

Mirnga

Sabongari

Nzuda Dambo

a

SGS SGS NGS NGS SS SS

Organic C (g/kg)

2004-baseline 11.3 9.9 13.7 10.0 9.2 6.1

Cereal-legume

10.8 14.3 12.6 14.3 9.5 5.7

Cereal-cereal 10.9 13.9 13.1 15.7 9.3 5.4

Total N (g/kg)

2004-baseline 1.09 1.96 1.93 1.68 0.98 1.49

Cereal-legume

0.86 1.35 1.27 1.47 1.03 1.17

Cereal-cereal 0.84 1.05 1.17 1.12 0.54 1.21

Available P (mg/kg)

2004-baseline 2.88 3.33 2.95 5.48 3.70 0.78

Cereal-legume

3.92 3.73 3.26 4.54 1.68 2.10

Cereal-cereal 3.50 2.80 4.60 5.30 2.20 2.40

Effect of cereal-Legume rotation on some soil chemical properties in PROSAB Project sites

SGS=Southern Guinea Savanna; NGS=Northern Guinea Savanna; SS=Sudan Savanna Kwari J.D. 2009

Page 7: Manipulating cropping systems to improve soil fertility

Kadesok Opwatetta Kapolin

Previous crop and N rate

2004 2005 2004 2005 2004 2005 Overall

5† 8 5 7 6 5 36

Sorghum 1.03 1.76 1.17 1.39 0.67 0.96 1.21

Cowpea 1.84 3.19 1.61 2.17 1.43 1.18 2.01

Sorghum + 30 kg N ha-1

2.30 3.49 1.65 2.43 2.05 1.36 2.33

Mucuna 2.64 3.98 1.76 3.00 2.81 1.47 2.75

LSD(0.05) 0.27 0.27 0.29 0.39 0.53 0.15 0.24

† Number of on-farm trails conducted

Kayuki et al., 2007

Sorghum grain yield (Mg ha-1), following either sorghum, cowpea, or mucuna in rotation, at three locations in a semiarid area of eastern Uganda, 2004 and 2005 [Farmer-managed trials]

Page 8: Manipulating cropping systems to improve soil fertility

Aboveground DM yields (t ha-1) of pure and mixed species legume fallows and natural weed fallow at Dindi and Owano farms in western Kenya

Ndufa et al., 2009

Page 9: Manipulating cropping systems to improve soil fertility

Treatment SR1999 LR2000 SR000 LR2001 SR2001 Total

Pigeon Pea (CC) 4.7 4.1 3.4 2.9 1.4 16.4

Colliandra colothyrus (Cal)

2.7 2.6 2.3 2.0 1.0 10.5

Crotalaria garhamania (Cg)

5.9 6.3 4.0 3.6 1.6 21.4

Siratro (Ma) 5.7 6.5 4.0 3.6 1.7 21.5

Sesbania sesban (Ss) 5.4 5.5 4.0 2.3 1.6 18.7

Ss + Cc 5.2 5.5 3.2 2.7 1.2 17.9

Ss + Cal 5.1 5.8 3.2 3.2 1.6 18.7

Ss + Cg 6.2 6.0 4.3 3.2 1.5 21.1

Ss + Ma 6.7 5.6 4.1 3.3 1.8 21.4

Natural Fallow 1.3 2.2 2.1 2.8 1.4 9.7

Maize + N 4.9 6.5 5.7 6.5 3.2 26.7

Maize –N 1.7 2.7 2.0 2.2 1.3 9.8

SED‡ 0.32*** 0.42*** 0.31*** 0.38*** 0.24*** 0.90***

*** P ≤ 0.0001; Ndufa et al., 2009

Maize grain yield of four cropping seasons (SR = short rains, LR = long rains) after monoculture and mixed-species legume as compared with continuous cropping, N fertilizer (100 kg N ha-1) and natural weed fallow

Page 10: Manipulating cropping systems to improve soil fertility

The need to move from fallow-based to legume-based systems

Mix species more beneficial due to differences in litter quality and nutrient release pattern: hence a better synchronized N release

Legume-based cropping system that combines suboptimum inorganic fertilizer rate can enhance nutrient-use efficiency and increase productivity

Summary