manipulating cropping systems to improve soil fertility
DESCRIPTION
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 productivityTRANSCRIPT
Manipulating cropping systems to improve soil fertility
S. BoahenIITA – Mozambique
Nampula
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
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
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
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?
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
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]
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
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
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