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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Manipulating cropping systems to improve soil fertility

  1. 1. Manipulating cropping systems to improve soil fertility S. Boahen IITA – Mozambique Nampula
  2. 2. <ul><li>Agricultural production in SSA characterized by low </li></ul><ul><li>productivity </li></ul><ul><li>Per capita food production in SSA declined by 1.0% annually </li></ul><ul><li>between 1980 and 1993 (World Bank, 1996) </li></ul><ul><li>Major factor: decline in soil fertility and increasing nutrient </li></ul><ul><li>depletions through nutrients removal from harvests, run-off </li></ul><ul><li>erosion, leaching etc </li></ul><ul><li>Long duration fallows traditionally use to restore soil fertility </li></ul><ul><li>are not feasible </li></ul><ul><li>-increasing population and resulting demand for agric land </li></ul>Background
  3. 3. <ul><li>Results: Continuous cropping with little or no external input </li></ul><ul><li>Inorganic fertilizers are expensive and majority of farmers </li></ul><ul><li>can’t afford </li></ul><ul><li>Moreover, the inorganic fertilizers are not easily available </li></ul>
  4. 4. <ul><li>Develop strategies that focus on organic sources of nutrients </li></ul><ul><li>to build up and maintain soil fertility </li></ul><ul><li>- Cropping systems </li></ul><ul><li>- A shift from fallow-based to legume-based </li></ul><ul><li>- Capitalize on the ability of legumes to fix free atmospheric N </li></ul><ul><li>- Options includes: crop rotations, green manures, </li></ul><ul><li>intercropping, improved fallow, alley cropping, agroforestry </li></ul><ul><li>- Yield advantages due to cropping system are well </li></ul><ul><li>documented </li></ul>Challenge
  5. 5. <ul><li>Increased soil organic matter </li></ul><ul><li>Enhanced Cation Exchange Capacity of the soil </li></ul><ul><li>Increased soil aggregation – indicator of soil structure </li></ul><ul><li>Increased soil microbial activity </li></ul><ul><li>Improved nutrient availability </li></ul><ul><li>Improved soil quality Observed Yield advantages </li></ul>How do these practices influence soil properties?
  6. 6. 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 2.40 2.20 5.30 4.60 2.80 3.50 Cereal-cereal 2.10 1.68 4.54 3.26 3.73 3.92 Cereal-legume 0.78 3.70 5.48 2.95 3.33 2.88 2004-baseline Available P (mg/kg) 1.21 0.54 1.12 1.17 1.05 0.84 Cereal-cereal 1.17 1.03 1.47 1.27 1.35 0.86 Cereal-legume 1.49 0.98 1.68 1.93 1.96 1.09 2004-baseline Total N (g/kg) 5.4 9.3 15.7 13.1 13.9 10.9 Cereal-cereal 5.7 9.5 14.3 12.6 14.3 10.8 Cereal-legume 6.1 9.2 10.0 13.7 9.9 11.3 2004-baseline Organic C (g/kg) SS SS NGS NGS SGS SGS Nzuda Damboa Sabongari Maina Harii Mirnga Tilla Ngwa Yimirshika Marama Treatment
  7. 7. † 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] 0.24 0.15 0.53 0.39 0.29 0.27 0.27 LSD (0.05) 2.75 1.47 2.81 3.00 1.76 3.98 2.64 Mucuna 2.33 1.36 2.05 2.43 1.65 3.49 2.30 Sorghum + 30 kg N ha -1 2.01 1.18 1.43 2.17 1.61 3.19 1.84 Cowpea 1.21 0.96 0.67 1.39 1.17 1.76 1.03 Sorghum 36 5 6 7 5 8 5† Overall 2005 2004 2005 2004 2005 2004 Previous crop and N rate Kapolin Opwatetta Kadesok
  8. 8. 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
  9. 9. *** 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 0.90*** 0.24*** 0.38*** 0.31*** 0.42*** 0.32*** SED‡ 9.8 1.3 2.2 2.0 2.7 1.7 Maize –N 26.7 3.2 6.5 5.7 6.5 4.9 Maize + N 9.7 1.4 2.8 2.1 2.2 1.3 Natural Fallow 21.4 1.8 3.3 4.1 5.6 6.7 Ss + Ma 21.1 1.5 3.2 4.3 6.0 6.2 Ss + Cg 18.7 1.6 3.2 3.2 5.8 5.1 Ss + Cal 17.9 1.2 2.7 3.2 5.5 5.2 Ss + Cc 18.7 1.6 2.3 4.0 5.5 5.4 Sesbania sesban (Ss) 21.5 1.7 3.6 4.0 6.5 5.7 Siratro (Ma) 21.4 1.6 3.6 4.0 6.3 5.9 Crotalaria garhamania (Cg) 10.5 1.0 2.0 2.3 2.6 2.7 Colliandra colothyrus (Cal) 16.4 1.4 2.9 3.4 4.1 4.7 Pigeon Pea (CC) Total SR2001 LR2001 SR000 LR2000 SR1999 Treatment
  10. 10. <ul><li>The need to move from fallow-based to legume-based </li></ul><ul><li>systems </li></ul><ul><li>Mix species more beneficial due to differences in litter quality </li></ul><ul><li>and nutrient release pattern: hence a better synchronized N </li></ul><ul><li>release </li></ul><ul><li>Legume-based cropping system that combines suboptimum </li></ul><ul><li>inorganic fertilizer rate can enhance nutrient-use efficiency </li></ul><ul><li>and increase productivity </li></ul>Summary

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