L. rusinamhodzi ca and cp with manure, a comparative analysis


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L. rusinamhodzi ca and cp with manure, a comparative analysis

  1. 1. Effects of conservation agriculture and manure application on maize grain yield and soil organic carbon: a comparative analysis Leonard Rusinamhodzi PhD Student Plant Production Systems Group
  2. 2. The challenge of soil fertility decline…. <ul><li>70% of smallholder farms are on infertile sandy soils </li></ul><ul><li>Majority of farmers use mouldboard ploughing </li></ul>Source: Rusinamhodzi et al ( 2011)
  3. 3. Farmers’ response………. <ul><li>Use of cattle </li></ul><ul><li>manure to improve </li></ul><ul><li>crop productivity </li></ul><ul><li>Use of crop </li></ul><ul><li>residues to improve manure </li></ul><ul><li>quantity and quality </li></ul><ul><li>of manure </li></ul>
  4. 4. Manure use………… <ul><li>Manure is spread on soil surface and ploughed under </li></ul><ul><li>Some farmers are now applying manure in planting basins </li></ul><ul><ul><li>Strategy make small quantities cover a large area </li></ul></ul>
  5. 5. Crop residue use……… Example: Manjonjo village, Murehwa, Zimbabwe CR from 70% of cropped area is used for feed/bedding Crop residues produced Left in fields Collected Mulch (ex-situ) Compost Livestock feed Bedding Burnt Mulch (in- situ) Available for livestock Kraal Burnt 40 ha 43 ha 3 ha 5.6 ha 13 ha 4.6 ha 13.5 ha 1.1 ha 40 ha 1.9 ha
  6. 6. Trade-offs ……………….. <ul><li>The allocation of crop residues for livestock feed meets two out of three critical objectives; </li></ul><ul><ul><li>it ensures feed during the dry season </li></ul></ul><ul><ul><li>improves quantity and quality of manure </li></ul></ul><ul><ul><li>but does not ensure permanent soil cover required under conservation agriculture (CA). </li></ul></ul>
  7. 7. Trade-offs……………… <ul><li>There are strong trade-offs for either allocating crop residues for livestock feed or using the crop residues directly for mulch thereby reducing the amount and quality of manure available and compromising the condition of livestock </li></ul>
  8. 8. Study objective……. <ul><li>To perform a comparative analysis of maize grain yield and soil organic carbon (SOC) changes in CA systems versus conventional tillage systems (with manure application). </li></ul><ul><ul><li>Crop yield- food security and income, </li></ul></ul><ul><ul><li>SOC - important determinant of soil fertility, productivity and sustainability </li></ul></ul>
  9. 9. Field experiments……………. <ul><li>Data obtained from two sets of long-term experiments under continuous sole maize ( Zea mays L.) </li></ul><ul><ul><li>experiment on manure application under conventional tillage </li></ul></ul><ul><ul><li>Experiment on no-tillage with mulch cover </li></ul></ul>
  10. 10. Manure experiment <ul><li>Established from 2002 to 2010 on both clay (Chromic Luvisols) and sandy (Haplic Lixisols) soils and two field types (homefield and outfield) in Murehwa, Zimbabwe. </li></ul><ul><li>Tillage- mouldboard ploughing </li></ul><ul><ul><li>Fertiliser treatments </li></ul></ul><ul><ul><ul><li>control, </li></ul></ul></ul><ul><ul><ul><li>100 kg N ha -1 , </li></ul></ul></ul><ul><ul><ul><li>100 kg N ha -1 + 5 t manure ha -1 </li></ul></ul></ul><ul><ul><ul><li>100 kg N ha -1 + 15 t manure ha -1 . </li></ul></ul></ul>
  11. 11. Tillage experiment <ul><li>Established in 1988 to 1999 at three sites, Domboshawa (sandy soils, Haplic Lixisols), Makoholi (sandy soils, Ferralic Arenosols) and Institute of Agricultural Engineering (IAE) (red clay soils, Chromic Luvisols) </li></ul><ul><li>Two tillage treatments </li></ul><ul><ul><li>Conventional mouldboard ploughing, 23 cm depth. </li></ul></ul><ul><ul><li>Mulch ripping (MR), ripping to a depth of 20 – 25 cm , crop residues maintained on the soil surface (40 and 60 % cover). </li></ul></ul><ul><ul><li>All treatments received 114 kg N ha -1 , 22 kg P ha -1 and 25 kg K ha -1 </li></ul></ul>
  12. 12. Soil analysis <ul><li>Total C was determined by dry combustion using a LECO TRUSPEC C and N auto - analyser (LECO Corporation, 2003). </li></ul><ul><li>Grain yield advantages were calculated as difference between yield in control and treatment </li></ul>
  13. 13. Results…….maize grain yield <ul><li>Addition of 5 t ha -1 manure resulted in more than double maize grain yield over the control </li></ul>
  14. 14. Results……..maize grain yield <ul><li>Effect of mulch and reduced tillage on yield was marginal with a yield gain of only 0.2 t ha -1 over a nine year period </li></ul>
  15. 15. Results…………SOC <ul><li>Manure application (5 t ha -1 ) under conventional tillage increased SOC by 0.13% and 0.09% per year on clay and sandy soils respectively </li></ul>
  16. 16. Results………….SOC <ul><li>Reduced tillage and mulch retention led to an increase of 0.02% per year for both sandy and clay soils </li></ul>
  17. 17. Discussion points <ul><li>the opportunity cost of losing mulch is offset by gains in animal productivity given that communal grazing is not adequate during the dry season </li></ul><ul><li>The results suggest that the decision by farmers to allocate crop residues to animals as feed and use manure is most suitable for their circumstances </li></ul><ul><li>manure application in combination with fertilizer provides calcium, magnesium and micronutrients that ensure high yields especially on degraded soils </li></ul>
  18. 18. Conclusion <ul><li>An optimal procedure for retaining adequate crop residues while providing sufficient feed for livestock is thus required to facilitate the adoption of CA on smallholder farms. </li></ul>
  19. 19. Thank you!