Integration of Canavalia brasiliensis into the crop-livestock system of the Nicaraguan hillsides: environmental adaptation and nitrogen dynamics

Transcription

1 Integration of Canavalia brasiliensis into the crop-livestock system of the Nicaraguan hillsides: environmental adaptation and nitrogen dynamics Sabine Douxchamps 13 November 2012

2 Facts: 80 % of population with less than $2/day 27% of population undernourished Hillsides: 80% smallholders (crop-livestock) Continuous cropping Use of marginal lands Nitrogen (N) depletion Agricultural productivity decrease Income decrease Food insecurity

3 1 st rainy season 2 nd rainy season dry season Maize Bean Livestock

4 1 st rainy season 2 nd rainy season dry season Maize Bean Livestock Introducing a cover crop legume: N input through symbiotic N 2 fixation as green manure benefit to the next crop build up organic matter stocks cover the soil against erosion as forage increase amount and quality of dry season feed

5 1 st rainy season 2 nd rainy season dry season Maize Bean Canavalia brasiliensis Livestock Canavalia brasiliensis produce a lot of biomass drought tolerant selected by farmers

6 when introducing a legume into a smallholder hillside system where to plant it? what limits its agricultural performance? what is its net N input to the system? how to use it? how do farmers want to manage it? what is the benefit to the next crop? how much remains in the soil?

7 when introducing a legume into a smallholder hillside system where to plant it? what limits its agricultural performance? biomass study - landscape scale m m 2 what is its net N input to the system? how to use it? how do farmers want to manage it? N budgets study - plot scale 1 m 2 what is the benefit to the next crop? how much remains in the soil? 15 N study - microplot scale

8 biomass N dynamics synthesis when introducing a legume into a smallholder hillside system where to plant it? what limits its agricultural performance? biomass study - landscape scale m m 2 what is its net N input to the system? how to use it? how do farmers want to manage it? N budgets study - plot scale 1 m 2 what is the benefit to the next crop? how much remains in the soil? 15 N study - microplot scale

9 MP GR PT canavalia biomass 07 (kg/ha) LP FC bean AR aim determine soil and topographic factors that influence canavalia biomass production material and methods soil chemical and physical properties soil profiles and rooting patterns topography Douxchamps et al. 2012, J. Agr. Sci 150

10 Biomass (kg ha -1 ) Canavalia biomass (kg/ha) Canavalia biomass (kg/ha) Canavalia biomass (kg/ha) background canavalia biomass production was significantly affected by soil depth, C and N, slope position, clay and stones 0 20 OA 40 C/Bh 0 20 B Bk 0 20 Ap B 40 Cm A river 40 C 60 B/C Cm C C 120 Cb CBm FC1 FC2 GR1 GR2 LP MP1 AR1 MP2 AR1 AR2 PTAR2 FC1AR1 FC2 FC2 AR2 GR1 FC1GR2 FC2 LPGR1 MP1 GR2 MP2 MP2LP PT PTMP1 Douxchamps et al. 2012, J. Agr. Sci 150 Profile groups Profile groups Profile groups

11 aim assess net N input from canavalia to the system describe how its use as forage or green manure affects soil N stocks material and methods NPK UREA N balance [kg N ha -1 ] = (N fert + N seed + N fix) (N export) 15 N natural abundance method 4 farms, 5 treatments (M/B and M/C with grazing simulation), 2 years Douxchamps et al. 2010, Nutr. Cycl. Agroecosyst. 88

12 -40 FC GR LP PT -60 results [kg N ha -1 ] N 2 fixation: bean ~ 3 canavalia ~ 20 seed: ~ 3 mineral fertilizer: export: maize: bean: 0-11 canavalia: 0-87 kg N ha -1 kg N ha FC FC GR GR LP LP PT PT M/B M/C0 M/C50 M/C75 M/C kg N ha FC GR LP PT Douxchamps et al. 2010, Nutr. Cycl. Agroecosyst. 88 M/B M/C0 M/C50 M/C75 M/C100

13 -40 FC GR LP PT -60 results [kg N ha -1 ] N 2 fixation: bean ~ 3 canavalia ~ 20 seed: ~ 3 mineral fertilizer: export: maize: bean: 0-11 canavalia: 0-87 kg N ha -1 kg N ha FC FC GR GR LP LP PT PT M/B M/C0 M/C50 M/C75 M/C canavalia as green manure: net N input due to symbiotic N 2 fixation canavalia as forage: depletes soil N return of animal manure? mineral fertilizers necessary for positive N balance kg N ha FC GR LP PT Douxchamps et al. 2010, Nutr. Cycl. Agroecosyst. 88 M/B M/C0 M/C50 M/C75 M/C100

14 aim determine the fertilizer value of canavalia residues and animal manure for maize material and methods 15 N direct and indirect labelling techniques: maize growing in microplots amended with mineral fertilizer, canavalia residues, or cow manure. Douxchamps et al. 2011, Plant Soil 341

15 recovery (%) background aim determine the fertilizer value of canavalia residues and animal manure for maize material and methods 15 N direct and indirect labelling techniques: maize growing in microplots amended with mineral fertilizer, canavalia residues, or cow manure. results Maize N OM + clay Nmin Nmic Mineral fertilizer Canavalia residues Check manure canavalia residues are a valuable source of N for maize canavalia built up soil organic matter with time Douxchamps et al. 2011, Plant Soil 341

16 Canavalia has the potential to improve the crop-livestock system: can produce high amounts of biomass and tolerate drought fixes significant amounts of N as green manure: as forage: - increases the N balance and benefit to the subsequent crop - decreases net annual income by 12% on the short term - increases milk yields during the dry season (1l/day.cow) - increases net annual income by 8% - risk of N depletion

17 Canavalia has the potential to improve the crop-livestock system: can produce high amounts of biomass and tolerate drought fixes significant amounts of N as green manure: as forage: - increases the N balance and benefit to the subsequent crop - decreases net annual income by 12% on the short term - increases milk yields during the dry season (1l/day.cow) - increases net annual income by 8% - risk of N depletion Farmers perceive a positive effect of canavalia to the system and want to use it as forage

18 the best way for mitigating soil nutrient depletion and increase livestock productivity would be to 1. use canavalia first as forage 2. improve animal manure management 3. use canavalia regrowth as green manure canavalia should be seen as one element of a management strategy for a progressive restoration of degraded soils and optimal nutrient flows - other soil conservation practices (life barriers or stone rows in slopes) - complex rotations with various legumes, diversification

19 Adoption by smallholders was facilitated through development and distribution of booklets for farmers and extensionists seed production seed release by local authorities farmers want to be involved in seed production government and other local institutions start to integrate it in their programs

20 acknowledgements Prof. Dr. Emmanuel Frossard (ETH) Dr. Astrid Oberson (ETH) Dr. Idupulapati Rao (CIAT Colombia) Dr. Axel Schmidt (CIAT Nicaragua) Dr. Rein van der Hoek (CIAT Nicaragua) Martin Mena (INTA) the farmers of Santa Teresa the North-South Center of ETH Zurich

21 acknowledgements Prof. Dr. Emmanuel Frossard (ETH) Dr. Astrid Oberson (ETH) Dr. Idupulapati Rao (CIAT Colombia) Dr. Axel Schmidt (CIAT Nicaragua) Dr. Rein van der Hoek (CIAT Nicaragua) Martin Mena (INTA) the farmers of Santa Teresa the North-South Center of ETH Zurich thank you for your attention