Managing maize-based cropping systems to increase soil carbon in northern Ghana

1. Managing maize-based cropping systems to increase soil carbon in northern Ghana J.B. Naab1, J.W. Jones2, J. Koo2, and K.J. Boote3 1Savanna Agricultural Research Institute, Wa, Ghana. 2Department of Bio. & Agric. Eng., University of Florida, USA. 3Agronomy Department, University of Florida, USA.

2. INTRODUCTION • Among various ways to sequester CO2 from the atmosphere, increasing plant productivity is an option that could also lead to increased agricultural productivity and food security, especially in developing countries. • Agricultural production in northern Ghana is often constrained by low soil fertility especially N and P with resultant low biomass production

3. Any increase in biomass also offers increased scope for carbon sequestration. • Improvements in crop management leading to greater crop residue production may allow sufficient residues to be returned to fields. • Fertilization is a primary means for increasing plant production and crop yield. • Cereal-legume rotations complimented with the use of mineral fertilizers are options to improve soil fertility for sustainable crop production

4. OBJECTIVES • Conduct on-station and on-farm experiments to assess the potential of different cropping systems to sequester soil carbon • Collect minimum data set needed for adapting the DSSAT-CENTURY model for use in simulating the potential of various cropping systems to sequester soil carbon

5. Experiment 1Cropping systems and fertilizer effects on maize productivity and soil carbon • Treatments - Continuous maize + 30 kg N ha-1 - Continuous maize + 80 kg N ha-1 - Peanut – maize rotation + 40 kg N ha-1 - Mucuna – maize rotation + 40 kg N ha-1 - Bush fallow–maize rotation + 40 kg Nha-1

6. Measurements • Soil carbon measurements in 2003, 2005, 2006 • Biomass accumulation and partitioning • End of season total biomass • Grain yield

7. Table 1: Effects of cropping system and fertilizer on residues returns to the soil each season

8. Effects of cropping system and fertilizer nitrogen on soil organic carbon

9. Effects of cropping system and fertilizer nitrogen on maize grain yield

10. Experiment 2Effects of nitrogen and phosphorus fertilizers on biomass production, soil organic carbon and maize grain yield • Initiated in 2003 • 3 x 3 factorial • Factor 1: 3 N levels (0, 60 & 120 kg N ha-1) • Factor 2: 3 P levels (0, 60, & 90 kg P2O5 ha-1)

11. Materials and methods cont…. • P source: single super-phosphate applied annually; • N source: Urea • Tillage: no-till in 2004, 2005 & 2006 • Residues returned to soil annually

12. Measurements • Soil carbon measurements in 2003, 2005, 2006 • LAI • Biomass accumulation and partitioning • Tissue analysis for N and P concentrations; • End of season total biomass • Grain yield

13. Effect of nitrogen and phosphorus fertilizers on crop residue returned to the soil

14. Effect of nitrogen and phosphorus fertilizers on soil organic carbon changes with time

15. Effect of nitrogen and phosphorus fertilizers on maize grain yield

16. Experiment 3On-farm evaluation of cropping systems and fertilizer on maize productivity and soil carbon • Locations: 2 villages – Piisi and Nakor • Treatments - Continuous maize + 30 kg N ha-1 - Continuous maize + 80 kg N ha-1 - Peanut – maize rotation + 40 kg N ha-1 • Replications: 15 farmers

17. Effect of cropping system and fertilizer on biomass production and soil carbon changes on some farmers’ fields † = Incorporated residues ‡ = Did not incorporate residues

18. Effect of cropping systems and fertilizer on maize grain yield on some farmers’ fields