Evaluation of Pearl Millet Production Systems for High Yield and Net Carbon Accumulation in Soil and Crop

Higher accumulation of carbon in agro-ecosystems by increasing crop production and soil organic carbon (SOC) through N-fertilizers and manure application is currently being discussed as one of the options to decrease the load of atmospheric CO₂ so as to reduce the greenhouse effect. We studied this possibility for eight consecutive years in eight high-input-based and three traditional production systems (PSs) of pearl millet. High input PSs involved application of urea, manure and urea+manure in varying quantities whereas in traditional PSs crop was grown without fertilizers and manure and in rotation with a legume crop or by keeping land fallow for one year between two pearl millet crops. Values of total and net C accumulated in high input PS ranged from 8735 to 15340 kg ha⁻¹ and 242 to 10049 kg ha⁻¹, respectively. Values of total C accumulated for traditional PS ranged from 4811 to 7313 kg ha⁻¹ and were similar to net C accumulated. Most of the accumulated C could be accounted for in crop biomass. Only in the PS involving manure application a substantial part of accumulated C was added to SOC. Crop biomass production was highest with application of urea+manure followed by urea and was lowest in the traditional PS. Biomass production increased with increasing application of both urea and manure. Combined application of urea (40 kg N) with 5 t manure ha⁻¹ yr⁻¹ produced highest crop biomass but showed a net C accumulation of only 839.6 kg C ha⁻¹ (second lowest). On the contrary, urea application (40 kg N ha⁻¹) that resulted in highest net accumulation of C ranked sixth in biomass production. Few PSs fell between these two extremes showing a balance between high biomass production and high C sequestration. These results when analyzed in the background of high productivity, a major objective of agriculture, suggest that high production in a PS does not necessarily mean high net C accumulation, but it can be achieved through proper selection of inputs.