Soil Respiration Rate and Soil Carbon Emission Efficiency of Maize and Its Response to Phosphorus Application in Red Soil

Purpose To investigate the effects of different phosphorus application gradients on maize yield and its stability, phosphorus fertilizer utilization efficiency, soil respiration rate and carbon emission efficiency, revealing the dynamic changes of red soil respiration and phosphorus application response at different growth stages of maize.

Methods Based on four consecutive years of field experiments, four phosphorus application gradients (P₀: 0 kg/hm², P₆₀: 60 kg/hm², P₉₀: 90 kg/hm², P₁₂₀: 120 kg/hm²) were set up to analyze the changes of biological yield, economic yield, yield sustainability, yield stability, soil respiration rate, total soil CO₂ emission and soil carbon emission efficiency of maize in low phosphorus red soil.

Results In low phosphorus red soil, compared with no phosphorus fertilizer for four consecutive years, the application of phosphorus fertilizer could increase the biomass of maize by 15.11 times on average, the economic yield of maize by 7.95 times on average, the sustainability index of maize yield by 6.90 times on average, and the yield stability by 1.60 times on average. With the increase of phosphorus application level, maize yield and yield sustainability index increased significantly, but yield stability was the highest in P₉₀ treatment; the agronomic efficiency, apparent utilization rate and partial productivity decreased gradually, but there was no significant difference between P₉₀ treatment and P₁₂₀ treatment. The soil respiration rate increased first and then decreased with the growth period of maize, and reached the highest value at the tasseling stage, and the soil respiration rate of P₆₀, P₉₀, and P₁₂₀ treatment increased by 69.43%, 43.04% and 42.22%, respectively, compared with P₀ treatment, with an average increase of 51.56%. Compared with P₀ treatment, the total CO₂ emissions of P₆₀, P₉₀, and P₁₂₀ treatment increased by 86.96%, 123.64% and 65.56%, respectively, with an average increase of 92.05%, while the carbon emission efficiency increased by an average of 3.35 times.

Conclusion Based on maize yield, carbon emission efficiency and apparent utilization rate of phosphorus fertilizer, the optimal phosphorus application rate of maize in red soil with low phosphorus is 79.10 kg/hm², and the recommended phosphorus application rate is 80 kg/hm², which can take into account the high yield of maize in red soil, the high efficiency of phosphorus fertilizer and the reduction of soil CO₂ emission, and promote the increase of yield and efficiency of maize in red soil and green low-carbon cultivation.