Long‐term manure application for crop yield stability and carbon sequestration in subtropical region

Yield stability and carbon sequestration of agricultural systems are impacted by nutrient management strategies. Major objectives of this study were to understand the effects of long‐term (43 years) manure application on a) environmental parameters such as soil organic carbon (SOC) sequestration, enzyme activities in surface and subsurface layers, and b) yield, and yield stability under a soybean–wheat cropping system in a Vertisol. For this, 100% recommended dose of nitrogen (N), N and phosphorus (NP), N, P and potassium (NPK), NPK + farmyard manure (NPKM) was compared with an unfertilized control (UC) and a fallow land. After 43 years, NPKM and NPK plots had ∼63 and 30% higher total SOC stock than UC, and 45 and 17% higher total SOC stock than fallow plots, respectively in the 0–30 cm layer. Acid hydrolysable C was ~ 42 and 57% higher for NPKM plots in those layers respectively than fallow land. The proportion of macroaggregates was less than 30% in both soil layers of cultivated plots. NPKM had 44 and 28% greater humic and fulvic acid‐associated C than fallow land in top layer. Enzyme activities improved in NPKM by ~ 60 and 61% as compared with fallow land. A steady decline in soybean productivity over the years might be due to residue effect. However, wheat yield increased steadily with manuring. Higher SOC accumulation (p