Effects Of Fertilization On Forage-planting Soil Organic Carbon And Carbon Sequestration Of Forage In Karst Region

The effect of different fertilization on organic carbon and enzyme activity in brown calcareous soil and red soil, forage yield and carbon sequestration were studied using the pot and field experiments in the karst region of Huanjiang, Guangxi, so as to provide scientific basis in the accumulation of soil organic carbon and the improvement of soil productivity in the region. The treatments in pot experiment included CK, N1(150mg N/kg soil), N2(250mg N/kg soil), N1P1(100mg P2O5/kg soil), N2P2(150mg P2O5/kg soil), N1P1K1(70mg K2O/kg soil), N1P1K2(105mg K2O/kg soil), N2P2K1and N2P2K2, while in field experiment, they were CK, N1(390kg N/hm2), N2(572kg N/hm2), N1P (240kg P2O5/hm2), N2P, N1PK (360kg K2O/hm2) and N2PK. The results are outlined as follows:1. Compared to no fertilization, all fertilization treatments increased the contents of organic carbon (SOC), microbial carbon (MBC), dissolved organic carbon (DOC), readily oxidizable carbon (ROC), daily mineralized carbon (DMC) and cumulative mineralized carbon (CMC) in brown calcareous soil. NPK treatment had the highest increase of29.6%,109.3%,28.8%,522.6%,75.6%and55.0%sampled on July17, respectively. NPK treatment increased the SOC, ROC and DMC in red soil by40.1%,738.7%and120.9%on July28, and CMC by30%on June9, respectively. N1treatment increased the MBC in red soil by26.4%(June9) and N2treatment increased the DOC by7.7%(July28).2. There was an extremely significant positive correlation between the SOC and different fractions of active SOC in brown calcareous soil, and there was also a significant correlation among several fractions of active SOC. However, there were no significant positive correlations between the SOC and different fractions of active SOC in red soil and among different fractions of active SOC. 3. Compared to no fertilization, applied chemical fertilizer increased the invertase and urease acitivity in brown calcareous soil. Fertilization also increased the urease acitivity in red soil, but had no significant effect on the invertase acitivity.4. Compared to no fertilization, fertilization increased forage yield and nutrient content. The NPK treatment had the highest increase in forge yield, by139.4%in pot experiment.5. Compared to no fertilization, fertilization increased carbon sequestration in shoot, root and rhizosphere soil by60.2%-144.3%,12.1%-59.4%and12.0%-59.5%, respectively. And the NPK treatment had better effect than other treatments.Therefore, NPK treatment not only increased the accumulation of active organic carbon in soil, but also was beneficial for CO2fixation by forge plants.