Changes in soil profile organic carbon and hydro-physical properties as impacted by long-term manure and inorganic fertilizer rates under a corn-soybean-spring wheat rotation system

Using manure appropriately can enhance organic carbon, and hydro-physical properties without negatively impacting the environment. However, how manure impacts soils, especially at deeper depths, is still not well studied. Therefore, the objective of this study was to assess the impact of different manure and inorganic fertilizer application rates on soil profile organic carbon and hydro-physical properties under corn(Zea mays L.)-soybean(Glycine max L.)-spring wheat (Triticum aestivum L) rotation at Beresford (initiated, 2003) and Brookings (2008) sites in South Dakota. Treatments included: low manure(LM), medium manure(MM), high manure(HM), medium fertilizer(MF), high fertilizer(HF), and control(CK). Four replicated intact soil cores were collected from all the treatments at 0-10, 10-20, 20-30, and 30-40 cm depths. Considering treatments by depth interactions, the HM increased the SOC and TN stocks by 16-62% as compared to the CK, MF, and HF at 0-10 cm for either site. However, treatments did not always impact these parameters beyond 20 cm depth. On observing treatment as the main effect, the MM and HM increased the SWR at 0, -5 kPa compared to MF, HF, and CK in Brookings, and the MM increased the SWR at -30 kPa as compared to the MF in Beresford at 0-40 cm depths. Data suggests continuous manure application may enhance organic carbon and hydro-physical properties at deeper depths. Therefore, this study concluded that long-term manure application is more beneficial when you consider the application rate and its timing. It can improve hydro-physical properties, thereby stabilizing the soil structure and improving water retention at deeper depths.