Figure 2
From: Long-term application of fertilizer and manures affect P fractions in Mollisol
Effect of long-term application of chemical fertilizer, organic manure, and straw on total phosphorus (P) and available P concentrations. * indicates significant difference at P < 0.05 level at same soil depth, ns indicates no significant difference between the total phosphorus (P) and available P concentrations at the same soil depth. CK, no fertilizer application; NPK, chemical fertilizer application; NPK + S, chemical fertilizer plus maize straw incorporation; OM, organic manure application.
