Effects of fertilizer regime, sample time and the interaction between them on soil physicochemical characteristics.

Values are means ± standard deviation (n = 6 or n = 18).NS: not significant (P>0.05).Fertilizer regimes: CK: control without fertilizers; NPK: chemical fertilizers; NPKM: 50% NPK fertilizer plus 400 kg/ha manure; NPKS: 100% NPK fertilizer plus crop straw; NPKMS: 50% NPK fertilizer plus 400 kg/ha manure and crop straw; NPKMOI: 30% NPK fertilizer plus 240 kg/ha manure organic-inorganic compound fertilizer.Means followed by the same letter for a given factor are not significantly different (P