Fluorescence Spectroscopy and ¹³C NMR Spectroscopy Characteristics of HA in Black Soil at Different Corn Straw Returning Modes

Table 1

Basic properties of the tested soil.

Depth (cm)	Organic matter (g/kg)	Total N (mg/kg)	Available P (mg/kg)	Available K (mg/kg)	pH
0∼20	12.20	78.73	95.86	235.80	6.6
20∼40	12.05	76.52	70.17	204.75	6.3