2.2 Experimental design
The field experiment was established in a randomized complete block
design with three triplicates, and each plot cover an area of 40
m2 (5 m×8 m). The summer maize variety was Zhengdan
958. Six treatments were (1) BF0: 100% NPK chemical fertilizer; (2)
BF30 (70% NPK chemical fertilizer + 30% bio-fertilizer); (3) BF50
(50% NPK chemical fertilizer + 50% bio-fertilizer); (4) BF70 (30% NPK
chemical fertilizer + 70% bio-fertilizer); (5) BF100 (100%
bio-fertilizer). All these treatments received same amounts of
fertilizers (225 kg N ha-1, 80 kg P
ha-1 and 80 kg K ha-1) during the
growing season. Both the chemical fertilizer and bio-fertilizer were
spread evenly on the surface of the soil in each plot and were
thoroughly mixed with the top 0-20 cm of the soil by rotary cultivator,
a week prior to maize sowing. In each plot, summer maize was planted at
a density of 65000 plants ha-1 about 5 cm deep in
early June, and harvested in early October each experimental year.
Bio-fertilizer used in this experiment was aerobically fermented from
wheat straw The bio-fertilizer (organic matter 29.7%, total N 12%,
total P 0.5%, total K 5%) contains approximately
0.2×109 CFU g-1 fungus
(Trichoderma asperellum ACCC30536), the fungus were previously
isolated from the rhizosphere soil of healthy soybean roots in a field
severely affected byFusarium
oxysporumin in Zhoukou, Henan province, China.