| With the good anatomical structure and physicochemical properties, widely source of material and broadly industrial development prospect, biochar has become research focus in the field of modern agriculture, energy and the environment, and it is also a kind of new functional material of multiple agronomic and environmental benefits, therefore it has a higher application value. Lou soil in Guanzhong area of Shaanxi and fruit stem and branch biochar as the research object in this study, pulleys in winter wheat and summer maize as a model, a field experiment was conducted. Fruit stem and branch biochar was produced under the condition of limiting oxygen and 450℃. A long-term field trial was carried out to investigate the effects of different rates of biochar(0, 20, 40, 60 and 80 t·hm-2) on soil water and thermal characteristics, aggregate content, soil carbon, nitrogen, phosphorus, potassium content, soil enzyme activity, plants nutrient uptake, crops agronomic characters and yield, and main conclusions are as follows:1. Water thermal properties and aggregate stability: Compared with the control(B0), the soil bulk density in 0-30 cm soil layer significantly decreased by 7.67%-10.91%, and the soil moisture content significantly increased by 10.04%-13.35%. Applying biochar at 40-60 t·hm-2 could buffer the change of soil temperature, and increase the soil thermal capacity. The water stable aggregates(WR0.25) with diameters greater than 0.25 mm significantly increased by 30.29%, the mean mass diameter(MWD) under dry sieving and wet sieving significantly increased by 15.18% and 31.61%, respectively, and the proportion of aggregate destruction(PAD) and unstable aggregate index(ELT) significantly decreased by 19.12% and 17.48%, respectively.2. Soil organic carbon and nitrogen and their fractions: In 0-10 cm soil layer, TOC, POCand EOCincreased with increasing rates of biochar. At 60 t·hm-2 biochar, SMBC, TN, AN, NO3--N, and SMBNwere the greatest, which were significantly increased by 87.22%, 33.33%, 18.76%, 94.79%, and 178.80%, respectively, compared to the control(B0). In 10~20 cm soil layer, TOC, POC, TN and NO3--N increased as biochar rates increased. EOC, SMBC, and AN were the highest at 60 t·hm-2 biochar, which were significantly increased by 78.05%, 23.85%, and 31.07%, respectively, over the control. Applying biochar at 40 t·hm-2 led to the highest SMBN, 50.87% higher than the control. In 0~30 cm soil layer, Applying biochar increased soil organic carbon reserves and nitrogen reserves by 37.92%~108.31% and 1.05%~14.94%, respectively. Soil nitrogen reserves reached the maximum at biochar rate of 60 t·hm-2.3. Soil phosphorus and potassium content and p H: In 0~10cm, 10~20cm and 20~30cm soil layer, compared with control B0, soil TP were increased 13.85%~21.54%, 10.61%~21.21% and 3.23%~25.81%, and reached the maximum at B40, B60 and B40, respectively; In 0~10cm, 10~20cm and 20~30cm soil layer, soil AP contents were increased 31.82%~74.91%, 11.09%~27.96% and 4.73%~27.71%, respectively, and reached the maximum at B60, B60 and B40; In 0~10cm, 10~20cm and 20~30cm soil layer, soil AK content were increased B0 19.96%~57.36%, 7.89%~24.39% and 10.48%~16.40%, respectively, and reached the maximum at B60. Soil p H change significantlyafter add biochar, but we can see, the soil p H increased by only 0.05~0.16 units. Obviously, the effect is very small that biochar on calcareous soil p H.4. Soil enzyme activity: In the different soil layers, the variation regularity of soil enzyme activities were the same, the overall trend was an increase and then decrease with the increase of the amount of biochar. The SEI indicated that the application of biochar significantly increased the SEI. By principal component analysis, The comprehensive scores of different soil layers are 0~10cm>10~20cm>20~30cm. In 0~10cm and 10~20cm, the comprehensive scores of different treatments were B60>B40>B20>B80>B0, and in 20~30cm soil, the composite score was B60>B80>B40>B20>B0, respectively.5. Crop nutrient uptake, biomass and yield: Summer maize straw nitrogen, phosphorus and potassium content increased significantly after application of biochar, straw nitrogen, phosphorus, potassium content highest than the B0 significantly increased 57.47% and 36.11% and 16.14%, respectively; There were certain influence on agronomic characters of summer maize after biochar application, the summer maize stem diameter, kernel number per spike, grain weight were significantly increased in the 40 t·hm-2 amount of biochar, and increased significantly 9.21% and 15.64%, 32.45%, compared to the respective control B0, respectively; The study that 40 t·hm-2 biochar dosage is best to enhance the summer maize 100-grain-weight, yield and biomass. Compared with the control B0, production was the most significant at 40 t·hm-2 amount of biochar, and significantly increased by 32.45%.Considering the effects of biochar on soil properties and crop growth, and problems of biochar production value and cost, it is recommended biochar dosage is 40 t·hm-2 in Lou soil. |
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