Influences of application of biochar and biochar-based fertilizer on brown soil physiochemical properties and peanut yields

【Objectives】 Biochar has been studied as soil amendment mostly by either short-term culture experiments or simulation tests. Biochar-based fertilizer is another way of biochar utilization in agriculture, but few relevant researches have been reported. Therefore, this study aimed to compare the effects of biochar and biochar-based fertilizer on improving soil physiochemical properties and the yield of peanut, so as to provide a theoretical reference for the use of biochar-based fertilizers in agriculture. 【Methods】 A micro-plot (2 m2) field experiment was conducted from 2009 to 2012 with peanut as tested crop. Four treatments were designed: corn straw returning in combination with NPK (CS), piggery manure in combination with NPK (PMC), biochar from corncob in combination with NPK (BIO), and biochar-based fertilizer (BF). All these treatments were under the same N, P and K nutrient inputs, the carbon-input of PMC was consistent with BIO, the biochar-input quantity of BIO was equal to the corn stalk pyrolysed residual content of CS, and the carbon-input of BF was less than that of BIO. Three replicates were set up for each treatment in a completely random way. The soil physiochemical properties before the experiment and after the harvest of 2012 were investigated, and the peanut yields of each treatment in four years were compared. 【Results】 In the fourth year of the experiment, all the treatments except the CS show improvement effect on soil pH, CEC and the nutrient contents. The peanut yields of all the treatments had been increased with the experimental years. The highest increase in soil organic C and total N is in the BIO treatment, in which the increases are 27.6% and 75.6%, showing a distinct advantage; the soil pH is increased by 0.14, which is significantly higher than that of CS and close to that of PMC. Soil available N, P and K and CEC of BIO are closed to those of CS or PMC. The capillary porosity and field capacity in BIO are higher than in the others, while the bulk density and the total soil porosity have no significant differences between CS and PMC. BIO holds the first place in the yield for 4 years, with the yields increased from 3198.5 to 4818.0 kg/hm2, which have no significant differences with the PMC. In the fourth year, the soil pH in BF is significant higher than in the other treatments, and the enhance of 0.57 unit shows a distinct advantage; the organic C and total N in the BF treatment are increased by 4.4% and 27.9% respectively and are significantly lower than those of BIO, and the effects of the adjustment on soil physical properties are not as good as BIO. Other indicators of BF have no significant differences with BIO, but they are generally closed to CS or PMC. The peanut yields of BF have no significant differences with BIO in the first three years, while it is reduced by 317.1 kg/hm2 in the fourth year compared with BIO, and it is significantly lower than that of BIO and between that of PMC and that of CS in the fourth year. 【Conclusions】 On the whole, the effects of the biochar and biochar-based fertilizer on improving soil physiochemical properties are similar to the straw returning and piggery manure application. Biochar is superior for enhancing soil organic C and total N contents, and biochar-based fertilizer is for improving soil pH. The peanut yield is steadily increased with both the application of biochar and biochar-based fertilizer.