The objective of this study was to investigate the effect of biochar-based fertilizer with different formulations on crop yield, grain quality and nutrients use efficiency, which could provide a scientific basis for biochar-based fertilizer development in agriculture. Field experiment was conducted in Luhe district, Nanjing City, Jiangsu province. There were five treatments in total including no any fertilizer (NoF), applying chemical compound fertilizer as base fertilizer (CF), and applying 3 biochar-based chemical fertilizers with different formulations instead of chemical compound fertilizer (abbreviated as BF1, BF2 and BF3). Crop yield, grain quality, nutrients use efficiency and soil nutrients content by crop harvest were analyzed. Compared to CF, BF2 had no effect on rice grain yield, whereas they increased the yield of winter-wheat significantly. The wheat yield under BF2 treatment increased by 20.39% compared with CF. The rice yields under BF2 and BF3 treatments were significantly higher than those under BF1 treatment, increasing by 22.61% and 19.38% respectively. During the entire crop rotation cycle, the total output of rice and wheat was the highest under the BF2 treatment, increasing by 8.58%, 14.76% and 7.67% respectively compared with the CF, BF1 and BF3 treatments. Compared to the CF treatment, the BF1 treatment significantly reduced the chalkiness of rice by 1.58 percentage points. The chalkiness of rice with the BF1 treatment was also significantly lower than the BF2 and BF3 treatment. The protein content of rice grains under BF2 treatment was 1.69 percentage points higher than the BF1 treatment. Compared to the CF treatment, protein content, wet wheat gluten percentage and hardness of wheat grains under the BF2 treatment increased by 1.90, 4.46 and 7.73 percentages respectively, and the sedimentation index of wheat under the BF2 treatment was significantly higher than that under the BF1 treatment. Compared to CF, BF2 treatment enhanced the fertilizer use efficiency during the rice and wheat seasons. During the rice season, the fertilizer contribution rate, the agronomic efficiency of fertilizers and the partial factor productivity of fertilizers increased; during the wheat season, they also increased. Moreover, the fertilizer use efficiency under the BF2 treatment was higher than that of the other two biochar-based fertilizer treatments. The responses of crop yield and grain quality to biochar-based compound fertilizer depends on crop type. In the short term, applying biochar-based compound fertilizer instead of chemical compound fertilizer could increase grain yield and fertilizer use efficiency of wheat and improve the appearance quality of polished rice. Elevating the ratio of K:P in biochar-based compound fertilizer could boost the agronomic effect of biochar-based fertilizer if the total amount of P and K were constant.
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The objectives of this study were to investigate the effects of biochar feedstocks, pyrolyzing temperatures and biochar components on plant growth and to uncover the mechanism that how biochar increased crop yields.
Six biochars were made from sawdust and maize stalk at pyrolyzing temperature of 350, 450, and 550 ℃. Each biochar was then separated into two parts through hot water extraction method, including the water soluble biochar extract and the washed biochar residue. A pot trial was conducted to investigate the effects of untreated biochar (BC), biochar extract (BE) and washed biochar residue (WB) application on the growth of non-heading Chinese cabbage (Brassica campestris ssp. chinesis).
The aboveground biomass of Chinese cabbage under the addition of maize stalk biochars and their components was 16.1 g/pot on average, which was significantly higher than the values under sawdust biochars and their components (13.0 g/pot) amendment and the control (13.5 g/pot). Similarly, the root morphology index of root length, surface area, root volume and number of root tips under the addition of maize stalk biochars and their components improved greatly compared with sawdust biochar and the control. The aboveground biomass under the addition of washed biochar residues was 16.5 g/pot on average, which were 26.9% and 17.9% higher than the values under the addition of untreated biochar and the biochar extracts, respectively. The root length, surface area, root volume and number of root tips under washed biochar residues addition increased by 64.1%, 51.1%, 38.3% and 80.0%, respectively compared with biochar extracts addition. The biochars under different pyrolyzing temperature had no significant effect on the aboveground biomass and root growth of Chinese cabbage. Compared with the untreated biochar, the washed biochar residue addition increased the concentration of nitrogen (N) in aboveground biomass by 25.9%, while the concentration of phosphorus (P) and potassium (K) decreased by 39.7% and 14.1%, respectively. Soil pH, the concentration of soil organic carbon, total N, available P and K under the addition of maize stalk biochar and their components increased by 0.1 unit, 20.3%, 19.1%, 29.1% and 189.2% respectively compared with wood biochar addition. Compared with the untreated biochar, the washed biochar residue addition decreased soil organic carbon, total N, available P and K by 14.6%, 6.6%, 41.3% and 55.1%, respectively, while soil pH increased by 0.13 unit. Soil organic carbon, total N and available P under the addition of biochar extracts decreased by 49.8%, 18.9% and 24.2%, respectively, while soil pH and available K content was not affect. Correlation analysis showed that the aboveground biomass was positively related to root length, surface area, root volume, the number of root tips and soil pH value; while it was negatively correlated to the P concentration in the aboveground of Chinese cabbage.
The feedstock and biochar component were the two main factors that regulating the response of plant growth to biochar amendment. The biochar from maize stalk was more suitable for soil amendment compared with wood biochar in terms of crop yield increase, and more crop yield could be obtained when maize stalk biochar was amended after hot water extracting. The water-soluble components presented in biochar played a key role in crop yield increase via promoting root growth. The promotion effect was closely related to biochar feedstock, pyrolyzing temperature and the chemical composition in biochar extracts.
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