SUPPLEMENTARY MATERIAL
Combined application of biochar with fertilizer promotes nitrogen uptake in maize by increasing nitrogen retention in soil
Jing Penga,1, Xiaori Hana,b,c※, Na Lia,b,1, Kun Chena, Jinfeng Yanga,b, Xiumei Zhana,b, Peiyu Luoa,b, Ning Liua,b
1 These authors contributed equally to this work and should be considered co-first authors.
※Corresponding author at: College of Land and Environment, Shenyang Agricultural University, No. 120 Dongling Road, Shenhe District, Shenyang, Liaoning Province 110866, China.
E-mail address: hanxr@syau.edu.cn (Xiaori Han) ORCID: 0000-0003-1250-2449
a College of Land and Environment, Shenyang Agricultural University, No. 120 Dongling Road, Shenhe District, Shenyang, Liaoning Province 110866, China
b Monitoring &Experimental Station of Corn Nutrition and Fertilization in Northeast China, Ministry of Agriculture, Shenyang 110866, China
c Biochar Engineering Technology Research Center of Liaoning Province, Shenyang 110866, China
Jing Peng, E-mail address: 2499172012@qq.com.
Corresponding author: Xiaori Han, E-mail address: hanxr@syau.edu.cn.
Na Li, E-mail address: lnxlina@163.com.
Kun Chen, E-mail address: chenkun083@163.com.
Jinfeng Yang, E-mail address: yangjinfeng7672@syau.edu.cn.
Xiumei Zhan, E-mail address: xiumeizhan@163.com.
Peiyu Luo, E-mail address: ibtyoufe@syau.edu.cn.
Ning Liu, E-mail address: lnbrisk@163.com.
The biochar (13C atom%=1.20%) derived from 13C-labeled maize straw pyrolysed at 450 ℃ was added to the C1PK and C1NPK plots in 2017. Briefly, a total of 32 mature maize plants were grown in a handmade miniature greenhouse under a 13CO2 gaseous environment (13C atom% > 99%, Shanghai Research Institute of Chemical Industry Co., Ltd.), and pulse-labeled four times from shooting stage to heading stage in 2016. An infrared gas analyzer and cooling measurement were used to monitor CO2 concentration and temperature to keep normal crop growth and photosynthesis. The labeling process started at 8:00 am on a bright sunny day and lasted for 4-5 h. The aboveground maize straw was harvested and dried at 60 ℃ in an oven, then smashed and sieved (2 mm mesh), and pyrolysed in a muffle furnace and stored in dry environment.
Table S1 The basic properties of the Maize stover and Biochar. The biochar (13C atom%=1.20%) derived from 13C-labeled maize straw pyrolysed at 450 ℃ was added to the C1PK and C1NPK plots in 2017
Maize stover 13C-Maize stover Biochar 13C-Biochar
pH(H2O) 7.7 7.7 9.8 9.8
Total C (g kg-1 ) 434.7 428.9 627.6 640.0
Total N (g kg-1 ) 15.6 14.9 24.8 26.2
δ‰13C -12.5 79.4 -12.7 79.7
Atom%13C 1.0975 1.1984 1.0972 1.1988
δ‰15N 3.8 4.8 3.9 4.0
Atom%15N 0.3677 0.3681 0.3677 0.3678
particle size (mm) < 2 < 2 < 2 < 2
BET Surface area (m2 g-1 ) / / 27.0 27.0
Average pore size (nm) / / 7.1 7.1
/ not determined.
In the present study, it is worthy to note that the effect of favorable nitrogen regulation was not triggered by the biochar nitrogen, but was modulated by the combined application of biochar and N fertilizer. Despite the high total nitrogen content in biochar produced from wheat straw (Fiorentino et al., 2019) or maize straw (Table S1), the available nitrogen is likely to be tiny (Fiorentino et al., 2019). Lehmann et al.(2003) also reported that the indirect effects of biochar on soil amendment and nutrient cycling are more significant than the direct effects of biochar itself.
To examine this, we did another experiment at the same site with the same tested soil and Maize (Zea mays L.) cultivar. This experiment is a part of a long-term field trial established in April 2013 using a randomized block design.
The experiment includes eight different treatments in three replicates, with each plot measuring 2.0 m×1.0 m (2 m2).
In this study, two treatments were chosen: NPK - the treatment with application of nitrogen-phosphorus-potassium using urea (N 46.3%), single superphosphate (P2O5 16%), and muriate of potash (K2O 60%) as chemical fertilizers;
C1NPK - biochar at 1.5 t ha-1 and the decreasing amounts of combined mineral fertilizer of nitrogen-phosphorus- potassium by 9%, 13%, and 22%, respectively. Therefore, these two treatments have the same nitrogen-phosphorus- potassium nutrients input, because we measured and calculated the nitrogen-phosphorus-potassium nutrients in biochar. The biochar and fertilizer were applied annually and mixed well with the topsoil (0-20 cm layer) by a shovel before sowing maize seeds. We also conducted isotope experiments the same to the Fig. 1b-h. The results were as
showed in Fig. S1-S5.
As shown in our previous study (Han et al., 2017) and in Fig. S1-S5, whatever we calculate biochar nitrogen or not, combined application of biochar improved N-use efficiency compared to the control, suggesting that the contribution of nitrogen from biochar to the crop uptake might be almost negligible.
Citations of Han et al. 2017: Han, X.R., Ge, Y.F., Li, N., Peng, J., Fan, Y., Gao, T.Y. (2017) Effects of Continuous Application of Biochar on Soil Physic-Chemical Properties and Nitrogen Use Efficiency. Journal of Shenyang Agricultural University 48, 392-398. http://en.cnki.com.cn/Article_en/CJFDTotal-SYNY201704002.htm (in Chinese with English abstract).
Fig. S1 Grain yields of maize in different years. The independent-sample t-Test comparison was conducted to compare the yield values of maize in application of nitrogen-phosphorus-potassium fertilizer with or without biochar, and the significant differences were showed as * (P < 0.05), ** (P < 0.01).
Fig. S2 δ15N mean values of stem, leaf, grain, corncob of maize in 2016 harvest. The independent-sample t-Test comparison was conducted to compare the mean values in application of nitrogen-phosphorus-potassium fertilizer with or without biochar, and the significant differences were showed as * (P < 0.05), ** (P < 0.01).
Fig. S3 δ15N mean values of stem, leaf, grain, corncob of maize in 2017 harvest. The independent-sample t-Test comparison was conducted to compare the mean values in application of nitrogen-phosphorus-potassium fertilizer with or without biochar, and the significant differences were showed as * (P < 0.05), ** (P < 0.01).
Fig. S4 δ15N mean values of root, stem, leaf, grain, corncob of maize in 2018 harvest. The independent-sample t-Test comparison was conducted to compare the mean values in application of nitrogen-phosphorus-potassium fertilizer with or without biochar, and the significant differences were showed as * (P < 0.05), ** (P < 0.01).
Fig. S5 δ15N mean values of root, stem, leaf, grain, corncob of maize in 2020 harvest. The independent-sample t-Test
comparison was conducted to compare the mean values in application of nitrogen-phosphorus-potassium fertilizer with or without biochar, and the significant differences were showed as * (P < 0.05), ** (P < 0.01).
