Abstract:

Continuous cropping of maize can lead to nutrient distribution problems and premature root senescence in maize. We conducted a trial to investigate the residual effects of biochar and N fertilizer on soil nutrients, root size distribution, and dry matter accumulation of maize in burozem. The experiment contained seven treatments: without nitrogen or biochar addition as control (CK); two nitrogen rates (conventional N rate of N 225 kg∙hm^-2 (N1); 10 % less N, or N 203 kg∙hm^-2 (N2); and three biochar rates of 0 (C0), 8.4 t∙hm^-2 (C1) and 21 t∙hm^-2 (C2). Measurements taken in the second year after biochar application showed that, compared with the control (CK), treatments N1C1 and N2C2 had significantly higher soil organic matter content. The high biochar rate increased soil alkaline-hydrolysis soil N storage at both N rates, by 29.9% in N1C2 and by 9.0% in N2C2. Total soil N content was significantly higher in the N1C2 and N2C1 treatments than in the control. The treatment with lower rates of N and biochar (N2C1) increased the root length in the 0-2 mm diameter class by 38.9% compared to CK (P˂0.05). The low biochar rate with the higher N rate (N1C1) produced 13.4% thinner roots, the 32.4% longer roots, and increased the total length of roots in the 0-2 mm diameter class by 37.9% at maize maturity. Nitrogen rate alone or combined with biochar had no significant effect on length of roots in the 2-3 or 3-4 mm diameter classes. The conventional N fertilizer rate without biochar (N1C0) produced a 40.5% (P<0.05) greater length of roots >4 mm in diameter compared to CK. The conventional N fertilizer rate with the low rate of biochar (N1C1) increased dry matter accumulation per plant of maize by 53.16 g at large bell stage. We conclude that a modest rate of biochar (8.4 t∙hm^-2) combined with 225 kg∙hm^-2 N fertilizer promotes fine root growth in maize, and that N fertilizer at a high rate of biochar (21 t∙hm^-2) can promote soil N fixation. The research provides a scientific reference for the straw recycling and provides new ideas for optimizing maize root structure.

Key words: biochar, soil nutrient, root morphology, root size distribution, dry matter accumulation

摘要：

为了缓解玉米连作带来的土壤养分失衡及根系早衰,探讨生物炭对土壤养分、玉米根系生长的主要径级水平、玉米干物质积累的后效作用。采用定位试验,设置不施氮肥、不施生物炭为对照（CK）,2个施氮量（常规施N量225 kg∙hm^-2,N1;减氮10%,N 203 kg∙hm^-2,N2）,2个生物炭量（8.4 t∙hm^-2,C1;21 t∙hm^-2,C2）共7个处理。在生物炭施用第二年,测定玉米不同径级根系生长及土壤养分含量。结果表明,与对照（CK）相比,常规施氮配施低量生物炭（N1C1）和减氮配施高量生物炭（N2C2）显著提高了土壤有机质含量;高量生物炭配施氮肥（N1C2和N2C2）分别提高土壤碱解氮储存量29.9%和9.0%;N1C2和N2C1处理显著提高土壤全氮含量。减氮配施低量生物炭（N2C1）促进大喇叭口期玉米0—2 mm径级根系的根长较CK提高38.9%（P˂0.05,下同）;低量生物炭配施常规氮肥（N1C1）促进成熟期玉米根系变细13.4%、根系变长32.4%,提高0—2 mm径级根系的总根长37.9%;单施氮肥或配施生物炭对2—3、3—4径级的根长无显著影响;常规单施氮肥（N1C0）较CK显著提高>4 mm径级根系根长约40.5%。低量生物炭配施常规氮肥（N1C1）提高大喇叭口期玉米单株干物质积累53.16 g∙plant^-1。综上,研究结果说明,8.4 t∙hm^-2生物炭配施225 kg∙hm^-2氮肥能更好地促进成熟期玉米细根生长。单施氮肥和配施21 t∙hm^-2生物炭均可促进土壤养分的固持。该研究结果为秸秆循环利用提供科学参考,同时为优化玉米根系结构提供新思路。

关键词: 生物炭, 土壤养分, 根系形态, 径级分布, 干物质积累