氮肥配施生物炭对旱地土壤养分和玉米根系径级分布的影响

Biochar and Nitrogen Fertilizer Effects on Soil Nutrient and Root Distribution in Dryland Maize

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。

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.