城市园林废弃物生物质炭对小白菜生长、 硝酸盐含量及氮素利用率的影响

【目的】我国温室种植蔬菜迅速发展,温室种植中肥料利用率低及蔬菜硝酸盐积累等问题日益突出。同时,我国城市化快速发展,城市园林废弃物日益增多,这些木质废弃物的处理也成为城市可持续发展的挑战。本文采用城市园林废弃物制成的生物质炭用于温室栽培生产,分析其对温室蔬菜产量和品质以及养分保持的影响,从而探索一种为绿色环保的现代城市农业服务的技术。【方法】本研究采用温室盆栽试验方法,以小白菜为研究对象,设置5个生物质炭添加水平。 C0 (0 g/kg, CK)、 C1(20 g/kg)、 C2(40 g/kg)、 C3(60 g/kg)和C4(80 g/kg)。研究生物质炭对小白菜产量、 植株硝酸盐含量、 土壤氮素含量与形态以及氮素保持效应的影响。【结果】与对照相比,添加不同比例的生物质炭均显著提高小白菜产量,其中,C3和C4处理下增产幅度达到75%,生物质炭添加量与产量呈显著正相关关系;生物质炭对小白菜植株地上部和地下部的影响并不一致,其中收获指数显著增加,提高幅度在2.5%～9.5%之间,有随着生物质炭用量增加而增加的趋势;对照处理小白菜地上部硝酸盐含量达504 mg/kg,各处理植株硝酸盐含量介于161～256 mg/kg之间,显著降低50%以上,特别是C1处理降低硝酸盐含量的幅度达到68%,而不同生物质炭添加量之间植株硝酸盐含量差异不显著;生物质炭的添加增加了土壤中总氮素的含量,氮素损失率由不施炭处理的5.6%降低到了3.3%以下,显著降低了42%,同时土壤氮素生产率较对照提高幅度大于35%;与C0相比较,生物质炭添加显著降低了土壤NO-3-N的积累,降低幅度在60%以上,生物质炭用量在4%左右时降低作用最大,达到80%,同时土壤NH+4-N在生物质炭添加下降低了77%,生物质炭对降低土壤中铵态氮和硝态氮的累积作用并不与其用量呈正相关,铵硝比随着生物质炭添加量而呈下降的趋势;同时从研究结果看,产量与土壤NH+4-N和NO-3-N含量呈负相关关系,与土壤全氮呈正相关关系,而蔬菜植株硝酸盐含量与土壤NH+4-N和NO-3-N含量具有相关性,但与土壤全氮含量相关性不显著。【结论】温室大棚栽培小白菜的土壤中, 加入不同量的生物质炭能显著提高小白菜产量,同时降低小白菜植株的硝酸盐含量,添加量在2%时效果最好;土壤硝态氮和铵态氮积累随生物质炭施入而降低;生物质炭显著降低氮素损失率而提高氮素生产率。本研究得出生物质炭通过降低损失、 吸持更多氮素而提高了氮素的持续供应,在增产的同时降低了蔬菜硝酸盐积累,提高了品质。因此,在温室大棚蔬菜生产的土壤中添加一定量生物质炭(本试验下添加2%～4%)可以达到高产和优质。

Effect of municipal green waste biochar addition on the growth,nitrate content and nitrogen use efficiency of greenhouse pakchoi

【Objectives】 With rapid development of greenhouse vegetable, problems such as low fertilizer use efficiency and nitrate accumulation in vegetables have arisen. Meanwhile, municipal green waste challenges the rapid development of urbanization in China. In this study, biochar made from municipal green wastes are used to investigate the effect of biochar on yield and quality of greenhouse vegetables and the soil nutrient conservation, in order to explore a green practice for urban agriculture. 【Methods】 A pot experiment was conducted in greenhouse andpakchoi was planted as tested material. Five levels of the biochar were added into soil including: C0(no biochar, CK), C1(20 g/kg), C2(40 g/kg), C3(60 g/kg) and C4(80 g/kg). Plant growth, shoot nitrate content, soil total N content and N forms and soil N retention were investigated.【Results】 Biochar amendment significantly increasespakchoi yield.Compared with the control, the yields are increased by up to 75% under the C3 and C4 treatments. There is a positive correlation between the yield and biochar amendment levels. Biochar has significant effect on aboveground and underground biomass which are increased in the harvest index by 2.5% to 9.5%, and the increases are in proportion to the biochar amendment rate. The nitrate contents in shoot ranges from 161 to 256 mg/kg in the biochar addition treatments, which are much lower than that of the control (504 mg/kg).The C1 treatment has the lowest shoot nitrate content, while no difference between the biochar amendment levels. The biochar addition increases soil total N content, decreases the N loss rate from 5.6% of the control to below 3.3% of the biochar treatments, significantly decrease by more than 42%, and enhances the N productivity by over 35% at the same time. The NO-3-N accumulation amounts in soil are decreased by maxmium of 80% with 4% biochar amendment, and the change of NH+4-N is similar to that of NO-3-N, which is decreased by 77%, while there is no correlation between biochar amendment levels and soil NH+4-N and NO-3-N accumulations. There is a decrease trend of NH+4-N/NO-3-N ratio with the increase of the biochar addition. The yields are negatively correlate with soil NH+4-N and NO-3-N contents, positively with the soil total N contents. The shoot nitrate contents significantly correlate with soil NH+4-N and NO-3-N contents, not with soil total N.【Conclusions】 The biochar amendment can improve the soil nutrient retention and reduce vegetable NO-3-N accumulation, increases the greenhousepakchoi yield, decreases the shoot nitrate content, increases the N productivity as a result. Therefore, it is a effective way of treating municipal green waste by making biochar and use them to improve soil fertility. The suitable biochar amendment is 2%-4% of the soil.