Acta Agriculturae Universitatis Jiangxiensis
Effects of Chinese milk vetch(astragalus sinicus L.)and nitrogen fertilizer reduction combined with biochar on soil physical and chemical properties and rice yield
(1. College of Environment and Resources,college of Carbon Neutrality,zhejiang A & F University, Hangzhou 311300,China;2.soil Fertilizer Station,agricultural Technology Promotion center of Jiande City, Jiande,zhejiang 311600,China;3.xinshui Construction CO.LTD of Jiande City,jiande,zhejiang 311600, China)
Abstract:[objective]in order to reduce the use of chemical nitrogen fertilizer,pot experiment was conducted to explore the effects of nitrogen(n)reduction combined with different ratios of biochar on improvement of soil nutrient and increase of rice yield under the condition of returning milk vetch to the field.the aim is to clarify the optimal nitrogen reduction and biochar addition ratio that are more conducive to fertilization and yield increase on the basis of replacing part of nitrogen fertilizer with Chinese milk vetch.the results could be used to provide scientific basis for production[. Method]a two-factor rice pot experiment was conducted,and four(0.25%,0.5%,1%,2%)biochar addition ratios and three(10%,20%,30%)n reduction ratios during topdressing were set.a total of 13 treatment combinations were set,and each treatment was repeated four times.a total of 52 pots were grown for 120 days.the effects of each treatment on soil physicochemical properties,rice yield and characters were compared after rice ripening.[result]the soil ph(p<0.01)was significantly increased by 12.02% compared with that of CK in thenfiedld with 30% N reduction combined with 2.0% biochar. The contents of soil organic matter(som),available phosphorus(ap)and available potassium(ak)were significantly increased by 20% N reduction combined with 2.0% biochar(p<0.01),and the contents of soil total N(p<0.05)were significantly increased by 38.8%,107.2%,25.4% and 24.9% compared with that of CK.THE content of alkali N was significantly increased by 49.6% when 20% N reduction was combined with 0.5% biochar(p<0.01). The highest yield was obtained when 30% N reduction 30% was combined with 1.0% biochar,which was significantly increased by 18.7%(P<0.01)compared with that of CK. However,the application of low biochar(0.25% biochar)was more beneficial to above-mentioned biomass accumulation, which was significantly increased by 90.04% compared with that of Ck(p<0.01).correlation analysis showed that soil organic matter,available phosphorus and available potassium in this study were the main soil environmental factors(p<0.05,r>0.5)to improve rice yield[. Conclusion]combined application of milk vetch, N reduction and biochar has a significant effect on fertilizer cultivation and yield increase.the application of 20% nitrogen reduction combined with 2.0% biochar under Chinese milk vetch returning to the field is more conducive to improving the nutrient content of paddy soil.it can reduce N loss and promote rice growth and yield increase,but excessive application of biochar has a certain inhibitory effect on rice yield and biomass.30% N reduction combined with 1.0% biochar in topdressing had the optimal effect on rice yield.
Keywords:milk vetch;rice straw biochar;nitrogen reduction;soil fertility;rice yield
【研究意义】我国是世界上主要的水稻生产国之一,水稻产量约为世界水稻产量的28%,我国65%以上的人口以稻米为主食[1]。在众多参与水稻生长发育过程的元素中,氮素对水稻的生长发育、产量提升的贡献率超过60%,并且,氮素是水稻等农作物合成核酸、磷脂和叶绿素等膳食蛋白的必需营养元素之30%。由于片面追求高产,氮肥利用过量现象普遍[3]。过量施用氮一[2]。但是我国氮肥利用率较低,仅约肥易造成土壤酸化、肥力下降、农业面源污染等环境问题,严重影响我国粮食的产量与安全[4]。【前人研究
进展】Zhang等[5]研究指出,绿肥具有固氮吸碳、提高土壤有机质、促进水肥协调等作用。紫云英是南方常
78%的氮来自生物固氮,紫云英翻压还田后见的绿肥作物,其固氮能力强大,研究[6-7]表明紫云英植株内能为当季水稻提供大量的有效态氮,代替部分化肥,提高水稻产量。此外,研究[8]发现,生物炭是一种优良的土壤改良剂,其表面有丰富的官能团和阳离子,能降低作物根系养分积累所需的自由能,因此具有
20%、40%化极强的吸附和保持养分的功能。为减少氮肥的使用,王利民等[9]研究表明紫云英配施减量肥仍能达到培肥增产效果,且具有良好的持续效应。徐彬等[10]研究发现在减氮条件下配施过高的生物质炭会降低水稻产量,80%化肥氮+5.0 t/hm2
生物质炭处理下的增产效果最佳。谢志坚等[11]研究表明,减氮20%配施生物质炭基肥与紫云英联合还田可显著促进水稻氮素积累,促进产量提升。【本研究切入点】紫云英的腐化分解受耕翻时间、田间土壤温度湿度、翻耕量等因素影响明显,养分释放速率可控性较低,难以及时满足作物对养分的需求,因此,在翻压紫云英后仍需配施适量的化肥或有机肥料才能满足水稻生长发育的需求[12]。目前,已有较多的研究探明了种植紫云英、氮肥减量、施加生物质炭等措施对改善土壤理化性质,促进水稻增产的作用;但是同时应用以上3项措施,探究在紫云英培肥下不同的追肥减氮比例和生物质炭施加比例对土壤理化性质和水稻产量的综合作用的研究缺失。【拟解决的关键问题】在盆栽试验开展前,试验样地已展开为期2年(2020-2022年)的紫云英-水稻轮作下氮肥减量的大田试验。试验的结果表明:第2年大田土壤理化性质及水稻产量均有所下降,其中土壤有效磷含量和水稻产量最大降幅分别为45.2%和18.7%(P<0.05) 。为减少化肥氮的使用,提高水稻绿色高效生产能力,本
[13-14]研究通过盆栽试验探究:在紫云英还田的基础上,何种追肥减氮比例和生物质炭添加比例最能提高稻田土壤理化性质指标和水稻产量。
1材料与方法1.1 试验地点与材料
盆栽试验于2022年5—10月在浙江农林大学试验大棚中进行,自然光照,温度25~35 ℃。盆栽供试土壤来自浙江省建德市航头镇珏塘村高标准农田示范区,供试土壤的基本理化性质如表1所示。2022年5月中旬分别采集冬种紫云英与冬闲(冬季不种植紫云英)稻田表层0~20 cm的耕层土壤,并连同根系一同采集盛花期紫云英样品,用以替代部分化肥;紫云英全氮含量为28.5 g/kg,含水率88.5%。生物质炭为水稻秸秆生物质炭,购于河南星诺环保材料有限公司,生物质炭外观为黑色粉末,其成分详见表2所示,水稻品种为晚稻“甬优15”,苗龄为16 d的水稻幼苗于2022年6月8日取自浙江省建德市航头镇珏塘村。肥料选择当地农户普遍使用的氮磷钾(18-12-16)复合肥、尿素和氯化钾。盆栽试验用盆为底径19.5 cm,高25.7 cm的无孔水培盆。
1.2 试验设计
采用双因素盆栽试验,以冬闲土壤+常规施肥为(CK)为空白对照;CB1~KB3处理为冬种紫云英土壤盆栽,共设置13个处理,每个处理4次重复,盆栽共52盆,试验处理组合如表3所示。剔除石块和根系后每盆装入新鲜湿土5 kg。剪成2~3 cm小段的紫云英以250 g/pot的量翻压进试验盆土壤中,并进行2~3 cm淹水处理 15 d加入不同比例的生物质炭,并继续淹水 CK处理(常规
[11]。在水稻移栽前 [15]。施肥)中的化肥N、P、K含量为225,105,150 kg/hm2。为保证水稻生长初期养分充足,本试验中的化学N肥以基肥和分蘖肥的方式,分2次施入。基肥期氮肥施用量相同,在追肥时进行减氮,N、P、K施用量如表3所示,水稻移栽前2 d等量施入基肥。试验于6月8日插秧,每盆移栽长势大致一致的水稻幼苗1穴2株,保持表层水深3~5 cm[16]。插秧 8 d后追肥即施加分蘖肥,后续不再施肥。在水稻收获前10 d不再保持淹水状态,待水分落干后收获,生长期为120 d。
表3 试验处理设置及施肥量Tab.3 Test treatment setting and fertilizer amount
1.3 样品采集及测定水稻性状及产量测定:本试验于水稻拔节期(30 d)、抽穗期(60 d)、灌浆期(90 d)、成熟期(120 d)分别测量水稻株高。水稻成熟期收获当天采集各处理0~20 cm的根际土样及表土以上的水稻植株样品。105 ℃杀青30 min、70 ℃烘干至恒重测定植株茎叶等测定有效穗数,剥离籽粒后,测定实粒重量,同日经地上部分生物量鲜重。土壤基本理化性质分析:土壤ph和电导率以水土比2.5∶1浸提,分别采用ph计和电导率仪测定[17];土壤有效磷(AP)、土壤有机质(OM)、土壤有机碳(TOC)、土壤速效钾(AK)、土壤全氮(TN)、土壤碱解氮(AN)根据《土壤农化分析》第3版测定[18]。1.4 数据处理试验测定数据由Excel 2021软件整理后,采用SPSS 26.0软件和Origin 2018软件进行统计分析及图形绘制,采用two-way ANOVA进行双因素方差分析,基于SSR中的Duncan进行多重比较,数据均为4次重复的平均值±标准差。2结果与分析2.1 紫云英培肥下不同减氮比例及生物质炭施加对土壤理化性质及肥力的影响2.1.1 对土壤ph和有机质的影响对减氮比例和生物质炭比例两因子进行双因素方差分析(表4)可知,不同比例的减氮处理单独作用
时对土壤ph无显著作用(P>0.05),但生物质炭和2种处理的交互作用均对土壤ph及有机质有极显著影响(P<0.01)。如图1所示,与对照(CK)相比,随着生物质炭添加比例的增加,土壤ph及有机质均显著提升(P<0.05)。土壤ph表现出了减氮30%>减氮20%>减氮10%的变化趋势;减氮30%配施2.0%生物质炭时的ph最高,为5.78,比CK提升了12.02%(P<0.05)。生物质炭添加量相同时,减氮20%更有利于提升土壤有机质含量。与CK有机质含量38.85 g/kg相比,减氮20%配施2.0%的生物质炭的有机质含量显著提升58.8%(P<0.05)。综上,减氮30%配施2.0%生物质炭和减氮20%配施2.0%生物质炭分别对土壤ph和有机质的提升效果最为明显。
表4 不同比例减氮处理及生物质炭处理下的土壤理化性质指标双因素方差分析Tab.4 Two-factor ANOVA of soil ph and conductivity under different ratio nitrogen reduction treatment and biochar treatment
***和**表示在P<0.001和P<0.01水平上极显著,*表示在P<0.05水平上显著。*** and ** are extremely significant at P<0.001 and P<0.01 levels,* is significant at P<0.05 levels. 2.1.2对全氮、碱解氮的影响
如表4所示,不同的减氮比例和生物质炭添加比例2种处理的主效应对土壤全氮和碱解氮的含量提升均无显著影响(P>0.05),但交互作用对土壤全氮和土壤碱解氮分别有显著作用(P<0.05)和极显著作用(P<0.001)。由图2可知,与CK全氮含量4.21 g/kg相比,各处理组的土壤全氮及碱解氮含量均显著提升(P<0.05),其中减氮30%配施2.0%生物质炭时(KB )全氮含量最高,为 5.25 g/kg,增幅为 24.9%(P<
3 0.05)。除了KB3,当减氮量相同时,添加0.5%生物质炭时的全氮含量最高;当生物质炭添加比例大于0.5%时,碱解氮含量则随着生物质炭添加比例的增加而降低。当生物质炭添加比例为0.5%时,不同减氮处理下的碱解氮含量均为最高,其中减氮20%配施0.5%生物质炭(NB
2 )的含量最高,为190.85 mg/kg,与CK 127.54 mg/kg相比显著提升了46.9%(P<0.05)。综上,减氮30%配施2.0%生物质炭对土壤全氮的提升效果最好,而减氮20%配施0.5%生物质炭时碱解氮含量最高。