Agricultural Sciences in China
2011, 10(8): 1254-1261 August 2011
A Field Study on Effects of Nitrogen Fertilization Modes on Nutrient Uptake, Crop Yield and Soil Biological Properties in Rice-Wheat Rotation System
GUAN Guan1, TU Shu-xin1, YANG Jun-cheng2, ZHANG Jian-feng2 and YANG Li3
1 College of Resource and Environment, Huazhong Agricultural University, Wuhan 430070, P .R.China
2 Institute of Agricultural Resources and Regional Planning, Chinese Academy of Agricultural Sciences, Beijing 100081, P.R.China 3 Institute of Plant Protection and Soil Fertilizer, Hubei Academy of Agricultural Sciences, Wuhan 430064, P .R.China
Abstract
Rational application of nitrogen (N) fertilizers is an important measure to raise N fertilizer recovery rate and reduce N loss. A two-year field experiment of rice-wheat rotation was employed to study the effects of N fertilization modes including a N fertilizer reduction and an organic manure replacement on crop yield, nutrient uptake, soil enzyme activity, and number of microbes as well as diversity of microbes. The result showed that 20% reduction of traditional N fertilizer dose of local farmers did not significantly change crop yield, N uptake, soil enzyme activity, and the number of microbes (bacteria, actinomycetes, and fungi). On the basis of 20% reduction of N fertilizer, 50% replacement of N fertilizer by organic manure increased the activity of sucrose, protease, urease, and phosphatase by 46-62, 27-89, 33-46, and 35-74%, respectively, and the number of microbes, i.e., bacteria, actinomycetes, and fungi by 36-150, 11-153, and 43-56%, respectively. Further, organic fertilizer replacement had a Shannonrsquo; s diversity index (H) of 2.18, which was higher than that of other modes of single N fertilizer application. The results suggested that reducing N fertilizer by 20% and applying organic manure in the experimental areas could effectively lower the production costs and significantly improve soil fertility and biological properties.
Key words: rice-wheat rotation, N fertilization mode, organic manure replacement, soil enzyme activity, microbial diversity
INTRODUCTION
Rice-wheat rotation is a very important cropping system and has been practiced mainly in subtropical zone in South Asia. In China, rice, with a total planting area of 27 million ha, is the most important food crop, and its yield accounts for over 40% of total grain yield (Ju et al. 2007). As estimated, there is a total area of 13 million ha of rice-wheat rotation field in China, and most fields are located in middle and lower reaches of the Yangtze River (Timsina and Connor 2001).
Fertilization method is the key to ensure crop yield and quality in rice-wheat cropping system. Winter wheat and mid-season rice rotation is currently the major form of paddy and dry land rotation system in middle and lower reaches of the Yangtze River. However, the imbalance of fertilizer application and the excessive application of N fertilizers has become the most serious problems limiting the crop yield and farming economic efficiency. More and more studies have showed that the efficiency of applying N fertilizers is decreasing (Ohnishi et al. 1999).
Irrational fertilization in rice-wheat rotation system
Received 8 September, 2010 Accepted 29 December, 2010
Correspondence TU Shu-xin, Professor, Tel: 86-27-87382137, E-mail: stu@mail.hzau.edu.cn; YANG Jun-cheng, Professor, Tel: 86-10-82106203, E-mail: jcyang@caas.ac.cn
copy; 2011, CAAS. All rights reserved. Published by Elsevier Ltd.
doi:10.1016/S1671-2927(11)60117-X
A Field Study on Effects of Nitrogen Fertilization Modes on Nutrient Uptake, Crop Yield and Soil Biological Properties 1255
deteriorates soil fertility and soil properties, especially the biological properties (Kalter 2003). Bhattacharya et al. (2006) reported that the excessive application of fertilizer has made the soil environment worse year by year and has affected the growth of plants and crop yield. Many studies found that the soil pollutants from fertilizers can move to hundreds or thousands of kilometers away along with rivers and storms (Veado et al. 2006; Cogun et al. 2006). As a result, the effects of chemical fertilizer on soil and ecological environment have attracted great attention.
By 2009, the consumption of N fertilizer in China exceeded 40 million ton, and ranked the first in the world (National Bureau of Statistics of China 2009). According to the national statistical data of soil and fertilizer in China, the input proportion of chemical fertilizer in productive costs is still increasing every year, and the average recovery rate of N fertilizer is just 32-45%, and is not more than 50% even under an effective farm management system.
Based on the reality of N fertilizer application in rice-wheat rotation in China, the paper studied the effects on crop yield, N fertilizer recovery rates, and soil fertility as well as soil biological properties by a field trial which included three treatments: N fertilizer rate of local farmers as control, a reduced N fertilizer rate, and a combinative application of organic and N fertilizer.
MATERIALS AND METHODS
Experimental site
Zhengmai 9023 wheat (Triticum aestivum) and rice ii-you 838 (Oryza sativa subsp. indica) were used. The experimental site was located at hinterland of the Jianghan Plain, and situated in Haokou farm of Qianjiang City, Hubei Province, China (30° 22 5́4.5acute;́N and 112° 37 2́1.5acute;́ E, 27.5 m above sea level). The soil is a sandy loam calcareous alluvisol, and the basic properties were as follows: pH 7.1, organic matter 20.62 g kg-1, total N 1.534 g kg-1, total P 2.022 g kg-1, total K 20.7 g kg-1, NaOH-hydrolyzed N 121.28 mg kg-1, available P 19.16 mg kg-1, available K 72.5 mg kg-1, and cation exchange c
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Agricultural Sciences in China
2011, 10(8): 1254-1261
水稻-小麦轮作系统氮肥施用方式对养分吸收、作物产量和土壤生物学特性的影响
GUAN Guan1, TU Shu-xin1, YANG Jun-cheng2, ZHANG Jian-feng2 and YANG Li3
(1华中农业大学资源与环境学院,湖北武汉430070
2中国农业科学院农业资源与区域规划研究所,北京100081
3湖北省农业科学院植物保护与土壤肥料研究所,湖北武汉430064)
摘要
合理施用氮肥是提高氮肥回收率、减少氮肥损失的重要措施。摘要通过为期两年的水稻-小麦轮作田间试验,研究了氮肥减量和有机肥置换两种施肥方式对作物产量、养分吸收、土壤酶活性、微生物数量和微生物多样性的影响。结果表明,当地农民传统氮肥用量减少20%,对作物产量、氮素吸收、土壤酶活性、微生物(细菌、放线菌、真菌)数量无显著影响。在氮肥减量20%的基础上,有机肥替代氮肥50%,蔗糖酶、蛋白酶、脲酶、磷酸酶活性分别提高46-62、27-89、33-46、35-74%,微生物数量即其中,细菌、放线菌和真菌的比例分别为36-150、11-153和43-56%。有机肥替代的Shannon多样性指数(H)为2.18,高于其他单施氮肥方式。结果表明,试验区氮肥减少20%,施用有机肥可以有效降低生产成本,显著提高土壤肥力和生物特性。
关键词:稻麦轮作,施氮方式,有机肥置换,土壤酶活性,微生物多样性
介绍
水稻-小麦轮作是一种重要的耕作制度,主要在南亚亚热带地区实行。在中国,水稻是最重要的粮食作物,种植面积2700万公顷,产量占粮食总产量的40%以上(Ju et al. 2007)。据估计,中国的稻麦轮作田总面积为1300万公顷,大部分位于长江中下游(Timsina and Connor 2001)。
在水稻-小麦种植系统中,施肥方式是保证作物产量和品质的关键。冬小麦和中稻轮作是目前长江中下游水稻旱地轮作制度的主要形式。然而,肥料施用的不平衡和氮肥的过量施用已成为制约作物产量和农业经济效益的最严重问题。越来越多的研究表明,施用氮肥的效率正在下降(Ohnishi et al. 1999)。
水稻-小麦轮作系统不合理施肥恶化土壤肥力和土壤特性,特别是生物特性(Kalter 2003)。Bhattacharya等(2006)报道,过量施肥使土壤环境逐年恶化,影响植物生长和作物产量。许多研究发现,肥料中的土壤污染物可以随着河流和风暴移动到数百或数千公里之外(Veado et al. 2006;Cogunet al. 2006)。因此,化肥对土壤和生态环境的影响引起了人们的广泛关注。
截至2009年,我国氮肥消费量超过4000万吨,居世界首位(国家统计局2009年)。根据中国国家土壤肥料统计数据,化肥投入占生产成本的比例仍在逐年增加,氮肥平均回收率仅为32-45%,即使在有效的农场管理制度下也不超过50%。
基于N施肥的现实在中国稻麦轮作中,本文研究了对作物产量的影响,氮肥复苏率、土壤肥力和土壤生物特性的现场试验包括三个治疗:当地农民的氮肥率控制,减少氮肥率,结合应用的有机N肥。
材料和方法
实验地点
小麦郑麦9023号和水稻二优838号(籼稻)。实验地点是位于江汉平原腹地,潜江市位于号口农场,湖北省,中国(30°22acute;54.5acute;acute;N and112°37acute;21.5acute;acute;E, 海拔27.5 米)。土壤为浅成壤土钙质冲积土,基本属性如下:pH值7.1, 有机物20.62 g kg-1,总N 1.534 g kg-1,总P 2.022 g kg-1,总K 20.7 g kg-1,NaOH水解N 121.28 mg kg-1,有效P 19.16 mg kg-1,有效K 72.5 mg kg-1,阳离子交换量(CEC) 14.85 mol kg-1。
田间试验设计
根据当地农民施氮量,设计了四种施氮模式:(1)对照(无N肥料,N0),(2) 100% N肥料(100%尿素-N),即农民传统的氮肥施用模式,(3) 80%氮肥(80%尿素-N),即氮肥施用减少模式,(4)氮肥:有机肥,3:5(30%尿素-N/50%有机氮),即有机肥置换模式。
氮肥利用率为100%(农户模式)是小麦225 kg N ha-1,大米210公斤kg N ha-1,以尿素为氮源[尿素氮肥料为尿素(N 46%)],鸡粪为有机氮源(N 1.8%, P2O5 10%, K2O 4.8%)。小麦采用120公斤过磷酸钙P2O5 ha-1(含P2O5 10%)和105公斤氯化钾K2O(含60% K2O),水稻采用75公斤P2O5和72公斤K2O (含120 kg KCl ha-1)作为基肥。基肥处理采用播种机播撒,然后用旋转式中耕机翻拌。氮肥经条施施于小麦上,除草后施于水稻上(表1)
采用随机区组设计(RBD),每个复制作为一个区,每个治疗在同一区内的每个小区随机进行。每块地面积为70平方米(28 mtimes;2.5 m),小麦条播种子率为82.5 kg ha-1,水稻幼苗生长30-40 d后移栽。所有田间管理措施,包括昆虫和杂草控制,都是根据当地的建议进行的。
实地考察、取样和样品制备
在2008年至2009年期间,在每个生长季的成熟期之前,从每个地块采集土壤和植物样本。在进行微生物活性和酶活性测定前,从20cm土层中取土壤样品,通过通风干燥,筛分(2mm), 4℃保存在松散的塑料袋中,以确保足够的曝气和防止水分流失。植物样品,包括小麦和大米的颗粒,立即在80°C下处理1小时,然后在60°C下干燥。干燥后的样品称重,研磨成粉末进行营养分析。
化学分析及方法
采用烘箱干燥法测定土壤水分。测定了土壤NaOH水解氮(玉米地1960),速效磷(Olsen et al. 1954)和速效钾(Pratt 1951)。土壤pH值由土壤和水按1:1混合,用pH计测定。土壤和植物总氮采用H2SO4-H2O2消煮和凯氏定氮法(Tkachuck 1969)测定,土壤有机质采用重铬酸盐滴定法(Walkley and Black 1934)测定。
分别用水杨酸比色法(Guan 1986)、对硝基苯酚-正磷酸盐钠比色法(Tabatabai 1994)、苯甲酸钠比色法(Tabatabai 1994)和茚三酮比色法(Kandeler 1996)测定土壤蔗糖酶、磷酸酶、脲酶和蛋白酶的活性。微生物,即。采用传统平板计数法对土壤样品中的细菌、放线菌和真菌进行计数(Xu和Zheng 1986)。
微生物多样性测定方法由Li等(2006)改进而来。简而言之,从土壤中提取总DNA,按照Zhou等人(1996)的方法进行纯化。按照Li等(2006)的方法对土壤DNA进行PCR扩增。以纯化的DNA为模板进行聚合酶链反应(PCR),得到一对特殊的引物,即F-968-GC (5acute;-CGC CCG GGG CGC GCC CCG GGC GGGGCG GGG GCACGG GGG GAACGC GAA GAACCT TAC-3acute;)和R-1401(5acute;-CGG TGT GTA CAA GAC CC-3acute;) 在V3区域使用16S rDNA基因。PCR扩增进行阿波罗ATC 201 PCR仪, PCR反应体系的构成根据达米亚尼等micro;L设计(1996)。制备10%聚丙烯酰胺凝胶对PCR产物进行分析,凝胶的变性范围为30-70%(100%变性剂为尿素7 mol L-1和40%去离子化甲酰胺的混合物)。电泳条件为:温度60℃,电压70 V,缓冲液1times;TAE,电泳时间16 h。电泳后用改进的硝酸银染色方法对样品进行染色(Bruce et al. 1992)。观察电泳条带并拍照。
采用美国加州大力神公司Bio-Rad公司的Quantity One分析软件对DGGE电波谱进行了分析。通过检测频带和匹配频带,扣除背景强度,得到各车道的强度剖面和相似矩阵。采用Shannon-Wiener指数(H)、丰富度(S)、均匀度(EH)评价微生物群落多样性(Shannon and Wiener 1949),计算公式为H=-sum;piln(pi),EH=H/Hmax=H/lnS.
统计分析
数据采用MS Excel 2003进行处理,图由SigmaPlot 10构建。采用SAS 8.0软件进行方差分析和均值显著性分析。除另有说明外,本研究结果中显著性水平为Plt;0.01。
结果
施氮方式对水稻和小麦养分吸收和产量的影响
与对照(N0)相比,三种施氮方式(100%尿素-N、80%尿素-N、30%尿素-N/50%有机N)的作物全氮吸收量显著增加。例如,总N吸收2008年和2009年增加了54.7-70.2和26.3-36.4%小麦、大米和62.8 -110.6和51.4-64.1%,分别为(表2)。同样,与100%尿素相比,农民模式,减少20%的氮肥不显著降低水稻和小麦的吸收。
与氮素吸收相似,三种氮素施用方式均显著提高了作物产量(表3),小麦在2008年和2009年的增长率分别为11.5-25.8%和15.9-18.0%,水稻为30.4-36.7%和19.8-24.3%。此外,减少20%的氮肥并没有导致水稻和小麦产量下降,有机肥替代模式的作物产量最高(表3)。
N施肥方式对土壤酶活性的影响
脲酶活性 施氮处理后脲酶活性显著高于对照(N0), 20%的N处理未改变脲酶活性(图a)。2009年,100%尿素氮处理、80%尿素氮处理和30%尿素氮/50%有机氮处理的脲酶活性均比对照高44-59%。80%尿素型和100%尿素型土壤的脲酶活性分别为8.33 mg g-1 NH3-N d-1和8.35 mg g-1 NH3-N d-1,差异不显著。同样的趋势也发生在水稻土壤中(图a)。
值得注意的是,在氮素供应量为80%的情况下,施用50%的有机氮替代氮肥(有机肥置换方式)有利于提高脲酶活性(图a)。2008年,与80%尿素处理相比,30%尿素氮/50%有机氮处理的小麦和水稻的脲酶活性分别提高11.0和10.8%,达到显著水平,说明有机肥对尿素酶活性有一定的促进作用。
蛋白酶活性 在100%尿素-N、80%尿素-N、30%尿素-N/50% org-N处理的土壤中,N施肥增加了蛋白酶活性,20% N的减少并没有导致蛋白酶活性下降(图- b)。相比之下,相比之下,除2008年小麦土壤外,三种模式的蛋白酶活性存在显著差异。例如,2009年三种氮肥处理的小麦和水稻土壤的促戏弄活性均增加了8.4-44.1%,80%尿素处理的蛋白酶活性比100%尿素处理的蛋白酶活性高10.4%。
降低氮肥20%和施用有机氮肥也能提高蛋白酶活性。在小麦和水稻土壤中,30%尿素氮/50%有机氮模式的蛋白酶活性分别显著高于80%尿素模式的11和38%,且在水稻成熟期蛋白酶活性的变化趋势更为明显(图- b)。
蔗糖酶活性 各施氮方式蔗糖酶活性均高于不施氮(图- c)。以2008年小麦土壤为例,三种模式下的蔗糖酶活性均比对照高22.3-53.1%,其他年份的蔗糖酶活性也有相同的趋势。施用有机肥替代化学氮肥显著提高了蔗糖酶活性(图- c),其中以2008年小麦土壤蔗糖酶活性变化趋势最为明显,30%尿素氮/50%有机氮模式蔗糖酶活性比80%尿素模式高12.9%。
磷酸酶活性 磷酸酶活性如预期,氮肥的施用提高了土壤磷酸酶活性。如图- d所示,2008年三种N施肥方式的磷酸酶活性均比对照高7.6-71.3%。氮肥减量20%,磷酸酶活性增加8.4%,其他年份也有相同的趋势。同样,用有机N代替尿素N也提高了磷酸酶活性,增加了83.3%,是本实验四种模式中酶活性最高的。
N施肥方式对土壤微生物的影响
氮肥的施用增加了细菌、放线菌和真菌的数量(表4),与对照相比,三种施氮方式的小麦土壤细菌数增加了20-167%。这一趋势在
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