施硫对‘豫麦50’籽粒灌浆特性及产量的影响

选用弱筋小麦品种‘豫麦50’为材料,通过大田试验研究了较高供氮水平下(施纯氮330 kg/hm2)施用低量(S 20 kg/hm2)、中量(S 60 kg/hm2)和高量(S 100 kg/hm2)硫肥对小麦籽粒灌浆特性和产量的影响.结果显示,不同施硫处理的小麦籽粒灌浆进程均“呈慢—快—慢”的S型曲线,拟合的Logistic方程决定系数均大于0.993 2,并达到极显著水平;灌浆持续期(T)、渐增期平均灌浆速率(V1),快增期和缓增期持续期(T2、T3)、灌浆期各阶段干物质积累量(m1、m2、m3)和理论最大千粒重(K)均随施硫量增加而提高,并以中硫处理的各项灌浆参数表现较优;中硫处理的千粒重(46.47 g)和籽粒产量(7 416.0 kg/hm2)显著高于低硫处理,极显著高于对照(不施硫)和高硫处理.表明在当前较高施氮水平下,每公顷施纯硫60 kg可有效改善小麦灌浆特性,显著提高籽粒产量.     

施硫对''''豫麦50''''籽粒灌浆特性及产量的影响

选用弱筋小麦品种‘豫麦50’为材料,通过大田试验研究了较高供氮水平下（施纯氮330kg／hm^2）施用低量（S20kg／hm^2）、中量（S60kg／hm^2）和高量（S100kg／hm^2）硫肥对小麦籽粒灌浆特性和产量的影响。结果显示,不同施硫处理的小麦籽粒灌浆进程均呈“慢-快-慢”的S型曲线,拟合的Logistic方程决定系数均大于0．9932,并达到极显著水平;灌浆持续期（T）、渐增期平均灌浆速率（V1）,快增期和缓增期持续期（T2、T3）、灌浆期各阶段干物质积累量（m1、m2、m3）和理论最大千粒重（K）均随施硫量增加而提高,并以中硫处理的各项灌浆参数表现较优;中硫处理的千粒重（46．47g）和籽粒产量（7416．0kg／hm^2）显著高于低硫处理,极显著高于对照（不施硫）和高硫处理。表明在当前较高施氮水平下,每公顷施纯硫60kg可有效改善小麦灌浆特性,显著提高籽粒产量。     

不同氮素水平下施硫对高产小麦碳氮运转和产量的影响

在大田栽培条件下,以2个不同穗型的高产冬小麦品种为试验材料,在施240 kg·hm-2(N240)和330 kg·hm-2(N330)纯氮水平下,分别施纯硫60 kg·hm-2(S60)和0 kg·hm-2(S0),研究了施硫对小麦不同器官碳氮运转及其对籽粒产量和蛋白质产量的影响.结果显示:(1)2个供氮水平下,施硫(S60)均比对照(S0)增加了2个小麦品种的叶片、茎、鞘、颖壳和穗轴等营养器官花前贮藏干物质、氮素的运转量和运转率以及总运转量和总运转率,提高了转运干物质、氮素对籽粒重和籽粒氮素的贡献率,极显著提高了籽粒和蛋白质产量.(2)施硫对豫农949品种籽粒和蛋白质产量提高幅度显著高于兰考矮早八;与对照(S0)相比,豫农949的N240S60和N330S60处理使籽粒产量分别增加12.74%和16.41%,蛋白质产量分别增加16.84%和16.14%.结果表明,中氮和高氮水平下施硫均可明显促进高产小麦植株的C-N运转,提高植株对氮的吸收利用和碳物质的积累,从而增加籽粒产量,但不同品种间的施硫效应存在差异.     

氮磷配施条件下作物产量及水肥利用效率

农田退水过程中氮、磷等污染物对黄河造成较严重的污染,需要合理调控农业生产过程中氮、磷配施水平,进一步削减氮、磷用量,从源头上解决农业面源污染问题。本研究分析了不同氮、磷配施条件下小麦玉米套作的产量及水肥利用效率。结果表明:随着施氮(磷)量的增加,小麦玉米套作的产量、百粒重(千粒重)、耗水量及水分利用效率表现为先增加后减少的规律,氮、磷合理配施能够显著增加土壤贮水量的消耗,提高作物对土壤水分的利用;氮(磷)肥的偏生产力及农学效率表现为随着施氮(磷)量的增加而降低,施氮(磷)量恒定时,在一定范围内增施磷(氮)肥能够有效提高作物的氮肥偏生产力及农学效率,施磷(氮)过量,则表现为降低趋势;小麦玉米套作达到最高产量的最佳施肥量为,小麦施氮191.7~216 kg·hm-2,施磷165.38~186.64 kg·hm-2,玉米施氮243~299.14 kg·hm-2,施磷168.38~189 kg·hm-2;氮、磷合理配施能够在保证产量的前提下,适量削减氮、磷施量,提高作物对水肥的利用,减轻农业面源污染。     

退耕还草对土壤水分养分演变的影响

研究了高原沟壑区1984～1998年种植小麦和退耕种植苜蓿期间,土壤水分、土壤有机碳氮含量的演变。结果表明,种植小麦在不施肥的条件下从1984年到1998年,0～300cm土层水分和耕层有机碳氮含量都保持相对稳定,增施氮磷肥或在氮磷肥基础上配施有机肥土壤80～200cm土层水分有降低趋势,而耕层有机碳氮含量分别提高14％～60％和12％～55％。地表植被在1984年由作物改种苜蓿后到1998年,0～300cm土层土壤水分由1984年的20％逐渐降低至10％,耕层有机碳氮含量分别增加23％～77％和20％～68％。无论种植小麦还是退耕种植苜蓿耕层以下土层的有机碳氮含量从1984年到1998年变化不大。在雨养农业区,水分利用效率是制约土壤水分和养分呈现相反变化的重要因素。     

硫硒配施对茎瘤芥生长和营养效应的研究

以茎瘤芥品种‘涪杂1号’为材料,通过盆栽实验探讨不同浓度的硫(S)、硒(Se)配施处理对茎瘤芥干物质积累、矿质元素吸收及膨大茎营养品质的影响,为生产中合理施用硫、硒肥提供理论依据.结果表明:与对照(S0Se0,未施硫硒肥)相比,增施硫、硒肥处理均能显著提高茎瘤芥的根、膨大茎、叶片和单株干物质产量,并以S50Se1[S/Se=50(mg/kg)/1(mg/kg)]和S100Se1的处理效果较好,其单株干物质产量分别比对照显著增加32.3%和36.2%;不同硫、硒浓度配施处理对茎瘤芥13种矿质元素积累的影响不同,主要显著促进了茎、叶对氮、磷、钾、硫、硒的吸收积累,而对其它元素的影响不显著,其中茎、叶的硒含量以S50Se3处理最高,硫含量以S100Se1处理最高;各硫硒配施处理对膨大茎营养品质的影响不同,其中S50Se1和S50Se3处理能显著提高膨大茎有机硒、总氨基酸和粗蛋白含量,而对维生素C和可溶性糖含量无显著影响.可见,适宜的硫硒配施可以明显促进其对矿质元素的吸收,提高植株干物质积累,有效改善茎瘤芥膨大茎营养品质,且硫硒配施用量以S 50mg/kg、Se 1mg/kg为宜.     

长期施肥和不同生态条件下我国作物产量可持续性特征

采用产量可持续性指数（SYI）法,研究了我国不同生态条件下20个长期试验点8个肥料处理的水稻、玉米和小麦产量的可持续性.结果表明：作物SYI值因施肥、作物种类和水热因子不同而呈显著差异.长期不施肥（CK）条件下,水稻、玉米和小麦的SYI值较低,分别为0.55、0.44和0.43;施肥尤其是NPK化肥配施有机肥可显著提高作物产量的可持续性,水稻、玉米和小麦的SYI值分别为0.66、0.58和0.57;单施N肥或NK肥的玉米和小麦的SYI值在0.36～0.47.SYI值大于0.55表明可持续性较好,小于0.45表明可持续性差.经纬度和气象因子对作物SYI也有不同程度的影响,3种作物不施肥时,水稻SYI变异较小,与各因子间没有显著相关性,玉米SYI变异最大且与各因子间存在显著的相关关系,小麦介于两者之间.因此,NPK配施有机肥有利于作物高产稳产,是维持系统可持续性的最优施肥模式.     

硫营养对重金属胁迫下玉米和小麦根系导水率的影响

以‘秦单4号’玉米和‘小偃22’小麦为供试材料,通过室内玉米水堵和小麦盆栽试验,采用静态压力室法测定了不同硫营养水平与不同重金属胁迫处理下根系导水率（Lpr）的变化。结果表明：玉米Lpr经100μmol／LHg^2＋、Zn^2＋、Cu^2＋胁迫处理后分别降低到CK的13％、79％和45％,Cu^2＋、Zn^2＋对其Lpr的抑制效应分别为同浓度Hg^2＋的62．9％及24．3％;施硫处理的玉米Lpr在无Cu^2＋胁迫条件下都极显著高于无硫处理,且低硫处理显著较高,在Cu^2＋胁迫条件下亦都极显著高于无硫处理,并且Cu^2＋胁迫对其Lpr的抑制效应随着硫浓度增大而逐渐减小;不施硫和施硫处理的小麦Lpr在500mg／kgZn^2＋胁迫下分别比相应CK降低36．89％和37．71％,在400mg／kgCu^2＋胁迫下则分别比相应CK降低了34．61％和12．29％。研究发现,重金属Cu^2＋、Zn^2＋对玉米和小麦根系导水率具有显著的抑制作用且Cu^2＋〉Zn^2＋,施硫对Cu^2＋胁迫下的玉米和小麦根系导水率都具有显著的保护作用,并随硫浓度增加而增强。     

旱地土壤铵态氮和硝态氮累积特征及其与小麦产量的关系

在陕西永寿和河南洛阳分别进行了11处和7处小麦大田试验,设对照(不施氮)和施氮(150 kg N·hm^-2)2个处理,测定了小麦生物量、籽粒产量及不同土层(0～20、20～40、40～60、60～80、80～100 cm)土壤铵态氮、硝态氮浓度.结果表明: 两地土壤铵态氮浓度均很低,而硝态氮浓度较高,其中硝态氮数量占铵态氮、硝态氮总量的91%,在反映土壤供氮特性方面与两者之和有完全一致趋势.不施氮情况下,永寿0～40、0～60、0～80和0～100 cm土层累积的硝态氮与小麦生物量和产量显著相关;而洛阳无显著相关关系.施氮后,永寿不同深度土层累积的硝态氮与小麦生物量和产量的相关关系显著下降,而洛阳出现负相关;两地小麦产量增量与0～80 和0～100 cm土层累积的硝态氮显著或极显著相关.小麦苗期主要依赖0～20 cm土层硝态氮;返青期、拔节期分别利用0～40 cm和0～60 cm土层硝态氮,成熟期则能利用0～100 cm土层累积硝态氮.小麦收获后对照土壤的铵态氮浓度与播前起始值无明显差异,而硝态氮大幅下降.     

不同水肥处理对夏玉米田土壤微生物特性的影响

以氮高效率型玉米品种(ZN99)为试验材料,研究了不同水肥处理对夏玉米田土壤微生物特性的影响.采用裂区设计,主区为灌水处理,设置了2个灌溉水平(玉米全生育期内灌水526和263 mm);副区为施肥处理,设置了3种肥料类型(无机肥U、有机肥M、有机无机混施UM)和2个施氮水平(N 100和200 kg·hm-2).结果表明:灌水量影响了肥料对土壤微生物生物量(碳、氮)和微生物多样性的调控,施有机肥只有在充足灌水条件下才能显著提高土壤微生物生物量碳(14.3%~33.6%)、微生物生物量氮(1.8~2.3倍)和丰富度.适量灌水、增施有机肥或有机无机配施可增加土壤中具有固氮能力的厚壁菌、γ-变形菌或α-变形菌的种类和相对数量.同一施氮量下,有机肥与无机肥对产量的影响差异不显著.从可持续生产角度考虑,适量灌水条件下,增施有机肥更有利于土壤微生物生物量及多样性的提高,增强土壤水肥供应能力.     

Comparative response of wheat and oilseed rape to nitrogen supply: absorption and utilisation efficiency of radiation and nitrogen during the reproductive stages determining yield

We investigated the response of spring wheat and oilseed rape to nitrogen (N) supply, focusing on the critical period for grain number definition and grain filling. Crops were grown in containers under a shelter and treated with five combinations of applied N. Wheat and oilseed rape produced comparable amounts of biomass and yield when corrected for the costs of biomass synthesis (SC). From the responses of biomass and yield to late N applications and the apparent contribution of mobilised biomass to yield, it seems that the yield of oilseed rape was more source-limited during grain filling than that of wheat, particularly at the medium and high N levels. Both species recovered equal amounts of N from the total available N in the soil and had similar N use efficiencies, expressed as yield per unit of N absorbed. However, oilseed rape had higher efficiency to convert absorbed N in biomass, but lower harvest index of N than wheat. Oilseed rape had similar or lower root biomass than wheat, depending on N level, but higher root length per unit soil volume and specific root length. The specific uptake rate of N per unit root dry weight during the critical period for grain number determination was higher in oilseed rape than in wheat. In wheat, N limitation affected growth through a similar or lower reduction in radiation use efficiency corrected for synthesis costs (RUE_SC) than in the cumulative amount of intercepted photosynthetically active radiation (IPARc). In oilseed rape, lower growth due to N shortage was associated more with RUE_SC than IPARc, during flowering while during grain filling both components contributed similarly to decreased growth. RUE_SC and the concentration of N in leaves and inflorescence (LIN%) decreased from flowering to maturity and were curvilinearly related. Oilseed rape tended to have higher RUE_SC than wheat at high N supply during the critical period for grain number determination, and generally lower during grain filling. The reasons for these differences and possibilities to increase yield potential are discussed in terms of the photosynthetic efficiency of the different organs and changes in source–sink ratio during reproductive stages. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effects of simulated acid rain on oilseed rape (Brassica napus) physiological characteristics at flowering stage and yield

A pot experiment was conducted to study the effects of different acidity simulated acid rain on the physiological characteristics at flowering stage and yield of oilseed rape (B. napus cv. Qinyou 9). Comparing with the control (pH 6.0), weak acidity (pH = 4.0-5.0) simulated acid rain stimulated the rape growth to some extent, but had less effects on the plant biomass, leaf chlorophyll content, photosynthetic characteristics, and yield. With the further increase of acid rain acidity, the plant biomass, leaf chlorophyll content, photosynthetic rate, antioxidative enzyme activities, and non-enzyme antioxidant contents all decreased gradually, while the leaf malonyldialdehyde (MDA) content and relative conductivity increased significantly. As the results, the pod number per plant, seed number per pod, seed weight, and actual yield decreased. However, different yield components showed different sensitivity to simulated acid rain. With the increasing acidity of simulated acid rain, the pod number per plant and the seed number per pod decreased significantly, while the seed weight was less affected.     

播种期和种植密度对冬油菜籽粒产量和含油率的影响

通过田间试验研究了播种期和种植密度对冬油菜籽粒产量和含油率的影响.结果表明： 播种期主要影响分枝花序籽粒产量,而种植密度不仅影响分枝花序籽粒产量,还对主花序籽粒产量产生一定影响;籽粒含油率不受播种期的影响.主花序籽粒产量占单株籽粒产量的比例随种植密度的增加而升高,主花序籽粒含油率比分枝花序高约1%,因此小区籽粒含油率随种植密度的增加显著升高.研究区冬油菜播种期不能晚于10月中旬,10月下旬播种会显著降低籽粒产量;种植密度在每平方米36～48株可以提高冬油菜籽粒产量和含油率.     

Response of oilseed rape leaves to sulfur and boron foliar application

Oilseed rape (Brassica napus L.) reacts differently to foliar application of sulfur (S) and boron (B), and for that reason it is important to find an early indicator that would inform about the direction of this reaction. This study aimed at evaluating the early response of two double-low cultivars of winter oilseed rape: hybrid (Nelson) and open pollinated (Digger) on the foliar fertilization with S and B in two terms: fall and spring, based on the rate of leaf greenness index (SPAD) and seven indicators of chlorophyll a fluorescence (FL). On 7th or 9th day after the application of liquid fertilizers, the selected parameters of FL and SPAD were determined on the leaves of rape. As a result, a significant effect of foliar B and S supplementation on the yield of oilseed rape was found. Principal component analysis (PCA) allowed for a separation for each of the cultivars the two parameters of FL, namely Tfm and Fv/F0, which are sensitive indicators of a physiological state of the rape plants shortly after foliar S and B dressing.     

Effects of previous cropping and fungicide timing on the development of light leaf spot (Pyrenopeziza brassicae), seed yield and quality of winter oilseed rape (Brassica napus)

Light leaf spot, caused by Pyrenopeziza brassicae, was assessed regularly on double-low cultivars of winter oilseed rape during field experiments at Rothamsted in 1990-91 and 1991-92. Previous cropping and fungicide applications differed; seed yield and seed quality were measured at harvest. In each season, both the initial incidence of light leaf spot and the rate of disease increase were greater in oilseed rape crops sown after rape than those sown after cereals. The incidence of diseases caused by Phoma lingam or Alternaria spp. was also greater in second oilseed rape crops. In 1991-92 there was 42% less rainfall between September and March than in 1990-91, and much less light leaf spot developed. However, P. lingam and Alternaria spp. were more common. Only fungicide application schedules including an autumn spray decreased the incidence of light leaf spot on leaves, stems and pods, as indicated by decreased areas under the disease progress curves (AUDPC) and slower rates of disease increase. Summer sprays decreased incidence and severity of light leaf spot on pods only. In 1990-91, all fungicide treatments which included an autumn spray increased seed and oil yields of cv. Capricorn but only the treatment which included autumn, spring and summer sprays increased yields of cv. Falcon. No treatment increased the yields of cv. Capricorn or cv. Falcon in 1991-92. Fungicide applications decreased glucosinolate concentrations in the seed from a crop of cv. Cobra severely infected by P. brassicae in 1990-91, but did not increase yield.     

Weeds in fields with contrasting conventional and genetically modified herbicide-tolerant crops. II. Effects on individual species

We compared the effects of the management of genetically modified herbicide-tolerant (GMHT) and conventional beet, maize and spring oilseed rape on 12 weed species. We sampled the seedbank before and after cropping. During the season we counted plants and measured seed rain and biomass. Ratios of densities were used to calculate emergence, survival, reproduction and seedbank change. Treatments significantly affected the biomass of six species in beet, eight in maize and five in spring oilseed rape. The effects were generally consistent, with biomass lower in GMHT beet and spring oilseed rape and higher in GMHT maize. With few exceptions, emergence was higher in GMHT crops. Subsequent survival was significantly lowered for eight species in beet and six in spring oilseed rape in the GMHT treatments. It was increased for five species in maize and one in spring oilseed rape. Significant effects on seedbank change were found for four species. However, for many species in beet and spring oilseed rape (19 out of 24 cases), seed densities were lower in the seedbank after GMHT cropping. These differences compounded over time would result in large decreases in population densities of arable weeds. In maize, populations may increase.     

Effects of selenium content in green parts of plants on the amount of ATP and ascorbate-glutathione cycle enzyme activity at various growth stages of wheat and oilseed rape

The aim of this experiment, conducted under greenhouse conditions, was to assess the influence of various H(2)SeO(3) concentrations added to soil (0.05, 0.15, and 0.45mMkg(-1)) on selenium and adenosine triphosphate (ATP) content, and on the activity of the ascorbate-glutathione cycle enzymes in green parts of wheat and oilseed rape. Selenium uptake by the test plants was found to vary, with content increasing from one developmental stage to the next over four stages of the developmental cycle. At the lowest H(2)SeO(3) dose (0.05mMkg(-1)), the wheat plants took up much more selenium than did the oilseed rape plants, while the amount of selenium taken up at higher doses (0.15 and 0.45mMkg(-1)) was markedly higher in rape. The increasing Se content in the wheat to about 10mgkg(-1) (in the dark) and to about 16mgkg(-1) (in the light) was accompanied by a concurrent increase in the ATP content, which remained unchanged in the light-exposed plants, while clearly decreasing in those kept in the dark. On the other hand, the ATP content of the light-exposed oilseed rape was maintained at a stable level to about 10mg Sekg(-1), following which ATP content was observed to decrease. In contrast, the tendency for the ATP content to decrease appeared immediately in the dark. The increasing plant selenium concentration was accompanied by decreased APX activity in wheat, increased activity in oilseed rape, no major change in the dehydroascorbate reductase (DHAR) activity in oilseed rape and a slight increase in wheat to about 8mg Sekg(-1), followed by a reduction. The glutathione reductase (GR) activity in wheat differed from the activity of DHAR; an increase in the selenium content to about 8mgkg(-1) was accompanied by a distinct reduction, while a significant increase was observed at higher selenium contents; in oilseed rape, the activity was observed to increase slightly within a narrow range of selenium contents (up to 5mgkg(-1)), and to decrease thereafter.     

CO2浓度增加和水分亏缺对典型绿肥植物光合性能及水分利用效率的影响

探讨大气CO₂浓度和水分变化对3种典型绿肥植物光合性能及水分利用效率的影响,可为未来气候变化情形下草地生态系统适应性管理提供理论支持。本试验利用可精准控制CO₂浓度的人工气候室,设置400(自然大气)和800 μmol·mol^-1(倍增)两个CO₂浓度,80%土壤田间持水量(FC)(充分灌水对照)、55%～60%FC(轻度水分亏缺)、35%～40%FC(中度水分亏缺)、<35%FC(重度水分亏缺)4个水分梯度,研究CO₂浓度增加和水分亏缺对甘蓝型油菜、白三叶和紫花苜蓿叶绿素含量、气体交换参数及水分利用效率(WUE)的影响。结果表明: 同一CO₂浓度下,与充分灌水对照相比,当土壤水分<40%FC时,3种植物的叶绿素含量和气体交换参数均显著降低;土壤水分为55%～60%FC时,3种植物的叶绿素总含量无显著变化,而白三叶和紫花苜蓿的光合速率(P_n)、蒸腾速率(T_r)降低了6%～25%,但WUE无显著性差异。与大气CO₂浓度相比,CO₂浓度倍增使充分灌水处理下甘蓝型油菜的P_n显著降低了21.5%,而显著增加了轻度水分亏缺下3种植物的P_n,且增加了中度水分亏缺下甘蓝型油菜和紫花苜蓿的P_n,但只对重度水分亏缺下紫花苜蓿的P_n有所改善;CO₂浓度倍增显著增加了白三叶和紫花苜蓿在所有水分处理下的WUE,但只增加了甘蓝型油菜在轻度水分亏缺下的WUE。CO₂浓度和水分的交互作用对3种植物的P_n均有显著影响,但仅对甘蓝型油菜的WUE有显著影响。综上,3种植物对大气CO₂浓度倍增和水分亏缺的响应存在明显差异,CO₂浓度升高能改善轻度水分亏缺对3种植物光合性能和WUE的不利影响,但只改善了重度水分亏缺下紫花苜蓿的光合性能。     

Studies on beet western yellows virus in oilseed rape (Brassica napus ssp. oleifera) and sugar beet (Beta vulgaris)

Oilseed rape (Brassica napus L. ssp. oleifera) was studied as a potential overwintering host for the sugar-beet yellowing viruses, beet yellows virus (BYV) and beet mild yellowing virus (BMYV), and their principal vector, Myzus persicae. In spring 1982, plants infected with a virus which reacted positively in enzyme-linked immunosorbent assay (ELISA) with BMYV antibody globulin were found in oilseed-rape crops; none of the plants contained virus which reacted with BYV antibody globulin. This virus was subsequently identified as beet western yellows virus (BWYV). No leaf symptoms could be consistently associated with infection of oilseed rape, but the virus was reliably detected by sampling any leaf on an infected oilseed-rape plant. Some isolates from oilseed rape did infect sugar beet in glasshouse tests, but the proportions of inoculated plants which became infected were low. Apparently there is therefore little danger of much direct transmission of BWYV by M. persicae from oilseed rape to sugar beet in spring. BWYV was introduced to and spread within oilseed-rape crops in autumn by M. persicae, and autumn-sown oilseed rape proved to be a potentially important overwintering host for M. persicae. In a survey of 80 autumn-sown crops of oilseed rape in East Anglia, northern England and Scotland in spring 1983, 78 were shown to be extensively infected with BWYV. Experimental plots of oilseed rape with 100% BWYV-infection yielded approximately 13.4% less oil than plots with 18% virus infection, the result of a decrease in both seed yield and oil content.     

The effect of three or five years of set-aside on the husbandry and grain yield of subsequent cereal crops in the UK

During the period 1993–1997, at six contrasting sites located throughout England, two successive cereal test crops were grown both with and without nitrogen fertiliser after three or five years of set-aside or after continuous arable cropping. Vegetation during set-aside included natural regeneration and perennial rye-grass (Lolium perenne) with or without white clover (Trifolium repens), managed by mowing on one or more occasions per year. Establishment of the successive cereal test crops after destruction of the set-aside was generally not a problem. Fertile tiller numbers were increased by inclusion of clover in the set-aside cover or application of inorganic nitrogen. The presence of couch grass (Elytrigia repens) or volunteer cereals in the set-aside covers provided alternative hosts for take-all (Gaeumanomyces graminis) and eyespot (Pseudocercosporella herpotrichoides) and take-all caused some yield reductions in following cereal crops. Management during the set-aside period significantly affected grain yields of the subsequent cereal crops in the majority of the site-year combinations. However, these effects were not as large as would be expected after traditional break crops and were frequently masked by the application of nitrogen fertiliser. Mean yields increased by 80% due to the application nitrogen at the optimum rate compared to nil nitrogen. Most of the effects of set-aside treatment on grain yield were shown to be attributable to soil mineral nitrogen content, but at some sites, infections by take-all or eyespot also accounted for some of the variation. There were no effects of pests that could be related to treatment. The presence of sown clover during the set-aside period had the most consistent effect across sites, affecting tiller populations, grain yield and grain quality of cereal crops. At some sites, establishing a sown cover during the set-aside period, or cutting the cover more than once a year, improved grain yield and quality, and reduced the incidence of some specific weeds and disease. This revised version was published online in June 2006 with corrections to the Cover Date.