Evaluation of monocropped and intercropped grain legumes for cover cropping in no-tillage and reduced tillage organic agriculture

Intensive tillage by means of mouldboard ploughing can be highly effective for weed control in organic farming, but it also carries an elevated risk for rapid humus decomposition and soil erosion. To develop organic systems that are less dependent on tillage, a two-year study at Reinhardtsgrimma and Köllitsch, Germany was conducted to determine whether certain legume cover crops could be equally successfully grown in a no-till compared with a reduced tillage system. The summer annual legumes faba bean (Vicia faba L.), normal leafed field pea (Pisum sativum L.), narrow-leafed lupin (Lupinus angustifolius L.), grass pea (Lathyrus sativus L.), and common vetch (Vicia sativa L.) were examined with and without sunflower (Helianthus annuus L.) as a companion crop for biomass and nitrogen accumulation, symbiotic nitrogen fixation (N₂ fixation) and weed suppression. Total cover crop biomass, shoot N accumulation and N₂ fixation differed with year, location, tillage system and species due to variations in weather, inorganic soil N resources and weed competition. Biomass production reached up to 1.65 and 2.19 Mg ha⁻¹ (both intercropped field peas), and N₂ fixation up to 53.7 and 60.5 kg ha⁻¹ (both common vetches) in the no-till and reduced tillage system, respectively. In the no-till system consistently low sunflower performance compared with the legumes prevented significant intercropping effects. Under central European conditions no-till cover cropping appears to be practicable if weed density is low at seeding. The interactions between year, location, tillage system and species demonstrate the difficulties in cover crop species selection for organic conservation tillage systems.     

Selection of cereals for weed suppression in organic agriculture: a method based on cultivar sensitivity to weed growth

Cereal cultivars conferring a high degree of crop competitive ability, especially against aggressive weeds, are highly beneficial in organic farming as well as other farming systems that aim to limit the use of herbicides. In this study, thirteen winter wheat cultivars, plus one spring wheat and one winter oat were assessed for their competitive ability at key growth stages, across three seasons. The natural population of weed species was allowed develop without agronomic intervention. Weed suppression ability for each cultivar (S _var) was calculated as the difference between weed growth in plots for each cultivar and the maximal weed growth (W _max) from adjacent uncropped areas. The sensitivity of S _var in response to changes in weed growth (S _var^W) was derived from the linear regression coefficient of S _var plotted against W _max. There was significant variation in S _var between cultivars and strong evidence for cultivars to vary in S _var^W. Amongst groups of cultivars with similar levels of S _var some could be defined as being of higher or lower sensitivity to changes in weed growth. Some cultivars also had relatively good S _var at high levels of weed growth. The use of both weed suppression ability and sensitivity across different levels of weed growth or weed populations has considerable potential for selecting new cultivars suitable for organic agriculture. Ideally new cultivars will be selected on the basis of high S _var and/or low S _var^W. This analysis provides the means to measure sensitivity of cultivar performance across a range of favourable and unfavourable conditions.     

Early assessment of ecological services provided by forage legumes in relay intercropping

In organic agriculture, weeds and nitrogen deficiency are the main factors that limit crop production. The use of relay-intercropped forage legumes may be a way of providing ecological services such as weed control, increasing N availability in the cropping system thanks to N fixation, reducing N leaching and supplying nitrogen to the following crop. However, these ecological services can vary considerably depending on the growing conditions. The aim of this study was to identify early indicators to assess these two ecological services, thereby giving farmers time to adjust the management of both the cover crop and of the following crop.Nine field experiments were conducted over a period of three years. In each experiment, winter wheat was grown as sole crop or intercropped with one of two species of forage legumes; Trifolium repens L. or Trifolium pratense L. Two levels of fertilization were also tested (0 and 100 kg N ha⁻¹). After the intercropping stage, the cover crop was maintained until the end of winter and then destroyed by plowing before maize was sown. Legume and weed biomass, nitrogen content and accumulation were monitored from legume sowing to cover destruction.Our results showed that a minimum threshold of about 2 t ha⁻¹ biomass in the aboveground parts of the cover crop was needed to decrease weed infestation by 90% in early September and to ensure weed control up to December. The increase in nitrogen in the following maize crop was also correlated with the legume biomass in early September. The gain in nitrogen in maize (the following crop) was correlated with legume biomass in early September, with a minimum gain of 60 kg N ha⁻¹ as soon as legume biomass reached more than 2 t ha⁻¹.Legume biomass in early September thus appears to be a good indicator to predict weed control in December as well as the nitrogen released to the following crop. The indicator can be used by farmers as a management tool for both the cover crop and following cash crop. Early estimation of available nitrogen after the destruction of the forage legume can be used to adjust the supply of nitrogen fertilizer to the following crop.     

Screening techniques and sources of resistance against parasitic weeds in grain legumes

Summary A number of parasitic plants have become weeds, posing severe constraints to major crops including grain legumes. Breeding for resistance is acknowledged as the major component of an integrated control strategy. However, resistance against most parasitic weeds is difficult to access, scarce, of complex nature and of low heritability, making breeding for resistance a difficult task. As an exception, resistance against Striga gesnerioides based on a single gene has been identified in cowpea and widely exploited in breeding. In other crops, only moderate to low levels of incomplete resistance of complex inheritance against Orobanche species has been identified. This has made selection more difficult and has slowed down the breeding process, but the quantitative resistance resulting from tedious selection procedures has resulted in the release of cultivars with useful levels of incomplete resistance. Resistance is a multicomponent event, being the result of a battery of escape factors or resistance mechanisms acting at different levels of the infection process. Understanding these will help to detect existing genetic diversity for mechanisms that hamper infection. The combination of different resistance mechanisms into a single cultivar will provide durable resistance in the field. This can be facilitated by the use of in vitro screening methods that allow highly heritable resistance components to be identified, together with adoption of marker-assisted selection techniques.     

The effect of organic and conventional management on the yield and quality of wheat grown in a long-term field trial

The performance of winter wheat was evaluated under organic (ORG) and conventional (CON) management systems in the Nafferton Factorial Systems Comparison (NFSC) long-term field trial. The present study separates out the crop protection and fertility management components of organic and conventional production systems using two levels each of crop protection (CP) and fertility management (FM). The experimental design provided the four combinations of crop protection and fertility (CON-CP CON-FM, CON-CP ORG-FM, ORG-CP CON-FM and ORG-CP ORG-FM) to evaluate their effects on yield, quality (protein content and hectolitre weight) and disease levels during the period 2004–2008. The conventional management system (CON-CP CON-FM) out-yielded the organic management system (ORG-CP ORG-FM) in all years by an average of 3.1 t ha⁻¹, i.e. 7.9 t ha⁻¹ vs. 4.8 t ha⁻¹. Fertility management was the key factor identified limiting both yield and grain protein content in the ORG management system. The CON-FM produced on average a 3% higher protein content than ORG-FM in all years (12.5% vs. 9.7%). However the ORG-CP system produced higher protein levels than CON-CP although it was only in 2008 that this was statistically significant. In contrast to protein content it was ORG-FM which produced a higher hectolitre weight than the CON-FM system (71.6 kg hl⁻¹ vs. 71.0 kg hl⁻¹). The clear and significant differences in yield and protein content between the ORG-FM and CON-FM systems suggest a limited supply of available N in the organic fertility management system which is also supported by the significant interaction effect of the preceding crop on protein content. The pRDA showed that although fertilisation had the greatest effect on yield, quality and disease there was also a considerable effect of crop protection and the environment.     

Contribution of green manure legumes to nitrogen dynamics in traditional winter wheat cropping system in the Loess Plateau of China

Excessive application of N fertilizer in pursuit of higher yields is common due to poor soil fertility and low crop productivity. However, this practice causes serious soil depletion and N loss in the traditional wheat cropping system in the Loess Plateau of China. Growing summer legumes as the green manure (GM) crop is a viable solution because of its unique ability to fix atmospheric N₂. Actually, little is known about the contribution of GM N to grain and N utilization in the subsequent crop. Therefore, we conducted a four-year field experiment with four winter wheat-based rotations (summer fallow-wheat, Huai bean–wheat, soybean–wheat, and mung bean–wheat) and four nitrogen fertilizer rates applied to wheat (0, 108, 135, and 162 kg N/ha) to investigate the fate of GM nitrogen via decomposition, utilization by wheat, and contribution to grain production and nitrogen economy through GM legumes. Here we showed that GM legumes accumulated 53–76 kg N/ha per year. After decomposing for approximately one year, more than 32 kg N/ha was released from GM legumes. The amount of nitrogen released via GM decomposition that was subsequently utilized by wheat was 7–27 kg N/ha. Incorporation of GM legumes effectively replaced 13–48% (average 31%) of the applied mineral nitrogen fertilizer. Additionally, the GM approach during the fallow period reduced the risk of nitrate-N leaching to depths of 0–100 cm and 100–200 cm by 4.8 and 19.6 kg N/ha, respectively. The soil nitrogen pool was effectively improved by incorporation of GM legumes at the times of wheat sowing. Cultivation of leguminous GM during summer is a better option than bare fallow to maintain the soil nitrogen pool, and decrease the rates required for N fertilization not only in the Loess Plateau of China but also in other similar dryland regions worldwide.     

不同除草剂对冬小麦田宝盖草的防除效果

为筛选防除冬小麦田宝盖草的高效土壤处理除草剂,连续两年选取6种除草剂对防除冬小麦田宝盖草的效果进行研究。结果表明,选用600g/L氟噻草胺悬浮剂和40%砜吡草唑悬浮剂喷雾作土壤处理,在剂量分别是162.0和210.0g(a.i)/hm ²时株数和鲜重防效都达到90%以上,并且对冬小麦安全。     

Low-input cropping systems to reduce input dependency and environmental impacts in maize production: A multi-criteria assessment

Intensification of cropping systems in recent decades has increased their productivity but affected air, soil and water quality. These harmful environmental impacts are exacerbated in Maize Monoculture (MM) and hasten the need for solutions to overcome the trade off between crop yield and environmental impacts. In a three-year cropping systems experiment, a conventional intensive maize monoculture (MM_Conv), with a winter bare fallow, deep soil tillage, non-limiting irrigation was compared to three Low Input Cropping Systems (LI-CS) designed as alternatives to the conventional system. They were managed with decision-rules implemented to reach specific objectives of input reduction. The LI-CS designed with Integrated Weed Management (IWM) techniques and other sustainable cropping practices, were:(i) MM_LI—an IWM Low Input MM; (ii) MM_CT—a Conservation Tillage combined with cover crop MM; and (iii) Maize-MSW—an IWM maize grown in rotation with soybean and wheat. A comprehensive multi-criteria assessment was carried out to quantify the agronomic, economic, social, and environmental performances of each system. A canonical discriminant analysis of performance metrics revealed large differences between the four systems. Yields were significantly higher in MM_Conv (11.0 Mg ha⁻¹) and MM_LI (10.3 Mg ha⁻¹) than in Maize-MSW (8.6 Mg ha⁻¹) and MM_CT (7.8 Mg ha⁻¹). MM_CT had the largest weed infestation (density and biomass) despite the greatest use of herbicides. The Herbicide Treatment Frequency Index (HTFI), used to indicate differences in herbicide use, revealed that the MM_LI (HTFI = 1.0) and Maize-MSW (1.1) halved the herbicide use as compared to the MM_Conv (2.1), despite having similar weed abundance levels. The LI-CS, especially MM_CT, produced high biomass winter cover crops and then less nitrogen fertilization was required as compared to MM_Conv. Gross margins in the MM_LI (1254 € ha⁻¹) and MM_Conv (1252 € ha⁻¹) were higher than the MM_CT (637 € ha⁻¹) and Maize-MSW (928 € ha⁻¹). MM_LI and MM_Conv had similar labour requirements. Water drainage, pesticide leaching, energy use, and estimated greenhouse gas emissions were higher in MM_Conv than in the LI-CS in most years. Results from this research show good potential for the MM_LI to reduce the environmental impacts of MM_Conv while maintaining its economic and social performance.     

The impact of variation in grain number and individual grain weight on winter wheat yield in the high yield potential environment of Ireland

Previous studies from regions that produce high proportions of global winter wheat have highlighted that difference in sink size influences the majority of variations in winter wheat yield. However, the potential for source limitation due to environmental differences in regions that consistently produce a large sink capacity (i.e. >20,000 grains/m²), such as Ireland, have not been widely studied. The aim of this study was to characterise the variation in growth pattern and yield components that contribute to variations in grain yield in regions of high yield potential, and to identify the periods of development that are most likely to influence yield in these regions. Monitor crops of winter wheat were grown at three sites with contrasting latitudes on the island of Ireland, during three growing seasons (2013–2015). Crops were assessed regularly for measurements of crop growth and development, including biomass accumulation, canopy development and light interception. Grain yield ranged between 10.7–15.8 t/ha at 15% moisture content, with a grand mean of 12.7 t/ha. Results indicated that variations in grains/m² had a larger effect on winter wheat yield than variations in individual grain weight. Variability in grains/m² was influenced by changes in spikes/m² more than the number of grains/spike. While spikes/m² at harvest was significantly related to the number of shoots/m² at GS59, no significant relationship was observed between the shoots/m² at the time of maximum tillers/plant and spikes/m² at harvest. Furthermore, a significantly negative linear relationship was observed between shoots/m² at the time of maximum tillers/plant and grains/spike. Therefore, high rates of tillering were not beneficial to yield formation in the majority of crops monitored. A strong effect of individual grain weight was observed at one site of the nine evaluated in the study, indicating that a partial source limitation of yield is possible in certain Irish environmental conditions. However, variations in grain yield of crops of winter wheat grown at different locations in Ireland in different seasons were primarily driven by variations in grain number, and therefore were generally sink-limited.     

Efficiency of grain production of winter wheat as affected by N fertilisation under particular consideration of single culm sink size

Grain yield and yield components of winter wheat were recorded during 2-year field trials in Southern Bavaria, Germany. The impact of single ear sink size on the efficiency of grain production was studied in plants differing in single ear weight. While total grain yield showed only slight differences between N fertiliser treatments, significant variations were detected in harvest index and N harvest index. For single culms, a decrease in ear weight was related to decreasing values of harvest index and N harvest index. This correlation could not be altered by means of N fertilisation. The most efficient grain production, i.e. high value of harvest index and N harvest index, was regularly recorded in plant stands developing large single ear weights. The study confirms that with increasing sink size, the efficiency of grain production in winter wheat is improved. A N fertilisation strategy, favouring the formation of a large sink size, is described. In this respect, lower N rates in early spring and emphasis on N fertilisation during stem elongation proved to be decisive. This strategy favoured the generative growth at the expense of vegetative growth without excessively decreasing the corresponding source size.     

黄淮海地区冬小麦关键生育期不同灌溉水平对产量影响的模拟

研究黄淮海地区不同灌溉水平下冬小麦产量的变化规律,对于识别干旱对冬小麦产量的影响和制定合理的节水灌溉措施具有指导意义。基于DSSAT作物模型,参考各生育阶段的水分亏缺量以及当地的灌溉习惯,制定模型输入的不同处理的灌溉量,模拟分析近30年黄淮海灌溉冬麦区4个典型站点冬小麦关键生育期不同灌溉水平下,产量及产量构成的相对变化规律,并且以典型处理为例,探讨2个关键生育阶段减产的累积概率。结果表明,拔节至抽穗期的水分胁迫对冬小麦的产量影响最大,产量相对变化主要由水分胁迫引起单位面积粒数的相对变化引起。在重度干旱条件下,拔节至抽穗期胁迫造成中等程度减产概率约为灌浆期胁迫的2倍(山东兖州点除外);在河北石家庄和天津点,轻度和重度减产主要由拔节至抽穗期胁迫引起,而在山东兖州和河南新乡点,拔节至抽穗期及灌浆期胁迫造成轻度减产概率差别不大,但灌浆期重度干旱导致一定概率的重度减产。因此,在黄淮海冬小麦灌区偏南部,不但要加强拔节至抽穗期的灌溉措施,还应该注重灌浆期的干旱风险。     

Optimising crop production and nitrate leaching in China: Measured and simulated effects of straw incorporation and nitrogen fertilisation

The sustainability of growing a maize—winter wheat double crop rotation in the North China Plain (NCP) has been questioned due to its high nitrogen (N) fertiliser use and low N use efficiency. This paper presents field data and evaluation and application of the soil–vegetation–atmosphere transfer model Daisy for estimating crop production and nitrate leaching from silty loam fields in the NCP. The main objectives were to: i) calibrate and validate Daisy for the NCP pedo-climate and field management conditions, and ii) use the calibrated model and the field data in a multi-response analyses to optimise the N fertiliser rate for maize and winter wheat under different field managements including straw incorporation.The model sensitivity analysis indicated that a few measurable crop parameters impact the simulated yield, while most of the studied topsoil parameters affect the simulated nitrate leaching. The model evaluation was overall satisfactory, with root mean squared residuals (RMSR) for simulated aboveground biomass and nitrogen content at harvest, monthly evapotranspiration, annual drainage and nitrate leaching out of the root zone of, respectively, 0.9 Mg ha⁻¹, 20 kg N ha⁻¹, 30 mm, 10 mm and 10 kg N ha⁻¹ for the calibration, and 1.2 Mg ha⁻¹, 26 kg N ha⁻¹, 38 mm, 14 mm and 17 kg N ha⁻¹ for the validation. The values of mean absolute deviation, model efficiency and determination coefficient were also overall satisfactory, except for soil water dynamics, where the model was often found erratic. Re-validation run showed that the calibrated Daisy model was able to simulate long-term dynamics of crop grain yield and topsoil carbon content in a silty loam field in the NCP well, with respective RMSR of 1.7 and 1.6 Mg ha⁻¹. The analyses of the model and the field results showed that quadratic, Mitscherlich and linear-plateau statistical models may estimate different economic optimal N rates, underlining the importance of model choice for response analyses to avoid excess use of N fertiliser. The analyses further showed that an annual fertiliser rate of about 300 kg N ha⁻¹ (100 for maize and 200 for wheat) for the double crop rotation with straw incorporation is the most optimal in balancing crop production and nitrate leaching under the studied conditions, given the soil replenishment with N from straw mineralisation, atmospheric deposition and residual fertiliser.This work provides a sound reference for determining N fertiliser rates that are agro-environmentally optimal for similar and other cropping systems and regions in China and extends the application of the Daisy model to the analyses of complex agro-ecosystems and management practices under semi-arid climate.     

A trait-based characterization of cover plants to assess their potential to provide a set of ecological services in banana cropping systems

Cover plants are one of the means to increase the functional biodiversity of fields and to enhance the ecological functions of the communities. However, the design of cropping systems including cover plants relies largely on expert knowledge. There is a lack of methods to select the best suited cover plants according to their role in the agrosystem. We propose to use functional traits to select cover plants suited to sustain ecological services in the banana agrosystems of the French West Indies. Our objectives were (i) to characterize a collection of cover plants on a trait basis, according to their potential to provide the services expected in a banana agrosystem and (ii) to discuss the potential use of this characterization for the design of innovative multi-species banana cropping systems. In these systems, four main services are targeted, i.e. controlling weeds, controlling plant-parasitic nematodes, improving soil fertility and particularly N availability, and avoiding competition with banana for resource acquisition. Three experiments were conducted, under field and controlled conditions, to evaluate the potential of a collection of 28 tropical cover plants to achieve the functions related to these services. For each cover plant, a functional profile was constructed from a combination of plant traits that are easy to assess experimentally. It described plants’ potential to achieve the functions expected in a banana agrosystem. Functional profiles required for cover plant usages were also identified. The comparison of the plant functional profiles and the functional profiles required for their usages enabled us to select the best suited plants for each usage. However, these functional profiles rarely corresponded, meaning that a cover plant is rarely sufficient to achieve all the functions required for a usage. Functional complementarities obtained by the mixture of different species of cover plants are thus often required. Compared to classical approaches of innovative cropping system design based on the experimental testing of spatial and temporal plant combinations, such a trait-based approach saves time by focusing on a shortlist of cover plants best suited according to their functions in the agrosystem.     

全球气候变化影响我国冬小麦生产之前瞻

将作物模型与大气环流模型（GCM）耦合，评价未来气候变化对我国冬小麦生育期、产量和灌溉需要量的影响，并采用一种农业经济模型，就研究区域未来冬小麦总产的变化进行估计；还根据若干农业所气候指标，分析当CO2倍增时研究区域冬小麦生长期干湿状况的改变，种植界线可能发生的地理位移，以及品种布局和种植制度的演进趋势等     

Screening techniques and sources of resistance to rusts and mildews in grain legumes

Summary In this paper we review the existence of sources of resistance and the various available screening methods for resistance in grain legumes against the airborne pathogens powdery mildews, downy mildews and rusts. Available resistance against these pathogens is not abundant and is particularly in risk of erosion owing to the constant generation and introduction of new races of the pathogen. A continuous search for more resistance sources is therefore a priority in legume breeding and special emphasis should be paid to selection of resistance mechanisms that are likely to be durable and to implementation of strategies to prolong the durability of existing resistance.     

Effects of row spacing and liquid manure on directly drilled winter wheat in organic farming

In the optimisation of grain yield and quality of wheat, plant distribution is a key factor. In contrast to high yield levels, at moderate levels, widening the row space did not decrease grain yield. To gain information about changes in the quality and yield with changing in row spacings in organic farming systems, experiments were conducted at two locations in the Swiss midlands in 2001/2002. Winter wheat (Triticum aestivum L., cv. Titlis) was directly drilled in rows 0.1875 and 0.3750 m apart at the same seeding rate per area. An unfertilised treatment and the usual application of 60 m³ ha⁻¹ liquid farmyard manure were compared. While the grain yield was not decreased by the wider row spacing, the thousand kernel weight (TKW), and grain protein content were increased from 42.6 to 43.5 g and from 11.7 to 12.7%, respectively, compared to the narrow row spacing. Liquid manure, on average of both experimental sites, increased the yield (from 3.725 to 4.765 Mg ha⁻¹) and the grain protein content (from 12.0 to 12.5%). Doubling the space between the rows from 0.1875 to 0.3750 m seemed to be a suitable strategy for managing directly drilled winter wheat in organic farming systems.     

过氧化物酶同工酶电泳技术在冬小麦抗白粉病鉴定中的应用

通过对１４个抗白粉病、２３个感白粉病的冬小麦品种、品系功能叶过氧化物酶同工酶分析证明，由于对白粉病反应不同，在拔节至抽穗期，抗、感品种功能叶的过氧化物酶酶谱有明显差别，据此可以对田间大量育种材料进行早期预测，以防使用感病材料接种花药和进行杂交。用叶片同工酶鉴定抗病性，不影响植株生长发育，可与育种试验同时进行，是一种简便易行的鉴定方法。     

旱地条件下冬小麦产量和农艺性状对养分投入的响应

以9个旱地冬小麦品种为材料,通过田间试验研究其产量及主要农学性状与养分投入水平的关系。与不施肥对照相比,在低、高水平养分投入条件下小麦籽粒产量分别提高20%和40%,生物量提高17%和35%,单位面积穗数增加11%和25%,穗粒数增加8%和10%。高产品种的生物量、单位面积穗数、穗粒数及其随养分投入增加而提高的幅度显著高于低产品种。千粒重不受养分投入水平的影响。旱地条件下,不同小麦品种的产量、生物量、单位面积穗数和穗粒数均随养分投入水平的提高而显著提高,并且存在品种间差异。高生物量、高单位面积穗数和穗粒数是旱地高产品种的重要特征,它们对养分投入的敏感响应是高产品种养分投入提高后产量提高的主要原因。     

Effects of biogas digestion of clover/grass-leys, cover crops and crop residues on nitrogen cycle and crop yield in organic stockless farming systems

The trend towards specialization in conventional farming led to large agricultural areas in Germany and in Europe lacking livestock. Also stockless organic farming has increased during recent years. In organic farming clover/grass-ley (CG) provides nitrogen (N) to the whole cropping system via symbiotic N₂ fixation and also controls certain weeds. A common practice in organic farming, when ruminants are not present, is to leave the biomass from CG in the field for their residual fertility effect. CG biomass, crop residues (CR) and cover crops (CC) represent a large unexploited energy potential. It could be used by anaerobic digestion to produce biogas. A field experiment was carried out by implementing a whole cropping system with a typical crop rotation for such farming systems on the research station Gladbacherhof from 2002 to 2005. The crop rotation consisted of six crops (two legumes and four non-legume crops). The aim was to evaluate whether the use of N could be improved by processing biomass from CG, CR and CC in a biogas digester and using the effluents as a fertilizer, compared to common practice. In the control treatment, represented by the usual stockless system, the CG, CR and CC biomass were left on the ground for green manure purposes. In the biogas systems these substrates were harvested for digestion in a biogas plant. The effluents of digestion were used to manure the non-legumes in the same crop rotation. Results indicate that digestion of CG, CR and CC can increase the crop dry matter and N yields and the N content of wheat grains in organic stockless systems. Harvesting and digestion of residues and their reallocation after digestion resulted in a better and more even allocation of N within the whole crop rotation, in a higher N input via N₂ fixation and lower N losses due to emissions and probably in a higher N availability of digested manures in comparison to the same amounts of undigested biomass.     

不同小麦品种产量对冬前积温变化的响应

为确定河北省中部地区小麦品种适播期,筛选耐迟播品种,2011年秋至2014年夏在河北藁城采用播期×品种二因子裂区试验,研究了不同播期对当地12个主栽小麦品种产量的影响以及不同品种对冬前积温的响应。结果表明,播期对小麦产量有显著影响;不同品种对播期响应差异明显,分为迟钝型、中间型和迟播敏感型。迟钝型品种对播期不敏感,适播期长,冬前≥0℃积温范围为324~560℃,迟播后穗数和产量稳定;中间型品种适播期较长,积温范围为362~566℃,迟播后粒数增加,穗数和产量降低;迟播敏感型品种对播期敏感,适播期较短,积温大于511℃,不宜晚播,晚播后穗数和产量明显下降。在试验地区,推荐小麦适播期为迟钝型品种10月7日至22日、中间型品种10月7日至19日、敏感型品种10月5日至10日。